Copper-Spark Method 

for Spectrochemical 

Determination of 

Strontium in Water

By MARVIN W. SKOUGSTAD

CHEMISTRY OF STRONTIUM IN NATURAL WATER

GEOLOGICAL SURVEY WATER-SUPPLY PAPEF 1496-B

Prepared on behalf of the U.S. Atomic 

Energy Commission and published with 

the p erm iss ion of the Co mm iss io n

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1961
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

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

Washington 25, D.C.
CONTENTS

Page

Abstract--..-_ ____________________________________________________ 19

Introduction-_ _--_--____________________________--_____-._-_------ 19

Procedure-.._..____-_._.___-__--___-_-______,.___.-__________ 22

Instrumentation. __ _ _________________.__-_--_---_-__----------- 22

Reagents._ ________-____-____________-__---_----__---_-_------ 23

Copper electrodes____________________________________________ 23

Sample preparation____________________________________________ 24

Excitation conditions._______--__-_____-__--___-_-_-_--__---_-- 26

Photographic processing.___________-____.--____-_-___---_------ 26

Calculations ____--____________-_--__-____-____-_-__----------- 26

Precision and accuracy_-_____-_________-_____-_-_-----__----------- 28

Summary_ _ _______-______________________----___----_--_-_------ 30

References cited._____-________________-____---_____---_--_-------- 31

ILLUSTRATIONS

FIGURE 1. Copper electrodes on which samples are evaporated____-____. 25 

2. Working curves for strontium.---------------------------- 27

TABLES

Page 

TABLE 1. lonization potentials of strontium and lanthanum. ____--_-__ 22

2. Excitation conditions.-______-_-----__-_----_------------ 26

3. Analytical and internal standard lines._______-_-___-_----_- 26

4. Reproducibility in successive determinations of strontium- _ _ . 29

5. Recovery of strontium added to water samples._____________ 29

6. Results of strontium determinations with the spectrographic

method and with a flame-photometric method-_____---__- 30

in

CHEMISTRY OF STRONTIUM IN NATURAL WATER

COPPER-SPARK METHOD FOR SPECTROCHEMICAL 

DETERMINATION OF STRONTIUM IN WATER

By MARVIN W. SKOUGSTAD

ABSTRACT

This is a rapid, reliable procedure which utilizes the copper-spark technique 

and an internal standard-buffer solution added in constant amount to each 

sample. The choice of lanthanum as an internal standard and the three convenient analytical line pairs, Sr: 4077.7/La: 4077.3, Sr: 4077.7/La: 3949.1, and 

Sr: 4215.5/La: 3949.1, permit the determination of strontium from 0.005 to 1.0 

ppm (parts per million) in water. Twenty-five milliliters of sample is sufficient and sample preparation is simplified so that a relatively large nrmber of 

samples can be conveniently and economically handled.

The average deviation of successive repeat analyses was less than 5 percent 

of the amount present. Recovery of strontium <added in known amount to water 

samples of widely different chemical composition (dissolved solids) ranged from 

88 to 105 percent of the amount added. Most results obtained by the spectrographic method agreed reasonably with results obtained independently by a 

combination ion exchange-flame photometric method.

This procedure is particularly suited to the determination of strortium in 

natural waters at concentration levels of less than 1.0 ppm. Although the procedure was used only for the determination of strontium, it could be used for 

the determination of other elements.

INTRODUCTION

The need for a rapid and reliable method for the determination of 

strontium in natural water led to the development of the r^ectrographic procedure described here. It is based on the copper-spark 

technique described by Fred, Nachtrieb, and Tomkins (1947) and by 

Nachtrieb (1950) and is a modification of the procedure use by Alexander, Nusbaum, and MacDonald (1954) for the determination of 

calcium, magnesium, and strontium in water.

