A novel derivatization of phenol after extraction from human serum using perfluorooctanoyl chloride for gas chromatography-mass spectrometric confirmation and quantification.

Phenol (carbolic acid) is widely used as a disinfectant as well as in the chemical industry as an intermediate in the synthesis of a variety of chemicals. Phenol is also the major metabolite of benzene which is used in many commercial solvents. Phenol is toxic and caustic and may cause death even from dermal absorption. Therefore, measurement of phenol in postmortem blood is essential. The concentration of phenol in blood can be measured by gas chromatography with flame ionization or mass spectrometry. Phenol can also be analyzed by high performance liquid chromatography. However, in forensic toxicology, unambiguous confirmation of phenol by mass spectrometry is as important as quantification in blood. Here we describe a novel derivatization of phenol after extraction with chloroform from human serum using perfluorooctanoyl chloride. The perfluorooctanoyl derivative of phenol showed a strong molecular ion at m/z 490 (relative abundance: 23%) whereas the base peak was observed at m/z 77. The derivative of the internal standard 3,4-dimethylphenol showed a very strong molecular ion at m/z 518 (relative abundance: 56%) and the base peak was observed as m/z 121. The derivative of p-cresol, a chemically related phenolic compound, showed a strong molecular ion at 504 m/z (relative abundance: 54%) and a base peak at m/z 107. We observed baseline separation between derivatized phenol (retention time: 6.1 min), p-cresol (retention time: 7.8 min), and the internal standard (retention time: 9.4 min). We observed no interferences in our assay from grossly hemolyzed serum. Within and between run precision was studied using a serum standard containing 25 mg/L of phenol. The within run precision was 6.6% (mean = 24.3, SD = 1.6 mg/L, n = 8) whereas the between run precision was 8.6% (mean = 25.5, SD = 2.2 mg/L, n = 8). The assay was linear for serum phenol concentrations of 10-200 mg/L. The detection limit was 1 mg/L of serum phenol concentration. The average recoveries were 92.1% to 94.0% for various serum phenol concentrations.