There are four main types of chromatography. These are Liquid Chromatography, Gas Chromatography, Thin-Layer Chromatography and Paper Chromatography. Liquid Chromatography is used in the world to test water samples to look for pollution in lakes and rivers.

Various chromatography methods have been developed to that end. Some of them include column chromatography, thin-layer chromatography (TLC), paper chromatography, gas chromatography, ion exchange chromatography, gel permeation chromatography, high-pressure liquid chromatography, and affinity chromatography [6].

Chromatography is a separation process involving two phases, one stationary and the other mobile. Typically, the stationary phase is a porous solid (e.g., glass, silica, or alumina) that is packed into a glass or metal tube or that constitutes the walls of an open-tube capillary.

the mobile phase is the solvent that moves through the paper, carrying different substances with it. the stationary phase is contained on the paper and does not move through it.

The elution order of solutes in HPLC is governed by polarity. For a normal-phase separation, solutes of lower polarity spend proportionally less time in the polar stationary phase and are the first solutes to elute from the column.

High-performance liquid chromatography (HPLC) is an analytical technique to separate, identify, and quantify components in a mixture. It is the single biggest chromatography technique essential to most laboratories worldwide.

www.ace-hplc.com Another factor that should be considered when choosing the mobile phase pH is the stability of the column. As a general rule, silica-based columns should be operated at 2<pH<8. At pH<2, bonded phase loss due to hydrolysis can occur. Above pH 8, the silica backbone becomes increasingly soluble.

The mobile phase was prepared by adding phosphoric acid or perchloric acid to adjust the pH to 2.5. These differences can significantly affect the retention time, as shown for dihydrocodeine in the example, and can lead to problems with the robustness of the analysis method.

Three different methods are common in pH measurement of mobile phases: measurement of pH in the aqueous buffer before addition of the organic modifier, measurement of pH in the mobile phase prepared by mixing aqueous buffer and organic modifier after pH calibration with standard solutions prepared in the same mobile …