A previous report by Horr (1959) presented a survey of methods 

for the quantitative determination of strontium. Strontium generally 

occurs in fresh water in concentrations of 0.01 to 1.0 ppm. Chemical 

methods for determination of strontium are not satisfactory when ap19
20 CHEMISTRY OF STRONTIUM IN NATURAL WATER

plied to water analysis because of the difficulty of separating; the 

small amount of strontium from the much larger amourts of calcium 

and magnesium normally found in natural water. Flame photometric 

and spectrographic techniques oifer the greatest promise for the routine determination of strontium in water where a relatively large 

number of samples is to be analyzed. Flame photometric methods for 

determination of strontium in water have been described by Horr 

(written communication, 1961).

Emission spectrochemical methods are commonly used for the determination of trace and minor elements in a variety of materials including natural water. Sample-handling techniques vary with the 

type of material being analyzed; relatively simple techniques are used 

for analysis of metals and alloys, where solid, electrically conducting, 

self-electrodes are employed. Samples of rocks, minerals, ceramics, 

and other nonconducting materials are prepared somewhat less easily 

for spectrographic analysis; however, techniques for tr°> analysis of 

these materials have become common and are extensively used. The 

handling of solutions for spectrographic analysis invokes problems 

that are not encountered with the handling of solids, particularly in 

introducing the liquid sample continuously, uniformly, and in a reproducible manner into the spark or arc.

A great variety of techniques has been proposed foT> introducing 

solutions into an arc or spark source for emission spectro^copy. Three 

techniques in general use are the porous-graphite cup electrode, the 

rotating graphite or metallic-disk electrode, and the vacuum-cup electrode. These have all been successfully used in the analysis of solutions but, nevertheless, possess certain inherent limitations, as a lack 

of sensitivity for certain minor elements or a lack of reproducibility. 

If graphite electrodes are used, a significant part of the analytical 

spectrum is obscured by cyanogen bands and is thus rendered useless 

for accurate quantitative measurements. The region of serious cyanogen-band interference ranges from about 3600 to 4200 A (angstrom 

units), a region which includes the two most sensitive strontium spark 

lines, the doublet at 4077.7 and 4215.5 A. Cyanogen-band interference 

can be eliminated and sensitivity can be increased by use of a rotating 

metallic disk (Meloche and Shapiro, 1954).

There are several alternatives to direct solution excitation. Three 

commonly used alternatives are: complete evaporation of solution 

to yield a dry residue; precipitation of the desired ions from solution 

to yield a precipitate for excitation; and evaporation of a small quantity of the sample solution on the flat ends of a pair cf graphite or 

metallic electrodes. All three alternatives are currently used by the 

U.S. Geological Survey in the analysis of water for minor constitu-
COPPER-SPARK METHOD FOR DETERMINATION OF STRONTIUM 21

ents. The first two alternatives are particularly useful where several 

elements are to be determined; the additional laboratory steps required to prepare the sample for arcing are justified when a number 

of elements can be determined in a single sample. These methods also 

possess the advantage of concentrating extremely small amounts of 

the sought-for elements from a large volume of sample (Haffty, 1960; 

Silvey, 1961).

The inherent high sensitivity of some emission spectrographic 

methods permits the use of extremely small amounts of sample, even 

for the determination of trace elements in the sample. Hence, certain 

elements can be determined satisfactorily from a single drop of sample 

that has been evaporated on the flat end of a spectroscopic electrode.

Sensitivity for trace elements is poor if untreated graphite or carbon electrodes are used because of absorption of solution by the electrodes. The sensitivity is improved by treating the electrodes with 

kerosene or a similar material to render them nonabsorbent; and 

the sensitivity is significantly increased if metallic, rather than carbon 

or graphite, electrodes are used. Furthermore, the use of metallic 

electrodes eliminates the presence of cyanogen bands that obscure the 

most sensitive spark lines of strontium.

The use of copper electrodes is the basis of the copper-spark method. 

This method offers several advantages over others, particularly if 

only one or a few minor constituents are to be determined. Excitation by a high voltage, condensed-spark discharge results in a high 

degree of reprodueibility and accuracy and in exceptionally good 

sensitivity for many elements. The absence of cyanogen-band interference permits use of the most sensitive strontium spark lines at 

4077.7 and 4215.5 A. Only a small sample volume is required; an 

analysis can be made on 25 ml, or even less, of sample. The sample 

requires no preliminary treatment other than the addition of internal 

standard-buffer solution; thus, sample preparation and preliminary 

operations are greatly simplified. Finally, the method reqrires no 

additional spectrographic accessory equipment other than the copper 

electrodes, which are inexpensive, readily available, and generally free 

of strontium.

