Thin-layer chromatographic analysis of cocaine and benzoylecgonine in urine

A high-performance thin-layer chromatographic technique to screen cocaine in urine samples

Qualitative identification of cocaine and its metabolites in urine samples is generally carried out by an immunoassay technique followed by a gas chromatographic/mass spectrometric confirmation of presumptive positives. Nevertheless, other chromatographic techniques such as thin-layer chromatography or gas chromatography could also be used to screen several types of drugs of abuse especially for forensic and legal purposes. In the present work, the capability of high performance thin-layer chromatography (HPTLC) to detect cocaine in urine samples and discriminate it from interfering substances (local anaesthetic, caffeine and nicotine) was studied. Twenty urine samples of drug addicts were submitted to the HPTLC method. Unaltered cocaine present in the urine samples and cocaine obtained after methylation of benzoylecgonine (main cocaine metabolite) with diazomethane were detected in all tested samples. In conclusion, the proposed HPTLC method showed to be useful to detect cocaine in biological matrices.

Screening for drugs of abuse. I: Opiates, amphetamines and cocaine

(1) In order to provide an efficient and reliable service for drugs of abuse screening in urine, the laboratory should analyse 20-30 samples per week, and the staff should include a scientist with special expertise in the subject. (2) Turnaround times should be between 2-3 days of sample collection. To achieve this aim it may be necessary to make special arrangements for the delivery of samples to the laboratory. Results should preferably be transmitted by electronic mail or facsimile with the necessary precautions for security and confidentiality: hardcopy reports may also be required. (3) Good communications between the requesting clinician and the laboratory are essential. An advisory service should be provided by the laboratory and clinicians should be encouraged to discuss requests and results with laboratory staff. It is important that the laboratory inform doctors of the range of substances detected and the sensitivity and specificity of laboratory assays. (4) Assays should be performed according to the manufacturer's protocols, or by modified methods that have been rigorously validated. Quality control samples should be included in each analytical run and participation in an external quality assessment scheme, e.g. UKNEQAS, is essential to provide independent confirmation and confidence that results compare with those from other laboratories. Other requirements include adequate training and supervision of staff, and careful recording of samples and results. (5) Drugs to be tested will depend on the drug 'scene' in the area but should include those drugs regularly prescribed for maintenance therapy (e.g. methadone, dihydrocodeine, benzodiazepines), and drugs frequently misused (e.g. heroin, buprenorphine, amphetamines, cocaine). (6) Positive results obtained by preliminary screening methods e.g. EMIT, should be confirmed by another analytical technique, e.g. TLC, GC or GC-MS. If there are potentially serious or legal implications, and in employment and preemployment testing, confirmation of positive results is mandatory. In some cases, e.g. checking for methadone or benzodiazepine compliance, it may be considered unnecessary to confirm positive results although possible spiking of samples cannot be excluded without checking for the presence of metabolites by a chromatographic procedure.

Quantitation of cocaine, benzoylecgonine and ecgonine methyl ester by GC-CI-SIM after Extrelut extraction

A method of gas chromatography-chemical ionization selected ion monitoring (GC-CI-SIM) is described for the determination of cocaine, benzoylecgonine and ecgonine methyl ester in biological materials using an Extrelut extraction technique. Recoveries of cocaine, benzoylecgonine and ecgonine methyl ester by this technique were 95, 81 and 97%, respectively. The method uses cocaine-d5, benzoylecgonine-d5 and lidocaine as internal standards, and isobutane as reagent gas for chemical ionization. Sensitivity of the method proved to be 1 ng/ml for cocaine and benzoylecgonine, and 10 ng/ml for ecgonine methyl ester when used in a 10-ml urine sample. With animal experiments, ecgonine methyl ester as well as benzoylecgonine was confirmed as a major metabolite of cocaine.

Cocaine radioimmunoassay--structure versus reactivity

Twenty-seven different cocaine-related substances were analyzed by radioimmunoassay (RIA) at several concentrations. An attempt was made to relate structural differences to the affinity of the compounds with the RIA benzoylecgonine (cocaine metabolite) antibody. The effects of substituent placement in the cocaine molecule were studied. Adding an alkyl group to the 2-carboxylic acid (conversion to an alkyl ester) increased reactivity, whereas changes in all other positions reduced reactivity.

TLC analysis of urine for benzoylecgonine and norpropoxyphene

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.

Measurement of benzoylecgonine and cocaine in urine, separation of various cocaine metabolites using reversed-phase high-performance liquid chromatography

The application of reversed-phase high-performance liquid chromatography to the measurement of benzoylecgonine and cocaine in urine is described. Following a simple extraction and clean-up procedure, chromatography is performed using a column containing an octadecylsilica coated packing, elution with 17% acetonitrile in pH 2.7 phosphate buffer and ultraviolet detection at 200 or 235 nm. The detection limit is ca.0.1 microgram of drug per ml urine, and using the ethyl ester of benzoylecgonine as an internal standard, benzoylecgonine and cocaine are quantified with coefficients of variation of 7.0 and 2.8%, respectively. The procedure has been applied to urines from subjects receiving intranasal cocaine, and compared to the enzyme multiplied immunoassay technique. The chromatography procedure also permits the separation of norcocaine and benzoylnorecgonine.

Single- and two-step extraction and thin-layer detection procedures for benzoylecgonine (cocaine metabolite) alone or in combination with a wide variety of commonly abused drugs in urine screening programs

Three extraction procedures for the detection of benzoylecgonine (a major metabolite of cocaine) in urine are presented. Each technique has its advantages, depending on the needs of a clinical operation. Procedures I and II involve the use of ion-exchange resin-loaded paper. Procedure I has a sensitivity of 1 microng/ml and requires 20 ml of urine, and is recommended when the aim is to test for the abuse of cocaine only. Procedure II is a two-step extraction method in which a wide variety of abused drugs are extracted by the first step and the benzoylecgonine left in the aqueous buffer phase is extracted in the second step. The sensitivity for benzoylecgonine using this procedure is 2 microng/ml and it requires 20-50 ml of urine. Procedure III involves the direct extraction of benzoylecgonine using 5 ml of urine and has a sensitivity of 0.5 microng/ml.

Metabolism of intranasally applied cocaine

Surprisingly little is known about the metabolism and toxicity of cocaine in man. In this study serum obtained following nasal surgery was assayed for benzoylecgonine (the major metabolite of cocaine) by radioimmunoassay. It was found that cocaine was rapidly hydrolyzed in the serum. Benzoylecgonine was detectable in the serum at 15 minutes. The peak blood level of the metabolite appeared at 4.5 hours with a peak concentrations of 872.9 ng/ml. The half time clearance of the metabolite from the serum was 5.5 hours. A discussion of variables which must be considered in deriving, by a scientific method, a maximum safe clinical dose is presented.