Correspondence Comment on “Metabolism Studies of Phenylsulfonamides Relevant for Water Works” SIR: Knepper et al. present an interesting study on the metabolism of phenylsulfonamide, explaining the formation of the ubiquitous sarcosine-N-(phenylsulfonyl) (SPS) by degradation of 6-[methyl(phenylsulfonyl)amino]hexanoic acid (HPS) via a 2-fold β-oxidation (1). Knepper et al. used the frequently applied diazomethane for derivatization, which creates a problem for the quantification of sarcosine-N(phenylsulfonyl), as shown by Krause et al. in a paper entitled “N-(phenylsulfonyl)glycinesa new contaminant in sewageand surface water” published in Chemosphere in 1998 (2). When SPS was detected by Heberer et al. in sewage farm waters and in sewage plants near Berlin (3-5) as well as in surface water samples at a number of locations in Germany and Italy (6, 7) and by Knepper et al. in several rivers in Germany (8, 9), Krause et al. addressed the question of whether further phenylsulfonylamides exist in the environment. River samples (e.g. river Rhine, river Neckar; Germany) and samples from municipal sewage treatment plants were investigated for glycine-N-(phenylsulfonyl) (GPS), alanineN-(phenylsulfonyl), and sarcosine-N-(phenylsulfonyl) as well as for their corresponding p-toluene analogues (10). To detect glycine-N-(phenylsulfonyl) and sarcosine-N-(phenylsulfonyl) simultaneously, Krause et al. applied diazoethane for derivatization. The distinguishing feature between GPS and SPS is the methyl group of SPS at the nitrogen. On derivatization with diazomethane, the secondary aminogroup of glycine-N-(phenylsulfonyl) is methylated, and thus GPS cannot be distinguished from sarcosine-N-(phenylsulfonyl) (see Figure 1). By using diazoethane GPS can be distinguished from SPS by retention time and mass spectrum, also after ethylation
of the secondary amino group. GPS was identified not only by the mass spectrum but also by its retention time comparing to the corresponding standard. So there is no doubt about the identification of GPS. As a result of the investigations carried out by Krause et al., glycine-N-(phenylsulfonyl) was identified as an hitherto unknown polar contaminant (2, 10). In surface waters, the concentrations of GPS ranged between 50 and 850 ng/L. In municipal sewage treatment plants the concentrations varied: GPS was only found in one influent waste water sample with a concentration of 1200 ng/L; in the biological clarification step and in the effluent its concentration ranged from 80 to 300 ng/L. The measured GPS concentrations were always lower than those of the sarcosine derivative, nevertheless the GPS concentrations could not be ignored. Thus by using diazomethane for derivatization Knepper et al. could not distinguish between SPS and GPS. Their measured SPS concentration is the sum of SPS and GPS!
Literature Cited (1) Knepper, P. K.; Kirschho¨fer, F.; Lichter, I.; Maes, A.; Wilken, R.-D. Environ. Sci. Technol. 1999, 33, 945-950. (2) Krause, S., Niedan, V., Scho¨ler, H. F. Chemosphere 1998, 37, 421-429. (3) Heberer, Th.; Stan, H.-J. Fresenius Environ. Bull. 1994, 3, 639643. (4) Heberer, Th.; Stan, H.-J. GIT Fachz. Lab. 1995, 39, 718-720. (5) Heberer, Th.; Stan, H.-J. Vom Wasser 1996, 86, 19-31. (6) Heberer, Th.; Stan, H.-J. Int. J. Environ. Anal. Chem. 1997, 67, 113-124. (7) Heberer, Th. Identification and Quantification of Pesticide Residues and Environmental Contaminants in Ground and Surface Water Applying Capillary Gas Chromatography-Mass Spectrometer (in German); Wissenschaft & Technik Verlag: Berlin, 1995; p 437. (8) Knepper, T. P.; Weber, A.; Haberer, K. Vom Wasser 1995, 85, 271-284. (9) Knepper, T. P.; Haberer, K. Vom Wasser 1996, 86, 263-276. (10) Krause, S.; Scho¨ler, H. F. Occurrence of N-(Arylsulfonyl)aminoacids in sewage plants, surface- and drinking water (in German); Presented at the annual meeting of the division of water chemistry in Lindau, Germany, 1997; pp 439-441.
Sonja Krause* and Heinz Friedrich Scho1 ler Institute of Environmental Geochemistry Heidelberg University Im Neuenheimer Feld 236 D-69120 Heidelberg, FRG
Thomas Heberer
FIGURE 1. Methylation of N-(phenylsulfonyl)glycine using diazomethane as derivatization agent forming N-(phenylsulfonyl)sarcosine.
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ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 34, NO. 5, 2000
Institute of Food Chemistry Technical University of Berlin Gustav-Meyer-Allee 25 D-13355 Berlin, FRG ES9910255
10.1021/es9910255 CCC: $19.00
2000 American Chemical Society Published on Web 01/21/2000