Spectrographic facilities of the Metallurgy Department of the 

Colorado School of Mines, Golden, Colo., were generously made available to personnel of the U.S. Geological Survey for the development 

of this procedure and for the analysis of a large number of water 

samples. Dr. N. C. Schieltz, of the School of Mines faculty, contributed many helpful suggestions during the course of thi^ work. 

Flame photometric analyses were made by C. A. Horr and Darwin 

Golden of the Geological Survey.
22 CHEMISTRY OF STRONTIUM IN NATURAL W^TER

This work was done on behalf of the U.S. Atomic Energy 

Commission.

PROCEDURE

Lanthanum was found to be preferable to molybdenum as an internal 

standard for the determination of strontium. Early experiments 

indicated that the duration of molybdenum emission in the spark 

was short in relation to the duration of strontium emission, possibly 

because the molybdenum tended to form the volatile trioxide. Lanthanum, conversely, possesses excitation characteristics similar to 

those of strontium (table 1) and volatilizes in the sparv at about the 

same rate as strontium. Moreover, several spark lines of lanthanum 

are of suitable intensity and are close to the most sensitive strontium 

lines, 4077.7 and 4215.5 A. Two lanthanum lines, 3949.1 and 4077.3 A, 

were selected as internal standard lines for this procedure. The relative intensities of these two lines were such that, at the proper concentration of lanthanum in the sample and under the excitation 

conditions employed, strontium in concentrations of 0.005 to 1.0 ppm 

could be determined directly from but one sample exposure. The fact 

that all analytical curves obtained for the three line pairs selected 

were linear, or nearly linear, indicated the general suitability of lanthanum as an internal standard for the determination of strontium.

TABLE 1. lonization potentials of strontium and lanthanum

Element

Lanthanum.. _ _ ________

Strontium. _ ________

First ionization

5. 6

5.67

Potential (volts)

Spark resonance

9. 1

8.7

Second ionization

11.4

10. 98

INSTRUMENTATION

The spectrograph used for the procedure described in this report 

is a 3-meter concave grating instrument (modified Eagle mounting). 

The grating has a ruling of 6,000 lines per centimeter and a linear 

dispersion of 5.5 A per millimeter in the first order. Sample excitation is provided by a commercially available multiple-source unit 

that provides a high-voltage, condensed-spark discharge to the sample 

electrodes.

The spectral region from 3500 to 4800 A is photographed in the 

first order on Eastman Spectrum Analysis, Type 103-0, spectroscopic 

plates. Exposed plates are processed in mechanically agitated trays, 

and developer, stop bath, and fixing solutions are maintained at a
COPPER-SPARK METHOD FOR DETERMINATION OF STRONTIUM 23

temperature of <2,Q0 ±y2 °C. A. densitometer-eomparator is u^ed for 

determining spectral-line densities.

REAGENTS

High purity strontium carbonate is used in the preparation of all 

standard strontium solutions. This reagent is stated by the manufacturer to be 99.99 percent pure and to contain no more than 3 

ppm of sodium and 2 ppm of calcium as major impurities. All 

reagents used in the preparation of the internal standard-buffer solution are either of analytical grade or of c.p. quality. A test showed 

that, in the dilution used in the analytical procedure, the internal 

standard-buffer solution contributed no detectable strontium to the 

samples.

Internal standard-buffer solution. Dissolve 0.15 g of LaCl3 , 0.60 

g of ethylenediamine tetraacetate, disodium salt, 6.4 g of NaCl, and 

3.1 g of CaCO3 in 200 ml of dilute (1:50) HC1. Dilute to 500 ml.

