HPLC is the most popular method for analyzing amino acid components, which have currently gained attention due to the boom in health foods.

Using UV detection for amino acids in most cases requires using the absorption of the carboxyl group (-COOH) in the 200 to 210 nm range. Some amino acids with benzene rings can also be detected in the 250 to 280 nm range, but in general, they are difficult to analyze as-is with sufficient sensitivity and selectivity.
Consequently, derivatization methods have long since been used. Since many amino acids contain amino groups (-NH2and -NHR) in their structures, a derivatizing reagent that selectively reacts with the amino group is used.

Pre-column Derivatization Method: In pre-column derivatization, the amino acids are derivertized before injection, and then the reaction products are separated and detected.

Post-column Derivatization Method: The post-column derivatization method involves separating the amino acids in the column, then delivering and mixing the derivatizig reagent to let it react with the amino acids, before finally sending the products to the detector.