Methods for Analysis of

Selected Metals in

Water by Atomic Absorption

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1540-C
Methods for Analysis of 

oelected Metals in 

"Vater by Atomic Absorption

F/ MARVIN J. FISHMAN and SANFORD C. DOWNS

SPECTROGRAPHIC ANALYSIS OF NATURAL WATER

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1540-C

A manual of procedures for determining calcium, copper, lithium,magnesium, 

manganese, potassium, sodium, strontium, and zinc in atmospheric precipitation, fresh waters, and brines by atomic 

absorption spectroscopy

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1966
UNITED STATES DEPARTMENT OF THE IFTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

WUliam T. Pecora, Director

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402 - Price 15 cents (paper cover)
CONTENTS

Page

Abstract. _________.__________________________ 23

Introduction. _____________________________________________________ 23

Principle of atomic absorption______________________________________ 24

Instrumentation_ ________________________________________________ 24

Special analytical techniques standard-addition method______________. 25

Analytical procedures______________________________________________ 26

Calcium______________________________________ 26

Copper_-________-_-_____-____________________________________ 28

Lithium.____________________________________ 30

Magnesium. __________________________________________________ 32

Manganese.--------_-_-_-_-_---_---_-_-----_-___-_-___---_--_ 35

Potassium ____________________________________________________ 36

Sodium. ____________________________.______ 38

Strontium.___________________________________________________ 41

Zinc..______________________.______________ 43

References _____________________________________________________ 45

ILLUSTRATIONS

Page 

FIGURE 3. Schematic diagram of Perkin-Elmer Model 303 atomic aHorpspectrophotometer optical system _______________________ 25

4. Diagram showing example of standard-addition method._____ 26

nz

SPECTROGRAPHIC ANALYSIS OF NATURAL WATER

METHODS FOR ANALYSIS OF SELECTED METALS 

IN WATER BY ATOMIC ABSORPTION

By MARVTN J. FISHMAN and SANFORD C. DOWNS

ABSTRACT

This manual describes atomic-absorption-spectroscopy methods for determining 

calcium, copper, lithium, magnesium, manganese, postassium, sodium, strontium, 

and zinc in atmospheric precipitation, fresh waters, and brines. The procedures 

are intended to be used by water quality laboratories of the Water Resources 

division of the U.S. Geological Survey. Detailed procedures, calculations, and 

methods for the preparation of reagents are given for each element along with 

data on accuracy, precision, and sensitivity. Other topics discussed briefly are 

c.he principle of atomic absorption, instrumentation used, and special analytical 

techniques.

INTRODUCTION

The purpose of this manual is to describe atomic-absorptior methods 

of water analysis to be used by water quality laboratories of the "Water 

Resources Division of the U.S. Geological Survey and to standardize 

procedures by serving as a guide for laboratory personnel. The procedures in this manual are applicable to the analysis of most natural 

-vaters, and some of them are applicable to the analysis of brines. If a 

particular element can be determined in a brine and if sufficient data 

"o support this determination are available, the individual procedure is 

discussed. Determinations of other elements that cannot be supported 

by current data are not discussed. Because atomic absorption permits 

~Tery low detection limits, precipitation waters can be analyzed readily 

by the procedures presented. Most of the procedures in this manual 

'-ere adapted from the Perkin-Elmer instruction manual (1964). 

" lodifications have been made where necessary to adapt the procedures 

"o water analysis. Additional information may be obtained from the 

manufacturer's manual.

The use of trade names of equipment, supplies, and reagents in this 

manual does not constitute endorsement. It is done only in iha< interest 

of standardization.

23
24 SPECTROGRAPHIC ANALYSIS OF NATURAL WATER 

PRINCIPLE OF ATOMIC ABSORPTION

It has been known for more than a hundred years that atoms of some 

elements are excited when vaporized and fed into a flame. As these 

atoms return to their ground state, they emit radiation of characteristic 

measurable wavelengths. This principle is the basis for flameemission photometry.

Most elements are not easily excited in a flame, and most of the atoms 

remain in the ground state. These unexcited atoms can absorb energy 

from a beam of light of the same characteristic wavelength. The beam 

of light from a hollow-cathode lamp made of the metal being determined was used by Walsh (1955) to develop atomic-absorption instrumentation. He found that a source of radiation of the same wavelength as that of the absorption line puts less demand upon the 

resolution of the monochromator than a source of broadband radiation. 

Since the wavelength of the light beam is characteristic of only the 

metal being determined, the light energy absorbed by the flame is a 

measure of the concentration of that metal in the sample. This 

principle is the basis of atomic absorption spectroscopy.

INSTRUMENTATION

Several manufacturers currently supply atomic-r.bsorption equipment. Among them are Jarrell-Ash, Beckman, Aztec, Hilger and 

Watts, Unicam, and Perkin-Elmer. Instruments offered by these 

manufacturers differ in design.

The selection of a given commercial product is based largely upon its 

design, durability, cost, and maintenance requirements, but also on 

standardization of equipment in all water quality laboratories of the 

"\Vater Kesources Division of the U.S. Geological Survey. Experience gained in individual laboratories, is evaluated, and the results are 

used by other laboratories.

A schematic diagram of the Perkin-Elmer optical system is shown in 

figure 3. The energy or light beam from the source, either a hollowcathode or vapor-discharge lamp, is divided by a rotating chopper into 

a reference beam and a sample beam. The water sample is aspirated 

into an atomizer-burner, and part of the sample beam passing through 

the flame is absorbed, the amount depending upon the concentration 

of the metal being determined. The remainder of the sample beam is 

recombined with the reference beam by a semitransparent mirror. 

The analytical wavelength of the metal being analyzed is isolated from 

all other energy in the light beam by a grating monochromator. Two 

gratings are mounted back to back one for the ultraviolent region 

and the other for the visible region. The extent to which the energy 

of the characteristic emission wavelength of the source lamp is
METHODS FOR ANALYSIS OF METALS BY ATOMIC ABSORPTION 25

n . .. , Reference beam Rotating chopper

Hollow-cathode lamp

/7/lt

Sample in Fuel in 

Atomizer-burner

Slits 

Photodetector

FIGURE 3.-

Electronics and readout

-Perkin-Elmer Model 303 atomic absorption spectrophotometer optical system. 

