/. P. Colombo

Summary: A simple photometric procedure was developed for the determination of thiocyanate (SCN~) in plasma and saliva without deproteinisation or dialysis. Fe(III) ions form a red coloured complex with SCN~ with a inaximum absorbance at 460 nm. Mercury(II) nitrate is used to run a sample blank. A manual and an automated Version (COBAS ΒΙΟ) of the method is described. The method is linear up to 5000 μηιοΐ/ΐ SCN~. The CV of the between^run precision is 2.8 — 8 % for the manual and 2.6 — 6.6 % for the automated method. The SCN ~ plasma concentration was 21 — 134 μιηοΐ/l in nonsmokers and 44—260 μιηοΐ/ΐ in smokers. In mixed saliva, the concentration is much higher than in plasma: 1.57—5.5 mmol/1 in smokers and 0.79 — 3.9 mmol/1 in nonsmokers. Plasma * but not oral fluid SCN~, is a valuable parameter for studying smoking habits in population surveys. Mowever, its use is limited. In our experience only heavy smokers can be distinguished from nonsmokers. Introduction Materials and Methode The plasma thiocyanate (SCN~) concentration is one Apparatus of several indicators for testing exposure to tobaceo Centrifugal analyser COBAS ΒΙΟ (F. Hoffmann-La R che, smoke. It has been widely used in he lth screening CH-4002 Basel, Switzerland), spectrophotometer UVIKON 810 programmes for the evaluation of smoking behaviour (Kontron ^stniments, CH-8010 Z rich, Switzerland)