Approaches for Extracting and Determining Additives, Contaminants, and Low-Molecular-Weight By-Products in Synthetic Polymers

Jan 01, 2013

This month's installment surveys traditional and modern approaches for extracting and determining additives, contaminants, and low-molecular-weight components that may be present in synthetic polymers or polymeric materials. After sample workup, components are typically analyzed by chromatographic methods. This information is needed for product certification to comply with governmental safety and health regulations.

High-purity polymers are typically required for special applications such as implants or prosthetics, pharmaceuticals, electronic devices, and polymer reference standards. Most polymers of commercial interest, however, contain low-molecular-weight additives that are intentionally added to extend the material's serviceable lifetime or alter its properties and performance. There are also nonpolymeric compounds, oligomers, and low-molecular weight components found in the polymer that originate from the polymerization process itself. Lastly, polymeric material can become contaminated during production, handling, storage, or transportation.

Component levels and their identification are needed for product certification, meeting end-use performance criteria, and for ensuring product stability and safety. (Please note that the term "component" is used throughout this survey as a general label for additives, residual solvents, unreacted monomers, oligomers, chain fragments, low-molecular-weight polymerization by-products or reaction side-products, or contaminants.) Because extractables and contaminants may pose health risks, especially if the polymer is processed into film, packaging, or parts that contact food, pharmaceuticals, viable organisms, and biologicals, accurate and precise analytical data are required.

To comply with governmental safety, health, and transportation regulations, it is necessary for agencies and companies to monitor, control, and certify product quality. This month's "Sample Preparation Perspectives" installment surveys approaches for extracting and concentrating polymer additives and side products that may be present in synthetic polymers or polymeric materials for subsequent chromatographic analysis.

The sample preparation process is an important part of the overall analysis and is often the rate-determining and error-prone part of the analytical cycle. Nonporous solid materials such as polymers represent a special sample preparation challenge because many of the additives are located deep within the matrix itself and must be released in a quantitative manner.