Sub-microgram estimation of morphine in biological fluids by gas-liquid chromatography

Highly sensitive gas chromatographic-mass spectrometric method for morphine determination in plasma that is suitable for pharmacokinetic studies

A sensitive method was devised to determine morphine plasma concentrations by gas chromatography-mass spectrometry (GC-MS) using selected ion monitoring (SIM) with nalorphine as the internal standard. This method was rugged, reliable, selective and sensitive and was used to determine the morphine content of over 2000 samples. Sample preparation involved extraction of basified sample using n-butyl chloride-chloroform (5:1) and evaporation of the extract to dryness. The residue was derivatised with pentafluoropropionic anhydride, evaporated to dryness, reconstituted in 40 microl toluene and injected onto the GC-MS. For a sample size of 1 ml, the limit of quantitation was 0.75 ng/ml (S/N ratio 10:1) and the estimated limit of detection was calculated to be 0.2 ng/ml (S/N ratio 3:1), expressed as morphine base. Precision (n=5) was 4.9% at 0.75 ng/ml, 6.8% at 1.5 ng/ml, 3.0% at 37.5 ng/ml and 2.3% at 150 ng/ml. Standard curves for the range of 0-750 ng/ml morphine in plasma were linear with all r2 values greater than 0.99. No interfering peaks were seen for either morphine or internal standard in the blank samples. The method is suitable for pharmacokinetic studies after subclinical doses of morphine where it has been used to study morphine plasma concentrations for 6 h after a dose of only 2 mg.

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.

A rapid method for the determination of blood morphine concentration suitable for use in studies involving acute and chronic pain

This communication provides an improved sample preparation method for blood morphine concentration determination prior to high-performance liquid chromatography analysis with electrochemical detection. The lower limit of sensitivity is 1 ng/ml of whole blood, and the standard curve is linear to an upper limit of 500 ng/ml. The coefficient of variation of replicate determinations of morphine at concentrations of 10 and 400 ng/ml were 4.7 and 2.5%, respectively. This assay procedure is rapid and accurate and allows the large number of samples (usually 30-40 samples) generated by pharmacokinetic studies in acute and chronic pain to be conveniently analyzed in one day.

The significance of drug analysis of sweat in respect to rapid screening for drug abuse

Morphine and methamphetamine, which are excreted in the sweat, are detected by the use of routine serological and physicochemical techniques for urinary examinations. Screening for drug abuse can be done with the same accuracy of that of urine. Rapid excretion of the drug via kidney (within one day) is followed by a slow but steady excretion of the sweat gland. Methamphetamine given orally in a dose of 10 mg is excreted in the sweat at a constant rate (1.4 microgram/ml). No significant difference of the amount excreted by both systems is found. Alveolar lining seems to prevent the elimination of the volatile methamphetamine via respiration. Not only narcotics and stimulants, but also many alkaloids and barbituarates are excreted in the sweat and detected quantitatively by the same principles. The toxicological analysis of the sweat promises a new scope of forensic investigation.

Pharmacokinetics of morphine and its surrogates I: comparisons of sensitive assays of morphine in biological fluids and application to morphine pharmacokinetics in the dog

A sensitive isotope derivatization assay was developed to quantify morphine in biological fluids in the nanogram per milliliter range. Morphine, derivatized with 3H-dansyl chloride, was separated from the reaction products by TLC. The spots were scraped from the plate, and the eluted radioactivity was determined by liquid scintillation. The standard deviations of this morphine assay were +/- 18.6 ng/ml in 100 microliter of plasma and +/- 1.86 ng/ml in 1 ml of plasma. The GLC analysis of pentafluoropropionated morphine in the range of 0--5 ng of morphine/ml of plasma had a standard deviation of +/- 0.46 ng/ml when 1 ml of plasma was taken. Liquid scintillation spectrometric analysis of 14C-morphine had a sensitivity of 1.5 ng/ml of plasma at double the background. There were no significant differences among the liquid scintillation, electron-capture GLC, and radioisotpoe derivatization methods for morphine obtained from the plasma of a dog given 14.00 mg iv of morphine. Morphine conjugates were assayed as morphine after the acid hydrolysis of plasma and urine preextracted to remove unconjugated morphine, and the equivalence of various methods was demonstrated to monitor plasma and urine pharmacokinetics in a dog.

