Development of systems for determination of nutrients in Thai foods by high performance thin layer chromatography

Abstract

Thin layer chromatography (TLC) was employed for detecting nutrients in Thai food and the results from TLC were evaluated by TLC densitometry technique. Three optimized systems for analyzing three groups of each nutrients i.e. essential oils, polar compounds and amino acids were developed. The optimized conditions for analyzing essential oils were as follows; the solvent for extraction was chloroform, the stationary phase was silica gel 60F TLC plate, the mobile phase system was toluene: ethyl acetate (85:15). The developed TLC plate was then subjected to derivatization by iodine and the efficiency for nutrient separation was visualized by photodocumentation under 254 nm light. The optimized conditions for polar compounds were as follows; the solvent for extraction was formic acid or distilled water, the stationary phase was silica gel 60F TLC plate, the mobile phase system was ethyl acetate: formic acid: acetic acid: water (100:11:11:26). The efficiency of nutrient separation was evaluated by visualization under 366 nm light. The optimized conditions for standard amino acids were as follows; the stationary phase was silica gel 60F TLC plate, the mobile phase system was n-butanol: acetic acid: water: methanol (4: 1: 1: 1). The developed TLC plate was subsequently derivatized by iodine and Ninhydrin solution. The efficiency of nutrient separation was evaluated by visualization under visible light. In addition, results from TLC densitometry indicated that there was a similarity in absorption spectrum among amino acids with the same polarity whereas their Rf values were different, suggesting that the developed system was specific for analyzing amino acids.