Reprinted by permission of Perkin-ELmer Corp.

absorbed in the flame is measured by a photodetector. The signal 

from the photodetector is amplified and fed into circuitry that produces 

a manual electronic null in combination with a digital readout which 

corresponds to the concentration of the metal being determined.

By varying the relative proportions of fuel and air in the atomizerburner, an oxidizing (air-rich) or a reducing (fuel-rich) flame is produced. The type of flame to be used depends upon the metal being 

analyzed. An oxidizing flame is preferable because of its greater 

stability. However, some metals tend to form refractory oyides in an 

oxidizing flame, and a reducing flame is necessary to increase the number of atoms available for absorption. The type of flame to be used 

is stated in each procedure under the operating conditions.

SPECIAL ANALYTICAL TECHNIQUES 

STANDARD-ADDITION METHOD

The standard-addition technique is used when the solids content of 

the sample is so high that its affect on absorption is difficult to duplicate 

with the aqueous standards or when an interference is present which 

cannot be corrected.

Equal volumes of the sample are added to a blank (distilled water) 

and to three standards containing different known quantities of the test 

element. The blank and standards must first be diluted tc the same 

volume. The percentage of absorption of each solution is determined 

and converted to the corresponding absorbance unit. Absorbance is 

then plotted against concentration on a graph, and the resulting line is 

extended back through zero absorbance. The intercept on the concentration axis is the concentration of the metal in the original sample.
26 SPECTROGRAPHIC ANALYSIS OF NATURAL WATER

The line should preferably be straight to insure accurate analyses, 

example of the standard-addition technique is shown in figure 4.

An

Extrapolate

4 20246 

In sample Added 

Concentration, in milligrams per liter 

FIGURE 4. Example of standard-addition method.

ANALYTICAL PROCEDURES

A Perkin-Elmer Model 303 atomic absorption sp^ctrophotometer 

was used to determine each metal.

CALCIUM 

DISCUSSION OF METHOD

A hollow-cathode lamp and a reducing flame are used to determine 

calcium. Phosphate, sulfate, and aluminum interfere but are masked 

by the addition of a 1-percent lanthanum solution to the sample. Low 

calcium values result if the pH of the sample is above 7; therefore, 

both standards and samples are prepared in 5-percent hydrochloric 

acid solution. Magnesium in concentrations higher than 1,000 ppm 

(parts per million) also causes low calcium values. Concentrations 

of up to 500 ppm each of sodium, potassium, and nitrate show no 

interference.

The 4227 A (angstrom) line is used to determine concentrations of 

calcium less than 20 mg per 1 (milligrams per liter). For concentrations of calcium greater than 20 mg per 1, dilution i? required. The 

calcium lamp is extremely quiet, and the results of the method are
METHODS FOR ANALYSIS OF METALS BY ATOMIC ABSORPTION 27

accurate and reproducible to ±0.1 mg per 1 for concentrations of calcium less than 20 mg per 1 and to ±0.2 ±1.0 mg per 1 for concentrations of calcium from 20 to 200 mg per 1. When excessive dilution is 

required, the accuracy and reproducibility are decreased. There is 

excellent agreement between results obtained by atomic absorption and 

by EDTA J titration.

The sensitivity for calcium concentrations of less than 20 mg per 

1 ranges from 0.15 to 0.30 mg per 1 per 1 percent absorption. With 

scale expansion concentrations of calcium less than 1 mg per 1 can be 

determined with an accuracy of ±0.01 mg per 1.

APPARATUS

Grating: Visible

Wavelength counter: 211.4 (4227 A)

Scale: 1 X

Slit: 5 (3mm,40 A)

Source: Calcium hollow-cathode lamp

Lamp current: 10 ma (milliampere)

Air pressure: 28 psi (pounds per square inch); 8.0 on flowmeter

Fuel: Acetylene. Pressure: 8 psi; 9.0 on flowmeter initially (use a

10 mg calcium per liter standard solution and adjust acetylene

flow rate to obtain maximum absorption) 

Flame: Reducing

Sample uptake: About 4 ml per min (milliliters per minute) 

The following absorption readings have been observed:

Calcium concentration,

mg per I Absorption, percent

5.0 ________________________________ 26. 4 

10__________________________________ 43. 6 

15_________________________________ 54. 4

20____________________ 6i. e

REAGENTS

Calcium chloride standard stock solution, 1.00 ml=0.50 mg calcium: 

Suspend 1.250 g CaCO3 , dried at 180°C for 1.0 hour before weighing, 

in distilled water and dissolve cautiously with a minimum of dilute 

HC1. Dilute to 1,000 ml with distilled water.

Calcium chloride standard working solutions: Prepare a series of 

standard solutions containing from 0 to 20 mg calcium per liter by 

diluting the CaCl2 standard stock solution. Add 1.0 ml of LaCl3- 

HC1 solution to each 10.0 ml working standards prepared. For 

example, to 500 ml of a working standard, add 50 ml LaCl3-HCl 

solution.

1 Ethylenediaminetetraacetic acid. 

223-850 66 2
28 SPECTROGRAPHIC ANALYSIS OF NATURAL YTATER

Lanthanum chloride-hydrochloric acid solution: Dissolve 58.65 g of 

La2O3 , slowly and in small portions, in 250 ml concentrated HC1 

(CAUTION! Reaction is violent) and dilute to 500 ml with distilled water.

PROCEDURE

1. Filter the sample (0.45/x (micron) micropore membrane filter) 

when necessary to avoid clogging the atomizer-burner.

2. Add 1.0 ml of LaCl3-HCl solution to 10.0 ml of sample.

3. Atomize each sample and standard, and record the percent absorption observed. Repeat, and average the two values. If the 

calcium concentration is greater than 20 mg per 1, the sample 

must be diluted. Be sure that the diluted sample contains the 

proper amount of LaCl3-HCl solution.

