Sample Handling - Field Through Laboratory

The allowable holding time for samples
depends on the nature of the sample, the
stability of the constituent(s) to be de-
termined and the conditions of storage.

1 For some constituents and physical
values, immediate determination is
required, e.g. dissolved oxygen, pH,

2 Using preservation techniques, the

holding times for other determinations

range from 6 hours (BOD) to 7 days
(COD). Metals may be held up to 6
months, (2)

3 The EPA Methods Manual”? includes

a table summarizing holding times and

preservation techniques for several

analytical procedures, This information

can also be found in the standard

references ’”’*’ as part of the
presentation of the individual
procedures,

4 If dissolved concentrations are
sought, filtration should be done in
the field if at all possible. Other-
wise, the sample is filtered as soon
as it is received in the laboratory.
A 0,45 micron membrane filter is
recommended for reproducible
filtration, .

The time interval between collection
and analysis is important and should be
recorded in the laboratory record book,

VII RECORD KEEPING

The importance of maintaining a bound,
legible record of pertinent information
on samples cannot be over-emphasized.

Field Operations

A bound notebook should be used, Informa-

tion that should be recorded includes:

3-4

1 Sample identification records (See
Part III)

2 Any information requested by the
analyst as significant

3 Details of sample preservation

4 A complete record of data on any
determinations done in the field.
(See B, next)

5 Shipping details and records
Laboratory Operations

Samples should be logged in as soon as
received and the analyses performed
as soon as possible.

A bound notebook should be used,
Preprinted data forms provide uniformity
of records and help ensure that required
information will be recorded. Such sheets
should be permanently bound,

Items in the laboratory notebook would
include:

sample identifying code

date and time of collection

date and time of analysis

the analytical method used

any deviations from the analytical

method used and why this was done

data obtained during analysis

results of quality control checks on the

analysis

8 any information useful to those who
interpret and use the data

9 signature of the analyst

oR OMe

aa


Flame Photometry

the same, or near the same wavelength,

For instance, calcium at 423 nm and
chromium at 425 nm couldinterfere
with each other by additive effect, The
correction may be té dilute out the un-
wanted metal or measure one of the

emissions at a different wavelength,

The emission energy of one element may
be enhanced or depressed by energies

fromother elements, This phenomenon
(radiation interference) occurs when one
element causes another to modify its ac-
tual emission intensity in either a neg-
ative or positive manner, Correction

is obtained by dilution or by controlled
interference addition,

Other types of difficulties encountered
are too numerous to list here, In gen-
eral, they may be overcome by improved
instruments (high resolution, narrower
slit openings, optics, flame adjustment)
or possibly by special techniques,

Some inexpensive instruments, designed
for hmiteduse, may employ illuminating
gas with air or propane with air as a
matter of economy or convenience.

STANDARD CURVE FOR SODIUM

=”
=
=
Lc
-
4. 1 1 " - re 1 4. n i 4

10 20
mg Sodium/1
Figure 3

v

TECHNIQUES

The following techniques are intended to
serve as examples of current procedures
in use for routine samples and for special
samples where corrective procedures are
indicated,

A

Emission Intensity vs. Concentration

This is the classical procedure in flame
photometry, Solutions (standards)
containing known concentrations of test
elements are compared withan unknown
sample, This technique is applicable
only when no interference is present,

Radiation Buffers

For measurements of alkaline earth
metals (sodium, potassium, calcium,
magnesium) radiation buffers are pre-
pared as solutions saturated with
regard to each metal, respectively, A
potassium buffer, for example, is pre-
pared by saturating distilledwater with
sodium, calcium, and magnesium
chloride. A calcium buffer in turn is
saturated with sodium, potassium and
magnesium chloride,

Preparation of Radiation Buffers

Fora sodium measurement, the buffer
solution is added equally to samples
and standards so that the interferences
are alike for all readings, thereby
cancelling each other (see Table 3).

Instrument Improvement

Potassium emits energy bands at 766,
405, and345 nm. The bands are at
opposite ends of the spectrum and the
405 and 345 bands are not usable in the
visible spectrum, The 766 line also
loses sensitivity because of its prox-
imity to the infrared region, Use of a
red sensitive phototube or photomulti-
plier, however, permits measurement
with an ordinary instrument at concen-
trations as low as 0.1 mg/l, or less.
This approach is applicable to other
elements also.

1-6



FLAME PHOTOMETRY

I PRELIMINARY

Flame photometry is the art and science of
applying thermal energy (heat) to elements
in order to effect orbital shifts which produce
measurable characteristic radiations. The
color of the emission and the intensity of
brightness of emission permit both qualita-
tive and quantitative identification.

The application ofa very hot flame (2000°C
or more) produces excitation of the element,
caused by the raising of an electron toa
higher energy level and is followed by the
loss of a small amount of energy in the form
of radiant energy as the electron falls back
into its original position or toa lower energy
level,

COLLIMATING
MIRROR

SAMPLE
ATOMIZER BURNER

YELLOW
RED

PHOTODETECTOR

Il INSTRUMENTATION ,

The six essential parts of a flame photo-
meter are: pressure regulators,and flow
meters for the fuel gases, atomizer, burner,
opticalsystem, photosensitive detector and
an instrument for indicating or recording
output of the detector, These components
are schematically shown in Figure 1,

A Atomizer and Burner

Numerous variations in atomizerand
burner designs have beenused, Figure
2 depicts the integral aspirator- burner
used in Beckman instruments. The
sample is introducedthrough the
innermost concentric tube, a vertical

AMPLIFIER

METER

FIGURE 1. SIMPLIFIED DIAGRAM OF A FLAME PHOTOMETER

CH. ME'’, toc, 12,71


Determination of Calcium and Magnesium Hardness

C Determination of Calcium Hardness
1 Principle of determinations
Murexide indicator forms a salmon-

colored complex with calcium whose
1onization constant 1s of a higher

value than that of the Ca EDTA complex.

2 Interferences Heavy metals and Sr

4 Procedure Time of tritation and
proper lighting conditions are critical
factors

4 Calculation of Ca hardness.

5 Precision and accuracy.

D_ Determination of Magnesium Hardness

1 Calculation by difference method
most commonly used.

2 Equivalent of Ca hardness 1s sub-
tracted from total hardness equiva-
lents, the difference attributable to
magnesium equivalents,

3 Other methods such as pyrophosphate
method, where calculation by differ-
ence method cannot be used

IV ANALYTICAL QUALITY CONTROL
METHODS

A The Environmental Protection Agency,
Analytical Quality Control Laboratory
has published a manual titled Methods
for Chemical Analysis of Water and
Wastes, 1974, .

B The procedure for the determination

of hardness, as discussed in this ,
manual, was excerpted from the
13th ed. of Standard Methods(4)
and part 23 of ASTM. (5)

REFERENCES

1 Barnard, A.J. Jr., Broad, W.C. and
Flaschka, H, The EDTA Titration.
J.T. Baker Company. 1957,

2 U.S,Public Health Service. Drinking
Water Standards. USPHS Report,
Volume 61, No. 11, 1946.

3 Rainwater, R.H,-and Thatcher, L. L.
Methods for the Collection and Anai-
ysis of Water Samples. U.S.Geo-
logical Survey Water Supply, Paper
1454, 1960. .

4 Standard Methods for the Examination
of Water and Wastewater, 13th ed.
APHA, AWWA, WPCF, Method
122B, 1971,

5 ASTM Standards, Part 23, Method
D1126-67, 1973,

6 Methods for Chemical Analysis, of
Water and Wastes, EPA-MDQARL,
Cincinnati, OH, 1974.°. | ~

This outline was prepared by B, V. Salotto,
Research Chemist, Waste Identification and
Analysis Section, MERL, EPA, and revised
by C, R, Feldmann, Chemist, ‘National
Trammg Center, MPOD, -QWPO, USEPA,
Cincinnati, OH 45268, .

Descriptors: Calcium, Chemical Analysis,
Hardness, Magnesium, Water Analysis,
Calcium Carbonate, Calcium Compounds,
Magnesium Carbonate


Methodology for Chemical Analysis of Water and Wastewater

The part applicable to water was formerly
Part 23, It1s now Part 31.

The methods are chosen by approval of the
membership of ASTM and are intended to

aid mdustry, government agencies and the
general public, Methods are applicable to
industrial waste waters as well as to other
types of water samples, .

EPA Methods Manual'3)

The United States Environmental Protection
Agency publishes a manual of "Methods for
Chemical Analysis of Water and Wastes."

EPA developed this manual to provide
methodology for monitoring the quality of
our Nation's waters and to determine the
impact of waste discharges. The test pro-
cedures were carefully selected to meet
these needs, using Standard Methods and
ASTM as basic references. In many cases,
the EPA manual contains completely
described procedures because they modified
methods from the basic references, Other-
wise, the manual cites page numbers in

the two references where the analytical
procedures can be found, °

ACCURACY AND PRECISION
Of the Method

One of the criteria for choosing methods

to be used for water quality analysis is that
the method should,measure the desired
property or constituent with precision,
accuracy, and specificity sufficient to meet
data needs, Standard references, then,
include a statement of the precision and
accuracy for the method which is obtained
when (usually) several analysts in different
laboratories used the particular method,

Of the Analyst . +

Each analyst should check his own precision
and accuracy as a test of his skill in per-
forming a test. According to the U. S, EPA
Handbook for Analytical Quality Control’),
he can do this in the following manner,

To check precision, the analyst should
analyze samples with four different
concentrations of the constituent of interest,
seven times each, The study should cover
at least two hours of normal laboratory
operations to allow changes in conditions
to affect the results. Then he should
calculate the standard deviation of each of
the sets of seven results and compare his
values for the lowest and highest concen-
trations tested with the standard deviation

value published-for that method in the reference

book. An individual should have better values
than those averaged from the work of several
analysts.

To check accuracy, he can use two of the
samples used to check precision by adding

a known amount (spike) of the particular
constituent in quantities to double the lowest
concentration used, and to bring an inter-
mediate concentration to approximately 75%
of the upper limit of application of the
method, He then analyzes each of the spiked
samples seven times, then calculates the
average of each set of seven results. To
calculate accuracy in terms of % recovery,
he will also need to calculate the average of
the results he got when he analyzed the
unspiked samples. Then:

Avg. of Spiked

Recovery = | Avg. of + Amt. of | X 100

Unspiked " “Spike

Again, the individual's %récévery should be
bettér than the published figure derived from
the results of several analysts.

Of Daily Performance

Even after an analyst has demonstrated his
personal skill in performing the analysis,

a dajly check on precision and accuracy
should be done. About one in every ten
samples should be a duplicate to check
precision and about one in every ten samples
should be spiked to check accuracy.

It is also beneficial to participate mn inter~
laboratory quality control programs. The
U.S. EPA provides reference samples at

no charge to laboratories. These samples

245


LABORATORY PROCEDURE FOR TOTAL HARDNESS

I REAGENTS
A Buffer Solution:

1 Dissolve 16.9 g of NH Clin 143 ml of
cone. NH,OH. 4

2 Dissolve 1.179 g of analytical reagent
grade disodium ethylenediamine tetra-
acetic acid dihydrate(Na, EDTA:2H,0)
and 0.644 g of MgCl, ‘61,0 in 50 rfl of
distilled water.

3 Adj the solution from (2) to the solution
from (1) with mixing, and dilute to 250
ml with distilled water. Addition of
small amounts of Na, EDTA‘2H,O or
MgCl,: 6H,O may be“necessary to attain
exact’ equivalence.

4 The buffer should be stored in a plastic
or resistant glass container tightly
stoppered to prevent CO, absorption
and NH, loss. Discard the buffer when
1 or 2 fAl added to the sample fails to
produce a pH of 10,0 + 0.1 at the end
point of the titration.

B Inhibitor:

1 Most water samples do not require the
use of aninhibitor. In the presence of
certain interferring ions, however, an
inhibitor may be needed to sharpen the
endpoint color change. Several types
of inhibitors may be prepared or pur-
chased, Sodium cyanide, NaCN, is one
of the simpler inhibitors to use.

2 Add 0,25 g of powdered NaCN to the
sample and adjust the pH to 9, 9-10. 1.
Caution: NaCN is poisonous, Use
Targe amounts of water when flushing
solutions containing NaCN down the
drain. 1o not acidify solutions contain-
ing NaCN; volatile, poisonous hydrogen
cyanide, HCN, would be liberated.

C Indicator:
1 Eriochrome Black-T dye (EBT) is use-
~ ful for the determination. Other commer-

c1al grades or laboratory formulations
of the dye are also satisfactory.

CH. HAR. lab. 3c. 1,76

2 Prepare the indicator in dry powder
form by grinding together 0.5 g of the
dye and 100 g of NaCl.

D Standard Calcium Carbonate, CaCOg:

Weigh 1.000 g of anhydrous, primary
standard grade CaCO, and transfer it to

a 500 ml Erlenmeyer‘flask. Add 1:1 HCl
(equal volumes of conc. HCl and water)
dropwise and with swirling of the flask
until the CaCO, has dissolved Bring

the volume of quid to about 200 ml with
water, boil a few seconds to dispel CO,,
cool, ‘and add a few drops of methyl red
indicator. Adjust the color of the solution
to an intermediate orange by the dropwise
addition of 1:1 HCl or 1:4 NH,OH (1 volume
o conc. NH,OH + 4 volumes $f water).
Transfer thé solution quantitatively to a
one liter volumetric flask and dilute to the
mark with water. (1,0 ml = 1.0 mgCaCO,)

E Na,EDTA:2H,O (0.01 M):

Dissolve 3.723 g of the dry reagent grade
Na, EDTA:2H,0 1n distilled water and
dilfte to 1 it@r. 1,0 ml of the 0.01 M
solution = 1.0 mg of CaCO,. Check the
concentration of this solution by titration
against the standard calcium carbonate
solution as described in Il below.

M STANDARDIZATION OF THE Na,EDTA:

2H,0:

A Dilute 25,0 ml of CaCO, standard to about
50 ml with distilled watdr in a 125 ml
Erlenmeyer flask against a white background.

B Add 1-2 ml of the buffer solution and check
the pH to ensure that it is 9.9 to 10.1.

C Add approximately 0,2 g of the indicator.

D Add the Na, EDTA-2H,O slowly and with
stirring unfil the coldh changes trom a
rose to a blue color. If the color change
is not sharp, repeat the determination
using the inhibitor. If the endpoint is still
not sharp, prepare a fresh supply of
indicator.

E The titration should take less than 5 minutes,
measured from the time of buffer addition

14-1


Determination of Lead

I Hold the beaker at a 45 degree angle, and
slowly add 2 ml of conc. distilled nitric
acid, rotating the beaker to effect thorough
contact of the acid with the residue.

J Place the beaker on a low temperature
hotplate and evaporate just to dryness.

K Add 2 ml of mtric acid (1-1) to the beaker
and heat for 1 minute. Cool, quantitatively
transfer the solution to a 10 mi volumetric
flask and bring to volume with distilled
water. The sample is now ready for
analysis.

{vV SUMMARY

The method of choice for the determination of
lead is the atomic absorption spectroscopy
method. In waters that are relatively clean,
such as drinking water, the lead can be
determined by direct aspiration of the sample
into the instrument. However, for water high

10-4

in solids or having a concentration of lead
below 100 yw g/1 the extraction procedure
should be used to enhance the detection
capabilities,

REFERENCES

Standard Methods for the Examination of Water
and Wastewater, 13th Ed. 1971.

Methods for Chemical Analysis of Water and
Wastes. 1974.

This outline was prepared by J. D. Pfaff,
National Training Center, MOTD, OWPO,
USEPA, Cincinnati, Ohto 45268,

Descriptors: Lead, Metals, Water Pollution,
Heavy Metals, Spectroscopy, Spectrophotometer
Chemical Analysis


Determination of Lead

polarography, emission spectroscopy,
neutron activation and x-ray fluorescence,

* ae} ‘96 1ts own strong and weak points,
.1uSt4  €apensive Lo the point of exclusion
in most laboratories but can be used to
determme the concentration of lead ina
sample,

C Atomic Absorption

Most metals, including lead, may be readily
determined by atomic absorption spectroscopy.
The method 1s usually simple, rapid and
applicable to a large number of metals in
drinking, surface and saline waters, and
domestic and industrial wastes. While
drinking waters may be analyzed directly,
domestic and industrial wastes require
processing to solubilize suspended material.
Sludges and sediments and other solid type
samples may also be analyzed after proper
pretreatment.

Detection hmuts, sensitivity and optimum
ranges of the metals will vary with the
various makes and models of satisfactory
atomic absorption spectrophotometers.

The data shown in Table 1, however,
provide some indication of the actual
concentration ranges measurable with
conventional atomization. In the majority

of instances the concentration range shown
in the table may be extended much lower
with scale expansion and conversely extended
upwards by using a less sensitive wavelength
or by rotating the burner 90 degrees.
Detection limits may also be extended
through concentration of the sample, through
solvent extraction techniques and/or the

use of the so called furnace techmiques.

The latter includes the heated graphite
atomizer, the carbon rod and the tantalum
strip accessories. When using furnace
techniques, however, the analyst should be
cautioned as to possible chemical reactions
occurring at elevated temperatures which
may result in either suppression or enhance-
ment of the analysis element. Methods of
standard addition are mandatory with these
furnace techniques to insure valid data,

For levels of lead below 100 ug/l, an

extraction procedure 1s recommended,
This extraction procedure is carried out

10-2

at a pH of 2.8 which 1s the optimum pH
for the extraction of lead. However, if
many of the metals are to be analyzed in
the same sample, either larger sample
volumes must be extracted or individual
extractions made for each metal being
determined.

Ill EXTRACTION PROCEDURE

Extraction procedure with pyrrolidine
dithiocarbamic acid (PDCA) in chloroform.

A Transfer 200 ml of sample into a 250 ml
separatory funnel, add 2 drops bromphenol
blue indicator solution and mix.

