Speciation Studies:

It has been well emphasized in the preceding discussion that HPLC can be successfully used for the separation of a wide variety of ionic, non-ionic and polar compounds. In many cases such as that arsenic, selenium, mercury ionic and organic forms are formed. Their detection is very difficult because of occurrence in very low concentrations in the environmental samples. In a typical case, four species of As (III), As (V) and organic species such as monomethylarsine (MMA) and dimethylarsine (DMA) and arsenocholine (As Choline) have been identified and quantified by HPLC as shown in Figure using a 15 cm × 4.6 mm column packed with Supelcosil reverse phase material.

The mobile phase was sodium phosphate buffer at pH 6.0 and 5 mM tetrabutylammonium hydroxide as ion interaction reagent at a flow rate of 2 mL/min.

Quantitative HPLC analysis ideally requires a linear relationship between the magnitude of the signal and the concentration of any particular solute in the sample. Most HPLC systems have in built computerized data handling system and prepare calibration curves using standard concentrations. It is possible to obtain an automatic set of results for the concentrations of individual components in samples matched with their corresponding retention times. It may be remembered that detector response may be different for various components of a mixture introducing a factor of uncertainty in results.