Reversed Electrode Polarity Stacking Sample Preconcentration Combined with Micellar Electrokinetic Chromatography for th
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Reversed Electrode Polarity Stacking Sample Preconcentration Combined with Micellar Electrokinetic Chromatography for the Analysis of Carbamate Insecticide Residues in Fruit Juices Apichai Santalad & Supalax Srijaranai & Rodjana Burakham
Received: 19 September 2010 / Accepted: 21 February 2011 / Published online: 4 March 2011 # Springer Science+Business Media, LLC 2011
Abstract Reversed electrode polarity stacking mode (REPSM) coupled to micellar electrokinetic chromatography (MEKC) was employed for the simultaneous determination of carbamate insecticide residues in fruit juice samples. A mixture of the studied insecticides (i.e., methomyl, propoxur, carbofuran, carbaryl, isoprocarb, and promecarb) in 10 mmol L−1 phosphate buffer (pH 7.0) was introduced into the capillary tube by hydrodynamic injection at 0.5 psi for 30 s followed by removal of the sample matrix at −15 kV for 0.5 min. The analytes were successfully separated within 8 min using 10 mmol L−1 borate buffer containing 60 mmol L−1 sodium dodecyl sulfate at pH 9.5, and photodiode array detection at 205, 214, and 225 nm. The REPSM–MEKC gave stacking enhancement factors of about 4–13, compared to that without stacking. The limits of detection were in the range 0.01–0.10 mg L−1, which is acceptable with respect to the maximum residue limits. Good precisions were obtained with relative standard deviation lower than 1.8% (for migration time) and 10% (for peak area). The recoveries for most fruit juice samples were acceptable (>80%). No contamination of the studied carbamates was observed in any sample. The proposed method is simple and effective for preconcentration and removal of matrix interferences in a single step for the determination of the studied carbamate insecticides. Keywords Reversed electrode polarity stacking mode . Micellar electrokinetic chromatography . Carbamate insecticides . Fruit juices A. Santalad : S. Srijaranai (*) : R. Burakham Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand e-mail: [email protected]
Introduction Carbamate pesticides are compounds derived from carbamic acid with the chemical structure: R-O-CO-N(CH3)-R′, where R is an alcohol, an oxime, or a phenol group and R′ is a hydrogen or a methyl group (Huertas-Pérez and GarcíaCampaña 2008). Examples of the important carbamate pesticides include methomyl, carbaryl, carbofuran, propoxur, etc. These pesticides are widely used as insecticides, fungicides, herbicides, and nematocides (Wu et al. 2009), and residues of these pesticides can be found in food, providing a potential risk to humans. Authorized agencies such as the European Union (EU) set the maximum residues limits (MRLs) in fruits and vegetables to guarantee the consumer safety (European Commission 2005). Although the MRLs of carbamate insecticides in food processed such as fruit juices have not been established yet, the values corresponding to those recommended for the original matrices can be applied (Gilbert-Lόpez et al. 2
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