The Use Of Infrared And Raman Microscopy To Characterise The Absorption Of Offset Ink In Paper

Previous studies have detected traces of mineral oils in food packaged in paperboard packaging, with the migration of the ink oil used on the outside of the packaging identified as a potential source of this contamination. This study examined the use of both infrared (IR) microscopy and Raman microscopy to evaluate their use in the detection of mineral oil migration from an offset printing ink through a bespoke set of laboratory made paper hand sheet samples. The IR microscopy was found to be largely unsuitable for this type of investigation due to the low IR reflectance of the materials used in the paper and the ink. Raman microscopy was able to clearly distinguish between the different ink and paper components and therefore characterise the migration within the paper samples. The initial results showed that the use of calcium carbonate pigments as a filler reduced the migration of mineral oil through the paper. For the coated papers, the majority of the mineral oil was detected within same region as the coating. This was in agreement with other studies that have examined the absorption of ink oils into the pore network of calcium carbonate paper coatings.