CALCULATIONS

1. Convert percent absorption to absorbance and determine the calcium 

concentration in the sample from a plot of absorbances of standards. For samples containing more than 20 mg calcium per liter, 

multiply by the proper dilution factor. Exact reproducibility is 

not obtained, and a working curve must be prepared with each 

set of samples.

2. ppm calcium=-T r X mg calcium per liter.

Report calcium concentrations less than 10 ppm to the nearest 

0.1 ppm, those between 10 and 200 ppm to the nearest whole 

number, and those greater than 200 ppm to two significant figures.

COPPER 

DISCUSSION OF METHOD

A hollow-cathode lamp operating at 3247 A is used to determine 

copper. Allow the lamp to warm up for about 30 minutes at a current 

of 15 ma before use.

Cations and anions normally found in water do not interfere. To 

determine copper concentrations less than 1.0 mg per 1, 10 X scale expansion is used, and the results are accurate and reproducible to 

approximately ±0.02 mg of copper per liter. Concentrations of 

copper greater than 1.0 mg per 1 can be determined by using less scale 

expansion. The maximum copper concentration that can be determined at the 3247 A line without dilution is approximately 20 mg 

peri.

The sensitivity for copper concentrations of less th?,n 1.0 mg per 1 

is approximately 0.02 mg per 1 for each scale division.
METHODS FOR ANALYSIS OF METALS BY ATOMIC ABSORPTION 29

APPARATUS

Grating: Ultraviolet 

Wavelength counter: 324.7 (3247 A) 

Scale: 10 X 

Slit:4 (1mm,6.5 A) 

Source: Copper hollow-cathode lamp 

Lamp current: 15 ma, or optimum operating current 

Air pressure: 28-30 psi; 9.0 on flowmeter (varies with different flowmeters and burners)

Fuel: Acetylene. Pressure: 8 psi; 9.0 on flowmeter 

Flame: Oxidizing 

Sample uptake: 2-5 ml per min 

Response-time control: 1 

The following readings have been observed:

Copper concentration,

mg per I Scale reading

0.10 ______________________________ 5. f

.20 ______________________________ 11. f

.50 ____________________________ 31. P

.80 ____________________________ 50.9

1.00 ___________________________ 63. T

REAGENTS

Copper nitrate standard solution 1,1.00 ml=1.00 mg copper: Dissolve 

1.00 g metallic copper in a slight excess of dilute HNO3 , and dilute 

to 1,000 ml with metal-free water.

Copper nitrate standard solution II, 1.00 ml=0.005 mg copper: Dilute 

5.00 ml Cu(NO3 ) 2 standard solution I to 1,000 ml with metal-free 

water containing one or two drops of concentrated HND3 .

Copper nitrate standard working solutions: Prepare a series of standard solutions containing from 0.00 to 1.0 mg copper per liter by 

diluting the Cu (NO3 ) 2 standard solution II.

PROCEDURE

1. Filter the sample (0.45ju, micropore membrane filter) when necessary to avoid clogging the atomizer-burner.

2. Atomize each sample and standard, and record the scale readings 

observed. Repeat, and average the two values.

CALCULATIONS

1. Determine the copper concentration in the sample fron a plot of 

scale readings of standards. Because a scale expansion of 10 X is 

used, scale readings need not be converted to absorbance. Exact 

reproducibility is not obtained, and a working curve must be 

prepared with each set of samples.
30 SPECTROGRAPHIC ANALYSIS OF NATURAL WATER

2. ppm copper= ; ^ X nig copper per liter.

Keport copper concentrations less than 1.0 ppm to the nearest 

0.01 ppm, and those greater than 1.0 ppm to two signficant figures.

LITHIUM 

DISCUSSION OF METHOD

A hollow-cathode lamp is used to determine lithium. The lamp current must be high enough to prevent excessive noise; 20 ma is suggested, although some lamps may require less. Higher currents are 

not recommended because the cathode will begin to melt at about 25- 

28 ma.

Concentrations of up to 1,000 ppm sodium, 100 ppm potassium, 200 

ppm magnesium, 200 ppm calcium, 1,500 ppm chloride, 2,000 ppm 

sulfate, and 100 ppm nitrate do not interfere. Strontium, at 

concentrations greater than 5 ppm, interferes.

The 6708 A line is used to determine lithium. Since the detection 

limit is 0.005 mg per 1 or less, three working curves ar3 recommended 

to cover the concentration range 0-10 mg lithium per liter. For the 

working curve 0.00-0.10 mg lithium per liter, results are accurate and 

reproducible to approximately ±0.002 mg per 1; between 0.1 and 1.0 

mg lithium per liter to ±0.01 mg per 1; and between 1.0 and 10 mg 

lithium per liter, to ±0.1 mg per 1. There is excellent agreement between lithium concentrations determined by both the atcmic-absorption 

and the flame-photometric methods (Beckman DU flame photometer).

The sensitivity for lithium concentrations of less than 0.1 mg per 1 

is approximately 0.005 mg per 1 for each scale division; for those between 0.1 and 1.0 mg lithium per liter, approximately 0.01 mg per 1 for 

each scale division; and for those greater than 1.0 mg per 1, approximately 0.1 mg per 1 per 1 percent absorption. The method is applicable to both fresh waters and brines. Brines must be diluted to 

concentrations of 15,000 ppm or less total dissolved solids.

APPARATUS

Concentration range: 1.0-10 mg lithium per liter 

Grating: Visible

Wavelength counter: 335.4 (6708 A) 

Scale :1 X 

Slit:5 (3mm,40A) 

Source: Lithium hollow-cathode lamp 

Lamp current: 20 ma maximum

Air pressure: 28 psi; 9.0 on flowmeter (varies with different flowmeters and burners) 

Fuel: Acetylene. Pressure: 8 psi; 9.0 on flowmeter
METHODS FOR ANALYSIS OF METALS BY ATOMIC ABSOPPTION 31

Flame: Oxidizing 

Sample uptake: About 4 ml per min 

Response-time control: 1 

The following absorption readings have been observed:

Lithium concentration,

mgperl Absorption, percent

2.0_________________________________ 28.0 

4.0________________________________ 47.8 

6.0________________________________ 59-6 

8.0________________________-______ 67.4 

10 ________________________________ 73.5

Concentration range: 0.1-1.0 mg lithium per liter. 

