Development, optimisation and validation of a liquid chromatography-mass spectrometry method for the detection of drugs of abuse and pharmaceuticals in drinking water

The quality of drinking water is fundamental to human health and welfare and therefore it is important to remove contaminants. Recent research has focused on the presence of drugs of abuse and pharmaceuticals in water which could have an adverse effect on human health via bio-accumulation. Therefore, the focus of this research is to develop a method to simultaneously analyse 20 traditional illicit drugs, novel psychoactive substances (NPS) and antidepressants in drinking water from the East Anglian, UK, which has never been investigated before. Furthermore, removal efficiencies were also determined to assess the drinking water treatment plants effectiveness in treating and eliminating such compounds. The analysis was based on solid-phase extraction (SPE) and liquid chromatography-mass spectrometry (LC-MS) using a C18 column for identification and quantification, followed by a biphenyl column for confirmation. 65 - 107 % SPE recoveries were achieved for 17 analytes. For the C18 column, precision was below 7.57 % and 15.04 % relative standard deviations for higher and lower concentrations and method accuracy was below ± 8.66 % bias at low, medium and high concentrations. Method detection and quantification limits (0.0056 - 1.0918 ng/L and 0.0187 - 3.6394 ng/L) were at sub ng/Ls. For the biphenyl column, the method was selective and instrumental detection limits ranged from 0.0115 to 0.4795 ng/mL. This is the first reported method for the analysis of 20 drugs of abuse and pharmaceuticals in drinking water using LC-MS. Cocaine, methamphetamine, citalopram, fluoxetine, ketamine, mephedrone and methylone were detected in drinking water between 0.139 and 2.814 ng/L. The latter two NPS have been found in drinking water for the first time. In addition, the removal efficiencies of drinking water treatment plants were determined for methamphetamine, fluoxetine, ketamine and mephedrone from -25.27 % to 98.76 %. The findings could help to identify and recognise the ever-changing composition of contaminants in drinking water, which can aid in the development of water treatments for their removal. Moreover, this research could inform drinking water regulatory bodies of the presence of drugs of abuse and pharmaceuticals, as they are currently not included within the regulatory framework.