B Prepare a blank and sufficient standards in
the same manner and adjust the volume of
each to approximately 200 ml with deionized
distilled water. All of the metals to be
determined may be combined into single
solutions at the appropriate concentration
levels,

C Adjust the pH by addition of 2N NH4zOH
solution until a blue color persists. Add
HCl dropwise until the blue color just
disappears; then add 2.0 ml HCl in excess.
The pH at ths point should be 2,3, (The
pH adjustment may be made with a pH
meter instead of usimg indicator. )

D Add 5 ml of PDCA-chloroform reagent
and shake vigorously for 2 minutes.
Allow the phases to separate and drain the
chloroform layer into a 100 ml beaker.

E Add a second portion of 5 ml PDCA-chloroform
reagent and shake vigorously for
2 minutes. Allow the phases to separate and
combine the chloroform phase with that
obtained in step (D).

F Determine the pH of the aqueous phase and
adjust to 4,5.

G Repeat step (D) again combining the solvent
extracts,

H Readjust the pH to 5.5, extract, readjust to
6.5 and extract a fifth time. Combine all
extracts and evaporate to dryness on a steam
bath,



Ldurners and Fuel Mixtures

Aluminum
Antimony
Arsenic
Barium
Berylhum
Cadmium
Calcium
Chromium
Cobalt
Copper
fron

Lead
Magnesium
‘Manganese
Mercury
Molybdenum
Nickel
Potassium
Selemum
Silver
Sodium
Thallium
Tin
Titanium
Vanadium
Zine

TABLE J

Methods in USEPA Methods Manual

Nitrous Oxide

Air

Gaseous Hydride Method
Nitrous Oxide

Nitrous Oxide

Air

Air

Nitrous Oxide

Air

Air

Air

Air

Air

Air

Cold Vapor Technique
Nitrous Oude

Air

Air

Gaseous Hydride Method
Air

Air

Air

Air

Nitrous Oxide

Nitrous Oxide ,
Air

Acetylene
Acetylene
Acetylene
Acetylene

“Acetylene

Acetylene
Acetylene
Acetylene
Acetylene
Acetylene
Acetylene
Acetylene
Acetylene
Acetylene
Acetylene
Acetylene
Acetylene
Acetylene
Acetylene
Acetylene
Acetylene
Acetylene
Acetylene
Acetylene
Acetylene
Acetylene


Flame Photometry Laboratory (Sodium)

38 If the point at which the needle moves no
further to the right ia overshot, turn the
wavelength about 1/4 turn to the right and
repeat step 37,

39 Close the shutter.

40 Replace cup 10 with cup 8,

41 Open the shutter,

42 Record the background transmittance
reading for this solution,

43 Close the shutter.

44 Repeat steps 40, 41, 42, and 43 using
cups 6, 4, 2, 0, and the unknown, in turn,

45 Aspirate distilled water for about 15 sec,

46 Turn the sensitivity knob to the standby
position,

41 Close the main valve on the hydrogen
cylinder,

48 Close the main valve on the oxygen cylinder,

49 Empty the eight plastic cups and discard
them,

50 Leave the power toggle switch (on left
side of instrument) on,

51 For each of the 6 solutions subtract the
background percent transmittance reading
from the peak percent transmittance
reading.

52 Using the graph paper provided in the
tnanval, plot the 6 differences vs, the
appropriate concentrations. Draw the
line to beat fit connecting the 6 points.
This is the calibration graph,

53 Find the difference percent transmittance
for the unknown on the percent trans-
mittance axis,

54 Draw a straight line to the right until it
intersects the calibration line,

55 From the point of intersection draw a line
straight down to the concentration axis,

56 This is the concentration of the unknown,

REFERENCE

Standard Methods for the Examination of Water
and Wastewater, 13th Edition, page 317,
Method 153A, 1971,


Determination of Mercury

There 1s also available an automated method
which utilized the Techmcon Auto Analyzer.
This method 1s described in detail in the
EPA Methods Manual, The method is
applicable to surface waters and may be
apphcable to saline water, wastewater
effluents and domestic sewage providing
potential interferences are not present.

Regardless of what instrument 1s used,

its calibration should be checked originally
upon receipt and standards run each time
samples are to be run in order to verify the
calibration, The standards are treated

in the same method except that 1f no
organic mercury 1s used as the standard,
the heating step can be omitted.

IV SUMMARY

The determination of the mercury content

of waters has become a necessary analysis
for the health of the consuming public. The
method of choice has become the flameless
atomic absorption procedure. Besides being
simple to perform 1t 1s sensitive enough to
determine the limit set for the permissible
content of mercury in water,

The method can be carried out on any atomic
absorption instrument that has enough physical
space in its burner compartment in which to
install the absorption cell. However, there
are available on the market, instruments
designed specifically to determine mercury
via the flameless method. These instruments
are generally considerably less expensive
than a conventional atomic absorption
spectrophotometer but have the drawback

of being able to be used for only that
determination,

REFERENCES

1 Methods for Chemical Analysis of Water
and Wastes. USEPA, Office of
Technology Transfer, Washington, DC
20460, 1974.

2 Hatch, W. R. and Ott, W. L. Analytical
Chemistry, 40, 2085, December 1968.

3 Westoo, G. Acta Chem, Scand. 22,
2277-2280, 1968,

This outline was prepared by J. D. Pfaff,
National Training Center, MOTD, OWPO,
USEPA, Cincinnati, Ohio 45268,

Descriptors: Heavy Metals, Mercury, Water
Pollution, Chemical Analysis, Metals,
Spectroscopy, Spectrophotometers


Atomic Absorption Spectrophotometry

b Premix

Those which introduce the spray into
a condensing chamber for removing
large droplets. (Figure 3)

3 Flame shape is important, The flame

Typical flame temperatures are shown
in Table I.

Table I

should have a long path length (but a Approximate

narrow width, such as a fishtail flame) Fuel-Oxidant Temp. ,°C

so that the source traverses an increased —

number of atoms capable of contributing Nitrous Oxide - acetylene sooo

to the absorption signal. Hydrogen = air 2100
4 The effective length of the flame may Hydrogen - oxygen 2700 - 2800

be increased by multiple passages Acetylene - oxygen 3100

through the flame with a reflecting Acetylene - air 2000 - 2200

mirror system, or by alignment of Propane - oxygen 2700 = 2800

several burners in series. Mluminating gas - oxygen 2800
5 The flame temperature need only be Cyanogen - oxygen 4900

high enough to dissociate molecular —_ 7 —

compounds into the free metzl atoms,

FLAME
FUEL : .
AUXILIARY
AIR
ORIFICE
CAPILLAR
— .
SPOILERS 0
ASPIRATING - MIXING CHAMBER
DRAIN ‘
Figure 3 ,

43


_Fiame Photometry

Internal-Standard Method

f& Standard Addition F
Equal volumes of the sample are added The method consists of adding to each
10 a series of standard solutions con- sample and standard a fixed quantity of
taming different known quantities of internal standardelement, The element
test element, all diluted to the same must be one not already present in the
voluine (see Table 4), Emission in- sample. Lithium is usually the inter-
tensities of the resulting solutions are nal standard used. This method 1s most
then determined at the wavelength of convenient when using instruments
maaimum emission and at a suitable having dual detectors. The emission
point on the flame background. After intensities of standards and samples
subtracting the background emission, are read simultaneously or succes-
the resulting net emissions are plotted ively depending upon instrumentation.
linearly against the concentration of
the increments of the standard solutions G_ Separation of Interferences
that were mixed withthe unknown The
percent transmission of the mixture In cases where certain elements inter-
containing unknown sample and zero fere, they may be physically removed,
standard (distilled water) 1s doubled or the interference may be "blocked
and the concentration corresponding out" by reading the emission at different
to this point on the graph will be the wavelengths. To measure lithium, for
concenti ation of the undiluted unknown example, calcium, barium, and
sample This can be explained alge- strontium are precipitated as carbon-
braically in conjunction with Figure 4, ates of the metals. The hthium is
retained in the filtrate and measured
at a wavelength of 671 nm.
NaCl KCL CaCly MgCl
Sodium Bufter - + + +
Potassium Buffer + - + +
Calcium Bufter + + - +
Magnesium Buffer + ; + + -
i ce _______ Table 3
! Cone. of standards 0.0 mg/1 5.0 mg/l 10.0 mg/l
‘Volume of standard
i
Laddedto sample 10.0 mi 10.0 ml 10.0 ml
i a a — ~o ~T
| Volume of sample used al 10,0 ml 10.0 ml 10.0 ml
| Concentration of element ro _ |
an each portion of mixture ‘ st O mg/l 3 + 2.5 mg/l 3 +5 mg/I
= ne a de c. oes
Table 4



Flame Photometry Laboratory (Strontium)

This outline was prepared by C. R. Feldmann,
National Training Center, MOTD, OWPO,
USEPA, Cincinnati, Ohio 45268,

13-6

Descriptors Chemical Analysis, Laboratory
Tests, Water Analysis, Strontium, Alkaline
Earth Metals, Metals


a a

CONTENTS
Title or Description Quthne Number

Chemical Analyses bh
Methodology for Chemical Analysis of Water and Wastewater 2
Sample Handling ~ Field Through Laboratory 3
Atomic Absorption Spectrophotometry 4
Energy Sources for Atomic Absorption Spectroscopy 5
Principles of Absorption Spectroscopy 6
Flame Photometry 7
Determunation of Calcium and Magnesium Hardness 8
Flameless Mercury for Analytical Methods for Trace Metals - 9 .
Determination of Mercury

Determination of Lead io
Burners and Fuel Mixtures v1
Flame Photometry Laboratory (Sodium) 12
Flame Photometry Laboratory (Strontium) 13
Laboratory Procedure for Total Hardness 14


Laboratory Procedure for Total Hardness

1 [In an analysis of this type it is advant-
ageous lo carry out a preliminary, rapid
titration in order to determine approxi-
mately how much titrant will be required.
This 1s accomplished by adding the
NagEDTA-2H,0 at a fast dropwise rate
unfil the colo# change is observed.

Il PROCEDURE
Repeat steps II A through II F using sample
in place of CaCOg standard. The amount of
sample taken should require less than 15 ml
of Na EDTA -2H,O titrant.

IV) CALCULATION

A Standardization of the Na EDTA-2H,0°

REFERENCES

1 Standard Methéds for tiie Examination
of Water and Wastewater 13th Edition,
A PIIA, - AWWA-WPCF (1971)
p.179, Method 122B.

2 ASTM Standards, Part 23, Water;
Atmospheric Analysis 1972
Pp. 170, Method D1126-67.

3 Methods for Chemical Analysis of
Water and Wastes, 1974,
Environmental Protection Agency,
MDQARL, Cincinnati, OH.

ml of Caco, equal to 1.0 ml of the Na ,EDTA-2H,0

ml of CaCOg

ed for titration

{symbol B) = RY OF NAGEDTA2 ZO required f

B Total Hardness

Hardness as mg CaCO ,/1 = AXBxU aun

This outline was prepared by C, R. Feldmann,
Chemist, National Training Center, MOTD,
OWPO, USEPA, Cincinnati, Ohio 45268,

Descriptors, Calcium, Calcium Carbonate,

A= ml of Na EDTA 2H,0 tor titration of sample Chemical Analysis, ‘iardness, Laboratory

14-2

Tests, Magnesium, Water Analysis, Calcium
Compounds


Principles of Absorption Spectroscopy

1, = radiation entering the medium.

log i = A = absorbance
(optical density)

K= 2,303 k

b = length of radiation passing
through the medium (i.e.,
the width of the cell, gener-
ally express in cm.)

Beer's Law

Each molecule of an absorbing
medium absorbs the same fraction
of radiation incident upon it regard-
less of concentration,

Mathematically:

“do,
an k' de (8)

On integration and converting base
e to base 10 logarithms,

log oe = Kte (9)

k' = a proportionality constant
whose value is governed by
the same factors which de-
termine the value of k.

de = increment concentration of
the absorbing medium,

K' = 2,303 k!

¢  * concentration of the absorb-
ing medium (in the case ofa
solution c is generally ex-
pressed in moles/ liter.)

Lambert-Beer Law

log 32 sebe (10)

e # a constant obtained by com-
bining K plus K'. Whenb is
expressed in cm and c in
moles/liter, e is calledthe
molar absorptivity.

The term transmittance is some-
times used to express how much

radiation has been absorbed by a
medium,

Transmittance(T) = + (11)
lo

% Transmittance (hT) = i 100 (12)

The relationship between absorbance
and transmittance is given by the ex-
pression:

A = log =

5 The application of the Lambért-
Beer Law toa problem involving
quantitative analysis is made by
the use of a calibration curve
(or graph). See Figure 5.

Several standard solutions
containing known concentrations ‘
of the material under analysis

are "read" in the spectrophoto-

meter. Figure 5 is prepared by
graphing concentrations ys. cor-
responding absorbance readings.

If a straight line is obtained, the
material is said to follow Beer's
Law in the concentration range
involved. The absorbance of tne
sample is then "read" and the
corresponding concentration ob-

‘ tained from the calibration curve,

Increasing
Absorbance

Pal

ceressing
Concentratio! on

Figure 5.

ACKNOWLEDGMENT:

This outline contains certain portions from
a previous outline by Betty Ann Punghorst,
former Chemist, National Training Center.


Sample Handling - Field Through Laboriatory

IX SUMMARY

Valid data can be obtained only from a repre-
sentative sample, unmistakably identified,
carefully collected and stored, A skilled
analyst, using approved methods of analyses
and performing the determinations within

the prescribed time limits, can produce data
for the sample. This data will be of value
only if a written record exists to verify sample
history from the field through the laboratory.

REFERENCES

1 ASTM Standards, Part 23, Water;
Atmospheric Analysis.

2 Methods for Chemical Analysis of Water
and Wastes, EPA-MDQARL,
Cincinnati, OH 45268, 1974,

3 Standard Methods for the Examination of
Water and Wastewater, 13th edition,
APHA-AWWA-WPCF, 1971,

4 Dean, R., Williams, R. and Wise, R.,
Dtsposal of Mercury Wastes from
Water Laboratories, Environmental
Science and Technology, October, 1971.

This outline was prepared by a, Donahue,
Chemist, National Training Center, MPOD,
OWPO, EPA, Cincinnati, Ohio 45268,

Descriptors: On-Site Data Collections,
On-Site Investigations, Planning, Handling,
Sample, Sampling, Water Sampling,
Surface Waters, Preservation, Wastewater

3-5



Atomic Absorption Spectrophotometry

V REMOVAL OF INTERFERENCES AND
CONCENTRATION OF SAMPLE

A Removal of Interferences

1 The methods for overcoming these inter-
ferences in atomic absorption are similar
to those used in flame emission, namely,
either separation of interfering ions or
suppression of the interference hy ad-
dition in excess of a substance that will
prevent formation of compounds between
interfering ions and the element being
determined.

B Concentration of Sample

1 Organic separations can be used to
concentrate a sample. Interferences
are removed, as seen above, and also
the organic solvent enhances the absorp-
tion.

2 Ion exchange has also been used success-
fully for concentrating samples for atomic
absorption,

VI CONCLUSIONS

Atomic absorption methods are as good

as or better than emission methods, for
elements to which they can both be applied,
in sensitivity, precision and accuracy.
They can be applied to a far wider range

of elements than can emission analysis,
The additional cost of hollow cathode dis-
charge tubes 18 compensated by the greater
range of analyses and greater reliability

of results.

VIL INSTRUMENTS AVAILABLE
A Perkin Elmer
1 Model 303 - double beam, AC - $5,920.00

1 Model 290 - single beam, AC - $2,900.00

B Beckman attachments for existing
spectrophotometers

1 Use with model D.U. and D.U. -2-
Single beam, DC - $2, 135.00

2 Use with model D. B. - single beam,
AC ~ $2,495, 00

C Jarrell-Ash

1 Dual atomic absorption flame spectrometer-
single beam, AC - $5, 800,00

DEEL
1 Atomic absorption spectrophotometer -
single beam, AC - $2, 850.00
ACKNOWLEDGEMENT
Certain portions of this outline contain

training meterial from a prior outline by
Nathan C. Malof.

REFERENCES

1 Walsh, A, Spectrochim. Acta. 7, 108.
1955,

2 Kahn, Herbert and Slavin, Walter. Atomic
Absorption Analysis. International

Science and Technology. November 1962.

3 David, D. J. The Application of Atomic
Absorption to Chemical Analysis, The
Analyses. 85:779-791. 1960,

4 Platte, J. A., and Marcy, V. M. A New
Tool for Water Chemicals, Industrial
Engineering. May 1965,

5 Buechler, D. G. Determination of Trace
Copper, Lead, Zinc, Cadmium, Nickel,
and Iron in Industrial Waste Water by
Atomic Absorption Spectrophotometry
After Ion Exchange on Dorvex A-1. >
Analytical Chemistry, 37-1054-1055. 1965.

6 Elwell, W. T., and Gidley, J.A.F. Atomic-
absorption Spectrophotometry. The Mac-
Millan Company. New York. 1962.

7 Willard, H.H., Merrtt, L.L., and Dean,
J.A. Instrumental Methods of Analysis.
D. Van Nostrand Co., Inc. N.Y. 1965.

This outline was prepared by P. F. Hallbach,
Chemist, National Traimng Center, MOTD,
OWPO, USEPA, Cincinnati, Ohio 45268,
Descriptors: Analytical Techniques, Atomic
Absorption, Instrumental Analysis, Metals
Analysis



an ca ivup, ROTATING SYSTEM
HSEEE? oe wba, AO DPPER SYS EAA
0 : fous
Saas ec aas' aria at We Ga PHOTO-
Pn we TO (2 f / pris WY DETECTOR
L\ SLIT )

VAPORIZING = AQNOCHROMATOR

f
“Ah t ELECTRONICS 5

AMPLE UN FUEL Od READOUT

WIGUW EF

ree ty he syeety * Vramers can be Clis ified a-
yor d

+ Tota

asumptior

Fhose which mtro ce tie sat ple
spray directly into une trade
(Figure 2)

sractory.
cyan
oo lines
coma
mobi

Poet oon

eee md ania,

etry

a) fore tions

tes sample ite

SAMPLE

stole. tne

FI-URE 2


Principles of Absorption Spectroscopy

SOURCE OF
RADIANT

RANGE ENERGY

ABSORPTION BY SAMPLE

, DETECTION OF

“CHEMICAL NATURE

OF SAMPLE

TYPE OF SAMPLE RADIANT ENERGY’
CELL USED TRANSMITTED |

Ultraviolet! Hydrogen Arc

Inorganic ions and
Organic Molecules

Quartz Fluorite Photoelectric Cells’

. (Photographic +
{ Plates !
L
| ; |
, Visible iIncandescent Colored Inorganic and | Glass Eye Photographic !
| Tungsten Bulb Organic Molecules Plates .
‘ [Photoelectric Cells
t mS
Infrared |Nernst Glower Organic Molecules Sodium Chloride or ‘Thermocouple, j
| Globar Lamp Potassium Bromide ‘
. , 1
1 beeen wee eh ee L
REFERENCES

1 Delahay, Paul, Instrumental Analysis.
The MacMillan Co., New York,
1957,

2 Mellon, M.G, Analytical Absorption

Spectroscopy. John Wiley & Sons,
Inc., 1950.