Scale: 5 X 

All other operating conditions the same as used for concentration

range from 1.0 to 10 mg lithium per liter. 

The following readings have been observed:

Lithium concentration,

mg per I Scale reading

0.25_________________________________ IP 5 

.50________________________________ 37.2 

.76______________________________ 54.0

1.0_________________________________ 74.2

Concentration range: 0.00-0.10 mg lithium per liter. 

Scale: 10 X 

All other operating conditions the same as used for concentration

range from 1.0 to 10 mg lithium per liter. 

The following readings have been observed:

Lithium concentration,

mg per I Scale reading

0.01__________________________________ £.0 

.05_________________________________ £.4 

.10________________________________ 1P.7

REAGENTS

Lithium nitrate standard stock solution, 1.00 ml = 1.00 mg lithium: 

Dissolve 9.9357 g LiNO3 in demineralized water and dilute to 1,000 

ml.

Lithium nitrate standard working solutions: Prepare a series of standard solutions containing from 0 to 10 mg lithium per lite r by diluting 

the LiNO3 standard stock solution.

PROCEDURE

1. Filter the sample (0.45j« micropore membrane filter) when necessary to avoid clogging the atomizer-burner.

2. Atomize each sample and standard, and record the percent absorption or scale reading observed. Repeat, and average the two 

values. If the lithium concentration is greater than 10 mg per 1, 

the sample must be diluted.
32 SPECTROGRAPHIC ANALYSIS OF NATURAL WATER

CALCULATIONS

1. Concentration range 1.0-10 mg lithium per liter: Convert percent 

absorption to absorbance, and determine the lithium concentration 

in the sample from a plot of absorbances of standards. For 

samples containing more than 10 mg lithium per liter, multiply 

by proper dilution factor.

2. Concentration ranges 0.10-1.0 mg lithium per liter and 0.00-0.10 mg 

lithium per liter: Determine the lithium concentration in the 

sample from a plot of scale readings of standards. Because scale 

expansion's of 5 X and 10 X are used, scale readings need not be 

converted to absorbance.

3. ppm lithium = = =- X mg lithium per liter.

 7

Report lithium concentrations less than 0.10 ppm to the nearest 

0.005 ppm, those between 0.10 and 1.0 ppm to the nearest 0.01 ppm, 

those between 1.0 and 10 ppm to the nearest 0.1 ppm, and those 

greater than 10 ppm to whole numbers.

MAGNESIUM 

DISCUSSION OF METHOD

A hollow-cathode lamp and a reducing flame are used to determine 

magnesium. Two magnesium lines one at 2852 A, and the groundstate line at 2025 A are employed to avoid excessive dilution of 

samples. Aluminum, in concentrations greater than 2 ppm, interferes 

at both lines; sulfate and phosphate interfere at the 2025 A line. 

These interferences, however, are masked by the addition of approximately 1 percent lanthanum. Low magnesium values result if the pH 

of the sample is above 7; therefore, both standards and samples are 

prepared in 5-percent hydrochloric acid solution. Sodium, potassium, 

and calcium, in concentrations less than 400 ppm, show no interference. 

There is also a, zinc line at 2025 A, but 2 ppm zinc shows no interference.

The 2852 A line is used to determine concentrations of magnesium 

less than 2 mg per 1. Magnesium concentrations of 2-10 mg per 1 are 

determined using the same line by dilution of the sample. The 2025 A 

line is used to determine magnesium concentrations between 10 and 50 

mg per 1. To determine magnesium concentrations greater than 50 

ing per 1, dilution is required.

For magnesium concentrations of less than 10 mg per 1, results are 

accurate and reproducible to ±0.1 mg per 1, and with extreme care the 

results are accurate and reproducible to ±0.02 mg per 1 at concentrations less than 2 mg per 1 without scale expansion. The results are 

accurate and reproducible to ±1 mg per 1 for concentrations of mag-
METHODS FOR ANALYSIS OF METALS BY ATOMIC ABSORPTION 33

nesium between 10 and 50 mg per 1. When dilution is required, for 

samples containing more than 50 mg per 1, the accuracy and reproducibility are decreased. There is excellent agreement between results 

obtained by atomic absorption and those obtained by EDTA titration 

for samples containing 10-50 mg magnesium per liter.

The sensitivity for magnesium concentrations of less than 2 mg per 1 

is approximately 0.03 mg per 1 per 1 percent absorption. For the 10- 

50 mg magnesium per liter range, the sensitivity is approximately 1 

mg per 1 per 1 percent absorption.

APPARATUS

Concentration range: 0-10 mg magnesium per liter (samples containing more than 2 mg magnesium per liter must be diluted)

Grating: Ultraviolet

Wavelength counter: 285.2 (2852 A)

Scale: 1 X

Slit: 5 (3 mm, 20 A)

Source: Magnesium hollow-cathode lamp

Lamp current: 10 ma

Air pressure: 28 psi; 8.0 on flowmeter

Fuel: Acetylene. Pressure: 8 psi; 9.0 on flowmeter initially (use 

a 1 mg magnesium per liter standard solutior, and adjust 

acetylene flow rate to obtain maximum absorption)

Flame: Reducing

Sample uptake: About 4 ml per min 

The following absorption readings have been observed:

Magnesium concentration,

mg per I Absorption, percent

0.5 _________________________________ 20.2 

1.0 ________________________________ 35.6

1.5 ________________________________ 48.3 

2.0 ______________________________ 58.8

Concentration range: 10-50 mg magnesium per liter 

Wavelength counter: 202.5 (2025 A) 

Response-time control: 1 

All other operating conditions same as used for concentration

range 0-10 mg magnesium per liter. 

The following absorption readings have been observed:

Magnesium concentration,

mg per I Absorption, percent

10__________________________________ 14.0 

25_________________________________ 29.8 

50_________________________________ 46.0
34 SPECTROGRAPHIC ANALYSIS OF NATURAL WATER

REAGENTS

Lanthanum chloride-hydrochloric acid solution: Dissolve 58.65 g of 

La2O3 , slowly and in small portions, in 250 ml concentrated HC1 

(CAUTION! Reaction is violent) and dilute to 503 ml with distilled 

water.

