A.C. Moffat

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.

Identification in human urine of Δ9‐tetrahydrocannabinol‐11‐oic acid glucuronide: a tetrahydrocannabinol metabolite

A Δ9 ‐THC metabolite has been identified in human urine as an ester linked glucuronide of Δ9 ‐THC‐11‐oic acid. Its identity was established by a comparison of mass spectra from the metabolite extracted from human urine and synthetically prepared material. Δ9 ‐THC‐11‐oic acid glucuronide was found to be responsible for the major part of RIA crossreactivity in urine with the Guildhay cannabinoid antiserum used in this study.

High-performance liquid chromatography of paraquat and diquat in urine with rapid sample preparation involving ion-pair extraction on disposable cartridges of octadecyl-silica

Abstract A high-performance liquid chromatographic system is presented which separates the paraquat, diquat and 1,1′-diethyl-4,4′-bipyridyldiylium (internal standard) dications in under 7 min. An octadecyl-silica (ODS-silica) column is used with an eluent of 25 % methanol (v/v) containing sodium heptanesulphonate (0.01 M) and a diethylamine-orthophosphoric acid buffer. The method is suitable for the analysis of paraquat and diquat in commercial weedkillers and human urine samples following poisoning. A rapid procedure for the extraction of the herbicides from urine has been developed using disposable cartridges of ODS-silica pre-treated with sodium heptanesulphonate. The quaternary compounds are extracted as ion-pairs with the hydrophobic sulphonate anions.

Comparison of amine modifiers used to reduce peak tailing of 2-phenylethylamine drugs in reversed-phase high-performance liquid chromatography

Abstract Chromatographic retention and peak shapes for a group of five 2-phenylethylamine drugs in reversed-phase high-performance liquid chromatography have been examined with a series of eluents containing various amines as part of the buffer system. An ODS-silica column was used with aqueous methanolic eluents containing orthophosphoric acid and sodium hydroxide to which the appropriatre amines were added. Eleven eluents containing different amines have been examined along with two control eluents containing only inorganic buffer components. Large improvements in peak shape are demonstrated by the addition of some amines. The importance of selecting amines of suitable hydrophobic character and molecular geometry is discussed.

Gas-liquid chromatographic retention indices of 1318 substannces of toxicalogical interest on SE-30 or OV-a stationary phase

Retention indices associated with 1318 substances likely to be encountered in toxicological analyses are presented. They are listed in ascending order of retention index for identification purposes and also in alphabetical order of compound name. The 4586 values used in this collection have been extracted from 36 sources, many of which have not been previously published. In many cases, where the quoted retention index is the mean of several determinations, the reproducibility and reliability of this value may be assessed. A histogram of the 1742 values listed is provided to help in determining the usefulness of a retention index for identification purposes. The reproducibility of inter-laboratory retention index measurements for twenty compounds on both SE-30 and OV-17 are presented and show the former, on average, to give more reproducible results.

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.

Otimum use of paper, thin-layer and gas-liquid chromatography for the identification of basic drugs. I. Determination of effectiveness for a series of chromatographic systems.

Abstract A method is described for the determination of effectiveness for a series of chromatographic systems which uses the concept of discriminating power. The discriminating power for a series of chromatographic systems is defined as the probability that two drugs selected at random from a large population would be discriminated in at least one of the systems. The series of systems with the highest discriminating power is shown to produce the best overall separations for a large specified drug population and therefore leads to the identification of an unknown drug using a minimum number of systems. The conditions for maximum discriminating power are described and discussed.

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.

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.

Optimum use of paper, thin-layer and gas-liquid chromatography for the identification of basic drugs : II. Paper and thin-layer chromatography

Abstract The concept of discriminating power has been applied to the paper and thin-layer chromatography of 100 basic drugs in eight systems which are representative of the systems in current use. The design of the most effective series of chromatographic systems for the separation and identification of a large drug population is discussed in terms of the individual discriminating powers of the systems and inter-system correlation. It is shown that both the substrate and solvent may have to be changed to obtain significantly different systems.