Tracing migration

29 September 2010



It is a shared responsibility of the ink industry and the printer to reduce and avoid undesirable migration in label and packaging printing, says Andreas Rascher, Product Manager Printing Inks at Zeller+Gmelin.


Ink manufacturer Zeller+Gmelin, based in Eislingen, Germany, has looked at different methods of avoiding migration through the selection of inks and using the facilities of the company’s in-house analysis laboratory. But the ink industry is dependent on the help of the printers to solve the problem and emphasises the need to observe certain basic requirements during the printing process to eliminate migration.

After the adoption of the 1935/2004 Directive for packaging in contact with food, Zeller+Gmelin expanded in the analysis of printing ink systems, focusing on the development of low migration inks for raw material control and raw material selection as well as for the internal verification of test samples.

Packaging and raw materials are tested via gas chromatography with mass spectrometry (GC-MS), and fluid chromatography with mass spectrometry (LC-MS). The examination method of chromatography involves a mixture of substances being separated, allowing the contained substances to be detected individually. An analytical separating column works on the same principle. The substances to be separated each remain in the separating column for different periods of time.

By means of mass spectrometry (MS or MS/MS) the individual substances can be clearly defined by their mass. If two substances have the same mass, their fragmentation pattern is examined (the way a substance breaks down). In this way, substances can be clearly identified.

The findings of the analytical centre were incorporated by Zeller+Gmelin into the development and production of all their low migration UV ink systems used for the printing of primary food packaging and labels. Whether printed on paper or foil, these low migration inks meet the specification of printing labels and flexible packaging, for which low migration is required.

External and internal analyses demonstrate that with migration tests a value of 10ppb (parts per billion) with 95% of ethanol can be improved on with an appropriate application of the inks.

These low migration inks, which have been approved by food giant Nestlé, have been assessed by independent analysis institutes, supporting the claim that the inks offer maximum product safety to printers, packaging customers and consumers.

Special customer service

Zeller+Gmelin offers the resources in the analysis centre to customers. Printers and manufacturers of primary food packaging and labels for food packaging can have their print products examined and analysed to obtain findings on the migration potential of the inks and printing process before sending the packaging to an external analysis institute. This way the printer is able to discover early in the process whether packaging complies with the legal limit value of 10ppb, to save time and money.

Not every printed sample is suitable for an analysis: conditions must be adhered to. Required are the original substrates, the original substrates irradiated with UV; printed samples without varnish; printed samples with varnish; all at least 10cm2 minimum.

With the printing of moulded containers, eg, yoghurt pots, a stack of 20 pieces/cups minimum is required. For ananlysis of metal decoration, the metal sheets should be taken from a pile of five to 10 sheets.

Cleaning of all components

The first prerequisite for low migration printing is thorough cleaning of the printing press: ink duct, press cylinders, ink feeding hoses, printing blankets and printing plates. The hoses need to be replaced. Before starting a low migration printing job the press should be run with low migration systems for several hours to draw out the existing residual substances on the rubber rollers. For the same reason printing samples for migration analysis should always be taken out at the end of a printing job.

Importantly, the use of a low migration printing ink, or a low migration varnish, need not alone guarantee that the print will meet low migration limits. The migration result depends on the substrate; cleanliness of the machine; UV radiators; press cylinders and rubber blankets; ink formulation, colour strength and ink laydown; and the design of the packaging or label.

To exclude the risk of contamination due to non-low migration systems, ideally a printing press should be used with low migration systems only.

Part of the process of producing a conforming packaging is a close exchange of information between the individual links of the packaging chain. Zeller+Gmelin believes that the printing ink manufacturer cannot shoulder the responsibility alone. All participants in the supply chain need to actively assume part of that responsibility. According to Zeller+Gmelin this understanding is being accepted in the industry and this is a good thing as only by working together can the industry meet the given legal requirements.


Gas chromatography with mass spectrometry (GC-MS). Zeller & Gmelin

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