Aluminium oxide (Alox) has long been recommended for use as an additional cleanup step to remove naturally occurring long-chain biogenic n-alkanes that interfere with the quantification of mineral oil saturated hydrocarbons (MOSH). However, the retention mechanism of Alox remains insufficiently understood, and the extent of MOSH loss across carbon-chain ranges during Alox treatment has not been systematically quantified. This study is the first to systematically quantify MOSH losses during Alox clean-up in a chain-length-resolved manner, based on the analysis of 150 vegetable oil samples representing 12 different oil types. The results demonstrate that MOSH below C20 is not measurably affected, while losses for C20-C25 remain below 5%, with progressively increasing losses observed at higher carbon numbers. These findings address the gaps described in earlier literature regarding Alox's uncertain retention behaviour as a pre-treatment method to quantify MOSH in vegetable oil samples. Quantitative MOSH profiling was further used to support a population-level dietary exposure assessment, indicating low MOSH exposure and high margin-of-exposure (MOE) values for the Chinese population. Collectively, this work provides critical analytical evidence supporting the appropriate application of Alox in MOSH determination and illustrates the relevance of the occurrence data generated in this study for screening-level exposure assessment of MOSH from vegetable oils.
Zhang et al. (Tue,) studied this question.