title: High performance separation of quaternary amines using microchip non-aqueous electrophoresis coupled with contactless conductivity detection.
abstract: This study describes the development of an analytical methodology for the separation of quaternary amines using non-aqueous microchip electrophoresis (NAME) coupled with capacitively coupled contactless conductivity detection (C4D). All experiments were performed using a commercial microchip electrophoresis system consisting of a C4D detector, a high-voltage sequencer and a microfluidic platform to assemble a glass microchip with integrated sensing electrodes. The detection parameters were optimized and the best response was reached applying a 700-kHz sinusoidal wave with 14Vppexcitation voltage. The running electrolyte composition was optimized aiming to achieve the best analytical performance. The mixture containing methanol and acetonitrile at the proportion of 90:10 (v:v) as well as sodium deoxycholate provided separations of ten quaternary amines with high efficiency and baseline resolution. The separation efficiencies ranged from 8.7×104to 3.0×105plates/m. The proposed methodology provided linear response in the concentration range between 50 and 1000μmol/L and limits of detection between 2 and 27μmol/L. The analytical feasibility of the proposed methodology was tested in the determination of quaternary amines in corrosion inhibitor samples often used for coating oil pipelines. Five quaternary amines (dodecyltrimethylammonium chloride, tetradecyltrimetylammonium bromide, cetyltrimethylammonium bromide, tetraoctylammonium bromide and tetradodecylammonium bromide) were successfully detected at concentration levels from 0.07 to 6.45mol/L. The accuracy of the developed methodology was investigated and the achieved recovery values varied from 85 to 122%. Based on the reported data, NAME-C4D devices exhibited great potential to provide high performance separations of hydrophobic compounds. The developed methodology can be useful for the analysis of species that usually present strong adsorption on the channel inner walls.
authors.affiliation: Instituto de Química, Universidade Federal de Goiás, Campus Samambaia, 74690-900, Goiânia, GO, Brazil.
authors.forename: Roger Cardoso
authors.initials: RC
authors.lastname: Moreira
authors.affiliation: Instituto de Química, Universidade Federal de Goiás, Campus Samambaia, 74690-900, Goiânia, GO, Brazil.
authors.forename: Marilia Sousa
authors.initials: MS
authors.lastname: Lopes
authors.affiliation: Centro de Pesquisas e Desenvolvimento Leopoldo Américo Miguez de Mello (CENPES), 21040-000, Rio de Janeiro, RJ, Brazil.
authors.forename: Iris
authors.initials: I
authors.lastname: Medeiros Junior
authors.affiliation: Instituto de Química, Universidade Federal de Goiás, Campus Samambaia, 74690-900, Goiânia, GO, Brazil; Instituto Nacional de Ciência e Tecnologia de Bioanalítica, 13084-971, Campinas, SP, Brazil. Electronic address: wendell@ufg.br.
authors.forename: Wendell K T
authors.initials: WKT
authors.lastname: Coltro
mesh_terms: D000588:Amines / Q000737:chemistry* / Q000302:isolation & purification; D004553:Electric Conductivity; D004566:Electrodes; D046209:Electrophoresis, Microchip / Q000295:instrumentation / Q000379:methods*
chemical_list: D000588:Amines
keywords: Capillary electrophoresis; Corrosion inhibitors; Electrochemical detection; Integrated microfluidic platform; Organic solvents; Petroleomics