Comparative study of headspace and headspace single drop microextraction combined with GC for the determination of methanol in wine

In this work, headspace single-drop microextraction (HS-SDME) method and headspace (HS) method were developed and compared to determine methanol by gas chromatography with flame ionization detector (GC-FID). Several factors influencing extraction efficiency, such as extraction time, temperature, sample volume, stirring rate and extraction solvent were investigated and the optimal conditions could be obtained using 2.0 µL DMF as extractant, 45 °C as heating temperature, 5 min as extraction time, 6 mL sample volume and 1.5 g KCl as addition of salt. The obtained dynamic range of HS-SDME-GC-FID was from 0.05 to 2 mg·L-1 with the limit of detection (LOD) of 0.001 mg·L-1 and that of HS-GC-FID was from 10.0 to 400.0 mg L-1 with LOD of 0.5 mg·L-1. The relative standard deviations (RSD) of HS-SDME-GC-FID was 1.9% (n = 5, C = 0.005 mg·L-1), 4.8%(n = 5, C = 0.02 mg·L-1) and 3.3%(n = 5, C = 0.1 mg·L-1), then the RSD of HS-GC-FID was 4.4%(n = 5, C = 5 mg·L-1), 5.8%(n = 5, C = 20 mg·L-1) and 4.0%(n = 5, C = 40 mg·L-1). Clearly, compared with HS-GC-FID, HS-SDME-GC-FID possessed lower LOD and better reproducibility and both of them were applied to determine methanol in imported wine and the recoveries for the spiked samples were between 83.99 and 117.24%. Overall, HS-SDME approach was confirmed to be a more sensitive and efficient sample pretreatment method and could separate matrix effectively.