New limits for the levels of permitted pesticides in water present a challenge to testing laboratories. For Cypermethrin, due to its high aquatic toxicity, a detection limit of 0.01 ng/L is proposed. Any method testing for it is therefore required to provide a high level of enrichment, in order to avoid the need for large sample volumes using traditional liquid-liquid extraction approaches, which can be both expensive and logistically challenging. Stir Bar Sorptive Extraction user Twister™ is known to provide a high level of enrichment and is particularly suited to extraction of non-polar analytes from aqueous matrices. Twister is a glass-encased magnetic stir bar coated with an extraction phase, typically polydimethylsiloxane (PDMS). This application note showed good precision (9%rsd, n= 6) and linearity (0.993) can be achieved with enrichment using twister and selective detection using GC-MS/MS acquisition MRM methods. The technique is simple and avoids the use of traditional liquid/liquid extractions or chemical ionisation while maintaining low detection limits.
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Determination of Trace (pg/L) Levels of Cypermethrin in Water Using Stir Bar Sorptive Extraction