Gas Chromatographic-Mass Spectrometric Identification and Quantitation of Benzyl Alcohol from Human Serum and Postmortem Blood after Derivatization with 4-Carbethoxy Hexafluorobutyryl Chloride: A Novel Derivative

Abstract

Benzyl alcohol is commonly used as an antibacterial agent in a variety of pharmaceutical formulations. Several fatalities in neonates have been linked to benzyl alcohol poisoning. Most methods for measuring benzyl alcohol concentrations in serum utilize direct extraction followed by high performance liquid chromatography. We describe a novel derivatization of benzyl alcohol using 4-carbethoxyhexafluorobutyryl chloride after extraction from human plasma, and subsequent analysis by gas chromatography-mass spectrometry (GC/MS). The derivative was eluted at a significantly higher temperature and the method was free from interferences from more volatile components in serum and hemolyzed specimens. However, with postmortem specimens, we observed multiple peaks which were eluted at a very high temperature, long after derivatized benzyl alcohol and the internal standard. Therefore, baking the column at 310 degrees C is recommended after analysis of a postmortem specimen. Another advantage of this derivatization technique is the conversion of low molecular weight benzyl alcohol (MW 108) to a high molecular weight derivative (MW 358). The positive identification of benzyl alcohol can be easily achieved by observing a distinct molecular ion at m/z 358 as well as other characteristic ions at m/z 107 and 91. Quantitation of benzyl alcohol in human serum can easily be achieved by using 3,4-dimethylphenol as an internal standard. The within run and between run precisions (using serum standard of benzyl alcohol: 50 mg/L) were 2.2% (mean = 50.6, SD = 1.1 mg/L), and 6.9% (mean = 50.8, SD = 3.5 mg/L). The assay was linear for the serum benzyl alcohol concentrations of 5 mg/L to 200 mg/L and the detection limit was 1 mg/L. We observed no carry-over problem in our assay as when 2 microL ethyl acetate was injected into the GC/MS after analyzing serum specimens containing 200 mg/L of benzyl alcohol, we observed no peak for either benzyl alcohol or the internal standard in the total ion chromatogram.