Simultaneous detection of drugs of abuse in waste water using gas chromatography-mass spectrometry

Sewage epidemiology is increasingly becoming an alternative method of estimating drug usage and consumption patterns for a given population. With the constant emergence of new psychoactive substances such as cathinones and piperazines, versatile, reliable, specific and sensitive analytical methods are needed for their detection in complex matrices such as waste water. This thesis reports the development of an analytical method based on solid phase extraction, derivatization with pentafluoropropionic anhydride and analysis by gas chromatography-mass spectrometry for the simultaneous analysis of 29 illicit and therapeutic drugs of abuse. All 29 drugs could be reliably identified in spiked waste water samples using selected ion monitoring and splitless injection. Recoveries for the majority of the drugs were above 70 %. Linearity varied based on the analyte but was assessed in the range 2.0 x 10-4 to 1.4 μg/mL. Intra-assay and intermediate precision of the instrument was determined at 0.005, 0.1 and 1.0 μg/mL, with the majority of relative standard deviations less than 10 %. Limits of detection and quantification for drugs such as amphetamine and methamphetamine were better than reported values for liquid chromatography-tandem mass spectrometry, a more commonly used technique. Untreated 72 h composite waste water samples from Cambridge, UK, were analysed using a six-point standard addition curve. Eleven drugs of abuse were detected, including amphetamine, methamphetamine, butylone and 4-fluoromethamphetamine. The latter two having been detected for the very first time in waste water. Using the validated method, the consumption of heroin, ketamine, cocaine, methamphetamine and amphetamine, in Cambridge, UK, was estimated to be 399.4 ± 90.8, 2463.5 ± 182.5, 195.5 ± 95.4, 84.3 ± 59.1 and 38.9 ± 24.8 mg/day per 1000 inhabitants. This is the first reported validated method for the detection of both classic drugs of abuse and new psychoactive substances in waste water using gas chromatography-mass spectrometry and derivatization with pentafluoropropionic anhydride.