Wai-Kit Leung

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A thin-layer chromatography (TLC) procedure for the screening and confirmation of urinary codeine and morphine has been developed. Urine samples are hydrolyzed to liberate free codeine and morphine, extracted into an organic solvent, and concentrated. For screening, the extraction residues are spotted on TLC plates which are developed in chloroform:ethyl(More)
PURPOSE This study investigated the intra-observer and inter-observer variation of Hertel exophthalmometry. METHODS Seventy normal Chinese adults had bilateral exophthalmometry performed by two examiners. The two examiners were masked to the measurement results. One examiner did the measurement twice and the other examiner measured it once; the order was(More)
A method suitable for large scale screening and confirmation of urine speciments for amphetamine, methamphetamine, methadone, and its primary metabolite (2-ethylidene-1,5-dimethyl-3,3-diphenlypyrrolidine) is described. The drugs are extracted from alkaline urine into an organic solvent. The amphetamine drugs are then back-extracted into a small volume of(More)
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(More)
A sensitive, rapid, and specific procedure is described for the mass screening and confirmation of PCP (phencyclidine) in urine specimens at concentrations as low as 0.3 microgram of PCP per mL. Specimens that test positive by radioimmunoassay must be confirmed by TLC using methylene chloride:n-butanol:concentrated NH4OH (85:15:0.5) as the developing(More)
A sensitive, rapid, and specific procedure is described for the mass screening and confirmation of methaqualone (Quaalude) in urine specimens. The method is sensitive to 1.0 microgram/ml levels of total methaqualone excretion products (free methaqualone, free hydroxylated methaqualone metabolites, and conjugated hydroxylated methaqualone metabolites). The(More)
This procedure positively identifies codeine and morphine in urine. Urine samples are hydrolyzed and extracted with organic solvent, and the extracts are evaporated and acetylated. The presence of codeine and morphine is ascertained by gas chromatography (3% OV-25 and 3% Poly-A 103 columns) and confirmed by thin-layer chromatography (system: ethyl(More)
A thin-layer chromatographic method for the simultaneous screening and confirmation of methadone and its primary metabolite (2-ethylidene-1,5-diemthyl-3,3-diphenylpyrrolidine) in urine specimens is presented. Urine is made basic and extracted with organic solvent. After separation and concentration, the residue is spotted, half on each of two thin-layer(More)
Two newly developed, thin layer chromatographic (TLC) solvent systems are presented to separate and identify commonly used phenothiazines in the presence of other drugs in urine specimens. These solvent systems are 1) ethyl acetate: n-butanol: concentrated ammonium hydroxide (89:10:1.5) and 2) ethyl acetate: O-dichlorobenzene: concentrated ammonium(More)