A combined micro-solid phase-single drop microextraction approach for trace enrichment of volatile organic compounds

Abstract

An attempt was made to combine μ-solid phase extraction and headspace single drop microextraction techniques and use their advantages for trace determination of some volatile organic compounds in aqueous samples. After performing the two-step preconcentration approach, the desired analytes were determined by gas chromatography-mass spectrometry. A resorcinol-formaldehyde-based xerogel was used as the extraction medium in the μ-solid phase extraction (μ-SPE) method. Then, the extracted BTEX was eluted with a rather large amount of methanol. To remove the laborious process including solvent evaporation and further reconstitution, which is usually accompanied by loss of analytes and accuracy, headspace single drop microextraction (HS-SDME) was employed as the second orthogonal enrichment technique. The combination of these two techniques led to enrichment factors ranging from 118 to 504 for the extracted BTEX indicating the enhanced capability of the method towards aromatic compounds. Under optimum conditions, the limit of detection (LOD) varied from 0.03 to 0.1 μg L⁻¹ and the linearity for the analytes was in the range of 0.1–100 μg L⁻¹, while the RSD% values (n = 5) were all satisfactory at two concentration levels of 0.1 and 100 μg L⁻¹. The applicability of the developed μ-SPE/HSSDME/GC-MS method was examined by analyzing river and paddy water samples and acceptable relative recovery percentages were obtained.