[Thin-layer densitometric determination of clotiazepam in tablets and blood plasma]

Quantitative determination of 7-ethyl-5-(2-chlorophenyl)-1-methyl-1,3-dihydro-2H-thieno[2,3-e]1, 4-diazepin-2-one (clotiazepam, Trecalmo) as pure substance and after extraction from tablets can be carried out by high performance thin-layer densitometry in absorbance at 243 nm. Detection limit was 10 ng/spot, and inaccuracy +/- 1.8% in the microgram range. For determination of clotiazepam in blood plasma, a more sensitive method was developed by fluorodensitometry above 460 nm after excitation at 313 nm. Analytical parameters are: detection limit 2.5 ng/ml, inaccuracy between 25 and 300 ng/ml +/- 5%, and imprecision at a concentration of 100 ng/ml +/- 5%. Plasma level determination up to 12 samples can be achieved in about 5 h. Thus, for determination of only a few samples, the HPTLC method is less time-consuming than the gas chromatographic assay.