Antioxidant analysis in edible oils and fats by normal-phase high-performance liquid chromatography.

Following a simple dilution in the appropriate phase, the sample is injected directly onto either of two normal-phase high-performance liquid chromatography systems (3,5-di-tert.-butyl-4-hydroxytoluene or 3-tert.-butyl-4-hydroxyanisole-tert.-butylhydroquinone) with UV detection at 280 nm. An isocratic ternary mobile phase, incorporating acetonitrile as the polar modifier, has been found to facilitate such an approach, thereby avoiding the discriminatory and recovery problems inherent in other techniques requiring prior sample manipulations. The three most commonly used antioxidants may be estimated at levels down to 3 ppm (3,5-di-tert.-butyl-4-hydroxytoluene or 3-tert.-butyl-4-hydroxyanisole) and 10 ppm (tert.-butylhydroquinone) within 30 min.