Introduction

Charged Aerosol Detectors (CAD) are widely used for the analysis of non-volatile and semi-volatile compounds that may not respond well to UV detection. Because the detector operates independently of a compound's optical properties, CAD systems can provide a valuable alternative for many chromatographic applications.

In most cases, the same Chemical Solutions Qualification Kits used for HPLC Performance Qualification (PQ) can also be used when qualifying a Charged Aerosol Detector. The core chromatographic aspects of the qualification procedure remain unchanged, allowing laboratories to use established qualification materials and workflows.

Using Existing HPLC Qualification Kits

The standard HPLC Performance Qualification Kit may be used for CAD qualification purposes.

• Performance Qualification Kits for HPLC Systems

The chromatographic conditions, test solutions, and overall qualification approach are generally comparable to those used for UV-based qualification procedures.

Important Considerations for Charged Aerosol Detectors

Although qualification materials remain the same, CAD detectors can vary significantly in sensitivity.  Differences may be observed due to:

• Detector model
• Detector generation
• Instrument configuration
• Operating parameters
• Laboratory setup

As a result, detector response can differ substantially from one CAD system to another.

Sensitivity Differences Between Older and Newer CAD Systems

Newer Charged Aerosol Detector models are often significantly more sensitive than earlier generations.  Because of these sensitivity differences, it can be difficult to provide a single set of universal recommendations regarding:

• Injection volume
• Detector range
• Signal intensity
• Response expectations

Unlike UV detection, response levels may vary considerably from instrument to instrument.

Qualification Testing for Older CAD Detectors

Older Charged Aerosol Detectors may exhibit lower sensitivity than many conventional UV detectors.  Under these circumstances:

• Lower-level test solutions may not generate a detectable response.
• Qualification procedures may need to focus on higher concentration solutions.
• Detector settings may require optimization.

If the lowest concentration solution is not detectable, higher-level qualification solutions can be used to evaluate detector performance.

Recommended Approach

For less sensitive CAD systems, it may be appropriate to evaluate:  Solutions L2 through L6  while maintaining the same:

• Mobile phase
• Column
• Injection volume

used in the qualification procedure.  This approach can help ensure that adequate detector response is obtained while still evaluating chromatographic performance.

Benefits of CAD Qualification

Routine qualification helps verify:

• Detector functionality
• Reproducibility
• Instrument readiness
• Consistent performance
• System suitability

These evaluations are important components of laboratory quality systems and instrument performance programs.

Conclusion

Chemical Solutions Qualification Kits used for HPLC Performance Qualification can also be applied to Charged Aerosol Detector qualification. While the qualification process remains largely unchanged, laboratories should account for substantial sensitivity differences between CAD models. Older detectors may require evaluation using higher-concentration solutions, such as L2 through L6, to ensure reliable detector response during qualification.