Novel zwitterionic HILIC stationary phase for the determination of ethyl glucuronide in human hair by LC-MS/MS

Some recent studies have described a shift from traditional reversed-phase to more hydrophilic LC chemistry for EtG determination in hair (hEtG). The reason relies on the poor retention of C8- and C18-based columns for polar compounds, even in presence of great amount of aqueous phase. This work presents the development, validation and application of a new hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-LC-MS/MS) method based on a novel zwitterionic stationary phase for the analysis of hEtG. The linearity was assessed in the range of 5-100 pg/mg hair, with a correlation coefficient of >0.99. The method was selective and sensitive, with a limit of detection (LOD) and limit of quantitation (LOQ) of 1.4 pg/mg and 4.5 pg/mg in hair, respectively. Suitable diagnostic sensitivity was achieved without the introduction of a sample purification step, or a post column solvent addition. The method was successfully applied to real hair samples after full validation. This method, based on a separation at neutral conditions, confirmed the optimum retention and thus selectivity for weak acids in zwitterionic HILIC columns.