Formulation and analysis of food-grade mineral hydrocarbons in toxicology studies

Methods are presented for the formulation and rapid determination of mineral hydrocarbons (MHCs) in animal diet and tissue. Food grade white oils and low melting point waxes are mixed as liquids with powdered diet. Higher melting point waxes are first powdered using a novel atomization technique before dry mixing with diet. MHCs sufficiently soluble in carbon tetrachloride (CCl4) are determined in diet by ultrasonic solvent extraction, adsorption of polar material on Florisil and analysis of the residue by quantitative Fourier Transform Infra Red (FT-IR) spectroscopy. Quantification in tissue is achieved by aqueous saponification, followed by extraction, clean-up and FT-IR analysis as for diet samples. A 10-fold increase in sensitivity over previous methods is achieved, below 0.002% (w/w) in diet and 0.1 mg/g in tissue. Over 80% of the CCl4 used can be recovered and recycled. Control diet seems to contain approximately 0.003% (w/w) background MHC. The method was modified for one powdered wax, only sparingly soluble in CCl4, high concentrations being extracted from diet by flotation in aqueous cetrimide and determined gravimetrically with a limit of detection of 0.1% (w/w) in diet. Application of these methods to 90-day feeding studies is described, and future developments due to the phasing out of CCl4 are discussed.