In High Performance Liquid Chromatography (HPLC), as opposed to GC, the analytes are in a liquid solution and they do not require sample volatilization. Therefore, HPLC is applicable to a much greater variety of compund mixtures than GC, including non-volatile or thermally unstable molecules. Its advantages include greater versatility, sensitivity and applicability to very complex mixtures.
A high number of different HPLC columns are available to undertake almost every separation problem. Ion chromatography uses ionic stationary phases optimized for the separation of ionic species (anions and cations). Normal phase chromatography uses hydrophilic stationary phases. Reverse-phase columns, that use hydrophobic stationary phases, are the common choice for the separation of most organic compounds.
HPLC systems can accept a variety of detectors. The commonly used diode-array detector (DAD) measures the absorbance of light of the eluting compounds in the UV or visible range. DAD can also provide additional information by measuring the UV-visible absorption spectra of the individual compounds present in the original mixture.
