Soya bean and linseed oils were analysed by successive application of silver-ion and reversed-phase thin-layer chromatography and densitometry. Direct quantitative determination of all the 20 possible triacylglycerol (TAG) classes including critical pairs (SD, + S,T; M,T + D, ; SDT + MDT; ST, + MT,) was performed. TAG molecular species down to 0.1% (32 in soya bean oil and 26 in linseed oil) were identified and quantified. The detection limit was 0.2 pg and the standard deviation between 0.1% and 1.0% for silver ion thinlayer chromatography (TLC) and between 0.1 % and 3.9% for reversed-phase TLC determinations. The accuracy of the analysis was confirmed by the good agreement between the quantitative results for the fatty acid composition as determined by gas chromatography and as calculated from the densitometric data for the TAG composition.

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A total of 82 dietary fats sold on the Bulgarian market in the period 1995-2000 were analyzed. The samples included 68 table margarines (50 of which were imported), 10 frying fats (6 imported) and 4 salad dressings (all imported). A validated analytical method, thin-layer chromatography-AgNO 3 -densitometry, was used. It enabled direct determination of all fatty acid groups, differing by degree of unsaturation and double bonds geometry. Low levels of trans fatty acids (TFA) down to 0.1% of the total for mono trans-trienoic (Tcct) and mono trans-dienoic (Dct), and down to 0.2% for transmonoenoic (Mt) were quantitated, with an error under 3% and a standard deviation of 0.1-1.5. The total content of TFA in table margarines varied from 0 to 26.9% with a mean value of 8.6 ± 7.2% for imported and 1.6 ± 3.4% for Bulgarian samples. Saturated fatty acids (SFA) content varied from 11.5 to 45.7%, with a mean value of 25.4 ± 5.7% for imported and 26.9 ± 5.2% for Bulgarian margarines. A general trend of lower levels of TFA and SFA in imported margarines was observed over the studied period. Additionally, the content of individual saturated fatty acids was determined by gasliquid chromatography in 37 of all studied samples.

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