Environ. Sci. Technol. 2000, 34, 919-920
Response to Comment on “Metabolism Studies of Phenylsulfonamides Relevant for Water Works” SIR: Thank you for giving us the opportunity to respond to the comments of Krause, Scho¨ler, and Heberer, regarding our paper (1). After the unequivocal identification of sarcosine-N(phenylsulfonyl) (SPS) utilizing GC/MS after various derivatization methods (2, 3) and quantifying this hitherto unknown compound in the aquatic environment (3, 6) it was us that addressed already in 1995 the question of 6-[methyl(phenylsulfonyl)amino]hexanoic acid (HPS) as a possible source of SPS. Since we only succeeded once in detecting HPS in one sewage influent and the corresponding effluent, we focussed in the following years on metabolism studies of HPS in order to confirm the formation of SPS. Thereby, we detected also another possible metabolite of HPS, namely 4-[methyl(phenylsulfonyl)amino]butanoic acid (BPS), which is the missing link in the degradation chain of HPS via β-oxidation. We were also the first to detect this “new” metabolite in the aquatic environment. During the metabolismstudiesreportedinref1wediscoveredalsomethyl(phenylsulfonyl)amide (MPS) as a metabolite being formed during the degradation of the recalcitrant SPS. After our findings Krause and Scho¨ler addressed the presence of further sulfonamides in the aquatic environment (7). Thereby they were able to detect glycine-N-(phenylsulfonyl) (GPS) in sewage and surface water. With regard to the methodology in question, among other derivatization reagents we used diazomethane for the reported metabolism studies (1). It is true that in applying this technique, GPS would also be methylated at the amidefunction and would thereby contribute to the measured concentration of SPS. Also the reported values of GPS are much lower than those of SPS; the values of SPS reported so far from environmental samples after derivatization with diazomethane could be the sum of GPS and SPS. Therefore, the comment from Krause et al. is worthwhile in order to perform in the future further quantification of such environmentally relevant sulfonamides by applying diazoethane for esterification. Anyhow, in our investigations and as already published in refs 3 and 5, we also identified SPS using isopropyl- and n-butylester and also as an underivatized compound by LC/ MS. This was done also in further investigations of various environmental samples for quality control. Thereby, we never detected GPS. Heberer et al. used pentafluorobenzenebromide as a derivatization agent and likewise also never detected the GPS (2, 4). We are also inclined about the appropriate identification of GPS in the environmental samples so far. In the mass spectra of the small signal beside SPS (as ethylester) in the chromatograms obtained from the real samples (Figures 4 and 5 in ref 7), the mass spectra shown did not correspond to the outlined ethylated GPS (predicted m/z ) 77, 130, 141, 198). Instead the characteristic masses of the mass spectrum of m/z ) 141 and 170 seem to belong to another compound, which could be N-butyl-N-phenylsulfonyl (a plasticizer with these characteristic fragment ions in the EI-spectrum) that can be routinely detected in sewage water and surface water (our unpublished results, 8). In addition, we also did investigations on the degradation of HPS using LC/MS and GC/MS without derivatization and 10.1021/es992030b CCC: $19.00 Published on Web 01/21/2000
2000 American Chemical Society
FIGURE 1. Possible formation of GPS out of N-butyl-N-phenylsulfonyl.
FIGURE 2. Comparison of SPS concentrations in the river Main, Germany measured in the floating wave in Dec 1994 and Dec 1998. Analyses were performed by GC/MS after diazomethane derivatization. have never detected any other metabolite other than the reported ones (1). With the recent investigations on the degradation of HPS on the test filter device, the isopropylester of the precursor as well as the biodegradation compounds were also detected, and it was again confirmed that only BPS, SPS, and MPS were found but not GPS (our own unpublished data). Therefore we are quite confident that GPS seems not to be a product of the degradation of HPS nor is it from BPS or SPS. We would assume that N-butyl-N-phenylsulfonyl (see above) could possibly undergo a ω-oxidation with a subsequent β-oxidation to form GPS (Figure 1). This could indeed be detected as SPS after derivatization with diazomethane. We already mentioned in ref 1 that our findings (9) led to the closure of the one and only HPS-producing branch in Germany in the year 1997/1998 (confidential data) resulting already in a measurable effect on the environment (Figure 2). Measurements in the floating wave of the river Main in VOL. 34, NO. 5, 2000 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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Germany were compared in December 1994 and December 1998. It is clearly shown that after HPS production had been stopped, SPS and also BPS (data not shown) could only be detected in very low concentrations. Our present up to now unpublished data show that today in all investigated river and sewage water samples there is a tremendous reduction in the SPS concentration. Despite the production stop, there seems to be still a slight entry of the HPS via the previous stocks, but it cannot be ruled out that, as published by Krause et al., GPS could contribute to these determined values.
Literature Cited (1) Knepper, T. P.; Kirschho¨fer, F.; Lichter, I.; Maes, A.; Wilken, R.-D. Environ. Sci. Technol. 1999, 33, 945-950. (2) Heberer, T.; Stan, H.-J. Fresenius Environ. Bull. 1994, 3, 639643. (3) Knepper, T. P.; Weber, A.; Haberer, K. Vom Wasser 1995, 85, 271-284. (4) Heberer, T.; Stan, H.-J. Vom Wasser 1996, 86, 19-31.
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(5) Knepper, T. P.; Haberer, K. Vom Wasser 1996, 86, 263-276. (6) Heberer, T.; Stan, H.-J. Int. J. Environ. Anal. Chem. 1997, 67, 113-124. (7) Krause, S.; Niedan, V.; Scho¨ler, H. F. Chemosphere 1998, 37, 421-429. (8) Huppert, N.; Wu ¨ rtele, M.; Hahn, H. H. Fresenius J. Anal. Chem. 1998, 362, 529-536. (9) Knepper, T. P.; Sacher, F.; Lange, F. T.; Brauch, H.-J.; Karrenbrock, F.; Ro¨rden, O.; Lindner, K. Waste Management 1999, 77-99.
Thomas P. Knepper ESWE-Institute for Water Research and Water Technology, Soehnleinstr. 158 D-65201 Wiesbaden, Germany ES992030B
