title: Cyclic oligomers in polyamide for food contact material: quantification by HPLC-CLND and single-substance calibration.
abstract: Cyclic oligomers are the major substances migrating from polyamide (PA) food contact materials. However, no commercial standards are available for the quantification of these substances. For the first time the quantification of cyclic oligomers was carried out by HPLC coupled with a chemiluminescence nitrogen detector (CLND) and single-substance calibration. Cyclic monomer (MW = 226 Da) and dimer (MW = 452 Da) of PA66 were synthesised and equimolar N detection of CLND to synthesised oligomers, caprolactam, 6-aminohexanoic acid (monomers of PA6) and caffeine (a typical nitrogen calibrant) was proven. Relative response factors (UVD at 210 nm) referring to caprolactam were determined for cyclic PA6 oligomers from dimer to nonamer, using HPLC-CLND in combination with a UVD. A method for quantification of cyclic oligomer content in PA materials was introduced using HPLC-CLND analysis and caffeine as a single nitrogen calibrant. The method was applied to the quantification of cyclic PA oligomers in several PA granulates. For two PA6 granulates from different manufacturers markedly different oligomer contents were analysed (19.5 versus 13.4 g kg⁻¹). The elution pattern of cyclic oligomers offers the possibility of identifying the PA type and differentiating between PA copolymers and blends.
authors.affiliation: Department of Chemistry and Food Chemistry, TU Dresden, Bergstrasse 66, D-01069 Dresden, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Heimrich
authors.forename: M
authors.initials: M
authors.lastname: Bönsch
authors.forename: H
authors.initials: H
authors.lastname: Nickl
authors.forename: T J
authors.initials: TJ
authors.lastname: Simat
mesh_terms: D015119:Aminocaproic Acid / Q000032:analysis / Q000737:chemistry; D002138:Calibration; D002209:Caprolactam / Q000031:analogs & derivatives / Q000032:analysis / Q000138:chemical synthesis / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D003297:Cooking and Eating Utensils / Q000592:standards; D005062:European Union; D018857:Food Packaging / Q000592:standards; D007202:Indicators and Reagents / Q000032:analysis* / Q000737:chemistry; D008163:Luminescent Measurements; D008970:Molecular Weight; D009757:Nylons / Q000138:chemical synthesis / Q000737:chemistry*; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D007202:Indicators and Reagents; D009757:Nylons; D011108:Polymers; C009916:nylon 6; D002209:Caprolactam; D015119:Aminocaproic Acid