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Wojtowicz, J. A. In Kirk-Othmer Encyclopaedia of Chemical Technology, 3rd ed.; Wiley: New York, 1979; Vol. 5, pp 580-611.
Hogfeldt, E. Stability Constants of Metal-Ion Complexes: Part A: Inorganic Ligands; Pergamon Press: Oxford, 1982; IUPAC Chemical Data Series No. 21. D’Aprano, A. J. Phys. Chem. 1971, 75, 3290-3293. D’Aprano, A.; Donato, I. D. Electrochim. Acta 1972, 17, 1172-1 180.
Butterfield, C. J.; Wattie, E.; Megregian, W.; Chambers, C. W. Public Health Rep. 1943,58, 1837-1866. Milbauer, R.; Grossowicz, N. Appl. Microbiol. 1959,7,71-74. Berg, J. D.; Matin, A.; Roberts, P. V. Appl. Environ. Microbiol. 1982, 44, 814-819.
(24) Haas, C. N.; Engelbrecht, R. S. J. Water Pollut. Control Fed. 1980,52, 1976-1989. (25) Haas, C. N.; Engelbrecht, R. S. Water Res. 1980, 14, 1749-1757. (26) Hoff, J. C.; Geldreich, E. E. J . Am. Water Works Assoc. 1981, 74, 40-44.
Received for review November 11,1985. Accepted March 20,1986. The work reported in this study formed part of the M.Eng. theses of M.A.Z. (M.Eng.,Rensselaer Polytechnic Institute), M.G.K., and D.M.B. ( M A , Illinois Institute of Technology). Portions of this work were presented at the 4th and 5th Water Chlorination Conferences.
Recovery of Several Volatile Organic Compounds from Simulated Water Samples: Effect of Transport and Storage Llnda C. Friedman, LeRoy J. Schroder,’ and Michael G. Brooks
Denver Federal Center, U.S. Geological Survey, Lakewood, Colorado 80225
Solutions containing volatile organic compounds were prepared in organic-free water and 2% methanol and submitted to two U S . Geological Survey laboratories. Data from the determination of volatile compounds in these samples were compared to analytical data for the same volatile compounds that had been kept in solutions 100 times more concentrated until immediately before analysis; there was no statistically significant difference in the analytical recoveries. Addition of 2% methanol to the storage containers hindered the recovery of bromomethane and vinyl chloride. Methanol addition did not enhance sample stability. Further, there was no statistically significant difference in results from the two laboratories, and the recovery efficiency was more than 80% in more than half of the determinations made. In a subsequent study, six of eight volatile compounds showed no significant loss of recovery after 34 days. W
Introduction The two laboratories of the U.S. Geological Survey daily receive hundreds of water samples from sampling sites located throughout the United States. Determination of purgeable or volatile organic compounds, as defined in volume 44 of the Federal Register (I), is requested for many of these samples. Although the US. Geological Survey has prepared and distributed Standard Reference Water Samples since 1962 (2-6)) volatile organic compounds have not been included in the program, and the laboratory quality-assurance program has relied on the use of the U S . Environmental Protection Agency’s (EPA) ampuled concentrates of volatile compounds (7, 8). A study was conducted in the summer of 1983 with the twofold objective of obtaining information about the stability of volatile organic compounds during their transport from the sampling site to the laboratory and of examining the comparability of data being produced by the two US. Geological Survey laboratories. Sample Preparation] Distribution, and Analysis In order to prepare samples that would closely replicate water samples that might be received from the field offices, five standards for bromoform, chlorobenzene, dichlorobromomethane, ethylbenzene, and 1,1,2,2-tetrachloroethane were obtained from EPA. These compounds were 826
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selected because they had been reported in water (9-13); compounds such as methylene chloride, carbon tetrachloride, and chloroform were avoided because of the likelihood of contamination from these compounds that are commonly present in chemical laboratories. The concentration of each of the five standards was 10000 mg/L, and all standards were in methanol. EPA data sheets indicated that concentrations of bromoform, chlorobenzene, and ethylbenzene had 10% uncertainties; concentrations of dichlorobromomethane and tetrachloroethane had 5 % uncertainties. Using serial dilution, three different mixed standards were prepared. Two of the mixtures contained all five compounds, whereas the third contained all compounds except chlorobenzene; chlorobenzene was left out of the third mixture to determine if a false positive value for chlorobenzene would be reported. For each dilution, compounds were added by inserting the appropriate pipet or syringe below the solution meniscus. Because of compound volatility, a 2% methanol solution was used instead of distilled water for the final dilution in order to reduce compound loss (14). Compound concentrations ranged from 4 to 40 pg/L (Table I). In addition to the 2% methanol mixtures, one solution containing four compounds was prepared in pure (gaschromatographic grade) methanol. The concentrations of compounds in this mixture were selected so that, when diluted 100 times, a solution would be prepared with concentrations equivalent to sample 3 in Table I. All solutions containing the volatile organic compounds were prepared within about 4 h. Simulating sample-handling procedures followed in the field (15,16), the 2% methanol solutions were transferred to 40-mL hermetically sealed vials. Each vial was filled to overflowing and sealed with a septum screwcap with the propylene-tetrafluoroethylene side of the septum in contact with the solution. Each sample was checked visually to make sure that no bubble or headspace was present, and each septum cap was wrapped with aluminum foil. The pure methanol solution was transferred to 2-mL vials and sealed with a septum crimp-cap with the ethylene-tetrafluoroethylene side of the septum in contact with the solution. The U.S. Geological Survey laboratories are located in Denver, CO, and Atlanta, GA. The samples were prepared
Not subject to US. Copyright. Published 1986 by the American Chemical Society
Table I. Summary of Recovery and Precision Data from Analyses of 2% Methanol Simulated Water Samples"
compound bromoform chlorobenzene dichlorobromomethane ethylbenzene 1,1,2,2-tetrachloroethane
sample 1 2 3 1 2 1 2 3 1 2 3 1 2 3
prepared concn, pg/L 12 6 16 8 16 10 6 10 4 20 14 10
40 20
All values are the average of three results except where noted. cThe three values reported were 3.5, 5.0, and
