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Biomedical subjects

A C Moffat

Publications and source records attributed to A C Moffat.

At least 91 records · Page 5Linked to original sources
PubMed1978

Combined high-pressure liquid chromatography and radioimmunoassay method for the quantitation of delta 9-tetrahydrocannabinol and some of its metabolites in human plasma.

A high-pressure liquid chromatography-radioimmunoassay (HPLC-RIA) method for the measurement of cannabinoid levels in plasma is described. The method is capable of quantifying 0.1 ng of a cannabinoid in 1 ml of plasma. The experimental procedure consists of an initial separation of cannabinoids in a plasma extract by HPLC followed by collection of the HPLC eluate and RIA. A chromatogram consisting of the cross-reacting cannabinoids in plasma may then be constructed. The plasma concentrations of cannabinoids with retention volumes equivalent to those of delta 9-tetrahydrocannabinol, cannabinol and mono-hydroxylated metabolites have been measured by this technique.

Chromatography, Gas↗
PubMed1978

Analysis of LSD in human body fluids by high-performance liquid chromatography, fluorescence spectroscopy and radioimmunoassay.

A scheme of analysis is described in which the particular advantages of high-performance liquid chromatography (HPLC), fluorescence spectroscopy and radioimmunoassay (RIA) are exploited to the greatest effect. RIA affords a rapid and sensitive preliminary screening method, while the subsequent HPLC analysis using fluorimetric detection yields quantitative chromatographic evidence together with characteristic fluorescence spectra. Fractionation of samples by HPLC followed by RIA of the fractions gives further confirmation of the presence of LSD and its metabolites. The combined methodology has been applied to the analysis of LSD in body fluids for forensic and clinical purposes. Levels down to 0.5 ng of LSD per ml can be detected using the minimum of sample.

Chromatography, High Pressure Liquid↗
PubMed1978

Photochemical detection in high-performance liquid chromatography and its application to cannabinoid analysis.

A novel technique of on-line photochemical derivatization is described which can enhance considerably both the sensitivity and specificity of detection in high-performance liquid chromatography (HPLC).. Material eluting from the column is irradiated with a high flux of UV light, which may induce a reaction to form fluorescent or highly UV-absorbing products. The irradiated eluent then passes into a suitable detector. The photochemical reactor as a neglible effect on resolution, and reaction is achieved in 1-5 sec. An example of the use of this technique is in the detection of cannabinol CBN), a component of cannabis, which is converted into a highly fluorescent compound on irradiation with UV light. Thus, if a sample containing CBN is chromatographed and the column eluent irradiated, CBN can be detected (as the fluorescent photoproduct) with a sensitivity of less than 1 ng. If the chromatogram is then repeated without UV irradiation, only naturally fluorescent products are detected. A compairson of the two chromatograms allows these to be eliminated and leads to a very high specificity for the method. This approach is being developed as the basis of a rapid, sensitive and specific method for the detection of cannabinoids in body fluids. It is expected, however, that photochemical derivatization will extend the use of HPLC to many substances that cannot be satisfactorily detected at present.

Cannabinoids↗
PubMed1977

Radioimmunoassay of lysergic acid diethylamide (LSD) in serum and urine by using antisera of different specificities.

We raised high-titre antisera to two LSD-bovine serum albumin conjugates, one linked via the indole nitrogen, the other via the amide side-chain. The antisera were specific for different parts of the LSD molecule, as demonstrated by cross-reactivity studies with LSD, its metabolites, ergot alkoloids, and closely related compounds. The antisera were used to develop a double-antibody radioimmunoassay with a detection limit of about 0.4 mug of LSD per liter of unextracted urine or serum. We saw no nonspecific interference by urine, serum, or from a series of commonly used drugs. There was good correlation between immunoassay values obtained with the two antisera (r = 0.91). However, the antiserum linked via the indole nitrogen gave consistently higher results for samples from persons who had taken LSD, owing to greater cross-reactivity with LSD metabolites. Radioimmunoassay by use of two such antisera is a more specific screening procedure for LSD abuse than has been available previously. In addition, antisera cross-reacting with LSD metabolites allow measurement of these compounds, for which there is no satisfactory method at the concentrations found in biological fluids in man.

Antibody Specificity↗
PubMed1976

High-pressure liquid chromatography of drugs. II. An evaluation of a microparticulate cation-exchange column.

A microparticulate cation-exchange column has been evaluated for the chromatography of thirty compounds selected as representative of a wide variety of drug substances. Although the column exhibited a strong partition effect besides the expected ion-exchange mechanism, the retention of drugs could be predictably influenced by variation of the eluent ionic strength and organic solvent content. For acidic drugs the column showed little selectivity (although a salting-out effect increased retention at high eluent ionic strengths), but for basic substances Partisil SCX may afford a useful separative medium offering reasonable chromatographic efficiency (HETP is approximately 0.1 mm). The column longevity, however, is at present questionable.

Cation Exchange Resins↗
PubMed1975

High-pressure liquid chromatography of drugs. An evaluation of an octadecylsilane stationary phase.

The performance of a commonly used high-pressure liquid chromatographic stationary phase, octadecylsilane, has been evaluated for 30 compounds selected as representative of a wide variety of drug substances. Chromatographic behavior is found to be highly predictable on the basis of pKa and partition coefficient, and the stationary phase should be especially valuable for the separation of acidic and neutral drugs. For basic drugs, however, the column efficiency is poor, detracting from the overall usefulness.

Amines↗
PubMed1975

The standardisation of thin-layer chromatographic systems for the identification of basic drugs.

Three thin-layer chromatographic systems have been selected on the basis of their discriminating power on which to standardise for the identification of basic drugs. They are systems of silica gel sprayed with 0.1 N NaOH, dried and run using one of the following solvents: cyclohexane-toluene-diethylamine (75:15:10), chloroform-methanol (90:10) or acetone. They can be used in combination since their correlation coefficients are low. Four reference compounds should be used, equally spaced across the plate. The inter-laboratory variation of measurement of RF values has been ascertained and the use of a graphical RF correction method reduced the mean deviation of measurement to 0.02. The measurement of RF values was found to be less reproducible in the middle of the chromatogram than in regions of very low or very high RF values.

Amitriptyline↗
PubMed1975

Use of SE-30 as a stationary phase for the gas-liquid chromatography of drugs.

The dimethyl silicone elastomer SE-30 has been chosen as the preferred liquid phase for the gas-liquid chromatographic analysis of drugs, and retention index data have been compiled for 480 drugs and commonly occurring chemicals such as plasticisers. The inter-laboratory variation in measurement of retention indices has been measured for three drugs in eleven laboratories and the standard deviations were between 20 and 15 retention index units.

Absorption↗