Direct Corona Charging: A New Strategy for Enhancing Sensitivity and Stability in Charged Aerosol Detection

The charged aerosol detector (CAD) is widely used for detecting nonvolatile compounds without UV absorption due to its high sensitivity, stability, and consistent response. However, the traditional plasma collision charging mode (PCCM) suffers from issues such as sample dilution, gas flow back-mixing, and disturbances, which reduce sensitivity and repeatability. To address these limitations, this study introduces the direct corona charging mode (DCCM), which eliminates the charging gas route by using a high-voltage corona needle to directly charge the dried aerosol. This approach avoids mixing collisions, simplifies the instrument structure, and reduces nitrogen consumption. Comparative analyses using samples like caffeine demonstrated that DCCM significantly improves sensitivity and stability over PCCM. The response under DCCM fits a quadratic curve with a correlation coefficient above 0.99 across 3 orders of magnitude. Direct injection of 22 analytes showed that DCCM achieved a peak area relative standard deviation below 10%, with better response consistency than PCCM. Gradient analysis of complex samples further confirmed DCCM's superior repeatability and sensitivity. Real-sample analysis highlighted DCCM-CAD's practical potential. In summary, DCCM enhances CAD performance, reduces costs, and simplifies design, paving the way for more efficient and reliable commercial CAD systems.