Magnesium chloride standard stock solution, 1.00 ml=0.50 mg 

magnesium: Dissolve 0.500 mg pure metallic magnesium in a minimum amount of dilute HC1 and dilute to 1,000 nil with distilled 

water.

Magnesium chloride standard working solutions: Prepare a series of 

standard solutions containing from 0 to 50 mg mrgnesium per liter 

by diluting the MgCL standard stock solution. £ dd 1.0 ml LaCl3- 

HC1 solution to each 10.0 ml of the working standards prepared. 

For example, to 500 ml of a working standard, add 50 ml LaCl 3- 

HC1 solution.

PROCEDURE

1. Filter the sample (0.45 /u micropore membrane filter) when necessary to avoid clogging the atomizer-burner.

2. Add 1.0 ml of LaCl3-HCl solution to 10.0 ml of sample.

3. Atomize each sample and standard, and record the percent absorption observed. Repeat, and average the two values. If the 

magnesium concentration is greater than 50 mg per 1, the sample 

must be diluted. Be sure that the diluted sample contains the 

proper amount of LaCl3-HCl solution.

CALCULATIONS

1. Convert percent absorption to absorbance, and determine the magnesium concentration in the sample from a plot of absorbances 

of standards. For samples containing more than 2 mg magnesium per liter (0-2 mg magnesium per liter working curve) 

or more than 50 mg magnesium per liter (10-50 mg magnesium 

per liter working curve) multiply by the proper dilution factor. 

Exact reproducibility is not obtained, and working curves must 

be prepared with each set of samples.

2. ppmmagnesium=^j r X mg magnesium per liter.

Report magnesium concentrations less than 10 ppm to the nearest 

0.1 ppm, those between 10 and 200 ppm to the nearest whole 

number, and those greater than 200 ppm to two significant figures.
METHODS FOR ANALYSIS OF METALS BY ATOMIC ABSORPTION 35

MANGANESE 

DISCUSSION OF METHOD

A hollow-cathode lamp is used to determine manganese, and the 

lamp should be allowed to warm up for about 30 minutes before use. 

The optimum current may differ slightly for different lamps. However, currents greater than the maximum stated on the lamp should 

not be used because the cathode may melt.

The 2795 A line is used to determine manganese. Although there 

are two iron lines and a magnesium line near this line, concentrations 

of up to 25 ppm iron, 100 ppm magnesium show no interference. Magnesium in concentrations greater than 100 ppm interferes when the 

manganese concentration exceeds 0.50 ppm. However, magnesium 

does not interfere when other cations, such as sodium, are present in 

the sample. Other cations and anions normally found in water do 

not interfere.

To determine manganese concentrations of less than 1.0 mg per 1, 

10 X scale expansion is used. Results are accurate and reproducible 

to approximately ±0.02 mg manganese per liter. Concentrations 

greater than 1.0 mg per 1 are determined directly by using less scale 

expansion. The maximum concentration that can be determined at 

the 2795 A line without dilution is about 25 mg manganese per liter.

The sensitivity for manganese concentrations of less than 1.0 mg 

per 1 is approximately 0.02 mg per 1 for each scale division.

APPARATUS

Grating: Ultraviolet

Wavelength counter: 279.5 (2795 A)

Scale: 10 X

Slit: 4(1 mm, 6.5 A)

Source: Manganese hollow cathode lamp

Lamp current: 10-15 ma

Air pressure: 28 psi; 9.0 on flowmeter (varies with different flowmeters

and burners)

Fuel: Acetylene. Pressure: 8 psi, 9.0 on flowmeter 

Flame: Oxidizing 

Sample uptake: 3-5 ml per min 

Response-time control: 1 

The following readings have been observed:

Manganese concentration,

mg per I Scale reading

0.25 ______________________________ 17.3

.50 ____________________________ 33.7

.75 ____________________________ 49.5

1.00 ____________________________ 66.9
36 SPECTROGRAPHIC ANALYSIS OF NATURAL WATER

REAGENTS

Manganous sulfate standard solution 1,1.00 ml=0.10') mg manganese: 

Heat 0.5 g MnSO4 -H2O for 1 hour at 180° C. Dissolve 0.2749 g in 

demineralized water containing 1 ml concentrated H2S(X (specific 

gravity 1.84). Add 2.0 ml formalin to inhibit mold growth, and 

dilute to 1,000 ml with demineralized water.

Manganous sulfate standard solution II, 1.00 ml= 0.010 mg manganese: Immediately before use, dilute 10 ml of MnSO4 standard solution I to 100 ml with demineralized water.

Manganous sulfate standard working solutions: Prepare a series of 

standard solutions containing from 0.00 to 1.0 mg manganese per 

liter by diluting the MnS04 standard solution II.

PROCEDURE

1. Filter the sample (0.45 ju. micropore membrane filter) when necessary 

to avoid clogging the atomizer burner.

2. Atomize each sample and standard, and record the scale reading 

observed. Repeat, and average the two values.

CALCULATIONS

1. Determine the manganese concentration in the sample from a plot 

of scale readings of standards. Because a scale expansion of 10 X 

is used, the scale readings need not be converted to absorbance. 

Exact reproducibility is not obtained, and a working curve must 

be prepared with each set of samples.

2. ppm manganese= ^ - X mg manganese per liter.

Report manganese concentrations less than 1.0 ppm to the nearest 

0.01 ppm and those greater than 1.0 ppm to two significant 

figures.

POTASSIUM

DISCUSSION OP METHOD

A vapor-discharge lamp operating at 350 ma is used to determine 

potassium. Some lamps may require a source current of 500 ma if the 

potassium arc is unstable, if absorption values are low, or if there is 

excessive noise. Additional current often produces considerably more 

light, and a smaller slit width may be required.

