Meaning
Chemical reactions between lipids and alcohols during sample preparation create new compounds that mask the presence of target analytes. Transesterification interference occurs when fats in a food sample react with the methanol or ethanol used in the extraction process. These reaction products can elute at the same time as mineral oil saturated hydrocarbons, leading to inaccurate results.
Chemical Reaction
Conversion of triglycerides into fatty acid methyl esters produces a series of peaks that clutter the chromatographic trace. This transesterification interference is particularly problematic when analyzing fatty foods or plastic packaging that contains natural oils. The resulting peaks can be mistaken for mineral oil contaminants if the analyst is not aware of the reaction.
Analytical Error
Overestimation of the hydrocarbon content occurs when the interference is integrated as part of the sample. Because the reaction products have similar physical properties to some mineral oils, they are difficult to remove using standard clean-up methods. Using non-alcoholic solvents or specific chemical inhibitors can reduce the formation of these interfering species.
Sample Preparation
Careful selection of the extraction reagents is necessary to avoid the unwanted transformation of the sample. When transesterification interference is suspected, the use of a different simulant or a modified clean-up procedure may be required. Accurate quantitation depends on distinguishing between the original migrants and the byproducts of the laboratory process.
