USP <197>, UV Identification And Assay
Spectrophotometric tests contribute meaningfully toward the identification of many compendial chemical substances. As according to USP <197>, the requirements are met if the UV absorption spectra of the test solution and the standard solution exhibit same maxima and same minima wavelengths, and absorptivities and/or absorbance ratios are within specified limits.
USP <201>, Thin-Layer Chromatography Identification and Purity Test
TLC identification is applicable as an aid in verifying the identities of the compendial drug substances, excipient, and botanical products in their respective dosage forms according to USP <201>. TLC is particularly useful in verifying the identities of active ingredients and by comparing the band distance Rf of the sample to the known reference standard. TLC is also used for testing substance purity by comparing results to log dilutions of active concentrations visualized by UV 254, UV 365 or spray indicator derivatization.