Meaning
The efficiency of an analytical extraction process is measured by the percentage of a target analyte that is successfully retrieved from a polymer matrix for quantification. This performance metric, called extraction recovery, indicates the accuracy of the testing method used to determine additive concentrations. It compares the quantity of additive recovered from the polymer to the known amount initially present or spiked.
Low recovery values suggest that the analyte is either strongly bound to the polymer or degraded during the extraction process.
Method Validation
Accurate quantification of plastic additives requires rigorous validation of the extraction procedure. If the extraction recovery falls below acceptable limits, the concentration of antioxidants or light stabilizers will be underestimated. Analysts use deuterated standards to trace loss pathways and calculate correction factors.
These standards are added to the polymer before processing, undergoing the identical thermal and mechanical forces.
Material Influence
Polymer density and crystallinity influence how tightly an additive is held within the polymer matrix. High-density polymers with closely packed crystalline regions show lower extraction recovery unless the extraction solvent is heated to swell the polymer. The temperature must be kept below the melting point of the resin to avoid generating a mass that traps the analyte.
A complete extraction requires a solvent that penetrates the amorphous zones without dissolving the polymer itself.
Process Optimization
Solvent extraction times and temperatures are adjusted to maximize recovery. Microwave-assisted extraction often accelerates the process. This reduces analysis time.
High recovery is achieved.