3 Willard, Merritt & Dean, Instrumental
Methods of Analysis. D.vanNo-

strand Co., Inc., 1958,

4 Dyer, Applications of Absorption
Spectroscopy of Organic Compounds
Prentice-Hall, Inc, 1965.

This outline was prepared by C. R. Feldmann,
National Training Center, MOTD, OWPO,
USEPA, Cincinnat, Ohio 45268. .

Descriptors: Chemical Analysis, Water Tests,
Spectroscopy, Spectrophotometry


Sample Handling - Field Through Laboratory

Iv SAMPLE CONTAINERS

A Available Materials
1 glass
2 plastic
3 hard rubber

B Considerations

1 Nature of the sample - Organics
attack polyethylene,

2 Nature of constituent(s) to be determined

- Cations can adsorb readily on some
plastics and on certain glassware.
Metal or aluminum foil cap liners can
interfere with metal analyses,

3 Preservatives to be used - Mineral
acids attack some plastics,

4 Mailing Requirements - Containers
should be large enough to allow extra

volume for effects of temperature
changes during transit. All caps
should be securely in place. Glass
containers must be protected against
breakage. Styrofoam linings are
useful for protecting glassware,

C Preliminary Check

Any question of possible interferences
related to the sample container should
be resolved before the study begins. A
preliminary check should be made using
corresponding sample materials, con-
tainers, preservatives and analysis,

D Cleaning

If new containers are to be used, prelim-
inary, cleaning 1s usually not necessary.

If the sample containers have been used
previously, they should be carefully
cleaned before use.

There are several cleaning methods
available. Choosing the best method in-
volves careful consideration of the nature
of the sample and of the constituent(s) to
be determined.

3-2

v

B

1 Phosphate detergents should not be
used to cledn containers for phosphorus
samples, .

2 Traces of dichromate cleaning solution
will interfere with metal analyses.

Storage

Sample containers should be stored and
transported in a manner to assure their
readiness for use.

SAMPLE PRESERVATION

Every effort should be made to achieve
the shortest possible interval between
sample collection and analyses. If there
must be a delay and it is long enough to
produce significant changes in the sample,
preservation measures are required.

At best, however, preservation efforts
can only retard changes that inevitably
continue after the sample is removed
from the parent population,

Functions

Methods of preservation are relatively
limited, The primary functions of those
employed are;

1 to retard biological action

2 to retard precipitation or the hydrolysis
of chemical compounds and complexes

3 to reduce volatility of constituents

General Methods

1 pH control - This’affects precipitation
of metals, salt formation and can
inhibit bacterial action.

2 Chemical Addition - The choice of
chemical depends on the change to be
controlled.

Mercuric chloride is commonly used
as a bacterial inhibitor, Disposal of
the mercury-containing samples is a
problem and efforts to find a substitute
for this toxicant are underway.


FLAME PHOTOMETRY LABORATORY (SODIUM)

I REAGENTS
A Deionized Distilled Water

To be used for the preparation of all reagents,
calibration standards, and as dilution water.

B Stock Sodium Solution
Dissolve 2,542 g of NaCl, previously
dried at 140°C, in deionized distilled
water and dilute to 1000 ml.
1,00 ml= 1,00 mg Na*

C Intermediate Sodium Solution
Dilute 10,00 ml of the stock sodium solution
to 100.0 ml with deionized distilled water.
Use this solution for preparing the
calibration curve in the sodium range of
1~10 mg/1.
1,00 ml= 100 ug Nat

D Standard Sodium Solution
Dilute 10.00 ml of the intermediate
sodium solution to 100 ml with deionized
distilled water, Use this solution for
preparing the calibration curve in the
sodium range of 0. 1-1. 0 mg/1.

1.00 ml = 10,0 ug Nat

ll INTERFERENCE CONTROL

Refer to the cited reference

Ill STANDARDS
Standards may be prepared 1n any of these

applicable ranges: 0-1.0, 0-10, or
0-100 mg/l.

CH. MET, lab, 2b, 1,76

IV INSTRUMENT OPERATING CONDITIONS

Theoretical wavelength 589 nm
Fuel pressure 7,5 lbs/in? ~
Oxygen pressure 10 Ybs/in?

For all other conditions needed, consult the
manufacturer's instrument manual,

V PROCEDURE

1 Number the six plastic cups provided 0,
2, 4, 6, 8, and 10,

2 Fill them 3/4 full with the appropriate
sodium standards; e.g., 0 mg/I standard
into cup 0, etc.

3 Fill a 7th plastic cup 3/4 full with the
unknown,

4 Fill an 8th plastic cup with distilled water.

5 The power toggle switch (on left side of
instrument) is already turned on,

6 Set the sensitivity knob to the standby
position.

7 Set the wavelength knob to the theoretical
valve of 589 nm (the scale is at the top of
the instrument),

8 The fltr - shtr - open knob is in the shtr
(closed) position,

9 Open the main valve on the oxygen cylinder;
all other oxygen gauges are already set.

10 Open the main valve on the hydrogen
cylinder; all other hydrogen gauges are
already set.

’

1-1

oT


METHODOLOGY FOR CHEMICAL ANALYSIS OF WATER AND WASTEWATER ”

I INTRODUCTION

This outline deals with chemical methods which
are commonly performed in water quality
laboratories, Although a large number of
constituents or properties may be of interest
to the analyst, many of the methods employed
to measure them are baged on the same
analytical principles, The purpose of this
outline is to acquaint you with the principles
involved in commonly-used chemical methods
to determine water quality,

Il PRE-TREATMENTS

For some parameters, a preliminary treatment
is required before the analysis begins, These
treatments serve various purposes.

A Distillation - To isolate the constituent by
heating a portion of the sample mixture to
separate the more volatile part(s), and then
cooling and condensing the resulting vapor(s)
to recover the volatilized portion.

B Extraction - To isolate/concentrate the
constituent by shaking a portion of the
sample mixture with an immiscible solvent
in which the constituent is much more
soluble,

C Filtration - To separate undissolved matter
from a sample mixture by passing a portion
of it through a filter of specified size,
Particles that are dissolved in the original
mixture are so small that they stay in the
sample solution and pass through the filter.

D Digestion - To change constituents to a form
amenable to the specified test by heating a
portion of the sample mixture with chemicals.

If! METERS

For some parameters, meters have been

designed to measure that specific constituent

or property.

CH. 14, 10.75

A

B

pH Meters

pH (hydrogen ion concentration) is meas-
ured as a difference in potential across a
glass membrane which is in contact with
the sample and with a reference solution,
The sensor apparatus might be combined
into one probe or else it is divided into an
indicating electrode (for the sample) and a
reference electrode (for the reference
solution), Before using, the meter must
be calibrated with a solution of known pH
(a buffer) and then checked for proper
operation with a buffer of a different pH
value,

Dissolved Oxygen Meters

Dissolved oxygen meters measure the
production of a current which is proportional
to the amount of oxygen gas reduced at a
cathode in the apparatus, The oxygen gas
enters the electrode through a membrane,
and an electrolyte solution or gel acts a5 a
transfer and reaction media. Prior to use
the meter must be calibrated against a known
oxygen gas concentration,

Conductivity Meters

Specific conductance is measured with a
meter containing a Wheatstone bridge which
measures the resistance of the sample
solution to the transmission of an electric
current, The meter and cell are calibrated
accprding to the conductance of a standard
solution of potassium chloride at 25°C,
measured by a standard” cell with electrodes
one cm square spaced one cm apart, This
ig why results are called specific’ con-
ductance,

D Turbidimeters

A turbidimeter compares the intensity of
light scattered by particles in the sample
under defined conditions with the intensity
of light scattered by a standard reference
suspension.


Principles of Absorption Spectroscopy

200, 000 (20u)

WAVELENGTH A° 2,000 4,000 000
X-Rays Ultraviolet Visible Near IR Far IR
Calories per mole 142, 000 71, 000 35, 000 . 1, 400

needed for change

Oto O%o Ofo

Inner Tonization Outer

Electron Shift Electron Shift

Figure 4, Electromagnetic Spectrum Showing Energy Ranges and
Corresponding Electronic, Vibrational and Rotational Motions

+ ”

O:o O:o

Vibration . Rotation

—_—

1 Displacement of electrons is a per-
mussible change which can occur
when energy of ultraviolet and
visible frequencies strikes certain
atoms and molecules.

a Inner electron shift

Electrons located in the inner
orbit of anatom may, when the
proper frequency of radiant
energy is available, shift to an
orbit farther removed from
the nucleus. This shift repre-
sents a change from a lower
energy to a higher one. If this
new position is unstable, the
electron may revert to some
position nearer the nucleus;
the energy which was gained
may then be emitted from the
atom as part of its emission
spectrum, The number of
energy changes possible within
an atom is a function of the
number of electrons and the
number of changes each may
enter, Each possible change
gives rise to a new spectral
frequency. Since the frequency
of radiation needed to accom-
plish such changes 1s of ahigh
order of magnitude, the energy
used is considerable in quantity.

Molecular aggregations often
disintegrate in such circum-

stances; thus, these higher
frequencies are used mainly
for work with elementsor
very stable compounds.

Ionization

Under a specific frequency of
radiation, an electron may be
physically separated from its
parent atom, This process
hasbeentermedionization. A
change of energy level of this
magnitude requirés less
energy than the inner electron
shift, Such changes are char-
acteristic of those of the rare
earths, inorganic ions, tran-
sition elements and many
organic compounds under
frequencies within the ultra-
violet range.

Outer electron shift

The various orbital electrons
in an atom may vary in the
amount of energy required to
shift them outwardly from the
nucleus. For example, it re-
quires less energy to shift an
electron from a position more
distant than it does to shift an
electron outwardly from the
inner orbit, Outer electron
shifts occur readily incolored
organic molecules for which

6-3


Flame Photometry Laboratory (Strontium)

14 Set the fltr - shtr - open knob in the shtr
position (closed position).

15 Open the main valve on the oxygen cylinder;
all other oxygen gauges are already set.

16 Open the main valve on the hydrogen
cylinder; all other hydrogen gauges are
already set.

17 Raise the door on the right side of the
burner housing (behind instrument).

18 Cautiously bring a lighted match to the tip
of the burner in the housing,

19 Close the door on the right side of the
burner housing.

20 Caution Do not place any part of your
body over the coils on the top of the burner
housing. Hot gases are escaping.

21 Raise the silver lever between the
instrument and the burner housing to
the vertical position.

22 Place the plastic cup containing distilled
water in the cup holder which is now
exposed at the right side of the burner
housing.

23 Push the silver lever clockwise so that
the cup holder swings into the burner
housing and the water is aspirated. A
distinct difference in sound will be noticed
when water or a sample is being aspirated,
If at any tame during the determination
this sound again changes, it will indicate
that all of the liquid has been aspirated
from the cup. Simply move the silver
lever and refill the cup with the appropriate
liquid,

24 Do not allow air to be aspirated for more
than about 15 sec. If there is any delay,
aspirate distilled water until the problem
causing the delay has been corrected.

25 Turn the sensitivity knob to position 1,

26 Turn the dark current knob until the
needle reads 0 on the percent transmittance
scale,

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

Turn the sensitivity knob to position 4,
Repeat step 26.

Swing the cup of distilled water out of the
burner housing and replace 1t with cup 20.
Swing this cup back into the burner housing.

Turn the fltr - shtr - open knob to the open
position (this opens the shutter),

Turn the wavelength knob slowly to the
left; the needle will move to the left. _

At some point the needle will suddenly
swing toward the right. It will probably

be necessary to make adjustments with

the slit knob in order to keep the needle
on-scale while finding the point at which

the needle swings back to the right. Record
this wavelength. It is the peak wavelength.
Do not change this setting until indicated

in the instructions.

If the pomt at which the needle swings back
to the right is overshot, turn the wave-
length knob about } turn to the right and
repeat steps 31 and 32,

Make the needle read 100% transmittance
by turning the slit knob. Record the sht
mm reading. Do not change this setting.
100 1s the peak pe percent transmittance
reading for this solution.

Turn the fltr - shtr - open knob to the shtr,
position (this closes the shutter).

Replace the cup 20 with 15.

Open the shutter.

Record the percent transmittance reading.
Close the shutter.

Repeat steps 36, 37, 38, and 39, using
cups 10, 5, and 0 in turn,

Aspirate distilled water and using the dark
current knob make the néedle read 0 percent
transmittance,

Aspirate cup 20.


Flame Photometry Laboratory (Strontium) t

Percent Transmission Readings

Background Peak

10,0 ml unknown

+
10.0 ml 0.0 mg/1 std.

Difference

10,0 ml unknown

+
10.0 ml 5,0 mg/1 std.

10.0 ml unknown

+
10,0 mi 10,0 mg/1 std.

10.0 ml unknown

+
10,0 ml 15,0 mg/1 std.

10.0 ml unknown
+

10.0 ml 20.0 mg/1 std.



aaqry (3m

IEpuUe;S

UOySspUSUBTT %

rect

BEE 10210

(3-8



Energy Sources for Atomic Absorption Spectroscopy

ANODE
; ja—END WINDOW a
NEON (quartz)
OR} FILLER OAS
| | \ ARGON
\ caTHODE

\ ENVELOPE (glass)

HOLLOW CATHODE LAMP
FIGURE 1

aw

This outline was prepared by J. D, Pfaff, Descriptors: Spectroscopy, Spectrophotometers
National Training Center, MOTD, OWPO,
USEPA, Cincinnati, Ohio 45268,

5-3


ie)

Chemical Analyses

pane

STATUS OF 1974 EPA MANUAL

A Regarding 1973 Guidelines

Iv

Some of the methods included in the
1974 EPA Manual are not automatically
acceptable for certification or permit
requirements. These methods were
published in anticipation of proposed
additions to the Federal Register Guide-
lines. When using this 1974 edition,
one must first consult the October 16,
1973 Federal Register in the table
column which classifies the method(s)
approved for a given parameter. Then
if the procedure for that specified
method is given in the 1974 EPA Chem-
ical Methods Manual, that procedure
1s acceptable for certification or permit
requirements,

Example of Use

For example, Federal Register
parameter no. 52, fluoride, is to be
measured using '"'Distillation-SPADNS. "
The 1974 EPA Manual has a procedure
for fluoride using the cited SPADNS
Method with Bellack Distillation, so
this procedure is automatically accept-
able for certification and permit
requirements. On the other hand, the
1974 EPA Manual also has an electrode
thethod for measuring fluoride. Since
the Federal Register does not currently
list an electrode as an approved method
for measuring fluoride, one may not
use this method without formal appli-
cation to do so,

METHODS NOT IN 1973 GUIDELINES
Apphlcation to Use

The system for application to use methods
not hsted in the October 16, 1973 ‘
Federal Register is given in that publica-

tion, One supplies reasons for using an
alternative method to the EPA Regional

1-2

Administrator through the state agency
which issues cettifications and/or permits.
If the state does not have such an agency,
the application is submitted directly to the
EPA Regional Administrator. |

B Order of Processing

Before approving such applications, the
Regional Administrator sends a copy to
the Director of the EPA Methods
Development and Quality Assurance
Research Laboratory (MDQARL), If the
Regional Administrator rejects any
application, a copy is also sent to
MDQARL. Within 90 days the applicant
18 to be notified (along with the appropri-
ate state agency) of approval or rejection.
MDQARL also receives a copy of approval
or rejection notifications for purposes of
national coordination.

V REQUIRED ANALYSES

Which measurements are to be done and
reported depend on the specifications of the
individual certifications or permits.

A Mandatory for Secondary Plants

By July 1, 1977 all municipal secondary
wastewater treatment plants will be
required to measure and report pH,
BOD, (biochemical oxygen demand),
suspended solids, fecal coliform bacteria
and flow, Many plants are required to
report these now.

B Addjtional for Secondary Plants

Other measurements which may be
required of secondary treatment plants
are residual chlorine, settleable solids,
COD (chemical oxygen demand), total
phosphorus, and the nitrogen series
(total N, NH,-N, NO,-N, NO,-N).

C Municipalities and Industries
Beyond these listings, required analyses

will depend on the specific situation of
municipality and of each industry.