The 7665 A line is used to determine potassium. Oily sodium interferes, and approximately equivalent amounts of sodium must be 

present in both standards and samples. At any given sodium concentration up to 1,000 mg per 1, the actual sodium concentration may vary
METHODS FOR ANALYSIS OF METALS BY ATOMIC ABSORPTION 37

by as much as ±50 nig per 1 without a significant effect on the amount 

of potassium observed. Therefore, 200 ing sodium per liter is added 

to each standard, and each sample is so prepared that its sodium concentration is between 150 and 250 nig per 1. Results are accurate and 

reproducible to ±0.1 nig per 1 for potassium concentrations of less 

than 10 mg potassium per liter, and to ±0.1-±1.0 mg per 1 for concentrations of potassium from 10 to 100 mg per 1. When excessive dilution is required, the accuracy and reproducibility are decreased. 

With scale expansion, results are accurate and reproducible to ±0.01 

mg per 1 for potassium concentrations of less than 1 mg per 1.

The sensitivity for potassium concentrations of less than 10 mg 

per 1 is approximately 0.1 mg per 1 per 1 percent absorption.

The atomic absorption method is applicable to a wide range of potassium concentrations, such as traces in rainwater and as much as 7,000 

mg per 1 in brines. For samples containing concentrations of potassium greater than 10 mg per 1, dilution is required.

APPARATUS

Grating: Visible

Wavelength counter: 383.2 (T665 A)

Scale: 1 X

Slit: 5 (3 mm,40 A)

Source: Osram potassium-vapor-discharge lamp

Lamp current: 350 ma, or optimum operating current

Air pressure: 28 psi; 9.0 on flowmeter (varies with different flowmeters

and burners)

Fuel: Acetylene. Pressure: 8 psi; 9.0 on flowmeter 

Flame: Oxidizing 

Sample uptake: About 4 ml per min 

The following absorption readings have been observed:

Potassium concentration,

mg per I Absorption, percent

2.0_________________________________ 21.5 

4.0_________________________________ 37.2 

6.0________________________________ 48.7 

8.0________________________________ 57.3 

10 ______________________________ 63.3

REAGENTS

Potassium chloride standard stock solution, 1.00 ml=0.10 mg potassium : Dissolve 0.1907 g KC1 in demineralized water and dilute to 

1,000 nil.

Potassium chloride standard working solutions: Prepare a series of 

standard solutions containing from 0 to 10 nig potassium and 200 mg 

sodium per liter by diluting the potassium standard stock solution 

and the NaCl standard stock solution.
38 SPECTROGRAPHIC ANALYSIS OF NATURAL WATER

Sodium chloride standard stock solution, 1.00 ml=1.00 mg sodium: 

Dissolve 2.542 g NaCl in demineralized water and cUlute to 1,000 ml.

PROCEDURE

1. Filter the sample (0.45 p. micropore membrane filler) when necessary to avoid clogging the atomizer-burner.

2. Adjust the sodium concentration of each sample to between 150 and 

250 mg per 1 by adding the calculated volume of the NaCl standard 

stock solution.

3. Atomize each sample and standard, and record the percent absorption observed. Repeat, and average the two values. If the concentration is greater than 10 mg per 1, the sample must be diluted. 

Be sure that the diluted sample contains between 150 and 250 mg 

sodium per liter.

CALCULATIONS

1. Convert percent absorption to absorbance, and determine the potassium concentration in the sample from a plo*, of absorbances 

of standards. For samples containing more than 10 mg potassium per liter, multiply by the proper dilution factor. Also, if 

the sample was adjusted to contain between 150 and 250 mg 

sodium per liter, multiply by the proper dilution factor. Exact 

reproducibility is not obtained, and a working curve must be 

prepared with each set of samples.

2. ppm potassium= -^ r- X mg potassium per liter.

Report potassium concentrations less than 10 ppm to the nearest 

0.1 ppm, those between 10 and 1,000 ppm to the nearest whole 

number, and those greater than 1,000 ppm to three significant 

figures.

SODIUM

DISCUSSION OF METHOD

A vapor-discharge lamp is used to determine sodium. The exact slit 

width and lamp current differs with the lamp used. The lamp current 

should be increased until the color of the arc is the characteristic yellow 

orange of the sodium discharge. Additional current often produces 

considerably more light and a smaller slit width may be required; a 

decrease in current has the opposite effect.

To avoid excessive dilution of the sample, two sodium lines are used. 

For waters containing less than 10 mg sodium per liter, the 5890 A line 

is used, and for those containing more than 10 mg per 1, the weaker 

resonance line at 3302 A is used. Two working curves are prepared
METHODS FOR ANALYSIS OF METALS BY ATOMIC ABSORPTION 39

for the 3302 A line: one for the sodium concentration range 6-60 mg 

per 1, and another for the range 40-200 mg sodium per liter.

Other elements found in water do not interfere, and the results are 

accurate and reproducible to ±0.1 mg per 1 for sodium concentrations 

of less than 10 mg per 1, and to rtl-=t2 mg per 1 for sodium concentrations between 10 and 200 mg per 1.

The sensitivity for sodium concentrations of less than 10 mg per 1 is 

approximately 0.05 mg per 1 per 1 percent absorption; for concentrations between 10 and 40 mg per 1, approximately 1 mg per 1 for each 

scale division; and concentrations greater than 40 mg per 1, rJbout 3 mg 

per 1 for each scale division.

The atomic absorption method is applicable to a wide range of 

sodium concentrations from traces in rainwater and to 100,000 mg 

per 1 in brines. For samples containing more than 200 mg per 1, 

dilution is required.

