Meaning
Analytical interference phenomenon occurs when co-eluting non-target substances in a sample reduce the ionisation efficiency of target analytes during mass spectrometry detection. In recycled polymer safety testing, matrix suppression effects diminish analytical signal responses when quantifying volatile organic compounds, chemical additives or migration contaminants in post-consumer resin extracts. The suppression distorts quantitative measurements by lowering the detector signal relative to pure standard solutions.
The effect applies specifically to instrument ionisation sources and does not alter the physical concentration of chemicals inside the solid polymer matrix.
Ionisation Interference
Liquid chromatography with electrospray ionisation suffers significant signal loss when matrix components enter the ion source simultaneously with target analytes. Non-volatile oligomers, plasticisers and slip agents change the droplet surface tension and evaporate slowly, preventing analyte ions from entering the gas phase. Gas chromatography-mass spectrometry encounters similar suppression when heavy polymer fragments foul the inlet liner or ion source.
Target peaks exhibit diminished peak heights and reduced peak areas despite constant analyte mass.
Analytical Correction
Testing laboratories apply internal standardisation and standard addition techniques to compensate for instrument signal loss. Stable isotope-labelled internal standards experience identical suppression to target compounds, allowing accurate ratio-based quantification. Analysts optimise solid-phase extraction, gel permeation chromatography and solid-liquid extraction to remove bulk polymer oligomers before instrument injection.
Failure to clean extract solutions leads to underestimating hazardous legacy contaminants in recycled plastic streams.
Testing Compliance
Regulatory screening for food contact compliance demands rigorous matrix effect evaluations during method validation. Post-consumer polyolefins carry complex formulations of antioxidants, degradation by-products and processing aids that suppress detection of target contaminants. Recyclers verify that matrix suppression remains within acceptable analytical recovery limits across different raw feedstock sources.
Accurate quantification ensures recycled pellets meet legal migration limits for direct food-contact packaging applications.
