Syarifatul Lailah

Department of Chemistry, Faculty of Mathematics and Natural Sciences, University of Jember

Dwi Indarti

Department of Chemistry, Faculty of Mathematics and Natural Sciences, University of Jember

Bambang Piluharto

Department of Chemistry, Faculty of Mathematics and Natural Sciences, University of Jember

Tinok Dwi Ananda

Department of Chemistry, Faculty of Mathematics and Natural Sciences, University of Jember

Tri Mulyono

Department of Chemistry, Faculty of Mathematics and Natural Sciences, University of Jember

DOI: https://doi.org/10.19184/icl.v5i1.60009

ABSTRACT 

Membrane osmometry is a crucial analytical technique for determining the molecular weight of macromolecules, demanding highly selective semi-permeable membranes to prevent solute leakage. This study investigates the effect of solvent evaporation time (1 to 5 minutes) during the phase inversion fabrication of cellulose acetate (CA) membranes on their physicochemical properties and semi-permeability. The synthesized membranes were evaluated for macroscopic appearance, density, swelling degree, and semi-permeability performance using dextran (100-200 kDa) as a model macromolecule. The results demonstrated that while the macroscopic structures remained uniform, prolonging the evaporation time significantly altered the microscopic morphology. Increasing the evaporation time to 5 minutes maximized the localized polymer concentration, resulting in the highest membrane density (1.55 g/mL) and the lowest swelling degree (17.62%). This highly compact structure provided a superior physical barrier, yielding the most optimal semi-permeability with minimal solute leakage. Furthermore, the application of this 5-minute optimized membrane in a membrane osmometer successfully determined the average molecular weight of dextran to be 122.45 kDa, which perfectly aligns with the theoretical range. The analytical measurement exhibited excellent reproducibility with a coefficient of variation (CV) of 1.8% and an accuracy of approximately 80%. These findings conclusively establish that controlling the evaporation time is a highly effective approach to tailoring the strict selectivity of CA membranes for precise osmometric applications.

Keywords: cellulose acetate, evaporation-time, membrane osmometry, molecular weight, phase-inversion.