CHEMICAL ANALYSES

I FEDERAL REGISTER GUIDELINES
A Authority

Section 304(g) Public Law 92-500 required
the EPA Administrator to promulgate guide-
lines establishing test procedures for the
analysis of pollutants that would include
the factors that must be provided in any
certification (section 401) or permit
application (section 402), These test
procedures are to be used by applicants
to demonstrate that effluent discharges
meet applicable pollutant discharge
limitations, and by the States and other
enforcement activities in routine or
random monitoring of effluents to verify
effec.iveness of pollution control
measures,

B_ Establishment

Following a proposed listing there was a
period for reply by interested parties,
The final rulemaking was published in

the Federal Register on October 16, 1973,

C Format

The Guidelines are given in a Table which
lists 71 different parameters, the method-
ology to be used to determine them and
the page numbers in standard references
where the analytical procedure can be
found,

1 Divisions
The 71 parameters are divided as

follows: there are 15 general
analytical parameters, 28 trace

CH, 13, 9,75

metals, 17 nutrients, anions or
organicg 6 physical or biological and
5 radiological,

2 Sources-of procedures

The standard references cited as
sources of the analytical procedures
for these listings are Standard
Methods, ! ASTM, Part 23° and the
EPA Chemical Methods Manual,
Additional sources of procedures are
given as footnotes to the Table.

ll EPA CHEMICAL METHODS MANUAL

The EPA Chemical Methods Manual was '
developed for their water quality laboratories
using Standard Methods and ASTM as basic
references,

A Analytical Procedures

The manual cites page numbers 1n these
two references where the analytical
procedures can be found. In some cases,
EPA modified methods from these
sources or else developed methods suit-
able for their own laboratories. ‘

B Other Features

For most of the measurements presented
in the EPA Chemical Methods Manual,
precision ‘and accuracy data from inter-
laboratory quality control studies are
given for the method cited. The manual
also contains a section on sampling and
preservation, This is in tabular form
and contains information on volumes
required for analysis, the type of container
that can be used, preservation measures
and holding times,

1-1


Datipee ctu Peau 1 urvugh Laboratory

To dispose of solutions of inorganic
mercury salts, a recommended
procedure is to capture and retain the
mercury salts aa the sulfide at a high
pH. Several firms have tentatively
agreed to accept the mercury sulfide for
re-processing after preliminary con-
ditions are met,

3 Refrigeration and Freezing - This is
the best preservation Tochalque avail-
able, but it is not applicable to all

types of samples, It is not always a
practical technique for field operations.

Specific Methods

The EPA Methods Manual”) includes a
table summarizing the holding times and
preservation techniques for several
analytical procedures. This information
also can be found in the standard refer-
ences (1, 2,3) ag part of the presentation
of the individual procedures.

METHODS OF ANALYSIS

Standard reference books of analytical
procedures to determine the physical
and chemical characteristics of various
types of water samples are available,

EPA Methods Manual

The Methods Development and Quality
Assurance Research Laboratory of the
Environmental Protection Agency, has
published a manual of analytical procedures
to provide methodology for monitoring the
quality of our Nation's Waters and to deter-
mine the impact of waste discharges, The
title of this manual is "Methods for Chem-
cal Analysis of Water and Wastes, ''(2)

For some procedures, the analyst is
referred to Standard Methods and/or to
ASTM Standards.

Standard Methode
The American Public Health Association,

the American Water Works Association
and the Water Pollution Control Federation

prepare and publish a volume describing
methods of water analysis. These include
physical and chemical procedures. The
title of this.book is "Standard Methods

for the Examination of Water and Waste-
water, "(3) .

C ASTM Standards «

The American Society for Testing and
Materials publishes an annual "book"

of specifications and methods for testing
materials, The "book" currently con-
sists of 33 parts, The part applicable

to water is a book titled, ‘Annual Book of
ASTM Standards, Part 22t Water;
Atmospheric Analysis",

D_ Other References

Current literature and other books of
analytical procedures with related in-
formation are available to the analyst.

E NPDES Methodology

When gathering data for National Pollttant
Discharge Elimination System report
purposes, the analyst must consult the
Federal Register for a listing of approved
analytical methodology. There he will be
directed to pages in the above cited
reference books where acceptable pro-
cedures can be found. The Federal
Register also provides information con-
cerning the protocol for obtaining approval
to use analytical procedures other than
those listed,

VII ORDER OF ANALYSES

The ideal situation is to perform all
analyses shortly after sample collection,
In the practical order, this is rarely
possible. The allowable holding time
for preserved samples is the basis

for scheduling analyses.

3-3


Chemical Analyses

REFERENCES

1 Standard Methods for the Examination of
Water and Wastewater, 13th ed., 1971,
APHA. New York, New York.

2 Annual Book of Standards, Part 23, Water,

Atmospheric Analysis, 1972, ASTM,
Philadelphia, Pennsylvania,

1-4

3 Methods for Chemical Analyses of Water
and Wastes, 1971, EPA, MDQARL,
Cincinnati, Ohio,

This outline was prepared by Audrey E.
Donahue, Chemist, National Training Center,
MPOD, OWPO, USEPA, Cincinnati, Ohio
45268,

Descriptors: Chemical analysis, chemical
guidelines, self-monitoring requirements,
non-approved analytical methods

%


Atomic Absorption Spectrophotometry

C Line Isolation

1 The use of a lne spectrum of the ele-
ment being determined, rather than a
continuous spectrum, makes possible
the use of monochromators of low
resolving power or even filters. When
a spectral lamp 1s used as a hght source,
it 1s only necessary to isolate the
resonance line from neighboring lines
of the ight source or vaporized sample.
‘The resolution of the method is implicit
in the width of the emission and absorp-
tion lines,

2 To realize the full potentialities of the
method, the strongest absorption line
must be used. For elements with
simple spectra, the resonance hne
arising from the lowest excited state 1s
usually the line exhibiting strongest
absorption,

3 Calibration curves depart from hnearity
at much lower concentrations in absorp-
tion work as compared with emission
work, Curvature results partly from
inc. eased pressure broadening s the
concentration of salt rises, but also
depends on source characteristics,
particularly self-absorption, and on
the nature and homogeneity of the flame.

Detectiou

1 Photo-electric detectors used 1n atomic
absorption analysis need be no more
sensitive than those used in emission
analysis, since in the atomic absorption
method, concentration of an element is
determined by measuring the reduction
in intensity of the resonance line emitted
from a source of high intensity.

re)

Single or double-beam circuits may be
adopted fur work with a single beam
instrument, results are directly depend-
ent upon source and detector stability.
Both must be powered by separate
power supphes, Ina double-beam
system small variations in the source
signal are compensated automatically.

Iv

EVALUATION
Sensitivity

1 For an air-acetylene flame of length
2 or 3 cm the lower limits of detection
of elements having low resonance-line
excitation potential (eg Na-K) are
approximately equal in a single-beam
atomic absorption and emission methods,

2 For elements having highly reversed
resonance lines or resonance hnes of
high excitation potential, the atomic-
absorption method has decided
advantages over emission methods.
Examples of elements in these categories
are Zn, Mg, Fe and Mn.

3 A disadvantage of the atomic-absorption
method, when compared with flame
emission, is the lack of a quick and
simple method of varying sensitivity
to deal with solutions of widely varying
element concentrations. The sensitivity
of an atomic-absorption instrument is
determined almost entirely by flame
characteristics, notably length of light
path through the flame.

4 A comparison of sensitivity obtained by
emission and adsorption techniques 1s
given in Table II.

B Precision .

1 Precision of a single-beam atomic
absorption instrument is primarily a
function of the stability of light output
from the spectral lamp. This in turn
1s dependent on the stability of the main
supply and inherent stability of the lamp.
The largest fluctuations are only + 2
percent for the hollow cathode tube and
sodium spectral vapor lamp, A double-
beam instrument significantly reduces
this error,

2 In common with flame-emission methods,
atomic absorption 1s subject to "noise"
from the flame and the detector. Changes
in absorption caused by fluctuations in


U.S. DEPARTMENT OF COMMERCE
National Technical Information Service

PB-263 560

Analytical Methods for
Trace Metals

National Training and Operational Tech Center, Cincinnati, Ohio

Jan 76

~*~



Determination of Mercury

chelation with ammonium pyrrolidine
dithiocarbamate and extraction with
methyi isobutyl ketone, reduced the
detection limit to about 0.2 mg/l. Addi-
tional sensitivity was claimed by using
the sample boat which evaporated one
mullihter of sample in a boat like device
followed by ignition of boat in the flame.
This helped reduce the detection limit to
around 0.02 mg/1 but here again in actual
practice the sensitivity was probably less.

D Gas Chromatography

A swedish method utilized an electron
capture detector to detect materials at a
sensitivity approaching 0.001 mg/1 in
favorable cases. This procedure was good
for the organic forms of mercury contami-
nation such as methyl mercury, ethyl
mercury and methoxy ethyl mercury, and
phenyl mercury. Dimethyl mercury and
the morganic forms of mercury gave no
response in this procedure,

E Flameless Atomic Absorption

It had long been known that the metallic ,
mercury vapor absorbed energy at 2537 A.
However, it was not until 1968 that a
method was practical. This method converts
all forms of mercury present in the sample
to the metallic form. Therefore, the
results in this method are only for total
mercury since there is no differentiation.
The detection limit for mercury was
lowered to a point that made adoption

of low standards analytically practicable.
The detection limit for mercury by the
flameless method was reduced to

0.0002 mg/1.

This procedure has become the standard
analytical procedure for the analysis of
mercury. Both the National Pollution
Discharge Elimination System's analytical
methods and the methods recommended

to meet the Primary Drinking Water
Standards recommend the flameless atomic
absorption techmique.

Ill

FLAMELESS METHOD
Chemistry

The procedure covered here 1s the procedure
recommended in the Environmental Protection
Agency's manual of "Methods for Chemical
Analysis of Water and Wastes. "' The method
1s applicable to drinking, surface, and

saline waters, domestic and industrial
wastes. :

In addition to inorganic forms of mercury,
organic mercurials may also be present in
asample, These organo-mercury compounds
will not respond to the falmeless atomic
absorption technique unless they are' first
broken down and converted to mercuric ions.
Potassium permanganate oxidizes many of
these compounds, but recent studies have
shown that a number of organic mercury
compounds, including phenyl mercuric
acetate and methyl mercuric chloride, are
only partially oxidized by this reagent.
Potassium persulfate has been found to give
approximately 100% recovery when used as
the oxidant with these compounds, Therefore,
a persulfate oxidation step following the
addition of the potassium permanganate has
been included to insure that organc-mercury
compounds, if present, will be oxidized to
the mercuric 10n before measurement. A
heat ‘step is required for methyl mercuric
chloride when present in or spiked to a
natural system, The range of the method
may be varied through instrument and/or
recorder expansion. Using a 100 ml sample,
a detection limit of 0.2 4g Hg/1 can be
achieved; concentrations below this level
should be reported as <0, 2.

Possible interference from sulfide 1s
eliminated by the addition of potassium
permanganate. Concentrations as high as

20 mg/1 of sulfide as sodium sulfide do not
interfere with the recovery of added inorganic
mercury from distilled water. Copper has
also been reported to interfere; however,
copper concentrations as high as 10 mg/1

had no effect on recovery of mercury from


Methodology for Chemical Analysis of Water and Wastewater,

either by the constituent of interest or else by
a substance containing the constituent of interest
which has resulted from some treatment of
the sample. The quantitative aspect of these
photometric methods is based on applying the
Lambert-Beer Law which established that the
amount of light absorbed is quantitatively
related to the concentration of the absorbing
medium at a given wavelength and a given
thickness of the medium through which the
light passes.

Each method requires preparing a set of
Standard solutions containing known amounts
of the constituent of interest, Photometric
values are obtained for the standards, These
are used to draw a calibration (standard) curve
by plotting photometric values against the
concentrations. Then, by locating the photo-
metric value for the sample on this standard
curve, the unknown concentration in the
sample can be determined,

A Atomic Absorption

Atomic Absorption (AA) instruments utilize
absorption of light of a characteristic wave-
length. This form of analysis involves
aspirating solutions of metal ions (cations)
or molecules containing metals into a

flame where they are reduced to individual
atome in a ground electrical state, In this
condition, the atoms can absorb radiation
of a wavelength characteristic for each
element. A lamp containing the element of
interest as the cathode is used as a source
to emit the characteristic line spectrum for
the element to be determined.

The amount of energy absorbed is directly
related to the concentration of the element

of interest, Thus the Lambert-Beer Law
applies, Standards can be prepared and
tested and the resulting absorbance values
can be used to construct a calibration
(standard) curve. Then the absorbance

value for the sample is located on this curve
to determine the corresponding concentration.

Once the instrument is adjusted to give
optimum readings for the element of interest,
the testing of each solution can be done in

a matter of seconds, Many laboratories
wire recorders into their instruments to
rapidly transcribe the data, thus conserving
time spent on this aspect of the analysis,

Atomic absorption techniques are generally
used for metals and semi«metals in solution
or elee solubilized through some form of
sample processing. For mercury, the '
principle is utilized but the absorption of
light occurs in a flameless situation with
the mercury in the vapor state and contained
in a closed glags cell,

Flame Emission

Flame emigsion photometry involves
meaguring the amount of light given off by
atoms drawn into a flame. At certain
temperatures, the flame raises the electrons
in atoms to a higher energy level. When

the electrons fall back to a lower energy
level, the atoms lose (emit) radiant energy
which can be detected and measured,

Again standards must be prepared and
tested to prepare a calibration (standard)
curve, Thén‘the transmigsion value of the
sample can be located on the curve to
determine its concentration. ”

Many atomic absorption instruments can be
used for flame emission photometry,

Sodium and potassium are very effectively
determined by the emission technique.
However, for many elements, absorption
analysis is more sensitive because there are
@ great number of unexcited atoma in the
flame which are available to absorb the
radiant energy.

Colorimetry

Colorimetric analyses involve treating
standards which contain known concentrations
of the constituent of interest and also the
gample with reagents to produce a colored
solution. The greater the concentration of
the constituent, the more intense will be

the resulting color,

The Lambert-Beer Law which relates the
absorption of light to the thickness and
concentration of the absorbing medium
applies. Accordingly, a spectrophotometer
is.used to measure the amount of light of
appropriate wavelength which is absorbed
by the same thickness of each solution,


Methodology for Chemical Aanlysis of Water and Wastewater

IV GENERAL ANALYTICAL METHODS
A Volumetric Analysis

Titrations involve using a buret to measure
the volume of a standard solution of a sub-
stance required to completely react with
the constituent of interest in a measured
volume of sample. One can then calculate
the original concentration of the constituent
of interest.

There are various ways to detect the end
point when the reaction 1s complete.

1 Color change indicators

The method may utilize an indicator which
changes color when the reaction 1s
complete. For example, in the Chemical
Oxygen Demand Test the indicator,
ferroin, gives a blue-green color to the
mixture until the oxidation-reduction
reaction is complete, Then the mixture
1s reddish-brown,

Several of these color-change titrations
make use of the 1odometric process
whereby the constituent of interest quan-
titatively releases free 1odine, Starch
1s added to give a blue color until enough
reducing agent (sodium thiosulfate or
phenylarsine oxide) is added to react
with all the 1odine. At this end point,
the mixture becomes colorless.

2 Electrical property indicators

Another way to detect end points 1s a
change in an electrical property of the
solution when the reaction 1s complete.
In the chlorine titration a cell containing
potassium chloride will produce a small
direct current as long as free chlorine
1s present. As a reducing agent (phen-
ylarsine oxide) is added to neutralize
the chlorine, the microammeter which
measures the existing direct current
registers a lower reading on a scale.
By observing the scale, the end point of
total neutralization of chlorine can be
determined because the direct current

3 Specified end points

For acidity and alkalinity titrations, the
end points are specified pH values for
the final mixture. The pH values are
those existing when common acidity or
alkalinity components have been neutral-
ized, Thus acidity is determined by
titrating the sample with a standard
alkali to pH 8.2 when carbonic acid
would be neutralized to (CO3)". Alka~
linity (except for highly acidic samples)
is determined by titrating the sample
with a standard acid to pH 4.5 when the
carbonate present has been converted

to carbonic acid. pH meters are used to
detect the specified end points.

Gravimetric Procedures

Gravimetric methods involve direct

weighing of the constituent 1n a container.

An empty container 1s weighed, the
constituent is separated from the sample
mixture and isolated in the container, then
the container with the constituent is weighed,
The difference in the weights of the container
before and after containing the constituent
represents the weight of the constituent.

The type of container depends on the method
used to separate the constituent from the
sample mixture. In the solids determinations,
the container 1s an evaporating dish (total or
dissolved) or a glass fiber filter disc in a
crucible (suspended), For oil and grease,

the container 1s a flask containing a residue
after evaporation of a solvent.

Combustion

Combustion means to add oxygen. In the
Total Organic Carbon Analysis, combustion
1s used within an instrument to convert
carbonaceous material to carbon dioxide,
An infrared analyzer measures the carbon
dioxide.

V PHOTOMETRIC METHODS

These methods involve the measurement of light

ceases. that 1s absorbed or transmitted quantitatively


Burners and Fuel Mixtures

REFERENCES

1 Manual of Methods for Chemical Analysis
of Water and Wastes, USEPA, Cincinnati,
Ohio, 1974,

2 Instruction Handbook, Instrumentation
Laboratory, Inc,

3° Operation Instruction, Perkin-Elmer Co,

4 Kahn, Herbert L, Principles and Practice
of Atomic Absorption. Advances in
Chemistry Series, Number 73, 1068.

5 Steensrud, James A. Choosing an A.A.
Spectrophotometer. Research/Develop-
ment. August 1975,

This outline was prepared by J, D, Pfaff,
National Training Center, MOTD, OWPO,
USEPA, Cincinnati, Ohio 45268,

Descriptors: Spectroscopy, Spectrophotometers

11-5


Flame Photometry

BIBLIOGRAPHY

1 Kingsley, George R. and Schaffert,
Roscoe R, Direct Microdeter-
munation of Sodium, Potassium
and Calcium 1n a Single Biological
Specimen with the Model Du Flame
Spectrophotometer and Photo-
multiplier Attachment.

Anal, Chem, 25:1937-41, 1953.

2 Gilbert, PaulT. Jr. Flame Photo-
metry - New Precision in Elemental
Analysis. Industrial Laboratories
Beckman Reprint R-56, Aug. 1952.

3 Detection Limits for the Beckman Model
Du Flame Spectrophotometer. Data
Sheet 1. Beckman Publication,
April 1952.

4 Baker, G.L, and Johnson, L. H.
Interference of Amons on Calcium
Emission in Flame Photometry.
Anal, Chem, 26.465-568. 1954,

5 West, P.W., Folse, P. and
Montgomery, D. The Application
of Flame Spectrophotometry to
Water Analysis. Anal, Chem, 22 667,
Beckman Reprint R-40. Model
10300. 1950.

