Basic Chrmatography基本的色谱法.pptVIP

If a chromatogram has narrow peaks then the column on which the analytes were separated is said to have a high efficiency. The measure of column efficiency is the parameter ‘plate height’ or H, the lower the plate height the more efficient the column. Chromatography - Distillation van Deemter Curves. * Chromatographic methods Chromatography is the science of physical separation of species in a mixture. It may be used to measure components of both qualitatively and quantitatively. The basis of all chromatographic techniques is the principal of retention. That under certain conditions molecules move at different rates through a separating bed. When to use Chromatography: To measure many different compounds in complicated multi-component mixtures. Analytes Pesticides, dioxins, PCBs, PAHs, benzene, hydrocarbons, chlorofluorocarbons, c.f. Spectroscopy Used for simple mixtures, or very specific measurements Matrices Soil/sludges, water, solvents, biological fluids, air, natural gas The most known chromatographic process is when a spot of ink on wet paper spreads out to leave ‘bands’ of colours which made up the colour ‘black’. The different ‘colours’ of ink travel at specific rates across the wet paper depending on the degree to which each colour ‘sticks’ to the surface of the paper. In chromatographic terms the paper is known as the ‘stationary phase’ and water, the ‘mobile phase’, two elements common to all chromatography. Any substance exposed to two such media will partition itself between them depending on its affinity to each phase. Molecules with a high affinity to the mobile phase will move more rapidly than one with high affinity to the stationary phase. In modern chromatographic techniques the system is housed within a column. Stationary phases either exist as an interior coating within the column or on the surface of a porous packing material. The type of stationary and mobile phases can be changed to make the system as efficient as possible for separatin