Determination of drugs of abuse in body fluids by radioimmunoassay

Only recently has radioimmunoassay been used for the detection of drugs of abuse in body fluids. The radioimmunoassay method is rapid, sensitive, specific, and can be performed with a minimum of sample, while conventional assay methods are time-consuming, relatively insensitive, and require a larger sample volume. Performance of individual radioimmunoassays is identical, and requires about one hour to complete. The radioimmunoassays which have been developed for measurement of drugs of abuse in humans are reviewed in this paper. These new techniques are of importance in individual and/or emergency testing, in screening, and in further research into the effect of these drugs on the functions of the human body.

Improved recovery of morphine from biological tissues using siliconized glassware

The adsorption of morphine onto glassware during analysis in aqueous solutions and biological tissues is a common problem, resulting in lower recoveries than expected. The problem can be remedied by siliconization of all glassware involved. The same glassware cannot be used repeatedly without incurring a significant loss of morphine.

Application of the extractive alkylation technique to the pentafluorobenzylation of morphine (a heroin metabolite) and surrogates, with special reference to the quantitative determination of plasma morphine levels using mass fragmentography

The pentafluorobenzylation of morphine and related phenolic alkaloids by extractive alkylation is described. The alkylation is performed using tetrabutylammonium as counter ion and ethyl acetate as solvent. Optimum reaction conditions are presented together with the gas chromatographic properties of the derivatives formed. The technique is applied to the quantitation of plasma morphine levels. Using morphine-d3 as internal standard mass fragmentographic analysis of morphine as its pentafluorobenzyl- and pentafluorobenzyl, mono-trifluoroacetyl derivatives is demonstrated, and a case report is presented. Quantitation to a plasma morphine level of 5 ng/ml is readily attainable.

Plasma pentobarbitone levels. Estimation by gas-liquid chromatography after clinical doses

A simple and relatively quick method of estimating pentobarbitone in plasma samples is reported using an ether extraction and gas-liquid chromatography. Glutethimide was used as the internal standard and proved reliable. Reproducible results were obtained in plasma following 100 mg pentobarbitone given by mouth or intramuscular injection. Evaporation in a heating block at 37 degrees C and storage of samples at -20 degrees C prior to analysis is recommended.

Quantitative determination of morphine in biological samples by gas-liquid chromatography and electron-capture detection

A highly sensitive method for the determination of morphine in plasma and brain samples down to 500 pg ml-1 in plasma and 100 pg in 30 mg of brain tissue is described. This sensitivity is in the range of that described for radioactive and radioimmunological tehcniques. The samples (50-500 mu-l) are extracted with toluene-butanol (9:1) at pH 8.9 and then re-extracted into 0.1 N sulphuric acid and back extracted to a toluene-butanol phase at pH 8.9. The pentafluoropropionic anhydride derivatives of morphine and the internal standard nalorphine were quantitatively determined by gas-liquid chromatography with a 3-H electron capture detector.

Stumbling blocks in the study of diamorphine

Although the centenary of the discovery of diamorphine is soon to be celebrated, much work remains to be done before its mode of action is thoroughly understood. The main stumbling blocks facing the would-be investigator can be summarized as follows:

(1) Diamorphine in solution has a limited shalf-life.

(2) The potency ratio of diamorphine to morphine is still a matter of dispute.

(3) No basic studies appear to have been carried out on the fate of orally administered diamorphine.

(4) Current methods of assay are not sensitive enough to detect diamorphine or its metabolites in serum after the administration of the drug when given in therapeutic amounts.

(5) The undersirable side-effects of diamorphine may vary according to posture and mobility.

(6) As the metabolic handling of the drug may be different in the two sexes, provision for a between-sex comparison should be included in the design of a clinical trial of diamorphine.

Morphine: radioimmunoassay

The development of a radioimmunoassay for morphine is described. The hapten morphine is made antigenic by coupling it to a protein at the phenolic group of the molecule. Extremely low concentrations of morphine (0.5 nanogram) can be measured by this assay procedure.