Specific spectrophotometric method with trifluoroacetic acid for the determination of selenium(IV) in selenitetriglycerides.

The role of selenium as an antioxidant and anticancer agent is very well documented in the literature. Selenium compound showing the highest activity as a free radicals scavenger and as an anticancer agent should contain selenium at +4 oxidation level. The synthesis of selenitetriglycerides (named selol) was carried out in the Department of Drug Analysis at Warsaw Medical University (Polish Patent 1999). Selenitetriglycerides showed a dimeric structure. In a single dose toxicity studies performed in rats, LD50 was 100 mg Se kg(-1) after oral administration of selol. The subcutaneous and intraperitoneal administration of selol showed extremely low toxicity. The aim of this work was to develop a new specific method for the determination of Se(IV) in selol. We stated that selenitetriglycerides react quantitatively with trifluoroacetic acid (TFA) in dichloromethane giving a red-coloured conjugate. However, recorded spectrum showed the maximum absorption in the wavelength 380 nm. The optimal conditions of the reaction were established, namely temperature 35 degrees C and reaction time 35 min. The reaction was proved to be specific because neither selenites nor other selol constituents react with TFA. The constructed calibration curve obeyed the Lambert-Beer law in the range of 0.1-7.4 mg ml(-1). Molar absorption coefficient is epsilon =9.46 x 10(3) l mol(-1) cm(-1) and epsilon =2.36 x 10(5) l mol(-1) cm(-1) calculated for selenium and selenitetriglyceride dimer (m.w. 1972.72), respectively. Obtained results for selenium determination were confirmed by AAS method. The developed method showed specificity and high sensitivity.