Solvent Residue
Chemical analysis quantifies non-volatile substances released from paper surfaces through immersion in dichloromethane. Dichloromethane extractables measure the mass of lipids, resins, waxes, and synthetic additives dissolved from a substrate into a halogenated solvent under controlled boiling conditions. This assessment identifies mobile components that might migrate from food packaging into fatty or aqueous contents during prolonged storage.
Analytical results derive from the weight difference of the original material sample after solvent evaporation and subsequent conditioning. The procedure effectively isolates organic compounds that remain distinct from the fibrous structure of the sheet.
Extraction Procedure
Laboratories perform this measurement by placing a precisely weighed portion of shredded substrate into a Soxhlet apparatus. Hot solvent circulates through the material to dissolve extractable matter over several hours. The liquid phase collects in a round-bottom flask where the solvent undergoes distillation for recovery.
Residual matter stays in the flask and undergoes drying to a constant mass in an oven. Technicians weigh the remaining solids to determine the proportion of the original sample that moved into the solvent.
Migration Impact
Regulators set threshold limits for these substances to ensure that secondary packaging stocks remain inert when they contact sensitive items. High concentrations of extractable waxes or processing aids increase the risk of contamination in products like margarine or shelf-stable meats. Paper mills minimize these values through thorough washing stages and strict control over internal sizing agents used during production.
Excessive readings indicate incomplete removal of sizing chemistry or the presence of unwanted impurities introduced during the pulp refining phase. Low levels ensure that substrates provide a stable barrier against chemical transmission.
