Charge-Transfer Complexes in Alkaloid Assay

• Published in: Journal of pharmaceutical sciences 1974-12, Vol.63 (12), p.1853-1857
• Main Authors: Taha, A.M., Ahmad, A.K.S., Gomaa, C.S., El-Fatatry, H.M.
• Format: Article
• Language: English
• Subjects: Alkaloids - analysis; Alkaloids-spectrophotometric assay; Alkaloids—spectrophotometric assay charge- transfer complexes; Alkaloids—spectrophotometric assay, chargetransfer complexes; charge transfer-alkaloid spectrophotometric assay; charge-transfer complexes; Charge-transfer complexes-alkaloid spectrophotometric assay; Charge-transfer complexes—alkaloid spectrophotometric assay; chargetransfer complexes; Chemical Phenomena; Chemistry; Chromatography, Thin Layer; Complexes; Complexes charge transfer—alkaloid spectrophotometric assay; Complexes, charge transfer—alkaloid spectrophotometric assay; Conductometry; Indicators and Reagents; Iodine; Methods; Osmolar Concentration; Solubility; Solvents; Spectrophotometry, Ultraviolet; Spectrophotometry-alkaloid assay; Spectrophotometry—alkaloid assay charge-transfer complexes; Spectrophotometry—alkaloid assay, charge‐transfer complexes
• ISSN: 0022-3549; 1520-6017
• DOI: 10.1002/jps.2600631206

The intense charge-transfer UV bands in the spectra of molecular complexes of iodine with amines were utilized in a sensitive spectrophotometric assay of alkaloids. Solutions of the alkaloids in chloroform or carbon tetrachloride when mixed with iodine in the same solvent exhibited blue-shifted iodine bands in the 270-305-nm range. Owing to the high molar absorptivities of the complexes, significant increases in sensitivity, accuracy, and precision were observed upon quantitation. The method is directly applicable to the purified alkaloid-containing chloroform fractions obtained in pharmacopeial assays or isolated from plant extracts and drug formulations in the general concentration range of lO−5-10−6M with a relative standard deviation of 0.015. The method is particularly recommended for assaying the tropane alkaloids and other weak UV-absorbing alkaloids such as ephedrine, codeine, and sparteine.