title: Sensitive fluorescence assay for d,l-methadone.
abstract: d,l-Methadone forms a fluorophore when reacted with paraformaldehyde in concentrated sulfuric acid. Based on this reaction, a fluorescence assay suitable for quantitative d,l-methadone analysis from plasma and other tissues was developed. d,l-Methadone was extracted at pH 9.2 from the deproteinized filtrate of plasma or of aqueous tissue homogenate into an organic phase of 25% isobutanol in ethylene dichloride. After an aliquot of the organic phase was evaporated to dryness at 50--55 degrees with an air jet, paraformaldehyde (0.1%, in concentrated sulfuric acid) was added, and fluorescence was read at 450 nm with excitation at 275 nm. By this method, d,l-methadone can be assayed in the presence of its metabolites, morphine, diacetylmorphine (heroin), codeine, and cocaine; however, amphetamine, meperidine, and quinine interfere.
mesh_terms: D000818:Animals; D001711:Biotransformation; D004361:Drug Tolerance; D006863:Hydrogen-Ion Concentration; D008691:Methadone / Q000032:analysis* / Q000378:metabolism; D008722:Methods; D051381:Rats; D013050:Spectrometry, Fluorescence; D013997:Time Factors
chemical_list: D008691:Methadone