6 Scott, R.K., Marcy, V.M. anc
Hromas, J.J. The Flame
Photometer in the Analysis of
Water and Water-formed Deposits
ASTM Bulletin, Model 10300.
(Abs.) May, 1951. page 12.

7 Burriel, F., Marte and Ramirez, J.
Flame Photometry. Munoz
Elsevier Pub.Co., N.Y. 1957,

8 Chow, T.J. and Thompson, T.G.
Standard Addition Method,
Anal. Chem. 27:18-21, 1955,

TEXTS.

1 Willard, H.H., Merritt, L.L. and
Dean, J.A. Instrumental
Methods of Analysis, D. van
Nostrand Co., Inc., N.Y, 1958,

2 Dean, J.A. Flame Photometry
McGraw-Hill Book Co., N.Y. 1960.

3 Clark, G.L. The Encyclopedia of
Spectroscopy. Reinhold Pub-
lishing Corp., N.Y. 1960.

“This outhne was prepared by R. C. Kroner,
Chief, Physical and Chemical Methods,
Analytical Quality Control Laboratory,
NERG EPA, Cincinnati, OH 45268.

Descriptors: Chemical Analysis, Water Tests,
Flame Photometry, Spectrophotometry,
Spectroscopy


Principles of Absorption Spectroscopy

E = hv (5) pais

Where E = Radiant Energy in ergs

ABSORPTION OF ENERGY BY ATOMS
AND MOLECULES

A Absorption of energies of given fre-
h = Planck's proportionality quencies by atoms and molecules can
constant (6.6 X 10°27 be used as abasis for their qualitative
erg sec.) identification, Absorption spectro-
scopy is based on the principle that
v = Frequency in waves per certain displacements of electrons or
second atoms within a molecule are per-
missible according to the quantum
theory. When radiant energy of the
Thus, it can be seen that the energy of same energy required to bring about
a given photon is directly proportional this permissible change is supplied to
to the frequency of the given Radiant the molecule, the change occurs and
Energy. energy is absorbed.
FREQUENCY 20 16 12. 8 4
Cyclos(or waves)/sec. 1 9. 10 19 19
WAVELENGTH 10 6 2 2 é
Centimeters(em) 8 T mh mT 8 Tr 1. Tr 19.
2 2 6 10 14
Nanometers (nm) £ r 19 19° 19 19
WAVE NUMBER 10 6 2 2 6
1 (or waves)/em. ee 4
Cosmic rays aE
X rays a
Ultraviolet =
Visible =
Infrared —
Radar
Television ——
Radio waves
Electric current —
FIGURE 2

| Crest

{ Trough

Li a 1 fj 4

0 5 10 13
q@) WAVE LENGTH x FREQUENCY = CONSTANT
(2) X x v = c

distance waves distance

3) —— —_—— = =——_—_— sg LOCI
3) wave x time time VE TY
(4) (cm/ wave) x v (waves/sec) = C=(3X 1010 cm/sec)

Figure 3, Relationship of Wave Length and Frequency

2



Determination of Mercury.

spiked samples. Sea waters, brines and
industrial effluents high in chlorides require
additional permanganate (as much as

25 ml), During the oxidation step chlorides
are converted to free chlorine which will
also absorb energy at 253 nm, Care must
be taken to assure that the free chlorine

is absent before the mercury is reduced

and swept into the cell, This may be
accomplished by using an excess of the
hydroxylamine sulfate reagent (25 ml),

In addition, the dead air space in the
aeration bottle must be purged before the
addition of stannous sulfate, Both inorganic
and organic mercury spikes have been
quantitatively recovered from sea water
using this technique.

Interference from certain volatile organic
materials which will absorb at this wave-
length (253 nm) is also possible. A
preliminary run without reagents should
determine if this type of interference is
present, If an interference is found to be
present, the sample should be analyzed
both by using the regular procedure and
again under oxidizing conditions only,
that is without the reducing reagents.

The true mercury value can then be
obtained by subtracting the two values,

The chemical procedure involves obtaining
a sample of at least 100 ml. Until more
conclusive data are obtained, preservation
of samples can be accomplished by
acidification with nitric acid to a pH of 2

or lower immediately at the time of
collection. The 100 ml sample is placed

in a 300 ml BOD bottle. Add 5 ml of
concentrated sulfuric acid and 2.5 ml of
concentrated nitric acid, mixing after each
addition, Add 15 ml of potassium
permanganate solution (5% solution) to

each bottle. For sewage samples additional
potassium permanganate may be required.
Shake and add additional amounts of potassium
permanganate, if necessary, until the
purple color exists for at least 15 minutes.
Add 8 ml of potassium persulfate (5%
solution) to each bottle and heat for two
hours in a water bath at 95°C. Cool and
add 6 ml of sodium chloride-hydroxylamine
sulfate (12 grams of each diluted to 100 ml)
to reduce the excess potassium permanganate.
Allow to stand at least 30 seconds,

Up to this point all samples and standards
being run can be treated ina group, However,
the final step should be done just before the
BOD bottle containing the solution is attached
to the instrument. Thia is to reduce the
possibility of logs of any mercury vapor.

The final step in the procedure is to add

5 ml of stannous sulfate (26 g diluted to 260 ml
with 0.5 N sulfuric acid). After the BOD
bottle has been attached the sample is

allowed to stand quietly without manual
agitation. The circulating pump is allowed

to run continuously. The absorbance will
increase and reach maximum within one
minute. As soon as the indicating device
(meter or recorder) levele off the' reading

is taken and the mercury vapor trapped,

Aeration Gas Flow Path

Once the mercury is reduced to metallic

mercury by the stannous sulfate, the metallic

vapor begins to escape from the solution,

In order to quantitatively drive off all the

vapor a pump is used to push air into the

solution through an aeration device such as

@ glass frit of coarse porosity, The air

acts as a carrier gas for the vapor. An

aeration device may be constructed as

shown in Figure 1, :

Any peristaltic pump capable of delivering
one liter of air per minute may be used,
The pump should be checked occasionally
via a rotometer to assure that sufficient
flow is being provided.

The flow path of the procedure can be set

up in two ways, in an open mode and a closed
mode, The closed mode recirculates the
mercury vapor through the entire flow path,
including the absorption cell, until a manual
valve shuhts the vapors toa trap. The open
mode allows the vapors to pass only one
time through the absorption tube and from
there it goes to a trap,

There are several pieces of equipment
involved in the flow path that are common

to both modes. The aeration bottle has been
mentioned before, next in line should come
a desiccant (of magnesium perchlorate) to
adsorb water vapors in order to prevent
these from condensing in the absorption
tube. Ifa conventional atomic absorption

8-3


PRINCIPLES OF ABSORPTION SPECTROSCOPY

I. INTRODUCTION

In any system employing principles of
absorption spectroscopy, there are three
basic components.

A SOURCE of Radiant Energy

B MEDIUM (Sample) which absorbs
Radiant Energy

C DETECTOR to measure the Radiant
Energy transmitted by the Sample

Figure 1, Basic Components of Avsorpto4

Spectroscopy System i

be ee ee ee

Il RADIANT ENERGY

A Wave Nature

1

The various forms of radiant
energy have been arranged ina
single schematic diagram referred
to as the electromagnetic spectrum
(see Figure 2), Allofthe energies
which make up this spectrum may
be represented graphically as
waves, All waves move through
space (and for most purposes air)
at a constant velocity, 3X 10
cm/sec.

Three variable characteristics of
individual waves serve to differ-
entiate each from all other waves
in the spectrum,

CH. MET.al, 5c. 1. 76

a The Wave Length

A - The linear distance be-
tween the crests of two
adjacent waves. (Units:
distance/ wave, )

b ” The Frequency

vy - The number of waves
which pass a given point
inaunitoftime, (Units:
waves/time unit, )

ce The Wave Number

‘y - The number of waves
which occur in a given
linear distance, (Units:
waves/ distance unit, )

2 It ig evident that more waves of

short wavelength will "fit" intoa
given linear distance than would
waves of a greater wavelength.
Thus, waves having short wave-
lengths will have higher wave
numbers, Mathematically, wave
length is the reciprocal of wave
number, if the same units of linear
measurement are used in each
expression, Since the velocity of
allwaves is equalandconstant, it
is also apparent that a greater
number of waves of short wave-
length can pass a given point ina
unit of time than waves having a
longer wavelength,

Particle Nature

Planck conducted certain experiments
which indicated that light has a particle
aswell asawavenature. Energy rays
can be said to consist of particles with
a definite amount of energy. These
particles or packets are referred to
as photons or quanta. The energy (E)
of each minute packet 18 given by
Planck's equation,


FLAME PHOTOMETRY LABORATORY (STRONTIUM)

1 GENERAL

‘This procedure 1s listed as being "tentative"

in the cited reference. Also, strontium 1s

not listed un Table I of the Federal Register,
Volume 38, Number 199, Tuesday, October 16,
1973; 1.e., as of October 16, 1973, strontium
1s not included in the National Pollutant
Discharge Elimination System,

Il REAGENTS

A Fifty percent by volume hydrochloric acid
B NH4OH, 3N

C Stock Strontium Solution

Weigh 1.685 g of anhydrous SrCOg and
place 1t in a 500 ml Erlenmeyer flask.
Place a small funnel in the neck of the
flask and add 50% HCl slowly until all of
the SrCO3 has dissolved, Add 200 ml of
distilled water and boil for a few minutes
to expel COg. Cool and add a few drops
of methyl red indicator. Adjust to the
intermediate orange color by adding 50%
by volume HCl or 3N NH4gOH. Transfer
quantitatively to a 1 liter volumetric
flask and dilute to the mark with distilled
water.

1,00 ml = 1.00 mg Sr*2

D Standard Strontium Solution
Dilute 25.00 inl of stock strontium solution
to 1000 m1 with distilled water. Use this
solution for preparing Sr standards in the
1-25 mg/1 range.

1,00 ml = 25,0 ug Srt2

lt] INTERFERENCE CONTROL

The radiation effect of possible interfering
substances 1s equalized throughout the
standards by use of the standard addition
techmique.

CH, MET. lab, 3c. 1.76

Iv INSTRUMENT OPERATING CONDITIONS

Theoretical wavelength 460, 7 nm
Fuel pressure 7.5 lbs/in?
Oxygen pressure 10 Tbs/in?

For all other conditions needed, consult the
manufacturer's instrument manual,

V PROCEDURE

1 Number the five volumetric flasks provided
0, 5, 10, 15, and 20,

2 Into each of the five, pipette 10,0 mi of the
unknown.

3 Using a clean pipette, add 10.0 ml of the
0 mg/1 standard into flask 0.

4 Again using a clean pipette, add 10,0 ml
of the 5 mg/1 standard into flask 5.

5 Proceed in a similar manner using the 10,
15, and 20 mg/1 standards and flasks 10,
15, and 20.

6 Stopper and shake all five flasks.

7 Mark five plastic cups 0, 5, 10, 15, and 20,

8 Fill the plastic cups about 3/4 full with the
appropriate solutions from the volumetric
flasks,

9 Fill a 6th plastic cup with distilled water,

10 The power toggle switch (on left side of
instrument) is already turned on,

11 Set the sensitivity knob to the standby
position,

12 Set the phototube voltage knob (on right side
of wnstrument) to position E.

13 Set the wavelength knob to the theoretical
value of 461 nm (the scale 1s at the top of
the instrument),

13-1


Chemical Analyses

VI

VIL

1 Non-specific

Non-specific measurements to assess
overall water quality might be required
like acidity, alkalinity, color, tur-

, bidity, specific conductance.

2 Organics

Various organic analyses might be
relevant such as total organic carbon,
organic nitrogen, phenols, oi] and
grease, surfactants.

3 Metals

Specified metals may be of interest.
Currently, the Federal Register lists
28 trace metals in the test procedure
guidelines.

4 Others

Cyanide, bromide, chloride, fluoride
and hardness are other measurements
that might be required of individual
industries.

METHODOLOGY AND SKILLS

Methodology

The analytical methods specifiedinthe Fed-
eral Register for these measurements range
from wet" procedures using equipment com-
monly found in most laboratories to proce-
dures requiring sophisticated instruments
such as anorganic carbonanalyzer or an
atomic absorption unit,

Skills

The degree of analytical skills required
to perform the analyses likewise varies,
as does the cost of having such analyses
performed by service laboratories,
OTHER ANALYTICAL CONSIDERATIONS
Sample

The importance of securmg a representative
sample of the type (grab or composite)

specified by the permit cannot be over-
stressed, ‘

B Record Keeping

Keeping complete and permanent records
about the sample is also essential. Such
records include conditions when the sample
was collected, chain of custody signatures
and details and results of analyses.

C Quality Control q

Whether the analyses are done in-house
or by a service laboratory, an Analytical
Quality Control Program should be estab-
lished, Fifteen to twenty percent of
analytical time (cost) should be given to
checking standard curves for colorimetry,
analyzing duplicate samples to check pre-
cision and analyzing spiked samples to
check accuracy. Recording precision and
accuracy data on quality control charts is
an effective method of using such data as
a daily check on analytical performance,
This can also be done with numbers
reported on "blind"! samples sent to service
labs.

VIII SUMMARY

The October 16, 1973 Federal Register
promulgates guidelines establishing test
procedures for the analysis of pollutants
which might be required for certification
(PL 92-500, section 401) or for permits
(PL 92-500, section 402). The issue lists
page numbers in standard references where
procedures can be found to measure the 71
parameters listed. It also sets forth the
regulations for application to use methods
not cited in the guidelines. The measure-
ments which must be made should be speci-
fied by the agency requiring the data.
Apparatus and professional skills to do the
measurements will vary. Representative
samples, complete records and analytical
quality control measures are all necessary
elements for producing reliable data.


U

ATOMIC ABSORPTION SPECTROPHOTOMETRY

INTRODUCTION

Atomic absorption spectroscopy has been
well known to physicists and astronomers
for more than 100 years, In 1850, Kirchoff
took light from the sun and collimated it
with a lens through the flame of an ordinary
laboratory burner, and then passed the
light through a prism which disperse‘ it
into the characteristic visible spectrum
with which we are all familiar, He then
took a platinum spoon containing a sodium
salt ana introduced st into the flame, He
observed that the yellow light that was
present in the spectrum disappeared and

in its place appeared the characteristic
resonance lines of sodium. Since then
astronomers have used the technique to
detect and measure the concentration of
metals in the vapors of stars In 1955,
Walsh'*’ recognized ts potential advantage
over emission spectroscopy for trace
metal analysis, He designed and built an
analytically useful atomic absorption
instrument. Shortly thereafter the ad-
vantages of atomic absorption instrumen-
tation were tecugnized in the United States.

THEORY

The basis of the method is the measurement
of the light absorbed at the wavelength of a
resonance line by the unexcited atoms of
the element, Elements not themselves
excited to emission by a flame may be
determined in a flame by absorption pro-
vided that the atomic state is capable of
existence.

Il

At the temperature of a normal air-
acetylene flame (2100 C) only about one

per cent of all atoms 1s excited to emission
in a flame; therefore absorption due to a
transition from the ground electronic

state to a higher energy level is virtually
an absolute measure of the number of atoms
in the flame, and the concentration of the
element in the sample. Electrons will
absorb energy at the same characteristic
wavelength at which they emit energy.

This 1s the principle upon which the tech-
nique of atomic absorption spectroacopy A
1s based,

CH, MET, aa, 2,12.71

The advantages of utomnt. absorption
spectroscopy as compared tu en ission
spectroscopy are (1) that ator ic
absorption is independent of the eacitation
potential of the transition involved and

(2) that it is lees subject to temperature
variation and interference fromm extraneous
radiation and interference from extraneous
radiation or energy exchange hetween
atoms.

Atomuc absorption analytical apparatus
(Figure 1) consists of a suitable source

of light emitting the line spectrum of in
element, a device for vaporiziig the
sample, a means of line tsolatson
(monochomator or filter) and -acto-
electric detecting and measur .ng equ-prient.

if the detector is placed to receive only
the resonance line of the element from the
light source, measurement can be maie of
the absorption of resonance-lne radition
on its passage through the vaporized
sample. The magnitude of this absorption
gives a measure of the concentration of
free ground-state atoms of the zlement in
the vapor and when referred to a calibra-
tion curve, provides a means of determining
the concentration of the element in the
sample.

INSTRUMENTATION

The general arrangement of an absorption
flame photometer is no different from an
emission flame photometer except for the
addition of a light source, An aerosol is
introduced into a flame which is placed on’
the optical axis between the entrance slit
of the monochromator and the monochromatic
light source. Energy of the wavelength
absorbed by the sample is provided by a
source lamp whose emitting cathode is
made of that element. This energy is
passed through the flame and then through
a dispersing.device. A detector measures
the absorbed and unabsorbed exciting
radiation,

Light Source

For the more volatile elements such as
the clkali metals mercury and thallium,

a)


Burners and Fuel Mixtures

Figure 3
Perkin-Elmer
Nitrous Oxide Burner Head

3 High solids head

This head looks similar to the nitrous
oxide head with the main difference being
the slot. The slot on the high solids
burner is both longer and wider, The
prime purpose of this burner head is to
allow analysis of one element in the
presence of overwhelming amounts of
another element. The head should be
used with the air-acetylene flame and
not with the nitrous oxide as danger of
flash-back would exist, Other heads are
made for more specific purposes by
each manufacturer and reference should
be made to the particular literature of
the manufacturer of the burner head.

II GASES (FUEL AND OXIDANT)

Table I shows that for the metals listed in the
Federal Register as being capable of analysis

by atomic absorption, only two fuel oxidant
mixtures are sted. Nitrous oxide and
acetylene-air can be used to analyze most of

the metals, The air-acetylene combination

is not hot enough to dissociate most of the
compounds of a number of elements such as
aluminum, boron and silicon, and it incompletely
dissociates those of other metals like chromium,
molybdenum and barium. An additional problem
is that the refractory elements are quick to

form stable oxides.

