Multi-analyte methods for the detection of photoinitiators and amine synergists in food contact materials and foodstuffs – Part I: HPLC-DAD screening of materials

Abstract

The objective of this work was to develop a HPLC-DAD method suitable for the screening of food contact materials for a total of 63 monomeric and polymeric photoinitiators and amine synergists. Such multi-analyte methods are worthwhile for official control laboratories, where normally no information about the composition of the applied inks or varnishes on the printed or lacquered materials is available and thus target analyses are not feasible. The polymeric analytes were each separated in a multitude of substance peaks, which largely overlaid those of the other compounds. Thus, for 13 polymeric photoinitiators and amine synergists a hydrolysis method was developed that reduced the number of ultraviolet (UV) detectable peaks to only one. This allowed easier identification and – preliminary – semi-quantification of these polymeric substances with adequate limits of detection. The remaining 50 photoinitiators and amine synergists were combined in one HPLC-DAD method. But since many of these substances are structurally related, partly retention times and spectra did not differ significantly. Thus selectivity was enhanced by preparing a database containing all spectra and retention times of the investigated compounds. Furthermore, the retention times of those 50 substances were calculated relative to two internal standards to overcome variances of retention from run to run or due to matrix effects. The developed method was tested for the analysis of food contact materials. Extractions of these were performed with acetonitrile and partially the extracts were subsequently concentrated in a steam of nitrogen. Limits of detection of photoinitiators and amine synergists in concentrated packaging extracts were in the range between 0.02 and 5.5 µg dm⁻².

Keywords:

• UV printing inks and varnishes
• food contact materials
• photoinitiators
• amine synergists
• HPLC-DAD screening
• polymeric photoinitiators
• polymeric amine synergists

Acknowledgements

The authors would like to thank Mrs Maria Roth and Mr Werner Altkofer for the opportunity to perform this work at the CVUA Stuttgart, and the teams from the commodities and the measuring laboratory at the CVUA Stuttgart for skilful technical assistance and for valuable discussions.