Simultaneous detection and quantification of free phenol and three structural isomers of cresol in human blood using gas chromatography-triple quadrupole mass spectrometry and their medical reference value ranges

Free phenol and cresol isomers in human samples have drawn interest, particularly in the field of forensic toxicology. In this study, a simultaneous analytical method for the detection of unchanged phenol and three structural isomers of cresol in human blood was developed using GC-MS/MS. This method was applied to authentic human heart and peripheral vein blood samples obtained from a fatal intoxication case involving accidental exposure to liquified phenol containing cresol isomers. In addition, we applied the method to blood samples from 110 healthy individuals. The QuEChERS method was employed for extracting the target compounds, followed by centrifugation. The supernatant of the organic layer was then evaporated by dry nitrogen flow. After the residue was derivatized with 30 μL of BSTFA reagent, the final reconstituted eluate was analyzed by GC-MS/MS. Quantification was performed using the internal standard method for o-cresol and m-cresol, and the standard addition method for phenol and p-cresol. All validation parameters met acceptable criteria. The concentrations of phenol, o-cresol, m-cresol, and p-cresol in heart blood were 335.27, 1.70, 25.27, and 14.21 μg/mL, respectively; in venous blood, the concentrations were 71.43, 1.25, 13.57 and 5.99 μg/mL, respectively. The 95% upper medical reference values (UMRVs) for free phenol and p-cresol in blood from 110 healthy individuals were <0.0865 μg/mL and <0.142 μg/mL, respectively. These data are valuable for evaluating exposure and determining cause of death in forensic investigations.