(9) Laitinen. 19) Laitinen, H. A A,. Kivalo. Kivalo, P.. P., .INAL. .IXAL.
ACKNOWLEDGMENT
Table IV. Precision Data for Beryllium Determination
(fine determinations) Standard Deviation Av. Be From Found Mean.
Be Concentration, pg. -4dded Peg. 2 (synthetic sample) 2 *0 2 f l 10 (synthetic sample) 10 f l 20 (synthetic sample) 20 f 2 50 (synthetic sample) 51 2 3 f 0 3 Standard granite G-1’ Reported values 2 to 3.3pg. Be ( 1 , 11).
\
The author thanks AC Spark Plug Division, General hIotors Corp., for permission to publish this paper. LITERATURE CITED
(1) Ahrens, L. H., “Quantitative Spectrochemical Analysis of Silicates,” Perga mon Press. London. 1954.
(4) Ibid., p.‘970.‘ f.51 Fairbairn. H. W..Geochim. et Cosmochzm. A c t a 4, 143 (i953). \ - ,
~
(6) Hodge, W.,“Some Sotes on Safe Handling Practices for Bwvlliuni,” Defense- Metals Information Center Memorandum 2, Battelle Memorial Center (1958). ( 7 ) Joensuu, O., “The Spectrochemical Analysis of the Rare Earths, Seandium, and Thorium Using the Stallivood Arc,” Paper presented a t the Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, PIIarch 2-6 (1959). (8) Joensuu, O., Suhr, K.,personal communication. ”
to background ratio, and the better control over interelement effects i t affords. The method has been extended to other elements and a fusion technique has been developed which will give quantitative data for major and minor concentrations of some 25 elements in a wide variety of materials.
,
,
-
I
CHEM.24,’ 24, 1467 (1952). (10) Landis, F. P., Coons, 311. C., A p p l . Spectroscopy 8, 7 (1954). (11) Merrill, J. R., Honda, AI., Arnold, J. R.. R., “Proc. 2nd Intern. Conference on Peaceful Uses of Atomic Energy,” Vol. 2, 251, 1958. (12) O’Xeil, R . L., Suhr, N. H., A p p l . Spectroscopy 14-2, 45 (1950). (13) Owen, L. E., Delaney, J . C., Seff, C. N.. Am. Ind. H u a . d s s o c . Quart. 12. 112 11951’1. (14) ‘Saidei, A. ‘ S., Prokofjew, W. K., Raiski, S. M.,“Spektral Tabellen,” 1st. ed., Berlin, 1961. (15) Shaw, D. M., Wickremasinghe, G., Yip, C., Spectrochim. A c t a 13, 197 (1938). (16) bill, C. W.>Willis, C. P., .&SAL. CHEM.31, 598 (1959). (17) Sill, C. W.,Willis, C. P., Flygare, J. K., Ibid., 33, 1671 (1961). . Ani. 118’1 Stallwood. B. J.. J . O D ~ SOC. ‘ 44, 171 (1954). (19) Tingle, W. H., blatocha, C. K.. h . 4 ~ CHEM. . 30,494 (1958). RECEIVED for review December 26, 1961. rlccepted April 17, 1962. Pittsburgh Conference on ilnalvtical Chemistrv and Applied Spectroscopy, Pittsburgh,” Pa., liarch 1962. l”
Concentration Method for the Spectrochemical Determination of Seventeen Minor Elements in Natural Water WILLIAM D. SILVEY and ROBERT BRENNAN Geological Survey,
U. S.
Departmenf of the Interior, Sacramenfo, Calif.
