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LC-MS method development for the screening of non-volatile and polar compounds present in paper and board and plastic food contact materials.
Project Code: A03037
Central Science Laboratory
Castle, L ; Read, W;
Food and Environment Research Agency, Sand Hutton, York YO41 1LZ
This work has tested the capabilities of LC-MS (liquid chromatography coupled to mass spectrometry) to analyse for a large number of chemicals used to make materials intended for food contact. The materials included plastics, paper, inks and coatings. The substances included monomers and other starting materials, plastics additives and processing aids. The substances to be tested were selected by agreement with the Food Standards Agency and they were then procured along with a selection of materials and articles of a type that may be expected to contain the substance(s).
Any existing LC methods available from the literature and considered to be likely candidates for extension onto LC with an MS detector, were evaluated, modified and then transferred onto an LC-MS. Using flow injection analysis (i.e. with no chromatography) solutions of each substance were examined using a variety of ionisation modes and conditions, to identify the major ions that could be used for monitoring purposes. This used the two most common ionisation modes in LC-MS, namely atmospheric pressure chemical ionisation (APcI-MS) and electrospray ionisation (ESI-MS). Each was explored in both positive-ion and negative ion modes with different instrument settings.
Having selected the best analytical conditions, performance characteristics of limit of detection, limit of quantitation and the repeatability were established. The performance of LC-MS for the various substances is summarised under ‘Key findings’. Packaging materials were then subjected either to migration testing using food simulants or extraction testing using solvents. The total migrate (overall migration) or the total extractables were determined gravimetrically and then this residue was redissolved and analysed by LC-MS for the substances of interest.
For all the different types of packaging material, the targeted substances were detectable at only low levels relative to the total migrate/extractate and so there was a large fraction of chemicals that was not identified. Size exclusion chromatography was used on paper samples to isolate the fraction below molecular weight 1,000 Daltons, thought to be the toxicologically-relevant fraction. This proved limited in scope and needs further development using alternative solvent systems.
It is concluded that for targeted substances, LC-MS can be used successfully to test for migration from packaging materials. It has good sensitivity and has the selectivity needed to ensure that the correct substance is monitored and confirmed. A suite of analytical methods and spectra has been established that deals directly with many important food packaging materials and substances. The methods and the understanding obtained and reported, should also help LC-MS users to develop new methods for food packaging migrants in the future.
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