รายละเอียดเอกสาร

Vegetable oils dissolved in methyl isobutyl ketone (MIBK) are analyzed for metals by direct aspiration. Calibration is based on MIBK solutions of organometallic reference compounds solubilized in purified vegetable oil. This method is intended for the analysis of crude or partially refined vegetable oils that contain at least 2.0 ppm of each measured metal in the form of oil-soluble derivatives. Hardened oils and animal fats have limited solubilities in MIBK and, even at reduced solute concentrations, they readily foul the burner. For these reasons this method is not recommended for such samples. AOCS Method Ca 18-79 has a lower detection limit (0.1 mg/kg, or 0.1 ppm, for an individual metal) as opposed to 2 mg/kg, or 2 ppm, for AOCS Method Ca 15-75. Therefore, when lower detection limits are required, as in the case of contractual trade methods, AOCS Method Ca 18-79 should be used.