Improved LC–MS/MS Method for the Simultaneous Determination of Synthetic Phenol Antioxidants and Relevant Metabolites Making Use of Atmospheric Pressure Chemical Ionization and a Trap Column

Abstract

The prevalently used LC–MS/MS methods for the simultaneous determination of synthetic phenol antioxidants (SPAs) and relevant metabolites suffer from a serious drawback of low sensitivity for 2,6-di-tert-butyl-4-hydroxytoluene (BHT) and a common issue of background contamination, which hampers the simple and accurate detection of these substances at trace levels in environmental samples. In this study, we developed an improved LC–MS/MS method for the simultaneous determination of eight SPAs and four relevant metabolites, including BHT. By use of atmospheric pressure chemical ionization (APCI), the sensitivity of BHT in the LC–MS/MS was enhanced approximately 260 times versus results obtained by using electrospray ionization (ESI), which allowed the analysis of BHT up to 1.1 ng/g in indoor dust and 0.06 ng/g in human plasma. Similarly, the sensitivity of 2,4,6-tri-tert-butylphenol and 2,6-di-tert-butyl-4-sec-butylphenol was also enhanced with APCI, which avoided their separate analysis by GC–MS. By installation of a C18 column after the eluent mixer and before the injector as a trap column, the target analytes leached out from the LC system were eluted at a much later retention time than those in the samples, which resulted in complete elimination of the instrumental background contamination. These improvements enable the method to be well applied to the real samples.