Aerosol-based detectors for liquid chromatography.

Aerosol-based detectors developed within the last few decades have increasingly addressed the need for sensitive, universal liquid chromatography detection in a wide variety of applications. Herein, we review the operating principles, instrumentation, analytical characteristics, and recent applications of the three general types of such detectors: evaporative light scattering detection (ELSD), condensation nucleation light scattering detection (CNLSD); commercially known as the nano-quantity analyte detector (NQAD), and charged aerosol detection (CAD). Included is a comparative evaluation of the operational and analytical characteristics of these detectors.

Corona discharge neutralizer for electrospray aerosols used with condensation nucleation light-scattering detection.

To obviate the use of radioactive materials, a simple unipolar electrical neutralizer based on a corona discharge was developed to neutralize electrospray aerosols used when coupling capillary liquid chromatography (CLC) and capillary electrophoresis (CE) to condensation nucleation light-scattering detection (CNLSD). The electrical neutralizer could be operated with either a positive or negative corona to generate ions to neutralize oppositely charged aerosols generated by electrospray and allow sensitive detection with CNLSD. The device could further be operated with organic solvents as well as aqueous buffer.

Condensation nucleation light scattering detection with ion chromatography for direct determination of glyphosate and its metabolite in water.

An ion chromatography-condensation nucleation light scattering detection (IC-CNLSD) method was successfully used to directly analyze glyphosate, a polar pesticide, and aminomethylphosaphonic acid, the major metabolite of glyphosate, in water without need of pre-treatment or derivatization. CNLSD gave a LOD of 53 ng/ml for glyphosate, which is much lower than the maximum contaminant level of 700 ng/ml for drinking water issued by the US Environmental Protection Agency. Spiked analytes in different matrixes were tested.

Sensitive, universal detection for capillary electrochromatography using condensation nucleation light scattering detection.

Condensation nucleation light scattering detection (CNLSD) was coupled with a pressurized capillary electrochromatography (pCEC) system using an electrospray interface. Supplementary pressure from a high-pressure pump was used to stabilize the electrospray and electrochromatography processes. Hydrodynamic injections were made with a 20 nl injection valve, and the inherent dead volume from the valve was successfully minimized, such that plate numbers in the range of 120,000 to 350,000/m were observed.