Traditionally, HPLC systems have used a UV absorbance technique to detect chemical compounds. But UV detectors are limited to analytes that contain a chromophore. Aerosol-based HPLC detectors offer an advantage because they can be used with any analyte that is less volatile than the mobile phase, with or without a chromophore.

Aerosol-based detectors nebulize the effluent continuously. The mobile phase is evaporated from the droplets, leaving behind residue particles suspended in air. When a nonvolatile analyte elutes the HPLC column, the particles left after evaporation will increase in size. The detector measures the increase in particle size and converts it to an analog or digital output.

Earlier aerosol-based detectors, such as evaporative light scattering, have low sensitivity due the low light scattering levels of small particles and photodetector drift. Detectors based on the measurement of charged aerosol are limited by inefficient charging of small particles and electrometer noise. The offers better sensitivity because it increases the number of particles detected by using a water condensation particle counter (WCPC)*. The WCPC condenses water vapor onto the particles, literally growing them to a size where individual particles can be detected easily using an optical detector.

Compared to other aerosol-based detectors, the detector is more sensitive to changes in the size shift of the aerosol distribution. Its dynamic range spans from less than 1 ng to over 10 µg on column. Also, it offers a linear response over several orders of magnitude for most analytes.

The detector detects a broader range of analytes than UV detectors and offers better sensitivity than other aerosol-based detectors. Its small size, inherent simplicity, and stability make it an ideal addition to the analytical chemist’s toolbox.

*U.S. Patent Number 6,712,881. Other patents pending