Some exceptions are noted to the fuel mixtures
noted above. These metals are easily

dissociated and other means can be used. For
example, the analysis of mercury is accomplished
without a flame and arsenic and solenium are

done using an argon-hydron flame in the gaseous
hydride procedure,

When using the nitrous oxide-acetylene flame

@ note on the safety of operation should be added.
Although not difficult to use, with modern
atomic absorption instruments this gas combi-
nation is somewhat more likely to flash-back
than air-acetylene when not used in accordance
with instructions. ,

Table I in the outline on the Fundamentals of
Atomic Absorption gives the burning temperatures
of most fuel oxidant mixtures. Some of the .
combinations are not used in atomic absorption
but are included as a means of comparison,

Iv SUMMARY

Each manufacturer of atomic absorption
instrumentation equips its instruments with a
standard burner head, Should the user desire,
he can purchase additional burner heads. These
are equipped with a common connector to the
burner body and no great problem exists to
change from one head to another. There are
basically two burners, the total consumption
and the laminar flow or pre-mix type.

The pre-mix type canutilize a number of heads
such as the Boling, nitrous oxide or high solids
each of which have specific uses,

Table I shows the metal elements of which the
NPDES program permits analysis by atomic
absorption and the fuel oxidant mixture
recommended for its analysis, Two mixtures
are of primary importance, that js the air-
acetylene and nitrous oxide-acetylene mixtures.

11-3


Flame Photometry Laboratory (Sodium)

OL 2 tay /Bw 9 UOTTEA Ua UO.) b untpog

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12-5


Flame Photometry

Table 1
Approximate Approximate
Wavelength Sensitivity Wavelength Sensitivity
mg/1 mg/l
Aluminum 484.2 2 Lead 405, 2
467.2 3 368, 2
396.2 4 364° 3
Barium 553.6 0.3 Lithium 670.8 0, 002
493 0.4
Magnesium 371, O.1
Beryllium 471 25 383 O.1
510 100 285, 2 0.2
Boron 548 1 Manganese 403 0.01
521 2 279" 1
495 3 561 2
Cadmium 326. v 2 Mercury 235, 7* 10
228. 8* 40
Potassium 766.5 0.001
Calcium 422.7 0, 003 404.6, 0.2
622 0. 004 344,7 3
554 0.01 >
Silver 338. 3, 0. 05
Chromium 425.4 0.1 328.1 o.1
360” 0.1 '
520 O.1 Sodium 589.3, 0, 002
° 330, 3° 1
Copper 324 0.01
327? 0.01 Strontium 460.7 0.02
681 0.01
Iron 372 0.2 407.8 0.5
386 0,2
373 0.3 Zinc 213, 9% 500
500 200

Ultraviolet spectrum
Doubtful detection in visible spectrum


Flame Photometry

the necessity for their measurement in water
is a rare occurrence,

Iv

A

INTERFERENCES
Spectroscopic Interferences

Energy at other wave lengths or from
other elements than those intended to

be measured may reach the detector.
This problem 1s related to the resolution

“of the instrument and slit widths used.

Many of the instrumental difficulties are
related to reproducibility of the flame.
The quality and composition of the fuel
affect the constancy and temperature of
the flame which 1n turn influences the
energy of emission, Likewise, slight
variations 1n fuel pressures and ratios
affect the reproducibility of the flame
with reference to shape, temperature,
background, rate of sample consumption,
etc. In some cases, the temperature
ot the flame 1s the hmiting factor in de-
termining the presence ofametal, (The
alkaline earth metals emit radiations
at "low'' temperatures, whereas other
metals require very "hot'' flames.)

Table 2 indicates temperatures obtain-
able with different fuel-oxidant mixtures.

Table 2.
Approximate Temperatures of
Fuel-Oxidant Mixtures for
Flame Photometer Use

[ESSERE
pproximate

Fuel-Oxidant Temp. °C

Hydrogen - ar 2100

Hydrogen - oxygen

2700 - 2800

Acetylene - oxygen 3100

Acetylene - air *

Propane - oxygen

2000 - 2200
2700 - 2800

Illuminating gas - oxygen 2800

Cyanogen - oxygen ** 4900

* Undesirable because of carbon deposits.
** Used in research problems.

TH4

Emission reading of spectral lines
always includes any contribution from
the flame background emission on which
the line is superimposed, When the
photometer includes a monochromator,
it is possible to read the background
radiation in the presence of the test
element, First, the line +background
intensity is measured in the normal
manner at the peakor crest of the band
system. Next, the wave length dialis
rotated slowly until emission readings
decrease toa minimum at a wave length
located off to one side or the other of
the emission lineorband. Itis usually
preferable to read the background ata
lower wave length than the peak, Back-
ground reading is subtracted from the
line + background reading.

Products of combustion may affect the
characteristics of the flame or may
affect the optical system by fogging or
coating of lenses and mirrors.

Factors Related to the Composition
of‘the Sample

An element may be sélf-~absorbing --
a phenomenon in which the energy of
excitation is not proportional to the con-
centration of the element, As previously
discussed, exictation 1s followed by
loss of energy inthe form of radiation
as the electron falls back to its original
position or to a lower energy level.
During passage of radiant energy through
the outer fringes of the flame, this
energy is subject to absorption through
collision with atoms of its own kind
present in the ground energy level.
Absorption of radiant energy weakens
the strength ofthe spectrum line. Using
the emission line at 589 nm for sodium,
Figure 3 indicates that the line ceases
to be linear at 13 mg/l. As the sodium
concentration increases, the self-
absorption effects become more
pronounced, Sample dilution to permit
reading on linear portion of the curve
1s often practiced,

Two or more elements present in the
sample may produce radiant energy at


Determination of Lead.

TABLE J
Atomic Absorption Concentration Ranges With

Conventional Atornzation: **
as — Opumum ——
Detection Concentration
Limit Sensitivity Range

___ Metal mel me/l . _ mg/l _
Aluminum 0.1 1 5 — 100
Antimony 02 0s 1 - 40
Arsenic? 0.002 - 0.002 - 002
Banum 003 04 1 - 20
Beryl 0.005 0025 005 - 2
Cadnnum 0.002 0025 005 ~ 2
Calaum 0.003 0.08 0.2 ~- 20
Chrommum 00? 0.1 0.2 ~- 10
Cobalé 003 02 os ~ 10
Copper 001 01 02 - 10
hon 002 012 03 - 10
Lead 005 Os 1 20
Magnesnun 0.0005 0007 002 - 2
Manganes> 001 005 ol ~- 10
Mercury * 0002 - 0.0902 00)
Molybdenum ol 03 os ~ 20
Nickel 002 O1S 03 - 10
Potassium 0005 004 o1 - 2
Selenusn’” 0.002 - 0002 — 0.02
Silver 001 006 0.1 - 4
Sodsum 0.002 0.015 0.03 - 1
‘Thalliuna 0.1 Os 1 - 20
Tin 08 4 10 - 200
Titaniuns 0.3 2 5 - 100
Vanadium 0.2 08 1 - 100

0.005 002 00s - 2

* Gaseous hydiide method.

* Cold vapor technique

*4° The conceniraions shown above aie not contrived valuzs and should be obLasnable with

COMvutOnalaspi ion on aby satisfactory efonnce absorption specteophotonieter


ENERGY SOURCES FOR ATOMIC ABSORPTION SPECTROSCOPY

I INTRODUCTION

The basic principle behind atomic absorption
spectroscopy can be said to be opposite that
of emission methods. In emission spectro-
scopy the sample is raised to a meta stable
excited energy level by an input of energy.
Then the sample is allowed to return to its
stable ground state. When the sample returns
to its ground state energy is given off and a
high proportion of this energy is at a wave-
length characteristic of the metal in the sample
that is being analyzed.

In atomic absorption the element under inves-
tigation is not excited but is merely dissociated
from its chemical bonds, and in an unexcited
ground state. It is then capable of absorbing
radiation at a characteristic wavelength, i.e.,
the same wavelength as would be emitted if

the element were excited.

This difference affects both the sensitivity
and stability of results obtained in analyzing
for elerments via atomic absorption. Due to
the fact that, even at optimum conditions in
emission spectroscopy, for every atom avail-
able in an excited state there are many more
available in the unexcited state. For example,
for every calcium atom in the excited state
there are about a thousand dissociated and
accessible to atomic absorption. For zinc the
ratio is even greater, for every one atom that

§ excited there are 10° available for atomic
ab: sorption,

These numbers do not indicate a direct pro-
portional increase in sensitivity, Some increase
is noticed but not as large as the numbers
indicate. In addition to the sensitivity increase,
an increase in the stability is also obtained,

If during analysis of zinc by emission spec~-
troscopy a change in flame would make available
another atom, a change of 100% in the emission
value has occurred but the change in atomic
absorption would not be significant.

In order to provide energy that the unexcited
atoms are capable of absorbing, a hollow
cathode lamp is used in atomic absorption.
Hollow cathode lamps are manufactured by
several firms and the shape of the lamp has

CH, MET. aa. 4, 1,76

little to do with its function, Basically, a
hollow cathode lamp is composed of an‘anode,
cathode, shielding, envelope, end window and
a filler gas,

To provide energy at the specific wavelength
needed for the element under analysis the hollow
cathode lamp has its cathode constructed from
or lined with the element of interest usually in
the shape of a cylinder closed at one end. As
each lamp emits the line spectra of the element
present in its cathode, a different lamp is
usually used for each element analyzed,

Each hollow cathode lamp operates under the
same general principle. The lamp envelope is
filled with an inert gas, usually argon or neon,
at a low pressure (1 to 10 mm Hg). Onge
sufficient voltage is applied across the electrodes
within the lamp, the inert gas ionizes and
current begins to flow. When this happens
positive gas ions bombard the cathode and
heating occurs. As the inner surface of the
cathode heats, it sputters and metal vapor

fills the cathode volume, Charged gas particles
collide with the metal atom, raising its valence
electrons to higher energy states. When these
excited electrons return to their ground state,
they emit light. The spectrum thus emitted
contains the same wavelengths of light required
for absorption by that metal atom under analysis.
As many cathodes are alloyed to obtain mech-
anical strength and as the gas fill is also
excited, the emission of a hollow cathode lamp
contains the spectra of more than one element.

Another step to increase the usefullness of a
hollow cathode lamp was to incorporate more
than one element into the cathode so the lamp
could be used for more than one element. This
has been done and there are available lamps
that contain as many as six elements, Not all
elements can be usefully combined in multi-
element lamps.

Some combinations are difficult or impossible
from a metallurgical viewpoint. More important
to the user, some combinations, though feasible
to manufacture, yield spectral interferences,
Here the emission lines from one element lie


Burners and Fuel Mixtures

lower than the instrument itself. The
manutacturer's directions for connecting
this drain should be followed closely—
most instruments provide a positive water
seal somewhere in the system, This is
done to prevent flashbacks in the burner.
Care should also be taken to follow the
yvuanufacturer's directions for cleaning
both the nebulizer, mixing chamber, and
burner head.

burner Head

vhe third part of the burner is the burner
head. Most instruments are so designed
to allow a quick change of the head, of
course caution should be taken that the
head being removed has had sufficient time
to cool, In most cases the burner head and
burner body have some locking device which
will not allow certain type heads to be used
with various gas mixes. For example, the
Bolng head should not be used with nitrous
oxide-acetylene gases and the collar or
locking device helps to prevent this from
accidentally being done.

There are basically three types of burner
heads with many variations of these three
for specific needs. This 1s partially due to
the manufacturers finding new ways to
improve the design of the heads. The three
types of heads are the Boling head, the
nitrous oxide head and a type of burner head
designed to allow the analysis of samples
with high solids content.

1 Boling burner head (Figure 1)

The Boling burner is distinctive in
appearance, having three separate
longitudinal orifices or slits at the top

of a compressed chamber with a triangular
cross section, This design provides a
long, flat flame which is actually composed
of three flames which are separately
supported and distinct at the base. This
burner can be used with air-acetylene,
air-hydrogen, air-propane or argon-
hydrogen flames. It can burn concentrated
solutions without clogging and provides
better sensitivities for many metals.

Many manufacturers provide this burner
head as the standard head for their
instruments.

, Figure 1
Boling Burner Head

2 Nitrous oxide head

The nitrous oxide burner head 1s, as its
name implies, used for elements which
need the hotter flame to atomize and for
the metals which readily form omdes in
the flame and for the rare earth elements.
The elements included in the USEPA
manual of Methods for Chemical Analysis
of Water and Wastes that are to be
determined by atomic absorption are
listed in Table I. There are six elements
that must be determined by the use of

the nitrous oxide-acetylene flame in order
to attain sufficient sensitivities to meet
the NPDES standards.

Figures 2 and 3 show two types of nitrous
oxide heads. They are both characterized
by a thick head and a short slot (5 cm).
Instrumentation Laboratory adds fins

on both sides of the head to aid in cooling
and two trenches along the slot to increase
ambient air flow and reduce carbon
buildup.

Figure 2
Instrumentation Laboratory
Nitrous Oxide Burner Head


Flame Photometry Laboratory (Sodium)

This outline was prepared by C. R. Feldmann, Descriptors: Chemical Analysis, Laboratory
National Training Center, MOTD, OWPO, Tests, Water Analysis, Sodium, Alhah Metals,
USEPA, Cincinnati, Ohio 45268, Metals

12-6


EPA+-430/1-76-002
January 1976

ANALYTICAL METHODS FOR TRACE METALS

This course is deaigned for chemists or technicians
who will perform trace metal analyses in industrial
or municipal wastewaters and treatment plant
effluents, The analyses presented conform to the
guidelines required pursuant to Section 304(g) of
the Federal Water Pollution Control Act Amend-
ments of 1972,

U. S. ENVIRONMENTAL PROTECTION AGENCY
Office of Water Program Operations
TRAINING PROGRAM

.

1a


FLAMELESS MERCURY FOR ANALYTICAL METHODS FOR TRACE METALS

DETERMINATION OF MERCURY

I INTRODUCTION

There are many forms of mercury, some

more toxic to humans than others. Although
metallic mercury and its inorganic, alkoxyalkyl,
and aryl compounds can have detrimental

effects on man and other animals, it has

become clear that methylmercury poses a
particularly serious problem. It appears

that mercury enters the food chain as methyl
mercury after conversion by microorganisms

in the silt of waterways.

Sources of mercury in industrial and agricul-
tural countries fall into ‘the following categories:
1) chlor-alkali plants, 2) industrial processes
involving the use of mercurial catalysts,

3) slimicides, used primarily in the paper-

pulp industry, 4) seed treatment, 5) burning

of fossil fuels, 6) natural occurence from
geological formations, and 7) miscellaneous
sources,

Early in 1970 fish in Lake St. Clair above
Detroit were shown to contain hazardous levels
of methyl mercury. However, even before this
other countries such as Japan were having
serious problems with mercury poisoning.
"Minamata Disease" or methyl mercury
poisoning due to ingestion of contaminated

fish occurred in a village near the Minamata
Bay, Japan, from 1953 through the 1960's, and
affected at least 121 children and adults,
Consequently, the finding of high levels of
methylmercury in Lake St. Clair caused the
United States and Canada to ban fishing in

the lake.

A study was carried out by the Office of Water
Supply during 1971 analyzing 698 samples of
raw and finished waters collected from 273
communities, Of these 273 communities,

261 showed no detectable quantities or
concentration of less than 0.001 ppm, In
eleven of the communities the mercury
concentration ranged from 0, 0010 to

0.0048 ppm.

CH. ME, hg. 1. 1.76

After the discovery of mercury contamination

in fish, the importance of the mercury content

of waters can be seen by the decreasing-allowable
limits. The 1962 edition of the Public Health
Service Drinking Water Standards did not list

a limit for mercury. However, in 1970 a
tentative standard of 0.005 mg/1 limit was
proposed, Recently, March 1975, the Interim
Primary Drinking Water Standards proposed

a limit of 0,002 mg/1. :

ll METHODS

A Dithizone

Until about 1964 the method of choice for
analysis of mercury was the dithizone
method. This method utilized a colorimetric
determination of the dithizone complex with
mercury. The method has been characterized
as relatively insensitive and requiring
excessive amounts of sample when levels of
mercury are low. The analyst must have
experience in order to obtain meaningful
results due to the possibility of loss of
volatile forms of mercury during a hot acid
digestion procedure, The method covered
the range of 0.005 mg/1 to .035 mg/l.

B Emission Spectroscopy

The emission spectrophotometric determination
of mercury was also carried out, However,
the cost of the instrument made this method
considerably more expensive than the

dithizone method. The detection limit fell

in the range of about 5 mg/1 so no increase

in sensitivity could be obtained.

C Atomic Absorption

The detection limit by direct aspiration of

a sample into the instrument was claimed to
be 0.5 mg/l. However, 1n actual practice
the limit was closer to 5.0 mg/l. A
concentration step before aspiration by


DETERMINATION OF CALCIUM AND MAGNESIUM HARDNESS

INTRODUCTION

A Definition of Hardness

USPHS - "In natural waters, hardness
is a characteristic of water which re-
presents the total concentration of just
the calcium and magnesium ions ex-
pressed as calcium carbonate, If
present in significant amounts, other
hardness-producing metallic ions should
be included,"

B_ Other Definitions in Use

1 Some confusion exists in understanding
the concept of hardness as a result of
several definitions presently used,

2 Soap hardness definition includes hy-
drogen 10n because it has the capacity
to precipitate soap. Present definition
excludes hydrogen 1on because it is not
considered metallic,

3 Other agencies define hardness as
“the property attributable to presence
of alkaline-earths".

4 USPHS definition is best in relation
to objections of hardness in water,

Il CAUSES OF HARDNESS IN WATERS OF

VARIOUS REGIONS OF THE U, S,

A Hardness will vary throughout the country

depending on:

1 Leaching action of water traversing
over and through various types of
geological formations.

2 Discharge of industrial and domestic
wastes to water courses.

3 Uses of water which result in change

in hardness, such as irrigation and
water softening process.

CH. HAR, 3c. 1.76

B_ Objections to Hardness
1 Soap-destroying properties

2 Scale formation

C Removal and Control

Hardness may be removed and controlled
through the use of various softening oper-
ations such as zeolite, lime-soda, and
hot phosphate processes, It can also be
removed by simple distillation or com-
plex formation with surface active agents
(detergents).

