GC-MS/MS quantification of benzyl salicylate on skin and hair: a novel chemical simulant for human decontamination studies

Human studies investigating the efficacy of emergency decontamination protocols for chemical incidents require the use of non-hazardous chemical simulants. Methyl salicylate (MeS) has almost exclusively been used for this purpose. Whilst MeS is a simulant of the chemical warfare agent (CWA) sulphur mustard, it is not an ideal simulant for many other chemical threats with greater persistence and lower volatility. Benzyl salicylate (BeS) has been investigated here as a low toxicity simulant for lower volatility, persistent chemical threat agents and toxic industrial chemicals (TICs). To evaluate the suitability of BeS as a simulant for human decontamination studies a gas chromatography-triple quadrupole mass spectrometry method was designed, optimised and validated, for the analysis of human skin and hair. Quantification was achieved using isotope-dilution, EI and collision-induced dissociation and multiple reaction monitoring for both qualifier and quantifier ion transitions. The mass transitions were m/z 285 → 91 and m/z 210 → 181, respectively for the quantifier and qualifier ions of BeS, and m/z 289 → 91 and m/z 214 → 185 for the quantifier and qualifier ions for the BeS-d4 internal standard, respectively. The method exhibited excellent coefficients of determination (R2 = 0.9992 to 0.9999) with LOD and LOQ values at 0.023 ng/ml and 0.23ng/ml. Across three Quality Controls (QCs), 11.5 ng/ml, 115 ng/ml and 1150 ng/ml) average accuracy (intra-day 95.6% to 100.3%, inter-day 98.5% to 104.91%) and precision (intra-day RSD (%) 2% to 13.7%, inter-day RSD (%) 3.3% to 8.8%) were determined. The validated method was applied in a proof of principle volunteer study for the determination of BeS recovered from skin and hair. The average total BeS recovery after 70 minutes was 37.9% from skin and there was a significant increase between baseline and post-intervention levels for hair. These data demonstrate that BeS is an appropriate simulant for persistent chemicals and that the analytical method employed here is suitable for BeS analysis in human studies.