Improving the Sensitivity of Detection of 3-chloropropane-1,2-diol (3-MCPD) using Gas Chromatography with Negative Chemical Ionisation Mass Spectrometry detection

Introduction

3-Chloropropane-1,2-diol (alpha-chlorohydrin; 3- monochloropropanediol; 3-MCPD) is a toxic contaminant that has been found in soy sauce and other food products that use acid-hydrolysed vegetable protein (acid-HVP) [Collier, 1992; SCF, 1995]. Acid-HVP is a widely used ingredient in savoury foods, produced from the hydrolysis of plant protein-containing raw materials, such as wheat, soybeans or peanuts, at high temperature in the presence of hydrochloric acid. During the manufacturing of acid-HVP, residual lipid components in the protein source can also undergo hydrolysis to form 3-MCPD [Velisek, 1980, Collier, 1991]. Some toxicological studies have shown that 3- MCPD has carcinogenic effects in animals [Lynch, 1998]. Although there is no direct evidence for toxic effects of 3-MCPD in humans, its occurrence in human diet should be minimised, and monitoring of 3-MCPD in food products is required. In fact, in March 2001, the European Commission adopted a regulatory limit of 0.02 mg/kg (based on 40% dry matter content) for 3-MCPD in soy sauce and acid- HVP, which is to be implemented in April 2002. Gas chromatography is usually the analytical method of choice for the quantitative determination of 3-MCPD. Brereton et al. recently published a validated method capable of measuring 3-MCPD ≥0.01 mg/kg, based on gas chromatography with mass spectrometric detection [Brereton et al., 2001]. This method is based on extraction of 3-MCPD followed by its derivatisation using N-heptafluorobutyrylimidazole (HFBI) to give compound. Negative chemical ionisation mass spectrometry (NCI-MS) provides a specific and sensitive detection for electronegative compounds. The technique is based on the formation and detection of negative ions. The presence of CFn moieties in the 3-MCPD derivative renders the molecule capable of forming negative ions in the mass spectrometer. The data presented here demonstrates that NCI-MS is suitable for the detection of 3-MCPD as its derivative. In Scan mode, NCI-MS provides qualitative information of 3-MCPD, and a comparable sensitivity to EI-MS in Selected Ion Monitoring (SIM) mode. In SIM mode, NCI-MS provides a lower detection limit than EI-MS.

October 29, 2004 GMT