Solvent Extraction
A laboratory technique uses a highly polar cyclic ether to completely dissolve polymer matrices for subsequent chemical analysis. In RoHS compliance testing for printed boards, tetrahydrofuran dissolution is used to break down cured solder masks and adhesive residues. This chemical process releases any trapped phthalate plasticisers into the liquid phase, making them accessible for separation and detection.
Dissolution Protocol
The method requires finely ground sample particles to be mixed with the solvent in a sealed vial and heated or agitated until the solid polymer structure disappears. Because tetrahydrofuran has an excellent affinity for both polar and non-polar polymers, it ensures complete extraction of restricted organic compounds. Following this step, a non-solvent such as methanol is often added to precipitate the polymer chain while leaving the analytes in the solution, which protects the gas chromatography columns from being fouled by dissolved plastics.
This filtration step is critical to ensure that only the extracted chemicals enter the analytical instrument, preventing system downtime and keeping peak resolution high.
Process Scope
This extraction method is limited to soluble thermoplastic materials and some moderately cross-linked polymers used in electronic assemblies. It fails to apply to highly cross-linked thermosetting resins like fully cured epoxy boards, which will only swell instead of dissolving, requiring alternative extraction techniques such as Soxhlet extraction or thermal desorption.