APPARATUS

Concentration range: 0.0-10 mg sodium per liter 

Grating: Visible

Wavelength counter: 294.4 (5888 A) 

Scale: 1 X

Slit:3 (0.3mm,4.0A)

Source: Osram sodium-vapor discharge lamp 

Lamp current: 900 ma, or optimum operating current 

Air pressure: 28 psi; 9.0 on flowmeter (varies with different flowmeters and burners)

Fuel: Acetylene. Pressure: 8 psi; 9.0 on flowmeter 

Flame: Oxidizing 

Sample uptake: About 4 ml per min 

The following absorption readings have been observed:

Sodium concentration,

mg per I Absorption, pe"cent

2.0_________________________________ 40.2 

4.0______________________________ 63.3 

6.0______________________________ 76.8 

8.0______________________________ 84.7 

10 _____________________________ 89.4

Concentration range: 6-60 mg sodium per liter 

Grating: Ultraviolet 

Wavelength counter: 330.2 (3302 A) 

Scale: 5 X 

Slit:4 (1mm, 13 A)

All other operating conditions same as used for concentration 

range 0.0-10 mg sodium per liter.
40 SPECTROGRAPHIC ANALYSIS OF NATURAL VTATER

The following readings have been observed:

Sodium concentration,

mg per I Scale reading

6.0_________________________________ 7.3 

10 ________________________________ 11.4 

20 ____________________-_________ 21.0

40 ______________________________ 38.4 

60 ______________________________ 56.6

Concentration range: 40-200 mg sodium per liter 

Grating: Ultraviolet 

Wavelength counter: 330.2 (3302 A) 

Scale: 2 X

Slit: 4 (1mm, 13 A)

All other operating conditions same as used for concentration 

range 0.0 10 mg sodium per liter. 

The following absorption readings have been observed:

m conce 

my per

40_______________ 16.0 _______________ 8.0 

60_______________ 23.6 _______________ 11.8 

80______________ 29.8 ______________ 14.9

18.3 

26.1 

32.8

REAGENTS

Sodium chloride standard stock solution, 1.00 ml = 1.00 mg sodium: 

Dissolve 2.542 g NaCl in demineralized water and dilute to 1,000 ml.

Sodium chloride standard working solutions: Prepare a series of 

standard solutions containing from 0 to 200 mg sodium per liter 

by diluting the NaCl standard stock solution.

PROCEDURE

1. Filter the sample (0.45 p micropore membrane filter) when necessary to avoid clogging the atomizer-burner.

2. Atomize each sample and standard, and record the percent absorption or scale reading observed. Repeat, and average the two 

values. If the sodium concentration is greater than 200 mg per 

1, the sample must be diluted.

CALCULATIONS

1. Concentration range 0.0-10 mg sodium per liter: Convert percent 

absorption to absorbance, and determine the sodium concentration in the sample from a plot of absorbances of standards.

2. Concentration range 6-60 mg sodium per liter: Determine the 

sodium concentration in the sample from a plot c f scale readings

sntratioiij

r I

0 _ _____ .

o__ _ __ .

0 ________ .

Scale 

reading

. _ __ 16.0 __ __.

. ____ 23.6 _ _ .

. ____ 29.8 __ _.

. ____ 36.6 __ __.

.__ __ 52.2 ____ .

. ____ 65.6 ___ _.

Absorpti
METHODS FOR ANALYSIS OF METALS BY ATOMIC ABSORPTTON 41

of standards. Because a scale expansion of 5 X is used, scale 

readings need not be converted to absorbance.

3. Concentration range 40-200 mg sodium per liter: Divide the scale 

reading by 2 to obtain percent absorption. Convert to absorbance, and determine the sodium concentration in the sample from 

a plot of absorbances of standards. For samples containing more 

than 200 mg sodium per liter, multiply by the proper dilution 

factor. Exact reproducibility is not obtained, and working 

curves must be prepared with each set of samples.

4. ppm sodium=-T ^jr~x mS sodium per liter.

Report sodium concentrations less than 10 ppm to the nearest 0.1 

ppm, those between 10 and 1,000 ppm to the nearest whole number, and those greater than 1,000 ppm to three significant figures.

STRONTIUM:

DISCUSSION OF METHOD

A hollow-cathode lamp and a reducing flame are used to determine 

strontium. Sodium and potassium decrease the strontium ionization 

in the flame. This effect levels off above concentrations of 100 ppm 

of either sodium or potassium. To control the ionization, 1,000 ppm 

of potassium is added to both standards and samples. Aluminum, 

phosphate, and silica interfere but are masked by the addition of 

lanthanum. No interferences occur for concentrations of up to 50 

ppm nitrate and 2,000 ppm each of sulfate, magnesium, and calcium. 

Above 2,500 ppm total dissolved solids, and depending upon the ratio 

of strontium to total dissolved solids present, low strontium values 

result even in the presence of potassium and lanthanum. Therefore, 

the standard-addition technique must be used for highly mineralized 

waters or for brines containing more than 2,500 ppm total dissolved 

solids.

The 4607 A line is used to determine concentrations of strontium 

less than 20 mg per 1. Two working curves are required. Results 

are accurate and reproducible to approximately ±0.02 mg per 1 for 

the concentration range 0.00-1.0 mg strontium per liter. For the 

concentration range 1.0-20 mg per 1, results are accurate r.nd reproducible to approximately ±0.1 mg per 1 for concentration less than 

10 mg per 1, and to approximately ±0.5 mg per 1 for concentrations 

greater than 10 mg per 1.

The sensitivity for strontium concentrations of less than 1.0 mg per 

1 is approximately 0.02 mg per 1 for each scale division, and for concentrations between 1 and 20 mg per 1, approximately 0.2-0.3 mg per 1 

per 1 percent absorption.
42 SPECTROGRAPHIC ANALYSIS OF NATURAL WATER

APPARATUS

Concentration range: 1.0-20 mg strontium per liter

Grating: Visible

Wavelength counter: 230.4 (4607 A)

Scale: 1 X

Slit: 4 (1mm, 13 A)

Source: Strontium hollow-cathode lamp

Lamp current: 15 ma

Air pressure: 28 psi; 8.0 on flowmeter

Fuel: Acetylene. Pressure: 8 psi, 9.0 on flowmeter initially (use a 

10 mg strontium per liter standard solution and adjust 

acetylene flow rate to obtain maximum absorption)

Flame: Reducing

Sample uptake: About 4 ml per min 

The following absorption readings have been observed:

Strontium concentration,

mg per I Absorption, percent

1.0_____________________________ 5. 6

5.0 ___________________________ 24.5

10 ____________________________ 41.5

15 ____________________________ 53.0

20 ____________________________ 62.6

Concentration range: 0.00-1.0 mg strontium per liter 

Scale: 10 X

Response-time control: 1 

All other operating conditions same as used for concentration

range 1.0-20 mg strontium per liter. 

