Derivatization of Perfluorocarboxylic Acids with N,N-Dimethylformamide Dimethylacetal Prior to GC–MS Analysis

Abstract

A simple derivatization reaction with N,N-dimethylformamide dimethyl acetal (DMF-DMA) was developed for the analysis of perfluorocarboxylic acids (PFCA, C4–C12) in solid samples by gas chromatography–mass spectrometry (GC–MS). After extraction with methyl tert-butyl ether (MTBE), the samples are mixed with derivatizing agent and injected into GC. The derivatization reaction takes place in injection block forming corresponding N,N,N′,N′-tetramethyl diamines. The method provides excellent separation of nine PFCA (C4–C12) in 15 min and is characterized by good precision (max. RSD = 6.21% for 10 ng/mL, n = 6), linearity and detection limits in the range of 0.15–0.38 ng/mL. The main aim of the study was to develop a quick and easy GC–MS screening for PFCA. The method was successfully applied for sewage sludge, textiles and dental flosses. To confirm the laboratory evaluation, two samples were measured by an external laboratory using LC–MS/MS and showed comparable results. The proposed method is very promising, taking into account its simplicity, mild conditions and application of cost-effective GC–MS system. Additionally, a comparison with two other derivatization methods for PFCA: reaction with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and benzyl bromide is presented.