Headspace Solid Phase Microextraction in Pesticide Residues Analysis: 2. Apple Samples

Abstract

Headspace solid phase microextraction method (HS/SPME), optimised previously for pesticide water solutions, was applied to trace residues of the pesticides chlorpyrifos, fenthion and bifenthrin in apple samples. One-hour extraction procedure was performed at 60oC extraction temperature. Nonpolar polydimethyl siloxane (PDMS) fiber was used. Detection and quantification were carried out by gas chromatography/mass spectrometry (GC/MS). A non-pesticide treated apple sample was fortified with the pesticides over a 0.025- 1.25 mg/kg concentration range in order to determine analytical parameters of the method applied. Linearity with regression coefficient (R) values higher than 0.99 were obtained over the whole concentration range investigated for chlorpyrifos and fenthion, while linear dependence was observed in the 0.1-1.25 mg/kg range for bifenthrin. Relative recovery values for samples fortified at different levels were in the 56.68-82.91% range. Limit of detection (LOD) values were determined as follows: 0.014 mg/kg for chlorpyrifos, 0.021 mg/kg for fenthion and 0.053 mg/kg for bifenthrin. Relative standard deviation (RSD) values obtained for multiple analysis of the sample fortified at 0.6 mg/kg level were not higher than 20%.

Metoda mikroekstrakcije u čvrstoj fazi - uzorkovanje iz gasovite faze (HS/SPME) optimizovana sa mešanim standardnim rastvorima hlorpirifosa, fentiona i bifentrina je testirana na uzorcima jabuka. Ekstrakcija u trajanju od 60 minuta je izvršena na temperaturi od 60oC sa 2 ml pripremljenog uzorka. Korišćeno je nepolarno 100 μm polidimetilsiloksansko (PDMS) vlakno. Detekcija i kvantifikacija su izvr.ene metodom gasno-masene spektrometrije (GC/MS). U cilju određivanja analitičkih parametara, pravljena je serija obogaćenja referentnog uzorka jabuka mešanim standardnim rastvorom pesticida tako da finalne koncentracije budu u rasponu 0.025-1.25 mg/kg. Linearnost (r2 > 0.99) je dobijena za ceo ispitivani koncentracioni opseg. Prinosi ekstrakcije za sve pesticide i sve koncentracije uključene u ispitivanje su u rasponu 56.68-82.91%. Granice detekcije metode (LOD) su bile 0.014 mg/kg za hlorpirifos, 0.021 mg/kg za fention i 0.053 mg/kg za bifentrin. Preciznost, odnosno ponovljivost merenja je određena na uzorku obogaćenom sa 0.6 mg/kg svakog pesticida. Izračunate RSD vrednosti su uvek bile ispod 20%.