b A method for the quantitative spectrochemical determination of microgram amounts of 17 minor elements in water i s given. The chelating reagents 8-quinolino1, tannic acid, and thionalide are utilized to concentrate traces ( 1 to 500 pg.) of aluminum, cobalt, chromium, copper, iron, gallium, germanium, manganese, nickel, titanium, vanadium, bismuth, lead, molybdenum, cadmium, zinc, and beryllium. Indium i s added as a buffer, and palladium is used as an internal standard. The ashed oxides of these 17 metals are subsequently subjected to direct current arcing conditions during spectrum analysis. The method can be used to analyze waters with dissolved solids ranging from less than 100 to more than 100,000 p.p.m. There i s no limiting concentration range for the determination of the heavy metals since any volume of sample can be used that will contain a heavy metal concentration within the analytical range of the method. Both the chemical and spectrographic procedures are described, and precision and accuracy data are given. 784 *
ANALYTICAL CHEMISTRY
A
which would permit the quantitative determination of a large number of elements in a microgram per liter concentration was needed for a study of the distribution and abundance of minor elements in the waters of California. -4 literature search indicated that the spectrochemical methods of Mitchell and Scott (3) and Heggan and Strock ( 2 ) would be suitable for the project. Both methods involve the concentration of the minor elements by precipitation with 8-quinolino1, tannic acid, and thionalide. This paper describes a modification of the above methods involving an increased concentration of the radiation buffer and the use of a different internal standard. The elements aluminum, beryllium, bismuth, cadmium, cobalt, chromium, copper, iron, gallium, germanium, manganese, molybdenum, nickel, lead, titanium, vanadium, and zinc can be determined in a concentration range of 1 to 500 pg. METHOD
EXPERIMENTAL
Reagents. T h e ammonium acetate
solution ( 2 N ) was prepared b y mixing 1 liter of 4X ammonium hydroxide
solution n-ith 1 liter of 4 9 acetic acid solution. Reagent grade ammonium acetate n as found to contain excessive concentrations of trace elements. All other chemicals used were commercially available and of reagent grade. The indium, palladium, all chemicals used to prepare standard solutions of the trace elements, and synthetic samples were ,Johnson RIatthey and Co. specpure chemicals obtained from the Jarrell-Ash Co., S e n tonville, Mass. Apparatus. A Jarrell-A\sh 2.4meter TYadsn orth grating spectrograph equipped n i t h a 15,000 lines per inch grating ha\ ing a reciprocal lin-ar per mm. in the dispersion of 3.5 second order n a s used. X direct current arc of 240 volts a t 6 amp. \\as used for excitation, and spectral line density was measured Itith a Jarrell-Aksh projection niicrophotometer. Xational Spectrographic cupped graphite electrodes No. 3909 specially machined with a thin cup nall Jvere used. Spectra were recorded on Eastman Kodak SA-1 spectrum analysis film. Procedure. Filter t h e nxter sample through a Nillipore membrane having a pore size of 0.5 micron and select a suitable aliquot which conA\,
calibration curve. The table reduces the possibility of error in reading the curve for each transmission value. Element lines used were chosen for the following reasons: the element line is never observed in the reagent blank; no other element lines interfere in the concentration range used, and the range of detectability is acceptable.
I
RESULTS AND DISCUSSION
OC31 80
60
4c
20
C
Figure 1 .
