The method is suitable for vitamin B1 (thiamine hydrochloride) determination in quality assurance, stability tests, etc. The methanolic solution of the drug is chromatographed on silica with methanol – NH3 -acetic acid – chloroform 18:2:1:1, then derivatized with potassium hexacyanoferrate. After stabilising the fluorescence intensity with paraffin oil the plate is evaluated by densitometry. The determination limit is 500 pg/spot.