Targeted and non-targeted analysis of organic compounds of moderate polarity in water using liquid chromatography-time of flight mass spectrometry in all ion mode with particular reference to analysis of pesticides

Abstract

We have developed a novel yet efficient method for the multi residue analysis of organic compounds of diverse polarities in water using Liquid Chromatography-Time of Flight mass spectrometry (LC-MS-TOF) equipped with a jet stream Electrospray ionization (ESI) source. Use of three different fragmentor voltages (low, medium and high) enabled the qualitative and quantitative analysis of a diverse range of targeted organic compounds in environmental waters. No prior optimization of compounds being quantified was required, the limiting factors were ionization behaviour of compounds under conditions of ESI and good chromatography. Same data file could be subjected to repeated post-run data analysis to figure out the presence of non-targeted compounds, including designer drugs if any. The technique has been illustrated with reference to a group of pesticides having diverse chromatographic and ionization behaviours. The optimized Solid Phase Extraction (SPE) followed by method validation yielded a robust yet simple quantitative method for a group of fourteen pesticides. We were able to achieve quantitation at 10 ng/L or lower depending upon ionization behaviour of substrates against the usual regulatory requirement of 1000 ng/L. The method was used for targeted and non-targeted detection of pesticides in Nueces estuary waters, TX, USA, and several untargeted pesticides, pharmaceuticals and personal care products were identified.