The HPLC is a master specialist in determining the identity and quantity of elements and molecules, such as the activity in an herb, the product of an enzymatic reaction, or any molecule which absorbs light or that can be made chromophore (able to absorb/transmit light). The HPLC is very specific in being able to absolutely determine what a substance is and exactly how much of it there is.
HPLC works by automatically injecting a small volume of liquid sample into a column packed with particles 1⁄20 the thickness of a white sheet of paper. The liquid sample is forced through the column by powerful micropumps. The detector sends a digital signal to the computer, where specialized software is used to identify and determine the quantity of the separated components.
We use it routinely to analyse the composition of compounds present in complex mixtures, such as water- and fat-soluble vitamins. We also use the HPLC to analyse a large variety of plant material, for example astragalus, dandelion, and red clover.
This is a typical liquid chromatogram of water-soluble vitamins; these are called chromatographic peaks, and each one represents a separated compound.