A rapid gas‐liquid chromatographic method for the estimation of nicotine in plasma is described. Nicotine is extracted from alkalinized plasma into diethyl ether. This is then concentrated by evaporation and, after an acid back extraction is re‐extracted into n‐heptane (nitrogen detector) or dichloromethane (flame ionization detector) before injection onto the gas chromatograph. Thirty samples a day can be analysed by this method which enables concentrations of 0.1 ng ml−1 nicotine to be measured. It is thus possible to measure nicotine in plasma and urine samples from non‐smokers.
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.
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