High throughput sample preparation in combination with gas chromatography coupled to triple quadrupole tandem mass spectrometry (GC-MS/MS): A smart procedure for (ultra)trace analysis of brominated flame retardants in fish

摘要

In this study, gas chromatography (GC) coupled to triple quadrupole tandem mass spectrometry (MS/MS) operated in electron ionisation mode (EI) has been shown to be an effective tool for the (ultra)trace analysis of several representative brominated flame retardants (BFRs) including polybrominated diphenyl ethers (PBDEs), pentabromotoluene (PBT), pentabromoethylbenzene (PBEB), etc. in complex food and environmental matrices. Using this type of instrumentation, improved selectivity and sensitivity of the instrumental analysis was achieved. In addition to GC-MS/MS (EI), a GC-MS method employing QqQ as a single quadrupole in negative chemical ionisation (NCI) mode was also developed, as this technique might be preferred for those compounds where EI did not provide suitable (intensive enough) mass transitions (e.g., decabromodiphenyl ethane). Following the development of the GC-MS/MS method, a substantial simplification of the sample preparation method was achieved by employing an ethyl acetate QuEChERS-based extraction followed by silica minicolumn clean-up. Using this novel approach, six samples may be prepared in approx. one hour, thus significant time savings were achieved compared to routinely used methods. In addition, the method employs the reduced amounts of organic solvent and other chemicals. Under the optimised conditions, recoveries of all target analytes using both GC-MS/MS (EI) and GC-MS (NCI) were within the range of 70-119% and repeatabilities of the analytical procedure were ≤16% at all three spiking levels (0.1, 1 and 5 μg kg~(-1)). Regarding quantification limits (LOQs), as expected, a single quadruple operated in NCI provided significantly lower LOQs compared to EI. However, using the triple quadrupole mass analyser, comparable LOQs were achieved for both methods (0.005-1 μg kg~(-1) and 0.005-0.1 μg kg~(-1) for GC-MS/MS (EI) and GC-MS (NCI), respectively). Moreover, when highly selective mass transitions in GC-MS/MS (EI) were used for identification and quantification, a significant decrease of problematic interferences was observed compared to NCI where most of the compounds were quantified according to the less selective m/z 79 corresponding to a bromine atom.