The detector is designed for charged aerosol detection with full compatibility in HPLC and UHPLC applications. In charged aerosol detection, an aerosol of dried analyte particles is formed after nebulization of column eluate. Electrical charge is imparted to these dried particles. The detector then measures the charge. Measured charge is proportional to the amount of analyte in the sample.
The following picture shows the interior components of the detector, and illustrates how the detector operates:
No. | Description |
---|---|
1 | Mobile phase from column |
2 | Nebulizer |
3 | Gas inlet |
4 | Gas filters |
5 | Spray chamber |
6 | Drain pump |
7 | Evaporation tube |
8 | Mixing chamber |
9 | Charger gas inlet |
10 | Corona charger |
11 | Ion trap |
12 | Electrometer (detection chamber) |
13 | Electrometer board |
14 | Gas exhaust |
Mobile phase from the column enters the detector (no. 1) and flows to the nebulizer (no. 2). Pressurized gas streams through the gas inlet (no. 3) and passes through the charcoal gas filter and then the HEPA gas filter (no. 4). In the nebulizer (no. 2), the filtered gas and the mobile phase merge at the nebulizer tip to create an aerosol within the spray chamber (no. 5).
The largest aerosol droplets condense within the spray chamber (no. 5) and are removed by the drain pump (no. 6) through the waste outlet. Smaller droplets pass into a temperature-controlled evaporation tube (no. 7), in which solvent and more volatile components are vaporized.
By the end of the evaporation tube, the resulting aerosol particles enter the mixing chamber (no. 8), where they collide with a secondary stream of ionized gas (no. 9) that has passed through a corona charger (no. 10). Each dried aerosol particle undergoes surface diffusional charging, where the level of charge per particle is proportional to particle size and the cumulative charge of the population is directly related to the analyte amount.
In the ion trap (no. 11), higher mobility ions and smaller charged particles are removed. Lower mobility charged particles pass to a conductive filter and aggregate charge is measured with a sensitive electrometer/detection chamber (no. 12). Signal is processed by the electrometer board (no. 13) and sent to the chromatography data system. The resulting gas flow exits the detector through the gas exhaust (no. 14).