Standard strontium solution., 100.0 ppm Sr. Dry approximately 

0.2 g of high purity SrCO3 for 2 hours at 120°C. Coo1 in an 

efficient desiccator, and transfer 168,5 mg of the reagent to r, 1-liter 

volumetric flask. Add 50 ml of distilled water to the SrOO3 in 

the flask, and add dilute (1:10) reagent grade HC1 in 0.5 ml portions until the salt is completely dissolved (about 2 ml of thQ. dilute 

HCO. will be required). Dilute to exactly 1 liter. Store in tightly 

capped polyethylene bottles.

The concentration of strontium in this solution is:

Q mgSrCO3 X 0.5935 ppm Sr=^f% 7 i 7-- 

1 L Liters of solution

Standard strontium' solution, 10.00 ppm Sr. Pipet exactly 50.0 

ml of the 100.0 ppm standard Sr solution into a 500-ml volumetric 

flask. Dilute to the mark with distilled water. Store in tightly 

capped polyethylene bottles.

Standard strontium solutions, 0.010 to 1$8 ppm Sr. Prepare a 

series of eight standard strontium solutions containing 0.010, 0.020, 

0.040, 0.080, 0.16, 0.32, 0.64, and 1.28 ppm of Sr. Take appropriate aliquots of the 10.0 ppm of standard stock solution and dilute 

to volume with distilled water. Store in tightly capped polyethylene 

bottles.

COPPER ELECTRODES

Either 0.25-inch-diameter commercial semihard, electrolytic copper, 

or 7-mm diameter, high purity copper may be used for the electrodes. The slightly larger (7-mm) electrodes are preferred because of the greater ease of evaporation of a 0.1-ml drop of sample

603286 O - 61 - 2
24 CHEMISTRY OF STRONTIUM IN NATURAL WATER

solution on the electrode face without part of the liquid running 

down the side of the electrode. If commercial copper is used for 

the electrodes, a blank must be run to determine electrode composition. Strontium impurity in the copper is extremely unlikely but 

if other elements in the sample are to be determined, their possible presence in the copper electrodes must be determined.

Prepare a set of 40 or 50 electrodes by cutting copper rods into 

uniform lengths of about 3.5 cm. With the electrode mounted in 

a metal-turning lathe, machine one end flat with a tool designed to 

leave as smooth a surface as possible. While the electrode is still 

mounted in the lathe, use a small, fine mill file to cut a sUght chamfer 

on the sharp edge of the electrode. Also, lightly file the side surface of the electrode back from the end about 1 cm to remove 

possible surface contamination. The electrode may be handled only 

with forceps from this point on and must be stored in a covered 

container that will protect the cleaned electrode from dust, dirt, 

and contamination from laboratory reagents. The electrodes will 

oxidize slowly in air on long standing and should preferably be 

cleaned just prior to use.

The electrodes must be cleaned again after each us^ in preparation for analysis of subsequent samples. They may be cleaned by 

washing with nitric acid; then by thoroughly washing successively 

with tap water, distilled water, and alcohol, and fnally by air 

drying. As an alternate, they may be cleaned by remachining each 

electrode face. Either method gives satisfactory results; however, 

cleaning by remachining, which is preferred in this laboratory, assures the complete removal of the previous sample. It rlso eliminates 

the possibility of contamination of the electrode face by the cleaning 

agents or by impurities in the cleaning agents. Electrode contamination must be avoided when an extremely small amonnt of an element is to be detected.

SAMPLE PREPARATION

Pipet exactly 10.0 ml of water sample or standard strontium solution into a small weighing bottle or other suitable container. Then 

place the bottle on a magnetic stirrer; drop in a small stirring bar; 

and add, with a 100 microliter micropipet, exactly 100 microliters 

of internal standard-buffer solution. Stir the solution for 2 or 3 

minutes to ensure complete mixing.

Transfer approximately 0.1 ml of the prepared sample or standard 

to each of four clean copper electrodes. Rinse the micropipet carefully between successive samples to avoid contamination of the subsequent sample. Possibility of contamination is reduced if, in a series
COPPER-SPARK METHOD FOR DETERMINATION OF STRONTIUM 25

of standards, the most dilute standard is prepared first and is followed 

by the next more concentrated.