-20 -40 LO^ Rat o
-60 0'
-8s
9 e a t be
-120
-CC litess
-42
-16C
-I83
'y
An example standard curve
tains t h e minor elements in a concentration range of 0.50 t o 0 002 ing. Acidify t h e sample aliquot with 5 ml. of 6.Y HC1 and evaporate t o approximately a 100-nil. volume. Quantitatively transfer t h e sample to a 400ml. beaker and add, in order, 15 ml. of indium solution (1 ml. = 2 mg. of In), 5 ml. of palladium solution (1 ml. = 0.2 mg. of Pd), and 10 ml. of a 5% solution of 8-quinolinol in 2.1- acetic acid. Adjust the p H to 1.8 using ammonium hydrovide and add, in order. 45 ml. of 2.Y ammonium acetate solution, 2 ml. of 1091, solution of tannic acid in 2 5 ammonium acetate, and 2 mi. of a lY0 solution of thionalide in acetic acid (sp. gr. 1.062). Adjust the pH to 5.2 with ammonium hhdrouide and allow the sample to stand overnight to ensure complete precipitation. Filter the precipitate using ashless paper. and transfer the precipitate to a fused quartz crucible. The precipitate is ashed a t 450" C. usually overnighl,. After ashing, add sufficient high purity graphite powder to each crucible to give a total Tveight of sample of 70 mg. The sample-graphite mixture is carefully and quantitatively transferred to pol!-styrene vials and subjected to the mixing action of the Wig-IA-Bug for 30 seconds. After mixing is complete, the sample is divided into t n o approximately equal portions and loaded into tm o graphite electrodes for duplicate arcing. It is not necesary to weigh the arcing mixture for loading since the ratio of internal standard (Pd) to sample is constant. Store the loaded electrodes in covered containers until ready for analysis. Arc the electrodes until the sample is completely burned. The thin wall of the electrode cup burns off a t the same rate 5s the sample, providing an additional visual indication that burning is complete. The reduction in the amount of graphite burned with the thin walled electrode
alba helps to reduce the continuum on the film since the carbon arc temperature is reached just as the sample is consumed and not before. Photometry. A calibration curve t o convert photographic line density to relative intensity was constructed using iron as the line source a n d a sixstep log filter. T h e per cent transniission of the iron lines \vas read every 200 to 300 A . in the 2450- t o 3400--L region. T h e per cent transmission values n ere converted to Siedel functions ( A ) ! and these rvere plotted against an arbitrary intensity scale of the siu-step log filter ( 1 ). Experience has shown that there is no appreciable change in gamma for film from the same lot; therefore, a table to convert per cent transmission to relative Intensity can be prepared from the
Table I.
The first effort to develop a suitable method for the quantitative analysis of water samples (4) was based on the work of Heggan and Strock using indium as the carrier-buffer as ne11 as the internal standard. The importance of using a large concentration of indium to achieve effective buffering \vas noted at that time. In expanding the number of elements determined from 7 t o 17, the large concentration of indium required for effective buffering would preclude its use as an internal standard. The use of gallium as a radiation buffer was investigated, but it was found to suppress the emission of some elements. As indium enhances the emission of most of the elements, it was decided to retain indium as the buffer and select a new internal standard. Palladium proved to be suitable for this purpose. Standard curves n-ere prepared for all I T elements from data obtained by analyzing standard solutions atJ leaet six times. These solutions were prepared by dissolving salts of the elements in deionized water to give a series of solutions ranging in concentration from 0.50 to 0.001 rng. per 100 ml. Each standard solution contained 311 17 elements a t the same concentration level. The standard curvea produced Kere all straight lines and exhibited almost unit slope, Figure 1. T o check the accuracy and precision of the method, a series of 10 synthetic
Analytical Range and Accuracy of Synthetic Samples Using a Single Line of Palladium (3287.2 A.) as Internal Standard S O .
Elenient
Aluminum Beryllium Bismuth Cadmium Chromiuiii
Element Lines. 1 2652 3
3131 1
Cobalt Copper
Gallium Germanium Iron
3067 2980 2780 3409 2824 2450 26.51 2823
Iron
2966 9
Lead
llanganese llolybdenuni Sickrl Titanium 1-anadiuni Zinc
i 6 7
2 4 1 6 3
2833 1 2949 2 3208 8 3411 8 3239 0 3110 7 3345 0
of
Range in li)
Deter- Synthetic Samples, minations Mg. in Electrock 22 0.10-0.005 18 8
18
18 20 22 1s 22 22 20
18
16 20 22 22 14
0.010-0.002 0.010-0.00: 0 250-0.010 0.100-0.010 0.050-0.003 0.25~--0.010 0.250-0 010 0.025-0 002 0.050-0 010 0 025-0 005 0 05G.O 05&0 00: OOi 0 010-0 002 0 010-0 002 0 025-0 0023 0 020-0 002 0.020-0 0.125-0 0 125-0 050
Over-all hvcrage
Average Error,