I DETERMINATION OF HARDNESS

A Two Methods in use’)

1 Compleximetric method (EDTA)

2 Calculation - by the use of appro-
priate factors, the hardness due
to ions other than calcium and
magnesium may be converted to
an equivalent calcium carbonate
hardness,

B_ Compleximetric Method
1 Principle of determination

Ethylenediaminetetra acetic acid
(EDTA) is a sparingly soluble amino
polycarboxylic acid which forms
slightly ionized and very stable color-
less complexes with the alkaline-
earth metals,

“2 Interferences: iron, manganese,
nickel, and zinc,

3 Procedure: Time and pH considera-
tions.

4 Calculations of total hardness
assuming a known volume of titrant
of EDTA.

5 Precision and accuracy.

8-1


Flame Photometry Laboratory (Strontium)

43 Open the shutter.

44 Slowly turn the wavelength knob to the left.
The needle will move to the right and at
about 10 - 30 percent transmittance will
move no farther to the right. Record the
wavelength reading. This is the back-
ground wavelength. Do not change this
setting. The percent transmittance is
the background reading for this solution,

45 If the point at which the needle moves no
farther to the right is overshot, turn the
wavelength about } turn to the right and
repeat step 44,

46 Close the shutter.

47 Replace cup 20 with cup 15.

48 Open the shutter.

49 Record the background transmittance
reading for the solution,

50 Close the shutter,

51 Repeat steps 47, 48, 49, and 50 using
cup 10, 5, and 0 1n turn,

52 Aspirate distilled water for about 15 sec.

53 Turn the sensitivity knob to the standby
position,

54 Close the main valve on the hydrogen
cylinder,

‘
55 Close the main valve on the oxygen cylinder,
56 Empty all six plastic cups and discard them,

57 Leave the power toggle switch (on left side
of instrument) on.

58 For each of the 5 solutions, subtract the
background percent transmittance reading
from the peak percent transmittance
reading.

59 Using the graph paper provided in the
manual, plot the 5 differences vs. the
appropriate concentrations. Draw a
straight line connecting the five points.
This is the calibration graph.

60 Double the difference value obtained for the
solution in cup 0.

61 Find the value on the percent transmission
axis.

62 Draw a straight line to the right until it
intersects the calibration line.

63 From the point of intersection, draw a line
straight down to the horizontal axis.

64 This is the concentration of the unknown,

REFERENCE

Standard Methods for the Examination of Water
and Wastewater, 13th Edition, page 328,
Method 155A, 1971.


Methodology for Chemical Analysis of Water and Wastewater

serve as independent checks on reagents,
instruments or techniques; for training
analysts or for comparative analyses within
the laboratory. There 1s no certification

or other formal evaluative function resulting
from their use,

X SELECTION OF ANALYTICAL
PROCEDURES

Standard sources'!+ 2-3) winl, for most
parameters, contain more than one analytical
procedure, Selection of the procedure to be
used in a specific instance involves consider-
ation of the use to be made of the data. In

some cases, one must use specified procedures,
In others, one may be able to choose among
several methods,

A NPDES Permits and State Certifications

A specified analytical procedure must be
used when a waste constituent 1s measured:

1 For an application for a National Pollutant
Discharge Elimimation System (NPDES)
permit under Section 402 of the Federal
Water Pollution Control Act (FWPCA),
as amended,

2 For reports required to be submitted by
dischargers under NPDES.

3 For certifications issued by States
pursuant to Section 401 of the FWPCA,
as amended,

Analytical procedures to be used in these
situations must conform to those specified
in Title 40, Chapter 1, Part 136, of the
Code of Federal Regulations (CFR). The
listings in the CFR usually cite two different
procedures for a particular measurement,
The CFR also provides a system of applying
to the EPA Regional Adminigtrator for
permission to use methods not cited in the
CFR.

B Ambient Water Quality Monitoring
For Ambient Water Quality Monitoring,

analytical procedures have not been
specified by regulations. However, the

2-6 >

selection of procedures to be used should
receive attention. Use of those listed in
the CFR is strongly recommended. If

any of the data obtained is gaing to be used
in connection with NPDES permits, or may
be used as evidence in a legal proceeding,
use of procedures listed in the CFR 1s
again strongly recommended,

XI FIELD KITS

Field kits have been devised to perform
analyses outside of the laboratory. The kit
may contain equipment and reagents for only
one test or for a variety of measurements,
It may be purchased or put together by an
agency to serve 1ts particular needs.

Since such kits are devised for performing
tests with minimum time and maximum
simplicity, the types of labware and reagents
employed usually differ significantly from the
equipment and supplies used to perform the
same measurement in a laboratory.

A Shortcomings

Field conditions do not accommodate the
equipment and services required for pre-
treatments lke distillation and digestion.

Nor is 1t practical to carry and use calibrated
glassware like burets and volumetric pipets.
Other problems are preparation, transport
and storage of high quality reagents, of

extra supplies required to test for and remove
sample interferences before making the
measurement, and of instruments which

are very sensitive in detecting particular
constituents. One just cannot carry and

set up laboratory facilities in the field which
are equivalent to stationary analytical
facilties,

B NPDES Permits and State Certification

Kit methods that thus deviate from standard
laboratory procedures are not approved for
obtaining data required for NPDES permits
or State construction certifications, If one
judges that such a method 1s justifiable for
these purposes, he must apply to the EPA
Regional Adminstrator for permission to
use it, .


BURNERS AND FUEL MIXTURES

I INTRODUCTION

The object of the burner and its fuel and
oxidant gases on an atomic absorption
spectrophotometer is to produce in the flame
a supply of dissociated atoms in their ground
or unexcited state. These atoms will then
be available to absorb the energy provided by
the hollow cathode lamp.

tl BURNERS

‘There are generally two classifications of
burners for atomic absorption, These are

the total consumption burner and the pre-mix
or laminar flow burner, These burners have
been covered in the outline on the Fundamentals
of Atomic Absorption, This outline includes
diagrammatic drawings of the two types.

The total consumption burner is primarily
used in flame photometry and when atomic
absorption came into existence the first
attempt was to use this type burner, However,
it has some severe limitations when applied

to atomic absorption, Consequently, experi-
mentation with various forms of burners led
to what is now the pre-mix or laminar burner.

Most manufacturers today use the pre-mix
type burner with some different modifications
as the standard burner on their atomic
absorption instruments. These burners are

a three part system. They contain an
independent nebulizer for sample introduction,
&@ pre-mix chamber and a burner head.

Any burner design whether different by principle
or manufacturer's design should have certain
criteria, The burner should be stable, its
absorption for a given concentration should
remain constant for as long as is possible.

A burner should also be quiet, both audibly
and instrumentally and not cause fluttering or
wavering in the output. Burners should have
as little carry over from one sample to the
next. They should also be easy to clean and
not easily corroded.

CH. MET, aa. 5, 1.76

Usually the pre-mix type of burner will have
the better results when the above criteria is
compared between it and the total consumption

burner. All these parameters can also vary

from manufacturer to manufacturer and thought
should be given when a new instrument is
contemplated or accessory equipment for
existing instrumentation purchased.

A Nebulizer

The nebulizer is simply a device used to
asperate the sample into the burner and
from there into the flame. This device
works on a venturi effect with the oxidant
being moved across the tip of a stainless
steel capillary tube, This causes a pressure
drop along the capillary's length. When

the other end of the tube is immersed in

a liquid, that liquid will be drawn through
the tube and discharged in the oxidant
stream where it is blown into a fine aerosol,

The rate of asperation is controlled by
adjusting the position of the end of the
capillary with respect to the oxidant flow.

A typical optimum flow rate is approximately
5 millihters per minute. Most manufacturers
provide some kind of adjustment device
usually located on the front of the burner
which is used to adjust the flow rate.

B Pre-Mix Chamber

When the sample leaves thé nébulizer’ section,
it ig mixed with more oxidant and fuel and
mixed again in the body of the burner itself.
All droplets of sample too heavy to progress
into the burner head are collected by the
baffling and sides of the burner and flow down
the drain into the waste collection vessel,
This wasted portions ‘ofiy! tiple can
typically amount té dinety fércent of that
asperated into the-burner. The pre-mix
section should be made of some material
which will resist corrosion,

The drain outlet of the burner should be
connected to some type of-drain receptacle

11-1


Flame Photometry Laboratory (Sodium)

11 Raise the door on the right side of the
burner housing (behind instrument),

12 Cautiously bring a lighted match to the
tip of the burner 1n the housing.

13 Close the door on the burner housing.

14 Caution Do not place any part of your body
over the coils on the top of the burner
housing. Hot gases are escaping.

15 Raise the silver lever between the instru-
ment and the burner housing to the vertical
position,

16 Place the plastic cup containing distilled
water in the cup holder which 1s now
exposed at the right side of the burner
housing.

17 Push the silver lever clockwise so that
the cup holder swings into the burner
housing and the water 1s aspirated. A
distinct difference in sound will be noticed
when water or a sample is being aspirated.
If at any time during the determination
this sound again changes, it will indicate
that all of the liquid has been aspirated
from the cup. Simply move the silver
lever and refill the cup with the appropriate
liquid.

18 Do not allow air to be aspirated for more
than about 15 seconds, If there is any
delay, aspirate distilled water until the
problem causing the delay has been
corrected.

19 Turn the sensitivity knob to position 1,

20 Turn the dark current knob until the needle
reads 0 on the percent transmittance scale.

‘21 Turn the sensitivity knob to position 4,

22 Repeat step 20.

25 Swing the cup of distilled water out of the
burner housing and replace it with cup 10.

Swing this cup back into the burner housing.

24 Turn the fltr - shtr - open knob to the open
position (this opens the shutter).

oy

25 Turn the wavelength knob slowly to the left;
the needle will move to the left.

26 At some point the needle will suddenly
swing toward the right. It will probably be
necessary to make adjustments with the slit
knob in order to keep the needle on-scale
while finding the point at which the needle
swings back to the right. Record this wave-
length. It is the peak wavelength. Do not
change this setting until indicated in the _
instructions,

27 If the point at which the needle swings back
to the right is overshot turn the wavelength
knob about 1/4 turn to the right and repeat
steps 25 and 26.

28 Make the needle read 100% transmittance h
by turmng the slit knob, Record the sht "
mm reading, Do not change this setting.
100 1s the peak transmittance reading °
for this solution.

29 Turn the fltr - shtr - open knob to the shtr
position (this closes the shutter),

30 Replace cup 10 with cup 8.
31 Open the shutter.

32 Record the percent transmittance reading
and close the shutter.

33 Repeat steps 30, 31, and 32 using cups
6, 4, 2, 0, and the unknown, in turn,

34 Aspirate distilled water and using the dark
current knob make the needle read 0 percent
transmittance,

35 Aspirate cup 10.
36 Open the shutter.

37 Slowly turn the wavelength knob to the left.
The needle will move to the right and at
about 1/4~ 1 percent transmittance will
move no further to the right. Record the
wavelength reading. This is the background
wavelength. Do not change this setting.

The percent transmittance 1s the background
reading for this solution, “


SAMPLE HANDLING - FIELD THROUGH LABORATORY

I. PLANNING A SAMPLING PROGRAM
A Factors to Consider:

1 Locating sampling sites

2 Sampling equipment

3 Type of sample required

a grab
b composite

4 Amount of sample required
5 Frequency of collection
6 Preservation measures, if any
B Decisive Criteria
1 Nature of the sample source
2 Stability of constituent(s) to be measured

3 Ultimate use of data

Il REPRESENTATIVE SAMPLES

If a sample is to provide meaningful and
valid data about the parent population, it
must be representative of the conditions
existing in that parent source at the
sampling location,

A The container should be rinsed two or
three times with the water to ve collected.

B Compositing Samples

1 For some sources, a composite of
samples is made which will represent
the average situation for stable
constituents.

2 The nature of the constituent to be

determined may require a series of
separate samples,

WP. SUR. sg. 6.3.74

C The equipment used to collect the sample ;
is an important factor to consider.
ASTM“) has a detailed section on various
sampling devices and techniques.

D Great care must be exercised when
collecting samples in sludge or mud areas
and near benthic deposits. No definite
procedure can be given, but careful
effort should be made to obtain a rep-
resentative sample,

Ill SAMPLE IDENTIFICATION -

A Each sample must be unmistakably
identified, preferably with a tag or label,
‘The required information should be planned
in advance,

B An information form preprinted on the
tags or labels provides uniformity of
sample records, assists the sampler, and
helps ensure that vital information will
not be omitted,

C Useful Identification Information includes:

1 sample identity code
2 signature of sampler
3 dignature of witness
4 description of sampling location de-
tailed enough to accommodate repro-
ducible sampling. (It may be more
convenient to record the details in the
field record book).
5 sampling equipment used
6 date of collection
7 time of collection
8 type of sample (grab or composite)
9 water temperature
10 sampling conditions such as weather,
water level, flow rate of source, etc,
11 any preservative additions or techniques
12 record of any determinations done in
the field
13 typé of analyses to be done in laboratory



BIBLIOGRAPHIC DATA |! Re WN 30/ 1-76-002 2 3. Recipient’s Accession No.
4. Title and Subtitle 5» Report Date
Analytical Methods for Trace Metals
6.
7. Auth 8. Performing Organization Rept.
ack Praft” Ne
9. Performing Organization Name and Address 10. Project/Task/Work Unit No.
EPA, OWPO, MOTD .
National Training and Operational Technology Center Vi. Contract /Grant No.
Cincinnati, Ohio 45268
12 Sponsoring Organization Name and Address 13. Type of Report & Period
~ overe
Same as #9 above
14,

15. Supplementary Notes

16. Abstracts

This course is designed for chemists or technicians of industrial or municipal
treatment plants who are required to perform analysis for trace metals, Participants
will learn theoretical concepts and will perform a variety of laboratory determina-
tions. Topics will include metal analysis by atomic absorption, flame photometry
and volumetric and colorimetric procedures, .-

17. Key Words and Document Analysis. 17a. Descriptors

Atomic Absorption - Trace metals - Analysis - Chemical analysis -
Data Handling- Municipal Wastes - Wastewater - Water analysis - Samples -

Sampling - Quality Control ~ Instrumentation - Laboratory Tests - Monntoring -
Reports.

17b. Identifiers /Open-Ended Terms

17. COSATI Field/Group O7B, 14B

18. Availability Statement 19. Security Class (This a ees
Report) .
. . 5
Release to public . by sc ENGL ASSIFLED —_— UNS LASSIELED
Y Page a ’
a INCLASSIFIED

SAM NTIS-35 (REV, 3-72)

Vote mime tnevern 7B


Flame Photometry

palladium capillary. A concentric
channel provides oxygen, and its tip is
constricted to formanorifice, Oxygen
1s passed from this orifice causing the
sample solution to be drawn up to the
tip of the inner capillary. There, the
liquidis sheared off and dispersed into
droplets. All droplets are introduced
directly into flame, with a sample con-
sumption of 1-2 ml per minute.

The main requirement of the burner 1s
production of a steady flame when sup-
plied with fuel and oxygen or air at
constant pressures. In the Beckman
aspirator-burner, a concentric channel
provides oxygen to operate the atomizer
and the flame. The additional concen-
tric channel provides fuel for the flame.

OpticalSystem, Photosensitive Detector
and Amphfier .

The optical system must collect the
light from the steadiest part of the flame,
render it monochromatic with a prism,
grating or filters, and then focus 1t on-
to the photosensitive surface of the de-
tector. Useof filter photometers is least
desirable due to their hmited resolution,
Flame spectrophotometers improve
application as they will separate emis-
sions in a mixture of metals, such as
manganese lines at 403,3 nm and the
potassium lines at 404.6 nm Place-
ment of a concave mirror behind the
flame so that the flame is at the center
of the curvature increases intensity of
flame emission by a factor of 2,

Any photosensitive device may be used
in a flame photometer, The detector
must have a response 1n the portion of
the spectrum to be used and have good
sensitivity, The photomultiplher tube
is the preferred detector for flame
spectrophotometers,

The amphfier increases the signalfrom
the phototube and improves resolution
between close spectral lines, It also
permits identification of elements
present in samples when the concen-
tration 1s very small,

Sample

Figure 2. DETAILED DIAGRAM OF
BURNER-ATOMIZER

Ill APPLICATIONS OF FLAME .
PHOTOMETRY TO WATER ANALYSES

Measurement of sodium and potassium in the
past has been confined to complex, tedious
and time-consuming gravimetric procedures,
The flame technique enables the analyst to
perform these determinations in a matter
of seconds. If these metals alone were the
only'elements capable of measurement by
flame photometry the use of the instrument
could still be justified m a great many
laboratories.

Other cations which may be detected and
measured in waters and waste materials
are calcium, magnesium, lithium, copper,
andothers, Table 1 includes those elements
which may be measured with commercially
available equipment, including ultra-violet
and photomultiplier accessories,

Table 1 does not include wavebands which
occur in the infrared spectrum. Sodium,
for example, has anemissionband at 819 nm
which 1s not detectable with the common
instruments.

