Different sorbents were deposited on dispersive solid-phase extraction silica.  Poly (methyloctadecylsiloxane) (PMODS), poly (methyloctylsiloxane) (PMOS), aminopropyl-terminated poly(dimethylsiloxane) (APPS) and a copolymer of (52 – 48%) dimethyl-(48 – 52%) methylphenyl-siloxane (DMMPS).  The PMODS, PMOS and APPS materials were obtained from UCT Specialties, Bristol, PA. 

Commercial sorbent primary-secondary amine (PSA) and mixtures of two sorbents, primary-secondary amine and poly (methyloctadecylsiloxane), were also used in the experiments.

The performance of the sorbents were evaluated by parameters such as color of the final extract, gravimetric measurement, recovery and matrix effect at the fortification level of 100 ng/g of pesticide mixture strawberries.

In this experiment, the PSA sample was the best in achieving optimal results.  The PSA and PMODS also offered good results in the determination of pesticide residues in strawberries.  Further experimentation in this area of mixed sorbents is continuing because of the low matrix effect and excellent recoveries obtained when using this technique.

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