Determination of glyoxal and methylglyoxal in atmospheric fine particulate matter by vortex-assisted micro-solid phase extraction and liquid chromatography-diode array detection

Determination of α-dicarbonyl compounds, glyoxal (Gly) and methyl glyoxal (Mgly), in atmospheric fine particulate matter PM2.5 (particulate matter with an aerodynamic diameter of less than 2.5 μm) which play vital roles in generating secondary organic aerosols in the ambient air, was carried out by vortex-assisted micro-solid phase extraction (VA-μ-SPE)˗liquid chromatography-diode array detection (LC-DAD), with on-sorbent derivatization by 2,4-dinitrophenylhydrazine (DNPH). This is the first time such an approach of combining on-sorbent derivatization and extraction in one step together with LC analysis has been applied to PM2.5. Extraction parameters such as selection of sorbent, extraction time, desorption time and sample volume were optimized using water samples spiked with Gly and Mgly. Under the most favourable conditions, good intra- (1.39%-2.78%) and inter-day (2.29%-6.56%) precision and linearity (ranging between 0.5 and 100 ng mL−1) along with coefficients of determination 0.998 and 0.997, were determined. The limits of detection were determined to be 0.14 ng mL−1 (derivatized Gly) and 0.15 ng mL−1 (derivatized Mgly) whereas the limits of quantification were 0.47 ng mL−1 and 0.50 ng mL−1, respectively. The developed method was successfully employed to the determination of Gly and Mgly associated with PM2.5. The latter was collected on glass fiber filters which were immersed in methanol: water (1:1 v/v) for μ-SPE, which was conducted using a sorbent pre-coated with DNPH. The concentrations of the Gly and Mgly were determined to be 0.38 ng m−3 and 0.41 ng m−3 in the sampled ambient air, with relative recoveries of between 69-97%.