Determination of mineral oil hydrocarbon in rice bran oil using liquid chromatography with gas chromatography flame ionization detector

Abstract

Rice bran oil is an edible oil which is used in food preparation. In Thailand, Standard conditions and methods in detecting mineral oil hydrocarbons (MOH) were not Regulated. Therefore all rice bran oil quality and safety control was done abroad. This research proposed determination conditions in detecting mineral oil hydrocarbon using an off-line liquid chromatography with gas chromatography flame ionization detector. This method was adapted from ISO 17780 : animal and vegetable fats and Oils determination of aliphatic hydrocarbons in vegetable oil. Silver nitrate impregnated With silica gel was used to purify and separate mineral oil saturated hydrocarbon (MOSH). GC-FID using pulse splitless injection system combining with pulse time at 0.5 minute, Inlet temperature at 250 °C, and inlet pressure at 30 psi were considered to be the best Conditions due to the largest area under the graph. The hump in the chromatogram Represents the mass fraction of MOSH. This fraction is only presented in an eluent fraction Of 55 mL hexane. Three crude rice bran oil samples were analysed, RBACTG25A, RBACTF27A, and RBACTF22A. Different levels of MOSH were detected with the highest Being RBACTF27A (164.2 mg/kg) followed by RBACTG25A (90.5 mg/kg) and RBACTF22A(34.1 mg/kg). The comparison between the result obtained and reference data showed a slight difference due to the differences in sampling and injection method used. However, it gives out the same trend as the reference data. The amount of C25-C35 MOSH which is the targe hydrocarbon is approximately 90% which is considered to be high and can not be refined to edible oil.