Rapid and sensitive analysis of morphine in serum by reversed-phase high performance liquid chromatography with electrochemical detection

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.

Ion-pair extraction and liquid chromatographic analysis of morphine in rat brain and plasma

A highly efficient and reproducible two-step liquid-liquid ion-pair extraction technique for the isolation of morphine from biological samples is described. A rapid normal phase high-performance liquid chromatographic procedure coupled with amperometric electrochemical detection has also been developed for subsequent quantification of morphine. Extraction involves the disruption of brain tissue or plasma in methanol, centrifugation, evaporation and reconstitution in ethyl acetate containing 10 mM di-(2-ethylhexyl) phosphoric acid, a liquid cation-exchanger, and back-extraction into 170 mM orthophosphoric acid. An acidic eluent consisting of acetonitrile-76 mM orthophosphoric acid-ammonia buffer (pH 3.0) (15:85, v/v) in combination with a strong cation-exchange column allows complete separation of morphine and the internal standard, nalbuphine. The limit of detection for morphine is 1.3 ng on-column.

Simple method for the determination of morphine and its active glucuronide metabolite in human plasma by high-performance liquid chromatography with electrochemical detection

A simple method for the simultaneous determination of morphine and its pharmacologically active metabolite morphine-6-glucuronide in 0.5 ml human plasma is described. It is based on the method of Svensson [J. Chromatogr., 230 (1982) 427 and 375 (1986) 174], but uses only one solid-phase extraction cartridge prior to chromatography and only a 20-microliter injection volume. Mean recoveries of 90 and 85% for morphine and morphine-6-glucuronide, respectively, were obtained, the limit of detection being 2 nmol/l (at a signal-to-noise ratio of 3.0).

Voltammetric assay of heroin in illicit dosage forms

The oxidation of heroin on a carbon paste electrode has been studied by using voltammetric techniques under both semi-infinite linear diffusion and hydrodynamic conditions. By employing a simple and rapid in situ pre-treatment of the electrode, excellent reproducibility of the current signal was obtained. Subsequently, the current was measured and the concentration of total heroin present could be determined. The method compared favourably with instrumental methods that are more commonly used for the quantification of heroin in clinical laboratories such as chromatographic, spectrophotometric or radiometric techniques. Moreover, the proposed method showed good selectivity and was superior with respect to cost and time of analysis, permitting the determination of heroin in seized drug samples over a wide concentration range.

High-performance liquid chromatographic determination of morphine in biological samples: an overview of separation methods and detection techniques

High-performance liquid chromatogrpahy with electrochemical detection at present suits most of the needs of toxicologists for the determination of morphine and some related compounds in biological samples, although fluorescence detection is still a useful alternative. Chemiluminescence detection may be promising, but needs further optimization of its coupling with HPLC to give the best performances. Morphine detection by absorbance spectrophotometry does not seem to allow the degree of sensitivity and selectivity from matrix interferences that is required in most instances. However, this approach is useful when morphine congeners undetectable by alternative means (i.e., heroin and morphine-3-glucuronide) are to be determined or when a general toxicological screening is required.

Simultaneous determination of biogenic amines and morphine in discrete rat brain regions by high-performance liquid chromatography with electrochemical detection

A simple and sensitive method has been developed for the simultaneous determination of norepinephrine, epinephrine, dopamine, 5-hydroxytryptamine, 5-hydroxyindoleacetic acid, and morphine in discrete rat brain regions by reversed-phase high-performance liquid chromatography with electrochemical detection. Perchloric acid extracts of the tissue were directly injected into the chromatographic system. Each of these compounds gave a linear response over the range of 20-160 ng/ml cerebellar homogenate (0.4-3.2 ng on column). Recoveries of these compounds, added to the homogenates, were complete when compared with standards dissolved in perchloric acid. The average between-run coefficients of variation for all these compounds were lower than 7.4% over the range of 20-160 ng/ml, and the within-run coefficients of variation at 20 ng/ml were lower than 8.7%. The present method has been applied to a study of the effects of intraperitoneal administration of morphine on biogenic amines in several discrete rat brain regions.

Coulometric high-performance liquid chromatographic analysis of morphine in biological fluids

A simple method is described for the determination of morphine in biological fluids (plasma and urine) by high-performance liquid chromatography with coulometric detection. The detector consists of three porous electrodes which are arranged in a way to give maximum selectivity and sensitivity. Quantitation of morphine is performed using naloxone as the internal standard. Sample preparation involves an extraction procedure from plasma and urine. The limit of quantification of the method is 1 ng/mL plasma. The methodology was applied to measure blood levels in rats after subcutaneous administration of a slow-release morphine pellet.

High-performance liquid chromatographic assay for morphine with electrochemical detection using an unmodified silica column with a non-aqueous ionic eluent

A quick, sensitive and accurate high-performance liquid chromatographic method for morphine measurement in plasma has been developed using an unmodified silica column with a non-aqueous ionic eluent. Small plasma samples (0.4 ml) were extracted with a liquid-liquid extraction column and dihydromorphine was used as internal standard. The limit of quantitation was 2 ng/ml. The electrochemical detector was capable of detecting 150 pg of morphine. A calibration line with a correlation of 0.9994 +/- 0.00026 was produced over the range 2-80 ng/ml.

Differential response to ethanol, pentobarbital and morphine in mice selectively bred for ethanol sensitivity

Males of two lines of mice, long sleep (LS) and short sleep (SS), that had been selectively bred for their differential sensitivity to ethanol-induced sleep, were examined for their responses to the hypothermic and analgesic effects of ethanol, pentobarbital and morphine, and to the cataleptic effect of morphine. SS mice were found to be less sensitive than the LS animals to ethanol but not pentobarbital-induced analgesia and hypothermia. The SS animals were also less sensitive to morphine-induced hypothermia, but were, by contrast, more sensitive than their LS counterparts to morphine-induced analgesia, while no line differences existed with respect to catalepsy. The rate of morphine disappearance from the blood was somewhat higher in the LS animals but this difference is probably too small to account for the observed differential responses to morphine.