An improved method has been developed for the quantitative determination of cyanide in human blood by headspace gas chromatography with electron-capture detection. In this novel method, cyanide was detected after conversion of hydrogen cyanide into cyanogen chloride by a reaction with chloramine T. The advantage of this new procedure lies in the fact that hydrogen cyanide formation and chlorination are carried out in a single step and in the same reaction medium. This method is simple, rapid, and specific for cyanide and does not suffer from any interference by cyanate and thiocyanate. The detection limit is 5 micrograms/L. The detection response is linear from 5 to 1000 micrograms/L, and the within-run coefficient of variation in this range is 8% or less. This method is particularly useful for routine diagnostic analysis of biological samples in case of acute cyanide poisoning.
Tetrachloroethylene (PCE) is a chlorinated aliphatic compound essentially used as a degreasing and drycleaning solvent. It is commonly found as a groundwater contaminant and because of its carcinogenic properties is considered a pollutant. Biotransformation of PCE in ethane or ethylene has been studied by many researchers at low concentrations under strict anaerobic conditions (De Bruin et al., 1992;Freedman and Gossett, 1989).The dechlorination process was observed in methanogenic, acetogenic, or sulfate-reducing habitats (Holliger and Schraa, 1994;Mohn and Tiedje, 1992). In anaerobic PCE-enrichment culture, methanogenesis and acetogenesis disappeared with high concentrations of PCE (Maymo-Gatell et al., 1995). Ecological understanding of such communities will probably be important in using dehalogenation in bioremediation processes (Mohn and Tiedje, 1992).A methanogenic and sulfate-reducing consortium degrading PCE was obtained in our laboratory from anaerobic-digested sludge from a wastewater treatment plant (Bourg-en-Bresse, France). Initially, high concentrations of PCE were dechlorinated in trichloroethylene (TCE) by methanogenic fermentation in batch conditions. The sulfate-reducing bacteria were not involved in PCE dehalogenation (Cabirol et al., 1996). This methanogenic and sulfate-reducing consortium was then cultivated continually in the presence of high concentrations of PCE. The methanogenic bacteria always had a deciding role in the dechlorination process after this enrichment period. The pollutant was completely degraded to carbon biomass and CO 2 . PCE dehalogenation has been studied in a semicontinuous fixed-bed reactor, revealing an attractive method for removing high concentrations of PCE in bioremediation processes (Cabirol et al., 1998 A methanogenic and sulfate-reducing consortium, which was enriched on medium containing tetrachloroethylene (PCE), had the ability to dechlorinate high concentrations of PCE. Dehalogenation was due to the direct activity of methanogens. However, interactions between methanogenic and sulfate-reducing bacteria involved modification of the dechlorination process according to culture conditions. In the absence of sulfate, the relative percentage of electrons used in PCE dehalogenation increased after an addition of lactate in batch conditions. The sulfate reducers would produce further reductant from lactate catabolism. This reductant might be used by methanogenic bacteria in PCE dechlorination. A mutualistic interaction was observed in the absence of sulfate. However in the presence of sulfate, methanogenesis and dechlorination decreased because of interspecific competition, probably between the H 2 -oxydizing methanogenic and sulfate-reducing bacteria in batch conditions. In the semicontinuous fixed-bed reactor, the presence of sulfate did not affect dechlorination and methanogenesis. The sulfate-reducing bacteria may not be competitors of H 2 -consuming methanogens in the reactor because of the existence of microbial biofilm. The presence of the fixed film may ...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.