An accurate analytical method for the determination of benzoic acid in curry paste using isotope dilution gas chromatography-mass spectrometry (GC-MS)

Abstract

A simple analytical procedure for the accurate determination of benzoic acid in curry paste using isotope dilution gas chromatography-mass spectrometry (GC-MS) has been developed. In brief, the analyte was extracted from the sample by steam distillation followed by liquid–liquid extraction using dichloromethane, and derivatisation before being analysed by GC-MS in selected ion monitoring (SIM) mode. Repeatability studies showed that the ID-GC-MS method was reliable and reproducible with a method precision of less than 0.6% RSD. Recoveries of fortified samples were within the range of 98.5–100.4%. The performance of the described method has also been evaluated through participation in the inter-laboratory comparison organised by the Asia Pacific Metrology Programme (APMP.QM-P14). The reported result (389 mg kg⁻¹) was in good agreement with the reference value (386 ± 8 mg kg⁻¹). The relative measurement uncertainty of the method with a coverage factor of 2 (at approximately 95% level of confidence) is estimated to be 1.8%. This method may serve as an alternative method for confirmation or litigation purpose where high accuracy and high precision results are required.