ANALYTICAL CHEMISTRY, VOL. 51, NO. 13, NOVEMBER 1979
Table 11. Chemiluminescence Bromide Concentration
[Br-1, M 0.003 0.005 0.007 0.01
% light emission (Cr only = 100%)
as a
Function of
[BY], h.I
% light emission (Cr only = 100%)
minescence technique to the determination of' chromium in seawater. Chemiluminescence intensity enhancements, with chloride or bromide ions, have also been observed for Co(II), Fe(II), and Ni(I1) ions.
LITERATURE CITED (1) W. R. Seitz. W. W. Suydam, and D. M. Hercules, Anal. Chem., 44, 957 (1972). (2) S . D. Hoyt and J. D. Ingle, Jr., Anal. Chim. Acta, 87, 163 (1976). (3) J. L. Bowling, J. A. Dean, G.GoMstein, and J. M. Dale, Anal. Chlm. Acta. 76, 47 (1975). (4) D. R. Kester et al., Limnol. Oceanogr., 12, 176 (1967). (5) R. Delumyea and A. V. Hartkopf, Anal. Chem., 48, 1402 (1976). ( 6 ) T. G. Burdo and W. R. Seitz, Anal. Chem., 47, 1639 (1975).
470 620
100 106
0.1
120
0.5
150
1.0
780 8 50
2.0
940
0.3
Spectrophotometer. Light emission is monitored at 430 nm. Samples have been analyzed as outlined previously ( I , 2) using standard addition methods and heating the samples in the presence of EDTA to determine the background signal. The signal responses have been corrected for the blank response in the absence of Cr(II1). In summary, the addition of chloride or bromide ions has been found to increase the sensitivity of the chemiluminescence analysis of trace metals. The detection limit for Cr(II1) has been lowered to 1.3 X M (ca. 7 parts-per-trillion) for freshwater systems, when 0.5 M Br- is present. These results may be compared to the 50 parts-per-trillion detection limit we found for the reference ( I ) method using our MPF-44A spectrafluorimeter. Further, we have extended the chemilu-
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Daniel E. Bause Howard H. Patterson* Department of Chemistry University of Maine Orono, Maine 04469 RECEIVED for review May 4, 1979. Accepted (July 16, 1979. The work upon which this publication is based was supported in part by funds provided by the Office of Water Research and Technology (No. B-016-ME), 1J.S. Department of the Interior, Washington, D.C., as authorized by the Water Research and Devlopment Act of 1978.
Brominating Solution for the Preconcentration of Mercury from Natural Waters Sir: In recent papers, workers have reported the application of a brominating solution ( I , 2) and bromine vapor (3)for the pretreatment of water samplzs prior to mercury determination by the cold vapor technique. The reagent makes available the Hg2+ion from organomercury associations in the sample. The use of a brominating solution as a preservative for water samples prior to analysis for mercury has also been suggested ( 2 ) . As a consequence, it might be inferred that the brominating reagent has a high affinity for the inorganic mercury ion. This has prompted us to use it in a preconcentration technique for mercury determination. A well documented general procedure (3-5) for preconcentrating mercury from natural waters prior to measurement by the cold vapor technique involves purging the sample after treatment with a powerful reducing agent and collection of the volatilized mercury vapor on a suitable absorbing medium. We have experimented with an acid-bromate-bromide solution (0.7% w/v HC1, 0.011% w/v KBr03, 0.04% w/v KBr) as an absorbing medium in the apparatus shown in Figure 1. The solution is prepared by adding 40 mL of 1%w/v potassium bromide-0.28% w/v potassium bromate reagent and 20 mL of hydrochloric acid (36% w/v) to distilled water and ARGON GAS IN FROM FLOWMETER
diluting to 1 L. Purging 850 mL of' the sample and added stannous chloride for 10 min with argon gas at a flow of 2 L/min, we found that 10 mL of the solution acted as an effective trap for mercury vapor. This is in spite of the fact that part of the bromine volatilizes from the solution during the passage of gas. With 2 such traps connected in series to a 25 ng/L mercury standard,
