A thin-layer chromatography (TLC) procedure has been developed for the analysis of urine samples for benzoylecgonine and norpropoxyphene, the major metabolites of cocaine and propoxyphene, respectively. Urine is made slightly acidic and methylated with dimethyl sulfate to convert the difficult-to-extract benzoylecgonine back into the much more readily extractable cocaine. The urine is then chilled, made basic, and extracted with chloroform/isopropanol. The organic layer containing the cocaine and norpropoxyphene is separated and evaporated to dryness. The residue is reconstituted and spotted on a TLC plate which is developed in hexane:chloroform:diethylamine (80:10:10) which separates the two substances without interference from other drugs, metabolites, and urinary substances. The two substances are visualized with acidified iodoplatinate spray and can be detected down to levels of 2.0 microgram/mL for benzoylecgonine and 1.0 microgram/mL for norpropoxyphene.
Twenty-six different opiates were analyzed by radioimmunoassay (RIA) at five different concentrations. At attempt is made to relate structural differences to the affinity of the compounds for the Roche RIA morphine antibody. The effects of substituent placement on the morphine molecule are studied. As expected, the basic 5-ring opiate structure is essential for reactivity. Addition of an alkyl group to the oxygen in the 3-position increased affinity, but alteration of other key functional groups had a reverse affect.
Over 90 different compounds having structural similarities to barbituric acid were analyzed by radioimmunoassay (RIA) using 125I-secobarbital reagents (Roche). Affinities were compared with molecular structures and a number of observations are made. It was found that all definitive components of the 5,5-dialkyl barbituric acid ring structure were essential for reactivity with the Roche RIA reagents; structural changes at any position of the ring reduced reactivity. No compounds studied were found to be more reactive than secobarbital [5-allyl-3-(1-methylbutyl) barbituric acid] and RO-2-1126[5-allyl-5-(1-carbamoylisopropyl) barbituric acid (the hapten used to prepare the RIA antibody)]. Changes in the 5-allyl and/or the 5-(1-methylbutyl) groups of secobarbital resulted in decreased reactivity.
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