Headspace Solid Phase Microextraction in Pesticide Residues Analysis: 1. Optimisation of Extraction Conditions

Abstract

The method of headspace solid phase microextraction (HS/SPME) was successfully used in a simultaneous multicomponent analysis of hexachlorobenzene (HCB), tefluthrin, heptachlor, aldrin, chlorpyrifos, fenthion and bifenthrin in aqueous medium. Measurements were performed using a nonpolar polydimethyl siloxane (PDMS) fiber. Detection and quantification were done by gas chromatography/mass spectrometry (GC/MS). Optimal conditions for HS/SPME were determined both by performing extraction at different temperatures and examining extraction time profiles at constant temperature. Optimal extraction temperature for each pesticide studied was determined as follows: 60°C for HCB and for heptachlor, 80°C for aldrin and for chlorpyrifos, fenthion and tefluthrin, and temperature exceeding 80°C for bifenthrin. For the pesticide mixture studied, 60°C was identified as the optimum extraction temperature. Based on the time profiles obtained, it was confirmed that satisfactory extraction sensitivity can be obtained even for extraction times shorter than the time required to reach a sorption equilibrium. This conclusion was confirmed by linear concentration profiles obtained for the following ranges: 0.05-10 ng/ml (HCB), 0.05-25 ng/ml (tefluthrin), 0.05-40 ng/ml (heptachlor), 0.05-40 ng/ml (aldrin), 0.05-25 ng/ml (chlorpyrifos), 0.05-25 ng/ml (fenthion) and 0.05-25 ng/ml (bifenthrin). Relative standard deviation (RSD) values for triplicate measurements did not exceed 15%.

Metoda mikroekstrakcije u čvrstoj fazi – uzorkovanje iz gasovite faze (HS/SPME) je uspešno primenjena za istovremenu višekomponentnu analizu heksahlorobenzena (HCB), teflutrina, heptahlora, aldrina, hlorpirifosa, fentiona i bifentrina u vodenoj sredini. U radu je korišćeno nepolarno polidimetilsiloksansko vlakno (PDMS). Detekcija i kvantifikacija analita je vršena metodom gasno-masene spektrometrije (GC/MS). Optimalni uslovi HS/SPME metode su odreðeni praæenjem efikasnosti ekstrakcije na različitim temperaturama, odnosno u funkciji vremena na konstantnoj temperaturi. Za svaki ispitivani pesticid, određena je optimalna temperatura ekstrakcije: 60°C za HCB i heptahlor, 70-80°C za aldrin, hlorpirifos, fention i teflutrin, temperatura veæa od 80°C za bifentrin. Za ispitivanu smešu, temperatura od 60°C je izabrana za praktičan rad. Na osnovu dobijenih vremenskih profila, utvrđeno je da se dobra osetljivost metode postiže i kada se radi sa vremenom ekstrakcije kraæim od ravnotežnog. Ovaj zaključak je potvrđen i eksperimentalno dobijenim koncentracionim profilima, pri čemu su dobijeni sledeći opsezi linearnosti: 0.05- 10 ng/ml (HCB), 0.05-25 ng/ml (teflutrin), 0.05-40 ng/ml (heptahlor), 0.05-40 ng/ml (aldrin), 0.05-25 ng/ml (hlorpirifos), 0.05-25 ng/ml (fention) i 0.05-25 ng/ml (bifentrin). Relativne standardne devijacije (RSD) računate na osnovu tri ponovljena merenja su uvek bile manje od 15%.