[Journal of Chromatography A] High performance separation of quaternary amines using microchip non-a
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 14 Vppexcitation 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 × 104 to 3.0 × 105 plates/m. The proposed methodology provided linear response in the concentration range between 50 and 1000 μmol/L and limits of detection between 2 and 27 μmol/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 6.45 mol/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.
Roger Cardoso Moreira a, Marilia Sousa Lopes a, Iris Medeiros Junior b, Wendell K.T. Coltro a, c a Instituto de Química, Universidade Federal de Goiás, Campus Samambaia, 74690-900, Goiânia, GO, Brazil b Centro de Pesquisas e Desenvolvimento Leopoldo Américo Miguez de Mello (CENPES), 21040-000, Rio de Janeiro, RJ, Brazil c Instituto Nacional de Ciência e Tecnologia de Bioanalítica, 13084-971, Campinas, SP, Brazil Received 3 January 2017, Revised 22 March 2017, Accepted 23 March 2017, Available online 27 March 2017 http://doi.org/10.1016/j.chroma.2017.03.062