Absolute quantification for benzoic acid in processed foods using quantitative proton nuclear magnetic resonance spectroscopy

The absolute quantification method of benzoic acid (BA) in processed foods using solvent extraction and quantitative proton nuclear magnetic resonance spectroscopy was developed and validated. BA levels were determined using proton signals (δH 7.53 and 7.98) referenced to 2-dimethyl-2-silapentane-5-sulfonate-d6 sodium salt (DSS-d6) after simple solvent extraction from processed foods. All recoveries from several kinds of processed foods, spiked at their specified maximum Japanese usage levels (0.6–2.5 g kg−1) and at 0.13 g kg−1 and 0.063 g kg−1, were greater than 80%. The limit of quantification was confirmed as 0.063 g kg−1 in processed foods, which was sufficiently low for the purposes of monitoring BA. The accuracy of the proposed method is equivalent to the conventional method using steam-distillation extraction and high-performance liquid chromatography. The proposed method was both rapid and simple. Moreover, it provided International System of Units traceability without the need for authentic analyte standards. Therefore, the proposed method is a useful and practical tool for determining BA levels in processed foods.