SPME-enantioselective gas chromatography with ECD and ICP-MS detection for the chiral speciation of the pesticide ruelene in environmental samples

Abstract

Most chiral pesticides are used as racemates despite the fact that the pesticidal activity is generally due to just one enantiomer while the other one may have toxic effects for nontarget organisms. Accordingly, a separation of the two enantiomers of the organophosphorus pesticide ruelene by capillary gas chromatography (CG) has been developed, using a commercial chiral column (CP-Chirasil-Dex CB) and a temperature program from 50 °C (held for 1 min) to 190 °C at 40 °C min⁻¹ with He as carrier gas. This enantioselective gas chromatographic separation of ruelene can be enhanced by a previous solid-phase microextraction (SPME) sample preparation. Experimental SPME conditions such as extraction time, extraction temperature, salt additives and pH have been optimised. The developed SPME-enantioselective GC procedure has been evaluated using two different detection systems: a classical electron capture detection (ECD) and a P-specific detection with inductively coupled plasma mass spectrometry (ICP-MS). The ICP-MS detector has proved to be superior to the ECD in terms of selectivity and sensitivity with excellent detection limits of 27 ng L⁻¹ (3 ng L⁻¹ as P) for each enantiomer of ruelene. The final determination of enantiomers of ruelene in different spiked samples (river water, red wine, orange and tomato juices) has been worked out. The general advantages of ICP-MS detection for chiral pesticides determinations in complex environmental samples are discussed.