CONDENSATION NUCLEATION LIGHT-SCATTERING DETECTION FOR CONVENTIONAL REVERSED-PHASE LIQUID-CHROMATOGRAPHY

This report demonstrates the interfacing of condensation nucleation light scattering detection (CNLSD) with conventional reversed-phase liquid chromatography (RPLC). CNLSD is an aerosol-based approach that responds to the size and number of particles present after solvent evaporation. As most HPLC grade organic solvents have listed residues after evaporation in the micrograms per milliliter range, solvent purity was found to be a limitation. In this report, increasing the organic content of the mobile phase is shown to increase the background intensity and hinder sensitivity. Two approaches to alleviating the influence of the organic solvent are also reported. The first approach involves the chemical purification of the organic solvent, and the second approach involves modifying the final or detected particle size distribution by removal of the smaller-sized particles. The latter approach, using diffusion screens, was found to provide an increase in sensitivity by a factor of 4 or more without significantly changing the response for low analyte concentrations, compared to the case where the diffusion screens were absent. Responses for various analytes are reported and shown to be nearly equivalent. For typical RPLC C18 columns, column bleed did not limit performance. Finally, results are summarized by comparing performance for the separation of sulfanilic acid and sulfanilamide, where nanogram level detection limits were obtained.