Transformation of cocaine during water chlorination.
The stability of cocaine and its two main human metabolites, benzoylecgonine and ecgonine methyl ester, in chlorine-containing waters has been investigated by direct injection of different reaction time aliquots in a liquid chromatograph (LC) coupled to a quadrupole-time-of-flight mass spectrometer (QTOF-MS). Factors potentially affecting cocaine degradation (the only compound showing a significant decrease in the preliminary study) were evaluated in detail by means of a Box-Behnken experimental design. Sample pH resulted to be the most important variable, increasing both the rate of chlorination-mediated reactions and the ester hydrolysis process. From these reactions, and due to the high mass accuracy measurements obtained with the QTOF system, four by-products could be positively identified: benzoylecgonine, norcocaine, norbenzoylecgonine and N-formylnorcocaine. Finally, their formation and cocaine degradation yields were assessed under chlorination experiments with two real surface water samples. In one of them, showing a low anthropogenic impact, benzoylecgonine and norcocaine were notably generated even after only 1 h of reaction, whereas at higher contact times also norbenzoylecgonine and N-formylnorcocaine could be determined with a lower yield. On the other hand, the second sample, with a higher organic matter content, consumed rapidly the chlorine, so that only benzoylecgonine was produced. These findings point out the convenience of monitoring the described transformation products, in addition to the precursor illicit drug, during drinking water production, taking into account that cocaine traces might be present in water catchments and particularly in areas with high population densities.
Department of Analytical Chemistry, Nutrition and Food Sciences, IIAA-Institute for Food Analysis and Research, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain.
Iria
I
González-Mariño
José Benito
JB
Quintana
Isaac
I
Rodríguez
Noemí
N
Sánchez-Méndez
Rafael
R
Cela
D001965:Bromides / Q000737:chemistry / Q000378:metabolism; D002713:Chlorine / Q000737:chemistry / Q000378:metabolism; D002853:Chromatography, Liquid; D003042:Cocaine / Q000031:analogs & derivatives / Q000737:chemistry* / Q000378:metabolism*; D004202:Disinfectants / Q000737:chemistry / Q000378:metabolism; D060766:Drinking Water / Q000737:chemistry* / Q000378:metabolism; D054879:Halogenation; D006801:Humans; D006863:Hydrogen-Ion Concentration; D013058:Mass Spectrometry; D018508:Water Purification
D001965:Bromides; D004202:Disinfectants; D060766:Drinking Water; D002713:Chlorine; D003042:Cocaine; C012209:benzoylnorecgonine; C034524:ecgonine methyl ester