Exactly 0.1 ml of sample on each electrode is not essential although 

an effort should be made to provide a volume very close to this in 

order that all samples be as nearly comparable as possible. The 

preparation of four electrodes permits analysis of each sample or 

of each standard in duplicate.

Evaporation of the sample on the electrodes is facilitated and hastened by the small nichrome wire heaters shown in figure 1. The small

FIGDRE 1. Copper electrodes on which samples are evaporated.

clamp-jig holds four electrodes in a vertical position under the spiral 

nichrome wire heating elements. With the electrodes in position in 

the clamp, place a measured drop (0.1 ml) of sample on each electrode. 

Then lower the heating coils to within 1 cm of the top of each electrode, and apply voltage slowly to the heaters through a rheostat to 

warm the sample drop. AJter the sample is warmed for about 30 

seconds, increase the voltage to evaporate the sample solution completely in as short, a time as possible. Two to three minutes is sufficient. 

If the sample drop is exposed directly to the high temperature of 

the heating coils operated at maximum voltage, the sudden expansion
26 CHEMISTRY OF STRONTIUM IN NATURAL WATER

of the drop will cause it to run down the side of the electrode; hence, 

it is necessary to gradually increase the temperature of the heating 

coils. With this precaution, pretreating the electrodes v^ith a coating 

of grease or other material is unnecessary to prevent the sample solution from running down the side of the electrode.

When evaporation is complete, place the electrodes that contain 

the dry sample residue in a desiccator until ready for sparking.

EXCITATION CONDITIONS

The samples are sparked by using a high voltage, cordensed spark 

discharge. Excitation conditions, specified in table 2, have given satisfactory reproducibility and sensitivity for strontium. Under these 

conditions and with the spectrographic equipment used, a sample that 

contains 0.005 ppm of strontium will just barely show a visible line 

at 4077.7 A.

PHOTOGRAPHIC PROCESSING

Develop the spectrographic plate for 4.0 minutes at 20°C in Kodak 

D-19 developer while continuously agitating. Rinse for 30 seconds 

in an acid stop bath and fix for 2 minutes (minimum) in Kodak Rapid 

Fixer. Wash the plate for 20 to 30 minutes in running water, rinse 

with distilled water, and dry.

TABLE 2. Excitation conditions

Input voltage___________________________________ 108 

Capacitance___________________________________ fit-. 0. 0025

Inductance ______________________-_ _________-- 0

R.F. spark current____________ _ _ 5. 5

Prespark__________________________ _ _______ sec 0

Exposure____________________________ ______ sec__ 50

Slit width___________________________________ ft.. 25

CALCULATIONS

The analytical and internal standard lines used for the determinatiou of strontium and the approximate concentration range covered 

for each of three line pairs used are shown in table 3.

TABLE 3. Analytical and internal standard lines

Range of strontium 

concentration (ppm)

0. 00-0. 15 

. 10- . 50 

. 40-1. 0

Wavelength (A)

Strontium

4077. 7 

4077. 7 

4215. 5

Lanthanum

4077. 3 

3949. 1 

3949. 1
COPPER-SPARK METHOD FOR DETERMINATION OF STRONTIUM 27

Measure the transmittance of each analytical and internal standard 

line, and convert to relative intensities by means of an emulsion calibration curve. The emulsion calibration curve may be prepared by 

any one of the standard methods.1

Prepare a set of three working curves from the data obtained from 

the standard strontium solutions by plotting the intensity ratio of 

each line pair against the strontium concentration in parts per million 

on logarithmic coordinate paper. Typical working curves obtained 

are shown in figure 2.

r~r

fcu

0.1

i i i i i

OJO 

STRONTIUM CONCENTRATION, IN PARTS PER MILLION

FIGURE 2. Working curves for strontium.

