title: Determination of glyphosate and AMPA on polyester-toner electrophoresis microchip with contactless conductivity detection.
abstract: This paper reports a method for rapid, simple, direct, and reproducible determination of glyphosate and its major metabolite aminomethylphosphonic acid (AMPA). The platform described herein uses polyester-toner microchips incorporating capacitively coupled contactless conductivity detection and electrophoresis separation of the analytes. The polyester-toner microchip presented 150 μm-wide and 12 μm-deep microchannels, with injection and separation lengths of 10 and 40 mm long, respectively. The best results were obtained with 320 kHz frequency, 4.5 Vpp excitation voltage, 80 mmol/L CHES/Tris buffer at pH 8.8, injection in -1.0 kV for 7 s, and separation in -1.5 kV. RSD values related to the peak areas for glyphosate and AMPA were 1.5 and 3.3% and 10.1 and 8.6% for intra- and interchip assays, respectively. The detection limits were 45.1 and 70.5 μmol/L, respectively, without any attempt of preconcentration of the analytes. Finally, the method was applied to river water samples in which glyphosate and AMPA (1.0 mmol/L each) were added. The recovery results were 87.4 and 83.7% for glyphosate and AMPA, respectively. The recovery percentages and LOD values obtained here were similar to others reported in the literature.
authors.affiliation: Instituto de Química de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil.
authors.forename: Eduardo R
authors.initials: ER
authors.lastname: da Silva
authors.forename: Thiago P
authors.initials: TP
authors.lastname: Segato
authors.forename: Wendell K T
authors.initials: WK
authors.lastname: Coltro
authors.forename: Renato S
authors.initials: RS
authors.lastname: Lima
authors.forename: Emanuel
authors.initials: E
authors.lastname: Carrilho
authors.forename: Luiz H
authors.initials: LH
authors.lastname: Mazo
mesh_terms: D004553:Electric Conductivity; D046209:Electrophoresis, Microchip / Q000379:methods*; D005998:Glycine / Q000031:analogs & derivatives* / Q000032:analysis; D006540:Herbicides / Q000032:analysis*; D057230:Limit of Detection; D011091:Polyesters / Q000737:chemistry; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000032:analysis*; D000097797:Glyphosate
chemical_list: D005998:Glycine; D006540:Herbicides; D011091:Polyesters; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D000097797:Glyphosate
keywords: Capacitively coupled contactless conductivity detection; Environmental; Pesticides; Polyester-toner microchip