Lagchromatografi

Lagchromatografi is a family of analytical techniques that separate components of a mixture by differential partitioning between a stationary phase and a mobile phase. As the mobile phase flows, substances interact with the stationary phase to varying degrees, causing separation along a plane or column. Retention depends on polarity, size, volatility, and the chemistry of the phases.

Common formats include thin-layer chromatography (TLC) and paper chromatography, which use a thin layer or sheet as stationary phase. Column chromatography uses a packed or coated column with normal-phase (polar stationary phase, nonpolar mobile phase) or reverse-phase (nonpolar stationary phase, polar mobile phase). High-performance liquid chromatography (HPLC) and gas chromatography (GC) provide higher resolution and automation. In TLC, separation is shown by spots with retention factors (Rf); in GC and HPLC, analytes are identified by retention times.

Performance is described by resolution, efficiency, and selectivity. Key metrics include the number of theoretical plates, plate height, and retention factor k'. Detectors such as UV/visible, refractive index, fluorescence, or mass spectrometry are used, often with coupling to provide identification and quantification. Choice of stationary and mobile phases and gradient conditions affects peak shape and separation.

Lagchromatografi is widely used in chemistry, biochemistry, pharmacology, environmental analysis, and food science for purity testing, structure confirmation, and trace analysis. It originated with Mikhail Tsvet in the early 1900s, who demonstrated plant pigment separations. Modern techniques, especially HPLC and GC, enable rapid, sensitive analysis of complex mixtures.