The following readings have been observed:

Strontium concentration,

mg per I Scale reading

0.10 ____________________________ 5.3

.50 ____________________________ 26.2

1.0 _____________________________ 52.4

REAGENTS

Lanthanum chloride-potassium chloride solution: Dissolve 117.3 g 

La2O3 in a minimum amount of dilute HC1. Add 19.1 g KC1, and 

dilute to 1,000 ml with distilled water.

Strontium chloride standard stock solution, 1.00 ml ==0.10 mg strontium : Dissolve 0.1684 g of SrCO3 in a minimum amount of dilute 

HC1, and dilute to 1,000 ml.

Strontium chloride standard working solutions: Prepare a series of 

solutions containing from 0 to 20 mg strontium per liter by diluting 

the SrCl2 standard stock solution. Add 1.0 ml of Er,Cl3-KCl solution to each 10.0 ml of the working standards prepared. For example, to 500 ml of a working standard, add 50 ml LaCl3-KCl solution.
METHODS FOR ANALYSIS OF METALS BY ATOMIC ABSORPTION 43

PROCEDURE

1. Filter the sample (0.45 p micropore membrane filter) when necessary to avoid clogging the atomizer-burner.

2. Add 1.0 ml LaCl3-KCl solution to 10.0 ml of sample.

3. Atomize each sample and standard, and record the percent absorption or scale reading observed. Eepeat, and average the two values. If the strontium concentration is greater than 20 mg per 1, 

the sample must be diluted. Be sure that the diluted sample 

contains the proper amount of LaCl3-KCl solution.

CAIiCULATIONS

1. Concentration range 1.0-20 mg strontium per liter: Convert percent absorption to absorbance, and determine the strontium concentration in the sample from a plot of absorbances of standards. 

For samples containing more than 20 mg per 1, multiply by 

proper dilution factor.

2. Concentration range 0.00-1.0 mg strontium per liter: Determine 

the strontium concentration in the sample from a plot of scale 

readings of standards. Because a scale expansion of 10 X is 

used, scale readings need not be converted to absorbance. Exact 

reproducibility is not obtained, and working curves must be 

prepared with each set of samples.

3. ppm strontium = -^ = X mg strontium per liter.

Report strontium concentrations less than 1.0 ppm to the nearest 

0.01 ppm, those between 1.0 and 10 ppm to the nearest 0.1 ppm, 

and those greater than 10 ppm to the nearest whole r umber.

ZINC 

DISCUSSION OF METHOD

A hollow-cathode lamp is used to determine zinc. The lamp should 

be allowed to warm up for about 30 minutes at a current cf 12 ma before use. The lamp current is then optimized by adjusting the source 

control to obtain a minimum noise level (not more than one or two 

divisions on the null meter). The final setting should be between 10 

and 15 ma and should not exceed the maximum stated on the lamp 

because the cathode will begin to melt.

The 2138 A line is used to determine zinc. Of the catione and anions 

normally found in water, only magnesium interferes. Magnesium 

concentrations greater than 100 ppm interfere unless other cations, such 

as sodium, are present in the sample. There is currently no explanation for this phenomenon.
44 SPECTROGRAPHIC ANALYSIS OF NATURAL WATER

To determine zinc at concentrations of less than 0.4 mg per 1, 10 X 

scale expansion is used, and results are accurate and reproducible to 

approximately ±0.02 mg per 1. Concentrations of zinc greater than 

0.4 mg per 1 can be determined by using less scale expansion. The 

maximum concentration that can be determined at the 2138 A line 

without dilution is 10 mg zinc per liter.

The sensitivity for concentrations of zinc of less than 0.4 mg per 1 is 

approximately 0.005 mg per 1 for each scale division.

APPARATUS

Grating: Ultraviolet 

Wavelength counter: 213.8 (2138 A) 

Scale: 10 X 

Slit: 5 (3mm,20A) 

Source: Zinc hollow-cathode lamp 

Lamp current: 12 ma, or optimum operating current 

Air pressure: 30 psi; 9.0 on flowmeter (varies with different flowmeters and burners)

Fuel: Acetylene. Pressure: 8 psi, 9.0 on flowmeter 

Flame: Oxidizing 

Sample uptake: 2-5 ml per min 

Response-time control: 1 or 2 

The following readings have been observed:

Zine concentration,

mg per I Scale reading

0.10_________________________________ 18.2 

.20________________________________ 35.6 

.30_______________________________ 50.5 

.40_____________________________ 68.2

REAGENTS

Zinc chloride standard solution I, 1.00 ml=0.100 mg zinc: Dissolve 

0.100 mg reagent-grade zinc (30-mesh) in a slight excess of HC1, and 

dilute to 1,000 ml with demineralized water.

Zinc chloride standard solution II, 1.00 ml=0.100 nig zinc: Immediately before use, dilute 10 ml of ZnCl2 standard solution I to 100 ml 

with demineralized water.

Zinc chloride standard working solutions: Prepare a series of standard 

solutions containing from 0.00 to 0.40 mg zinc per liter by diluting 

the ZnCL standard solution II.

PROCEDURE

1. Filter the sample (0.45/x, micropore membrane filter) when necessary to avoid clogging the atomizer-burner.
METHODS FOR ANALYSIS OF METALS BY ATOMIC ABSORPTION 45

2. Atomize each sample and standard, and record the scrle reading 

observed. Repeat, and average the two values.

CALCULATIONS

1. Determine the zinc concentration in the sample from a plot of scale 

readings of standards. Because a scale expansion of 10 X is 

used, scale readings need not be converted to absorbance. Exact 

reproducibility is not obtained, and a working curve must be 

prepared with each set of samples.

2. ppm zinc=- X mg zinc per liter.

Report zinc concentrations less than 1.0 ppm to the rearest 0.01 

ppm and those greater than 1.0 ppm to two significant figures.

REFERENCES

Perkin-Elmer Corp., 1964, Analytical methods for atomic absorption spectrophotometry: Norwalk, Conn. 

Walsh, Allan, 1955, The application of atomic absorption spectra to chemical

analysis: Spectrochim. Acta, v. 7, p. 108-117.