title: Sensitive detection of malachite green and crystal violet by nonlinear laser wave mixing and capillary electrophoresis.
abstract: An ultrasensitive label-free antibody-free detection method for malachite green and crystal violet is presented using nonlinear laser wave-mixing spectroscopy and capillary zone electrophoresis. Wave-mixing spectroscopy provides a sensitive absorption-based detection method for trace analytes. This is accomplished by forming dynamic gratings within a sample cell, which diffracts light to create a coherent laser-like signal beam with high optical efficiency and high signal-to-noise ratio. A cubic dependence on laser power and square dependence on analyte concentration make wave mixing sensitive enough to detect molecules in their native form without the use of fluorescent labels for signal enhancement. A 532 nm laser and a 635 nm laser were used for malachite green and crystal violet sample excitation. The use of two lasers of different wavelengths allows the method to simultaneously detect both analytes. Selectivity is obtained through the capillary zone electrophoresis separation, which results in characteristic migration times. Measurement in capillary zone electrophoresis resulted in a limit of detection of 6.9 × 10(-10)M (2.5 × 10(-19) mol) for crystal violet and 8.3 × 10(-11)M (3.0 × 10(-20) mol) for malachite green at S/N of 2.
authors.affiliation: Department of Chemistry and Biochemistry, San Diego State University, San Diego, CA 92182, United States.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Maxwell
authors.affiliation: Department of Chemistry and Biochemistry, San Diego State University, San Diego, CA 92182, United States. Electronic address: william.tong@sdsu.edu.
authors.forename: William G
authors.initials: WG
authors.lastname: Tong
mesh_terms: D019075:Electrophoresis, Capillary / Q000379:methods*; D005840:Gentian Violet / Q000032:analysis* / Q000737:chemistry; D057230:Limit of Detection; D016014:Linear Models; D015203:Reproducibility of Results; D012394:Rosaniline Dyes / Q000032:analysis* / Q000737:chemistry
chemical_list: D012394:Rosaniline Dyes; C005095:malachite green; D005840:Gentian Violet
keywords: Capillary; Crystal violet; Electrophoresis; Gentian violet; Malachite green; Wave mixing