Many analytical techniques have been used in quality control, such as spectrophotometry, spectrofluorimetry, HPLC, and other hyphenated techniques. Among them, spectrophotometry is considered to be one of the most commonly used simple techniques. Drugs that
lack chromogenic groups can be readily determined by using the chromogenic reagents, which
react with the functional groups present in the drugs and produce a chromogenic group that can
be detected in the visible region using a spectrophotometer. Chromogenic reagents play a vital
role in the estimation of such types of drugs. Vanillin is one of the chromogenic reagents that
possess a carbonyl group that reacts with the drugs that possess amine moiety and results in the
formation of Schiff’s base, which is a yellow-colored compound that can be detected by spectrophotometry. The present review gives insights into the reaction conditions and applications
of the drugs that are estimated by using vanillin as a chromogenic label.