1.0

Adjust the amount of lanthanum in the internal standard-buffer 

solution, after a trial run, so that when the strontium concentration 

in a standard sample or in a water sample is 0.030 ppm, the intensity

1 Several specific procedures for constructing emulsion calibration curves are given in 

''Methods for Emission Spectrochemical Analysis," October 19>57, A.S.T.M., Philadeluhia, 

Pa.
28 CHEMISTRY OF STRONTIUM IN NATURAL WATER

ratio for line pair Sr :4077.7/La :4077.3 is close to 1.00. This concentration of lanthanum will provide optimum intensity ratios for this 

line pair for samples of less than 0.15 ppm of strontium and, at the 

same time, it will provide convenient intensity ratios for the other 

two line pairs for strontium concentrations up to 1.0 pp^n.

When the strontium concentration exceeds about 0.15 ppm, the 

the strontium line at 4077.7 becomes so intense with respect to the 

adjacent lanthanum line at 4077.3 that the two lines are no longer 

resolved. Therefore, at concentrations in excess of O.lf ppm, use of 

the line pair Sr: 4077.7/La: 3949.1 is necessary. Similarly, the strontium line at 4077.7 is, under the conditions of analysis, excessively 

intense at strontium concentrations more than 0.50 ppm. The line 

pair Sr: 4215.5/La: 3949.1 is, therefore, preferable when the strontium 

content exceeds 0.50 ppm and is suitable for concentrations as much 

as 1.0 ppm.

Analysis of samples. Determine the intensity ratio of Sr/La for 

the appropriate line pair or pairs for each sample. From the corresponding analytical curve, determine the concentration of strontium. 

Two or three standard strontium solutions, preferably those that 

represent the high and low ends of the concentration range should 

be included with each series of samples analyzed; thus a constant check 

is provided on the validity of previously prepared analytical curves.

PRECISION AND ACCURACY

Each sample was sparked in duplicate on a single spectrographic 

plate, and the average of the two values for strontium concentrations 

obtained was taken as the value for the sample. Whenever the two 

values for strontium concentration differed by more than 10 percent, 

the sample was resparked on a subsequent plate. TH reproducibility and the precision of the method were tested by analyzing several 

samples two or more times on different plates and at different times. 

The results of some of these repeated analyses, given in table 4, show 

that an average deviation of less than 5 percent of the amount present 

may be expected.

Recovery of strontium added to water samples was checked to obtain an indication of the accuracy of the method. A known amount 

of standard strontium solution was added to each of four naturalwater samples of widely different composition with respect to major 

constituents. The strontium content of each of these samples was 

detennined before and after the addition of the measured amount of 

strontium, and the difference in the two values thus obtained was 

compared with the amount added. Results are shown in table 5.
COPPER-SPARK METHOD FOR DETERMINATION OF STRONTIUM 29 

TABLE 4. Reproducibility in successive determinations of strontium

Sample

2596-______._._____

2791-______________

2885_______________

2904_. _____________

2907_______________

2910_______________

2969. _

3000_______________

Spectrographic 

plate

38

39 

40

78

83 

29

36 

47

86 

26

27 

37

27

37 

50

60 

24

36

Concentration 

(ppm)

0 094

103 

109

10

18 

045

045 

044

047 

089

091 

085 

075

076 

31

34 

098

092

Average concentration 

(ppm)

}

1 0. 102

} .185

} .045

| . 0455

1 .088

} . 0755

. oZo

} .095

Average deviation 

(ppm)

0. 0053

.005

.000

.0015

.0023

.0005

.015

. 003

Average deviation 

(percent)

5.2

2.7

.0

o. &

2.6

.7

46

3.2

TABLE 5. Recovery of strontium added to water samples

Concentration of strontium (ppm)

Sample

2972A

g

C. .__. ____

g

C

3435A

g

3535A

g

Q

Added

0 00

22

11

00

22

11

00

11

00

11

22

Calculated, 

total

0.30

1Q

.49

.38

.34

.22

.33

Found

0 08

29

20

27

48

37

23

34

11

20

29

Difference

-0.01

+.01

-.01

-.01

.00

-.02

-. 04

A large number of water samples was analyzed by flame photometer 

as well as by spectrograph. The flame photometric procedure irvolved 

a tenfold concentration of strontium from the sample by means of a 

strongly acidic cation exchange resin prior to analysis. The sensitivity of this procedure is 0.02 ppm of strontium. Agreement was reasonable between most of the results obtained with, the two independent 

analytical methods (table 6.)

