Fractional factorial design based microwave-assisted extraction for the determination of organophosphorus and organochlorine residues in tobacco by using gas chromatography-mass spectrometry.

Sample preparation is often the main bottleneck in analyzing biological samples. Particularly, effective evaluation of sample preparation conditions usually involves multiple factors and tedious and time-consuming experiments. In this study, fractional factorial design, specifically orthogonal array testing, was employed to screen and optimize multiple extraction parameters in concise but representative experiments. An efficient and sensitive method was developed to determine organophosphorus and organochlorine pesticide residues in tobacco, via microwave-assisted extraction and gas chromatography coupled with mass spectrometry detection. With orthogonal array design, screening, and optimization tests were subsequently conducted to determine the range, impact rank, and possible interactions of extraction temperature, time, microwave power, additive salt, and additive water. Orthogonal array testing selectively reduces the size and cost of experiments and meanwhile provides more information compared to the traditional experimental design that optimizes one factor at a time. A good linear range (0.02-2.00 μg/mL), limits of detection (0.001-0.098 μg/mL), and recovery rates (70.4-107.1%) were demonstrated by spiking known concentrations of multiple pesticide standards in tobacco samples. The established method was then successfully applied to the determination of multipesticide residues in raw tobacco leaves and commercial cigarettes.