Cases with atypical esterase activity were found by determining esterase inhibition in numerous sera. A suitable inhibitor was the local anaesthetic dibucaine (cinchocaine, TN Nupercaine, Perkain). A good discrimination between typical and atypical sera was obtained under the following conditions: The esterase activity of human serum diluted 1:100 was measured with a recording spectrophotometer at 240 mμ. The substrate was 5 × 10−5 M benzoylcholine dissolved in M/15 phosphate buffer, pH 7.4. The concentration of the inhibitor was 10−5 M. With the experimental temperature around 25 °C, the average inhibition of the typical enzyme was 78.8 ± 0.3%. The inhibition of the atypical esterases was less; in rare cases the inhibition was only 16%. For each person, the inhibition characteristics were constant over a period of several months, and independent of the esterase level. The degree of inhibition measured under these conditions and expressed in per cent has been termed "Dibucaine Number".

Cases with atypical esterase activity were found by determining esterase inhibition in numerous sera. A suitable inhibitor was the local anaesthetic dibucaine (cinchocaine, T N Nupercainc, Perkain). A good discrimination between typical and atypical sera was obtained under the following conditions: 'I'he esterase activity of human serum diluted 1:100 was measured with a recording spectrophotometer a t 240 mp. l'he substrate was 5 X M benzoylcholine dissolved in M / 1 5 phosphate buffer, pH 7 . 4 . The concentration of the inhibitor was M . With tlie experimeiltal temperature around 25" C., the alTerage inhibition of the typical enzyme was 78.8 + 0.3%. The inhibition of the atypical esterases was less; in rare cases the inhibition was only 16'56. For each person, the inhibition characteristics were constant over a period of se\.eral months, and independent of the esterase level. l'he degree of inhibition mrasured under these conditions and expressed in per cent has been termed "Dibucaine Number". 'ManuscriptCan. J. Biochem. Physiol. Downloaded from www.nrcresearchpress.com by San Francisco (UCSF) on 12/09/14For personal use only.

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Methods are described by which lysergic acid diethylamide (LSD) can be identified and determined in the presence of heroin, other narcotics and controlled drugs. Thin layer chromatography and an Ehrlich's‐reagent spray is applied to the LSD‐containing material. For confirmation, thin layer chromatography after ultra‐violet irradiation and acid hydrolysis should be carried out where ergot alkaloids are present. Spectrophotofluorometric analysis of LSD can be used in the presence of heroin, other narcotics and controlled drugs with a standard error of ±2%. If ergot alkaloids are present, thin layer separation, elution and subsequent fluorometric analysis are recommended.