The flame photometric determinations were made with an independent set of standards. Thus the results are comparable to having 

the analyses performed by two different laboratories. The agreement 

between the results is considered to be satisfactory.
30 CHEMISTRY OF STRONTIUM IN NATURAL WATER

TABLE 6. Results of strontium determinations with the spectrographic method and 

with a flame photometric procedure

Sample

3247-_--___-_ -__-______ .._ _________ ___..__

2714__ ________________________________________

3044_____ __ _________________________ _ ____

3584__ ________________________________________

3078_____ ____________________ ______________

3168-- __ __________________________________

3077__ ________________________________________

2888_ _ __ __ _ _.. _ _ __ 

2599__-_______. _____________ ___ _ __ ___ ____

2794___ __________________________ _____________

3348______________________________ ___ _ ____

2785____ ______________________________________

3456-__-____-_. ______ ______________ _ _ _

Concentration of strontium (ppm)

Flame 

photometer

0 03 

04 

06 

065 

14 

16 

23 

28 

22 

36 

48 

47 

73

Spectrograph

0 

0. 040,

028 

040 

046 

058 

14 

15 

16 

25 

26 

33 

34 

38 

64

SUMMARY

The copper-spark, spectrographic procedure described is suitable 

for the determination of stable, nonradioactive strontium in natural 

waters. A spectroscopic buffer solution, consisting of calcium and 

sodium chlorides in a 0.1-percent ethylenediamine tetraacetate solution and added in constant amount to each sample, minimizes the 

effects of differences in the composition and amounts of dissolved 

solids present in different waters.

Lanthanum is particularly suitable as the internal standard because its excitation characteristics are similar to those of strontium. 

Moreover, several lanthanum lines are close to the two most sensitive 

spark lines of strontium; therefore, by proper adjustment of lanthanum concentration and proper choice of analytical line pairs, 

strontium concentrations between 0.005 and 1.0 ppm may be determined from one sample and exposure.

High-voltage spark excitation and metallic (copper) electrodes provide satisfactory sensitivity, precision, and reproducibility. The 

method satisfies the requirements for convenience, speed, and accuracy. 

One chemist can analyze as many as 15 samples per day.

Although the method, as descril>ed, was devolped exclusively for 

determination of strontium in natural waters that contain less than 

500 ppm of total dissolved solids, it undoubtedly can be used, with 

suitable modification, for the analysis of mineral waters and waters, 

that contain more than 500 ppm of dissolved solids.
COPPER-SPARK METHOD FOR DETERMINATION OF STRONTIUM 31

REFERENCES CITED

Alexander, G. V., Nusbaum, R. E., and MacDonald, N. S., 1954, Strontium and

calcium in municipal water supplies: Am. Water Works Assoc. Jour., v.

 46, p. 643. 

Fred, M., Nachtrieb, N. H., and Tomkins, F. S., 1947, Speetrochemieal analysis

by the copper spark method: Am. Optical Soc. Jour., v. 37, p. 279. 

Haffty, Joseph, 1960, Spectrographic analysis of natural waters. Residue

method for common minor elements: U.S. Geol. Survey Water-Supply

Paper 154Q-A. 

Horr, C. A., 1959, A survey of analytical methods for the determination of

strontium in natural water: U.S. Geol. Survey Water-Supply Paper 1496-A. 

Meloche, V. W., and Shapiro, Rubin, 1954, Determination of calcium and magnesium in lake waters by means of a rotating silver disk electrcde: Anal.

Chemistry, v. 26, p. 347. 

Nachtrieb, N. H., 1950, Principles and practice of speetrochemieal analysis:

New York, McGraw-Hill Book Co., 324 p. 

Silvey, W. D., 1961, Concentration method for speetrochemieal determination of

strontium in water: U.S. Geol. Survey Water-Supply Paper 1540-F p. 11-22.

U.S. GOVERNMENT PRINTING OFFICE : 1961 O 603286