The main difference between preparative and analytical liquids lies not in their appearance but in their purpose.
The purpose of the analytical liquid phase is of course to analyse the sample, what it contains and how much it contains, also known as qualitative quantification. To do a good job with analytical liquids, the main concern is separation and sensitivity, to be able to separate, to measure and to be accurate.
The preparation of the liquid phase uses the separation power of the column to remove impurities and obtain a high-purity sample. In the laboratory, infrared, ultraviolet and nuclear magnetic instruments all require samples of sufficient purity to give accurate results. In addition to the laboratory, the production of pharmaceuticals also requires purification, especially for biologics and pharmaceuticals.
In the laboratory, the liquid phase used for preparation by a preparative liquid chromatography system is configured in much the same way as an ordinary analytical solution. There are pumps, a sample injector, a column and a detector. To collect the separated compounds, the preparative liquid phase is often equipped with a fraction collector.
There are many different ways of classifying preparative phases, for example, by pressure or by yield, and there is no clear standard. The different types of preparative phases have different characteristics.
The purpose of preparing liquid phase is to extract and purify the monomer of a product. Compared to traditional purification methods (e.g. distillation, extraction), preparative liquid phase is a more efficient separation method and is therefore widely used for the extraction and purification of samples and products. With the increasing demand for high purity components in the synthetic, phytochemical, biochemical and pharmaceutical fields, the field of application of preparative liquid chromatography is rapidly expanding and developing.