Solid-Phase Microextraction in Targeted and Nontargeted Analysis: Displacement and Desorption Effects

An aqueous multicomponent mixture containing a wide range of volatility and polarity compounds (log K-ow range 1.26-8.72) was used to clearly define the capabilities and limitations of headspace solid-phase microextraction in quantification of multicomponent complex samples. Commercially available fiber coatings were evaluated by investigating the extraction efficiency and desorption carryover. Comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry was selected to map out the differences between the coatings. The investigated components were chosen to represent several homologous groups of metabolites most frequently present in complex food and environmental samples, including straight-chain hydrocarbons, primary alcohols, secondary alcohols, 2-ketones, aldehydes, ethyl esters, and terpenes. Particular emphasis was placed on examination of coating saturation and interanalyte displacements. These effects were assessed by evaluating the linear dynamic range obtained for spiked aqueous samples with divinylbenzene/Carboxen/poly(dimethylsiloxane) fiber. This coating was found to provide the optimum extraction coverage and sensitivity for the widest range of analytes. Displacement investigations were extended to apple homogenate characterized by high chemical diversity. The results indicate that interanalyte displacements are infrequent in the naturally occurring samples considered in this study. When displacements take place, they tend to occur for analytes characterized by small distribution constants, and they can be effectively detected by adding such compounds to the sample and corrected by selecting a shorter extraction time.