Objective To investigate the influencing factors for the high blank value in the determination of per- and polyfluoroalkyl substances (PFASs) in human urine by solid phase extraction-ultra performance liquid chromatography-tandem mass spectrometry (SPE-UPLC-MS/MS), and to propose treatment measures.
Methods The samples were firstly extracted and eluted by solid phase extraction (SPE), then dried by nitrogen and redissolved in methanol, and finally analyzed by UPLC-MS/MS. The blank values of 18 PFASs were analyzed in terms of the factors of experimental instruments (UPLC-MS/MS), experimental reagent, experimental consumables, pretreatment procedures, and experimental environment.
Results Among the 18 target analytes, four perfluorinated carboxylic acids (PFCAs, C4-C7) and perfluorooctane sulfonate acid (PFOS) were found to have blank values, among which perfluorobutanoic acid (PFBA), perfluoropentanoic acid (PFPeA), and perfluorohexanoic acid (PFHxA) had relatively high blank values (> 0.500 ng/mL), and the blank value of PFBA was up to 40.0 ng/mL. A relatively low concentration of PFBA was detected in ammonia, and its influence on the blank value could be ignored; PFPeA was detected in artificial urine, which should be taken seriously in the experiment; formic acid played a key role in the issue of blank value, which was solved by changing the brand and specification of formic acid.
Conclusion UPLC-MS/MS, experimental consumables, and experimental environment are not the influencing factors for the blank values of PFASs, and experimental reagent is the main cause of the detection of blank values of the above five PFASs. Therefore, this study provides an important reference for the determination of PFASs in human urine.
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