Quantification of nine phthalate esters in a plastic sample using relative molar sensitivities obtained by gas chromatography post-column reaction flame ionization detection and gas chromatography-mass spectrometry

Abstract

Gas chromatography combined with mass spectrometry (GC–MS) has been commonly used in various analytical fields because of its high selectivity and sensitivity; however, for reliable quantification, this method requires a calibrant for each target. By contrast, GC combined with post-column reaction flame ionization detection (-r-FID) can quantify all organic compounds from a single reference on the basis of their number of carbons, which is attributed to the conversion of organic compounds into methane after separation; however, it is not suitable for matrix extracts because GC-r-FID detects all carbon-containing compounds injected into the GC. In this study, we developed a novel method for the reliable quantification of target analytes by combining GC/MS and GC-r-FID. The relative molar sensitivity (RMS) of each target analyte was obtained beforehand from the responses of GC–MS and GC-r-FID using calibration solutions, and each target analyte in matrix-extracts was quantified from the GC–MS responses and RMS. Because the reliability of RMS is important in this method, we examined the reliability of RMS as the first step. We then applied the developed method and verified it by quantifying nine phthalate esters in a matrix-type certified reference material (NMIJ CRM 8152-a, phthalate esters in polyvinyl chloride resin). The analytical results obtained using this method were comparable to those obtained using the conventional method (internal standard method) and those certified or information values. Since RMS can be obtained using common reagents, this method should be suitable for the reliable quantification of target analytes even when corresponding reference materials are not available.