Coupled two-step microextraction devices with derivatizations to identify hydroxycarbonyls in rain samples by gas chromatography–mass spectrometry

Coupling a two-step liquid-phase microextraction (LPME) with O-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine/bis(trimethylsilyl)trifluoroacetamide (PFBHA)/(BSTFA) derivatization was developed to detect hydroxycarbonyls in rainwater samples using gas chromatography–mass spectrometry (GC–MS). LPME provides a fast and inexpensive pre-concentration, and miniaturized extraction to analyze the target compounds rainwater samples. Derivatization techniques offer a clear method to identify target compounds. The hydroxycarbonyls were determined using two-step derivatizations. Dynamic-LPME was applied in the first derivatization, and head-space single drop derivatization was employed in the second reaction. The LODs varied from 0.023 to 4.75 μg/l. The calibration curves were linear for at least two orders of magnitude with R2 ≥ 0.994. The precision was within 6.5–12%, and the relative recoveries in rainwater were more than 89% (the amount added ranged from 0.3 to 15 μg/l). A field sample was found to contain 2.54 μg/l of hydroxyacetone and 0.110 μg/l of 3-hydroxy-2-butanone. Hydroxyacetone was also detected in one of the tested samples at a concentration of 2.39 μg/l.