LSD converts to its epimer iso-LSD at temperatures above 37 °C and pH levels over 7.0. At pH 7.0 or higher, a 9:1 ratio of LSD to iso-LSD is reached after one week at 45 °C or two weeks at 37 °C. Starting from iso-LSD, achieving the same 9:1 ratio requires six weeks at 45 °C and pH 9.7, indicating more vigorous conditions are needed. This ratio represents an equilibrium concentration with an equilibrium constant K = 9. The study used proton NMR to follow the reaction by integrating the C-9 resonances of LSD and iso-LSD, appearing as singlets at 6.35 and 6.27 ppm respectively. This is the first quantitative measurement of LSD epimerization by NMR.
A new homogenous microparticle-based immunoassay (Abuscreen OnLine) detects LSD in human urine at a cutoff of 0.5 ng/mL, matching the sensitivity of the existing Abuscreen RIA. All 31 samples previously confirmed positive by gas chromatography-mass spectrometry also tested positive with both the OnLine and RIA assays. Among 1,000 presumed negative samples, 992 (99.2%) were negative; the 8 OnLine positives were negative by RIA. The assay shows greater than 35% cross-reactivity to nor-LSD and similar cross-reactivity to other related compounds as the RIA. Within-run precision was less than 2.5% and between-run precision less than 3.0%.