EVALUATION OF DIODE-LASER-BASED INDIRECT FLUOROMETRIC DETECTION FOR HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

A diode-laser-based indirect fluorometric detector that monitors a near infrared dye, IR 125, added to the mobile phase for reversed-phase high-performance liquid chromatography, was evaluated. Analytical measurements of n-alkyl alcohols were made by measuring the induced change in the IR 125 fluorescence signal at the alcohol retention times. Limits of detection were on the order of 10(-8) mol injected. Several isocratic separations were carried out at different IR 125 concentrations in different acetonitrile:pH 6 sodium phosphate aqueous buffer mobile phase ratios. The results indicate that a small dye/analyte transfer ratio is limiting the capabilities of the detector. However, the low noise and highly selective excitation characteristics of the diode laser present the potential for this detection scheme to attain a detection limit of 10(-11) M at the detector for analytes with a transfer ratio of 1.