Analysis of waxes using HPLC-CAD

Instrumental: The Ultimate 3000 HPLC system consists of a quaternary pump (620 bar), autosampler, column compartment, and charged aerosol (CAD) detectors (Thermo Scientific). The compounds were separated on the Acclaim C30 column (2.1×150 mm, 3 µm, Dionex) using a linear gradient of acetonitrile/.

The CAD can be used for the detection of any compound less volatile than the mobile phase solvents.

Alkanes are usually analyzed using GC-FID or GC-MS techniques due to the good resolving capability of GC columns and the high sensitivity of FID or MS detectors. These non-polar compounds do not have chromophores or reactive chemical groups and cannot be detected by photometric or chemical detectors nor ionized using ESI or APCI ionization. However, any compound significantly less volatile than a mobile phase can be detected using the charged aerosol detector.

The compounds of low volatility may have discriminational effects in the GC injector and as a result, decreased response in FID or MS detectors. In such cases, HPLC-CAD may be a good alternative for quantitative analysis.