Rapid determination of alcohols in human saliva by gas chromatography differential mobility spectrometry following selective membrane extraction

Abstract

A fast quantitative assay for the selective and sensitive measurement of methanol and ethanol in human saliva has been developed. A hyphenated thermal desorption (TD) – gas chromatography (GC) – differential mobility spectrometry (DMS) technique was developed to characterise methanol in human saliva at concentrations between 25 mg dm⁻³ and 1000 mg dm⁻³, in the presence of elevated ethanol concentrations. A temperature-controlled polydimethylsilicone capillary membrane was used in the sampling procedure to extract methanol in the presence of elevated ethanol concentrations. A flow of nitrogen through the central channel of the membrane swept the volatile analytes into an adsorbent trap. TD-GC-DMS was used to isolate, detect and identify each compound with an analysis time of less than 3 min. The method was optimised using a 2 factor (temperature and dispersion field strength), 2 centroid point, central composite design, to enhance the resolution and sensitivity of DMS responses to methanol and ethanol. The optimum DMS cell temperature was found to be 80 °C with an optimum dispersion field strength of 24 kV cm⁻¹. A linear response was obtained for methanol over the range 25 to 500 mg dm⁻³ (R² = 0.998) The development of this method to provide point-of-care testing for ethanol and methanol exposure is discussed.