title: Micellar electrokinetic chromatography with amperometric detection and off-line solid-phase extraction for analysis of carbamate insecticides.
abstract: Six selected primary carbamate insecticides, methomyl, carbaryl, carbofuran, propoxur, isoprocarb, and promecarb, were hydrolyzed in alkaline solution, resulting in electroactive derivatives detectable at a platinum (Pt) electrode poised at +0.8 V vs Ag/AgCl (3 M NaCl). The Pt electrode was inserted into a small electrochemical cell and positioned close to the capillary outlet as an end-column detector to detect the carbamate derivatives after electrophoretic separation. Based on their predicted pK(a) values and aqueous solubilities, micellar electrokinetic chromatography (MEKC) was optimized for baseline separation of the derivatives using 20 mM borate, pH 10.2 containing 20 mM sodium dodecyl sulfate as a running buffer. When combined with solid-phase extraction (SPE) on octadecyl silica, a preconcentration factor of 100-fold achieved detection to 0.5 microM methomyl and to 0.01 microM for the remaining five pesticides, significantly below the level regulated by government agencies of most countries. The SPE-MEKC method when applied to the separation and analysis of spiked river water and soil samples, yielded results with excellent reproducibility, recovery and selectivity.
authors.affiliation: Irish Separation Science Cluster, Department of Chemistry and Analytical and Biological Chemistry Research Facility, University College Cork, Cork, Ireland.
authors.forename: Apichai
authors.initials: A
authors.lastname: Santalad
authors.forename: Lin
authors.initials: L
authors.lastname: Zhou
authors.forename: Fengjun
authors.initials: F
authors.lastname: Shang
authors.forename: Dara
authors.initials: D
authors.lastname: Fitzpatrick
authors.forename: Rodjana
authors.initials: R
authors.lastname: Burakham
authors.forename: Supalax
authors.initials: S
authors.lastname: Srijaranai
authors.forename: Jeremy D
authors.initials: JD
authors.lastname: Glennon
authors.forename: John H T
authors.initials: JH
authors.lastname: Luong
mesh_terms: D001881:Borates / Q000737:chemistry; D002219:Carbamates / Q000032:analysis* / Q000737:chemistry; D020374:Chromatography, Micellar Electrokinetic Capillary / Q000379:methods*; D004566:Electrodes; D019075:Electrophoresis, Capillary; D004785:Environmental Pollutants / Q000032:analysis / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007306:Insecticides / Q000032:analysis* / Q000737:chemistry; D016014:Linear Models; D010984:Platinum / Q000737:chemistry; D015203:Reproducibility of Results; D045483:Rivers / Q000737:chemistry; D012680:Sensitivity and Specificity; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry; D012989:Soil Pollutants / Q000032:analysis / Q000737:chemistry; D052616:Solid Phase Extraction / Q000379:methods*; D012995:Solubility; D013056:Spectrophotometry, Ultraviolet
chemical_list: D001881:Borates; D002219:Carbamates; D004785:Environmental Pollutants; D007306:Insecticides; D012989:Soil Pollutants; D012967:Sodium Dodecyl Sulfate; D010984:Platinum