High-performance liquid chromatography sample injector

High-performance liquid chromatography employs very fine particles, and uses high-pressure pumps to force the mobile phase through the column. The mobile phase passes from a reservoir through the pump, an injector, the column and a flow-through detector to a waste collection reservoir. The injector allows the introduction of sample mixtures into the flowing mobile phase with little or no disturbance to the flow. 

A typical high-performance liquid chromatography (HPLC) system consists of two pumps, a mixer, an injector, a guard colunm, a separation column, a detector, an electrospray nozzle, and a mass spectrometer. The two pumps and the mixer allow establishment of desired solvent gradients. The injector is used to inject a small amount of sample into the column. In all separation techniques, definition of a small volume of injected sample is cmcial in preventing adverse broadening of peaks and a consequent loss in compmient resolution. The injected compounds are separated in the separation colunm and then detected via a simple detector or a mass spectrometer. All of the parts of the HPLC system have been miniaturized, and several research groups have been able to demonstrate on-chip HPLC separations. 

The injector is an interface that achieves reproducible and accurate transfer of a sample volume between the system operator and the chromatographic column in a front (band) as narrow as possible. Usually, for analysis by high-performance liquid chromatography (HPLC), samples are prepared in a liquid state (as a solution in an appropriate solvent or mixture of solvents, obtained as a result of sample preparation of solid or liquid samples). For practical reasons (avoiding column overloading), even for analytes in a liquid state under ambient conditions, dilution in appropriate solvents is more often used. 

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