Gas chromatographic method for the sensitive determination of 2,5-hexanedione using electron capture and mass-selective detection

2,5-Hexanedione (2,5HD) is the principle metabolite of n-hexane and methyl ethyl ketone in human urine. In this paper, a rapid and highly sensitive method for the determination of urinary 2,5HD by gas chromatography-electron capture detection and gas chromatography-mass selective detection is described. The method comprises, optionally, acid hydrolysis before the analyte is being derivitized with 2,4,6-trichlorophenyl hydrazine (TCPH) towards the formation of a chlorinated hydrazone derivative for 2,5HD analysis. The reaction conditions such as temperature, time, reagent concentration and pH were optimized properly. The detection limit of the method -defined as signal to noise ratio=3 -is as low as 0.4 and 1.5µM using the ECD and MSD (SIM mode), respectively. The linearity of the detection systems extends up to 50µM of 2,5HD with correlation coefficients better than 0.9995. The withinday and between-day reproducibility for a urine sample of 10µM in 2,5HD were 2.6 and 3.2%, respectively. Spiked pooled samples with various concentrations in the range 5-10µM were processed following the proposed procedure. The recovery was satisfactory enough ranging from 92 to 104%. The method was applied to the analysis of urine samples received from people working in a chemical laboratory and the results revealed variable, yet low concentrations of 2,5HD in the hydrolyzed samples.