Many other metals, including the rare earths,
can be measured using the flame technique
but they are not included in the table because


Atomic Absorption Spectrophotometry _

Element Sensitivity mg/I
Flame. —AA_
Aluminum 2 0.8
Antimony 0.2
Arsenic 1,0
Barium 0.3 1,0
Beryllium 25 0.05
Bismuth 0.2
Cadmium 2 0.01
Calcium 0,003 0.01
Cesium 0.08
Chromium 0.1 0,01
Cobalt 0,15
Copper 0.01 0,008
Gallium 1.0
Gold OL
Imdium 0.5
Iron 0.2 0.05
Lead 2 0.15
Lithium 0.002 0,008
Magnesium O14 0,003
Manganese 0,01 0.01
Mercury 10 0.8
Molybdenum 0.2
Nickel 0.05
Palladium 1.0
Platinum 0.8
Potassium 0,001 0.005
Rhodium 0.3
Rubidium 0.02
Selenium 1.0
Silver 0.05 0,02
Sodium 0, 002 0,005
Strontium 0,01 0,02
Tellurium 0.8
‘Titanium 1.0
Thallium 0.2
Tin 2.0
Vanadium 0.8
Zine 200 0,005
Table

flame temperature are much less than
those in emission because the strength
of the absorption line is principally
dependent on Doppler width whereas

the intensity of emission from the flame
is much more sensitive to temperature,

C Accuracy

This ia shown by the typas of interference
found in flame emission and atomic ab-
sorption spectroscopy, There are three
types:
1 Physical
Collision of atoms and electrons or
atoms and molecules will transfer

energy thus causing an enhancement or
depression of analysis-line emission,

. This hus a large effect on flame

emission analysis but has only a
negligible effect on atomic absorption,
»

Radiative ‘

Light from elements other than the one
being measured pass the line isolating
device (monochromator or filter), This
occurs in flame emission work, for
example, the interference of calcium
and magnesium in sodium determinations,
This interference is also encountered

in atomic absorption using a D.C.
system but is very small because of the
large signal from the hollow-cathode
tube, Radiative interference is elimina-
ted in an A.C, system,

Chemical

Emission from an element in the flame
is depressed by the formation of com-
pounds, which are not dissociated at
flame temperatures, This also affects
absorption because the formation of
temperature - stable compounds in the
flame causes proportionate reduction
in the population of ground-state and
excited atoms,

Investigations to date suggest chemical
interference is confined, almost
entirely, to the alkaline-earth elements
and that calcium absorption is more sub-
ject to this interference than is magne-
sium absorption, .

Typical calibration curves are shown
in'Figure 5,

0,32]

0.10

0.08)

0.06)
<

0.04)

0.02}

r —— 7 r a

50 100 FT 50 300 350 = 400

50200 2
METAL, ppb

Figure 5 4s


U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF WATER PROGRAM OPERATIONS <,-


Determination of Mercury

AIR IN—»

GLASS FRIT
COURSE POROSITY

iran

GLASS TUBING

AIR AND MERCURY VAPOR OUT

RUBBER STOPPER

300 mi.
BOD BOTTLE

Figure 1, Aeration Bottle

spectrophotometer 1s being used, the
desiccant can be replaced with a small

60 watt lamp. This 1s positioned to shine
on the tube itself to raise the temperature
inside the tube thus preventing condensation.
Next in the flow path after the desiccant
would come the absorption cell, or
instrument.

In the open mode a trap for the mercury
vapors would follow the absorption tube,
In the closed mode a valve would follow,
The position of each of these pieces can
be seen in Figure 2,

The absorption tube or cell can be a
standard spectrophotometer cell that 1s

10 cm long and having quartz end windows.
Suitable cells may be constructed from
plexiglass tubing 1 inch outside diameter
and 44 inches long. The ends are ground
perpendicular to the longitudinal axis and
quartz windows 1 inch in diameter and

one sixteenth of an inch thick are cemented
in place, Gas inlet and outlet ports (also
of plexiglass but } inch outside diameter)
are attached approxmately 4 inch from
each end,

9-4

C Instrumentation

Any atomic absorption spectrophotometer
having an open sample presentation area

in which the absorption tube can be mounted
1s suitable. The absorption tube is strapped
to a burner for support and aligned 1n the
beam by use of two 2 x 2 cards. One inch
diameter holes are cut in the center of each
card; the cards are placed over each end

of the cell, The cell is then positioned

and adjusted vertically and horizontally to
give the maximum transmittance.

There are available on the market instruments
designed specifically for the determination

of mercury by the flameless atomic absorption
method, Usually they are complete and
contain the absorption tube and pump inside
the instrument. The main advantage’ of

these instruments 1s that they are considerably
cheaper than an atomic absorption instrument.
However, their cmef disadvantage lies in

the fact that they can be used only for
mercury while an atomic absorption
instrument with some additional equipment
(lamps) can be used for about 40 metals.


Principles of Absorption Spectroscopy

electronic transitions are
made easier by the presence
of chromophore groups which
participate in resonance,
Thus, the excitation of the
delocalized outer electrons
(pi electrons) 18 relatively
easy and requires energy in
the visible range.

Vibration of atoms within molecules
1s a permissible change which can
occur when energy of near infrared
frequency strikes certain organic
molecules,

The atoms withina molecule are

held together by attractive bonding
forces, Atoms within a molecule
are constantly moving toward and
away from other atoms, but for

purposes of theory can be said to
have a certain "average" position,

The change 1n position of an atom
in relation to another atom 1s called
vibration, The mechanics of vibra-
tion require energy; the manner
and rate of vibration of the atoms
depend upon frequencies of electro-
magnetic radiation which strikes
them, Therefore, a specific part
of a molecule may absorb significant
quantities of certain spectral fre-
quencies. Such absorption will be
reflected in the absorption spectrum
of the compound, The energy re-
quirements for this type of energy
change are of a lower order of
magnitude than those above;
therefore, we would expect that the
frequency required wouldbe lower
and the wave length longer. Such
changes occur in organic com-
pounds under infrared radiation,

Rotation of molecules is a permis-
sible change which can occur when
energy of far infrared frequency
strikes certain organic molecules,

A molecule rotates around its sym-
metrical center, The manner and

rate of rotation again depends upon
the energy supplied to it.

Specific spectral frequencies of

electromagnetic radiation can be
employed to increase the rate of
rotation, The used radiation is,
in effect, absorbed and reflected
in the absorption spectrum.

Organic molecules utilize infra-
red radiation while varying their
rate and manner of rotation.

The Lambert-Beer Law provides the
basis for quantitative analysis by
absorption spectroscopy. It 1s a com-
bination of the Bouguer (or Bouguer-
Lambert) and Beer Laws,

1

Bouguer (or Bouguer-Lambert) Law

When a beam of monochromatic
radiation passes through an ab-

sorbing medium, each infinitesi-
mally small layer of the medium
decreases the intensity of the
beam by a constant fraction.

Mathematically
afew (6)

On integration and converting base
e to base 10 logarithms,

log = A=

-dI = increment by which in-
cident monochromatic
radiation 18 decreased
(or absorbed) by the
medium.

I = intensity of the radia-
tion emerging from the
absorbing medium,

k = proportionality constant
whose value depends on
the wave length and the
nature of the medium,

i,e., the solvent used
if the absorbing medi-
um is a solution , and
the temperature.

db = increment thickness of
the absorbing medium,


Flame Photometry,

50
c
°°
a
a
E
@
g
G
£
&
BS
| °
0 5 i: i)
x x x x
(Zt0) Gyre. 5) (Fs. 5) (tS)
Concentration-mg/1
Let x ® concentration of element in oy Oye St 3,5 (from the example in
unknown sample. Figure 4)
Then Y © % transmission of an equal by substitution, xo $+ 3.5
mixture of unknown sample .
and zero standard, or
Reais
773.
ye x48 which simplifies to 2¥ = x
x= 7 mg/l

Figure 4


Energy Sources for Atomic Absorption Spectroscopy

too close to those of another element, so that
spurious absorption signals can results, 1f
the second element 1s also present in the sample.

When three or more elements are combined in
alamp, itis also frequently true that the
emission from the individual elements 1s not
as bright as that from single-element lamps.
However, one chief advantage lies in the cost.
A multi-element lamp 1s not proportionately
as expensive as a single-element lamp. Also,
the curves of absorbance versus concentration
obtained with multi-element lamps may be less
lianear than those from single element sources,
particularly at hgh absorptions,

The operating current of a hollow cathode lamp
can be a critical parameter in optimizing an
atomic absorption measurement. Lamp
intensities and resulting absorbance in the
flame do not change linearly with operating
current. Typically high absorbance and good
signal-to-noise ratios are obtained at current
near one-third the maximum lamp currents,
Increasing the hollow cathode lamp current
will increase its output intensity, But sensi-
tivity is reduced through line broadening and/or
self reversal for some elements. Asa result,
we can expect better sensitivity at lower lamp
currents.

Most manufacturers will provide a rated max-
imum current beyond which the lamp should
not be operated. Any operation above this
current produces the danger of destruction of

this waitmg period, The use in some instru-
ments of multiple-lamp turret assembly
facilitates the operation of many lamps at
different operating currents to speed the time
of analysis by eliminating warm-up time when
lamps are changed. In single beam instruments
a multi-element lamp 18 attractive because

all its elements are ready when one element is
ready.

Lamp life is hard to estimate; however, most
manufacturers guarantee their lamps for a

use period of five ampere hours. When this
figure 18 divided by typical operating currents, .
the average guarantee extends to between 300
and 500 hours of use. In practice, most lamps
last a great deal longer. If lamps are not
used regularly, itis wise to operate them for
at least one hour per month on normal current
am order to reduce the possibility of fluctuation
when the lamp is finally put into-use.

I SUMMARY

In atomic absorption spectroscopy, the hollow
cathode lamp is perhaps the most important
component, The usefulness of a given analysis
depends directly on the brightness, spectral
purity and stability of the lamp. Also, the
economic feasibility of owning atomic absorption
equipment is often closely tied to hollow cathode
lamp life.

the cathode. It is best to follow the manufacturer's REFERENCES

suggested operational current when using its
lamp. If warm-up of the lamp is necessary, as
in a single beam spectrophotometer this can be
done at currents below the operating current,
bringing the lamp to proper current just before
use. Lamp current will affect lamp life.
Experimental data have shown that lamp life

is reduced by the square of the current increase.
Thus, lower lamp current can only improve

the performance and life of a hollow cathode
lamp.

Each hollow cathode lamp will have a different
warm-up time which can vary from 5 to 20
minutes. Use of a lamp in a single beam
instrument will require a warm-up time but

a double beam instrument does not require

1 Kahn, Herbert L. Principles and Practice
of Atomic Absorption, Advances in ,
Chemistry Series. Number 73. 1968.

2 Steensrud, S. A. Choosing an A. A.
Spectrophotometer. Research/Development.
August 1975.

3 Technical Bulletin. Varian Techtron. 1970.

4 Technical Bulletin. Perkin-Elmer, 1969,

5 Instrument Manual. Instrumentation
Laboratory, Inc.


Methodology for Chemical Analysis of Water and Wastewater

The results from the standards are used to
construct a calibration (standard) curve.
Then the absorbance value for the sample
1s located on this curve to determme the
corresponding concentration.

Many of the metals and several other
parameters (phosphorus, ammonia, nitrate,
mitrite, etc.) are determined in ths
manner.

VI GAS-LIQUID CHROMATOGRAPHY
Chromatography techniques involve a separa-
tion of the components in a mixture by using
a difference in the physical properties of the
components. Gas-Liquid Chromatography
(GLC) involves separation based on a differ~
ence in the properties of volatility and solu-
bility, The method 1s used to determine
algicides, chlorinated organic compounds
and pesticides,

The sample 1s introduced into an injector
block which 1s at a high temperature (e.g.
210°C), causing the liquid sample to volatilize.
An inert carrier gas transports the sample
components through a liquid held in place as

a thin film on an inert solid support material
an a column.

Sample components pass through the column

at a speed partly governed by the relative
solubility of each in the stationary liquid.

‘Thus the least soluble components are the

first to reach the detector. The type of
detector used depends on the class of compounds
involved, All detectors function to sense and
measure the quantity of each sample component
as 1t comes off the column, The detector
signals a recorder system which registers

a response.

As with other instrumental methods, standards
with known concentrations of the substance of
interest are measured on the instrument. A
calibration (standard) curve can be developed
and the concentration in a sample can be
determined from this graph.

Gas-lquid chromatography methods are very
sensitive (nanogram, picogram quantities) so
only small amounts of samples are required.
On the other hand, this extreme sensitivity
often necessitates extensive clean-up of
samples prior to GLC analysis.

2n4

VIL AUTOMATED METHODS

The increasing number of samples and
measurements to be made in water quality
laboratories has stimulated efforts to automate
these analyses. Using smaller amounts of
sample (semi-micro techniques), combining
reagents for fewer measurements per analysis,
and using automatic dispensers are all means
of saving analytical time.

However, the term "automated laboratory
procedures" usually means automatic intro-
duction of the sample into the instrument,
automatic treatment of the sample to test for

a component of interest, automatic recording
of data and, increasingly, automatic calculating
and print-out of data. Maximum automation
systems involve continuous sampling direct
from the source (e.g. an in-place probe) with
telemetering of results to a central computer.

Automated methods, especially those based on
colorimetric methodology, are recognized for
several water quality parameters including
alkalinity, ammonia, nitrate, nitrite, phosphorus,
and hardness.

VIIL SOURCES OF PROCEDURES

Details of the procedure for an individual

measurement can be found in reference books.
There are three particularly-recognized books
of procedures for water quality measurements

A Standard Methods‘)
The American Public Health Association,
the American Water Works Association
and the Water Pollution Contro] Federation
prepare and publish "Standard Methods for
the Examination of Water and Wastewater."

As indicated by the list of publishers, this
book contains methods developed for use by
those interested in water or wastewater .
treatment.

ASTM Standards(2) °

The American Society for Testing and
Materials publishes an "Annual Book of
ASTM Standards" containing specifications
and methods for testing materials. The
“book" currently consists of 47 parts.


Flame Photometry Laboratory (Sodium)

Percent Transmission Readings

Background Peak Difference

0.0 mg/1

2.0 mg/l

4.0 mg/1

6.0 mg/l

8.0 mg/l

10.0 mg/1

Sample



Determination of Mercury

vawe
nOTOMaTIR
SUNecANT
Thar
amaror
SYS1UH ONE. LIOUID TRAP cLOsID SYSTEM
vaue
— ro
reap RBIONPTION TUB
ROTOMETER
DESICCANT
ai
AERATOR

AERATOR

SYSTEM TWO - SOLID TRAP CLOSED SYSTEM

TRAP

ABTORPTION TUN

ROTOMETER

SYSTEM THREE - SOLID TRAP-DPEN SYSTEM

Figure 3, Flow Systems

9-5


DETERMINATION OF LEAD

1 INTRODUCTION

Lead (Pb) is a serious cumulative body poison;
it is well known for its toxicity in both acute
and chronic exposures. In technologically
developed countries the widespread use of lead
multiplies the risk of exposure of the population
to excessive levels, For this reason, constant
garveillance of the lead exposure of the general
population via food, air and water is necessary,

The presence of lead in water may arise from
industrial, mine and smelter discharges, or
from the dissolution of old lead plumbing.

Tap waters which are soft, acid, and not
suitably treated may contain lead resulting
from an attack on the lead service pipes.
Lake and river waters of the United States
usually contain less than 0.05 mg/1 of lead,
although concentrations in excess of this

have been reported, Young children present
a special case in lead intoxication both in
terms of tolerated intake and the severity of
the symptoms. The most prevalent source

of lead poisoning of children up to three years
of age has been lead-containing paint still
found in some older homes,

Because of the toxicity of lead to humans and
because there is little information on the
effectiveness of treatment processes in
decreasing lead concentrations, it has been
recommended that 0.05 mg/1 of lead not be
exceeded in public water supply sources.
This number then would tend to set the limit
for any analytical method which might be
under consideration for use in analyzing for
lead,

METHODS

The methods used to analyze for lead are,

in general, the same as those of any other
heavy metal, However, there is no method

for lead similar to the flameless method for
mercury, The method recommended by the
USEPA Methods manual is an atomic absorption
method utilizing a concentration:-of the lead
content by a chelating-extraction procedure,

CH. VE. pb. 5. 1.76

Other methods are available for those who
are not bound to use the USEPA method,

A Dithizone

This method has been used for many years
for the determination of many of the heavy
metals including lead, Dithizone dissolved
in carbon tetrachloride will extract lead
from a slightly basic (8,5 -9,0) solution,
The lead and dithizone form a metal complex,
lead dithizonate, which is soluable in carbon
tetrachloride, with the formation of a red
color. Measurement of the amount of red
color formed yields an estimation of the
lead present,

The method has sufficient sensitivity to
meet the standard limit of 0.05 mg/1,
Standard Methods gives the approximate
minimum detection limit in water as 2 yg
of Pb. The main drawback of the method

is in the many operations the analyst must
perform, The precision and accuracy of
the method can suffer greatly due to the
analyst's handling of the various operations.
Analysts with long experience with the
method have been able to produce acceptable
results,

The procedure for the dithizone method for
normal drinking waters, low in organic
matter and tin, is brief and adequate.
However, for industrial wastes and waters
containing high organic concentrations a
pretreatment step must be added, This
additional step is a digestion procedure,
either with a mixture of nitric and sulfuric
acide or, when the organic matter is difficult
to oxidize, with nitric and perchloric acids.
This procedure can introduce even more
error in loss of the metals during heating to
dryness and is even hazardous if not followed
closely,

B Other Instrumental Methods
There are other instrumental methods

available even when atomic absorption is
excluded. These methods would include

10-1


| Methodology for Chemical Analysis of Water and Wastewater

C Uses

Even though the results of field tests are
usually not as accurate and precise as those
performed in the laboratory, such tests do
have a place in water quality programs.

In situations where only an estimate of the
concentrations of various constituents is
required, field tests serve well, They are
invaluable sources of information for
planning a full-scale sampling /testing
program when decisions must be made
regarding location of sampling sites,
schedule of sample collection, dilution of
samples required for analysis, and treat-
ment of samples required to remove inter-
ferences to analyses.

REFERENCES

1 Standard Methods for the Examination of
Water and Wastewater, 13th Edition,
1971, APHA-AWWA-WPCF, 1790
Broadway, New York, NY 10019.

2 1974 Annual Book of ASTM Standards,
Part 31, Water, ASTM, 1916 Race
Street, Philadelphia, PA 19103,

3 Methods for Chemical Analysis of Watér

and Wastes. 1974, U. S. EPA, EMSL,
Cincinnati, OH 45268.

Analytical Quality Control un Water and
Wastewater Laboratories. 1972. U. S. EPA,
EMSL, Cincinnati, OH 45268.

This outline was prepared by A. E. Donahue,
Chemist, National Training Center, MPOD,.
OWPO, USEPA, Cincinnati, Ohio 45268,

Descriptors, Analysis, Chemical Analysis,
Methodology, Wastewater, Water Analysis

2-7