chromatograph

A chromatograph is an instrument used to perform chromatography, a separation technique that analyzes mixtures by distributing their components between a mobile phase and a stationary phase. The term may also refer to a person who conducts chromatographic analysis. Modern chromatographs cover gas chromatography (GC) and liquid chromatography (LC), including high-performance (HPLC) and ultra-high-performance (UHPLC) variants.

A typical chromatograph comprises a sample injector, one or more separation columns, a pump or carrier for the mobile phase, a detector for signal generation, and a data system for recording retention times and peak areas. The sample is introduced, and its components interact differently with the stationary phase as the mobile phase moves through the column, causing separation. Each component elutes at a characteristic retention time and is identified by its detector response and often by comparing with standards.

Gas chromatographs use a gaseous mobile phase and are common for volatile compounds, with detectors such as flame ionization (FID) or thermal conductivity (TCD). Liquid chromatographs use liquids as the mobile phase and can employ UV–visible, refractive index, or mass spectrometric detectors. Columns are packed with a stationary phase, typical silica or polymeric materials, with various chemistries like C18 for reversed-phase LC.

Chromatographs are widely used in analytical chemistry, pharmaceuticals, environmental testing, food safety, and forensics. The technique can be coupled to mass spectrometry (GC-MS, LC-MS) for enhanced identification and quantification. The development of chromatography devices dates to early 20th-century work by Mikhail Tsvet, with modern instruments increasingly automated and capable of high throughput.