Monochromatic wavelength dispersive X-Ray fluorescence as a tool for monitoring the source of chlorine in the formation of monochloropropane-diol esters during vegetable oil refining

This study presents the applicability of monochromatic wavelength dispersive X-ray fluorescence spectrometry (MWD-XRF) to quantify low range of concentrations, from 0.2 to 10 mg/kg of total chlorine in vegetable oils and bleaching clays effluents. The combination of total chlorine analysis by MWD-XRF and monochloropropanediol fatty acid esters (MCPDE) analysis by LC-MS of vegetable oils at different steps of the refining process allows to identify clays and technical aids used for bleaching as entry points of chlorine, potentially resulting in MCPDE formation during heat treatment of vegetable oils. Efficient washing of clays and technical aids monitored by chlorine measurement in successive effluents by MWD-XRF demonstrates the impact of washing by keeping total 3- MCPD content at low level in bleached vegetable oil. Further investigation on pH of the bleaching clays effluents shows that acidity is a key parameter during the formation of MCPD.