Liquid extraction surface analysis in-line coupled with capillary electrophoresis for direct analysis of a solid surface sample |
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Authors: | In Hye Sung Young Woo LeeDoo Soo Chung |
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Affiliation: | Department of Chemistry, Seoul National University, Seoul 151-747, Republic of Korea |
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Abstract: | A surface-sampling technique of liquid extraction surface analysis (LESA) was in-line coupled with capillary electrophoresis (CE) to expand the specimen types for CE to solid surfaces. The new direct surface analysis method of LESA–CE was applied to the determination of organophosphorus pesticides, including glufosinate-ammonium, aminomethylphosphonic acid, and glyphosate on the external surface of a fruit such as apple. Without any sample pretreatment, the analytes sprayed on the surface of a half apple were directly extracted into a liquid microjunction formed by dispensing the extractant from the inlet tip of a separation capillary. After extraction, the analytes were derivatized in-capillary with a fluorophore 4-fluoro-7-nitro-2,1,3-benzoxadiazole and analyzed with CE-laser induced fluorescence (LIF). The limits of detection for glufosinate-ammonium, aminomethylphosphonic acid, and glyphosate were 2.5, 1, and 10 ppb, respectively, which are at least 20 times lower than the tolerance limits established by the U.S. Environmental Protection Agency. Thus, we demonstrated that LESA–CE is a quite sensitive and convenient method to determine analytes on a solid surface avoiding the dilution from sample pretreatment procedures including homogenization of a bulk sample. |
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Keywords: | LESA, liquid extraction surface analysis EPA, environmental protection agency OPPs, organophosphorus pesticides AMPA, aminomethylphosphonic acid ACN, acetonitrile NBD-F, 4-fluoro-7-nitro-2,1,3-benzoxadiazole LIF, laser induced fluorescence MEKC, micellar electrokinetic chromatography SPE, solid phase extraction |
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