title: Difference spectrophotometric assay of 1,2-diphenolic drugs in pharmaceutical formulations II: Germanium dioxide reagent.
abstract: A rapid, difference UV spectrophotometric assay of formulated drugs containing a 1,2-diphenolic group is described. In this assay are utilized the bathochromic shift of the absorption band of 1,2-diphenolic substances from approximately 280 to approximately 287 nm and the concomitant hyperchromic effect induced by the addition of germanium dioxide to an aqueous solution of the drug buffered at pH 6. The absorbance of the solution of the complexed drug relative to that of an equimolar solution of the free drug, which is maximum at approximately 292 nm, is proportional to the concentration of the drug and is unaffected by the presence of other UV-absorbing substances in the formulations that lack the 1,2-diphenolic moiety. Applications of the assay are described for formulations containing epinephrine, isoetharine, isoproterenol, levodopa, and methyldopa.
mesh_terms: D002396:Catechols / Q000032:analysis*; D055598:Chemical Phenomena; D002621:Chemistry; D005857:Germanium; D006863:Hydrogen-Ion Concentration; D004364:Pharmaceutical Preparations / Q000032:analysis*; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013607:Tablets
chemical_list: D002396:Catechols; D004364:Pharmaceutical Preparations; D012996:Solutions; D013607:Tablets; D005857:Germanium; C040516:germanium oxide