Molecular Weight Cut-Off Determination of Pressure Filtration Membranes via Colorimetric Detection Method

Abstract

Molecular weight cutoff (MWCO) of commercial and in-house fabricated membranes is obtained at 90% rejection of various types of solutes with different molecular weights (MWs). PEG quantification methods have been favorably employed to determine membranes' MWCO. Most of the quantification methods utilizing high-end equipment using high performance liquid chromatography (HPLC) and low-end colorimetric method. HPLC method requires an established chromatographic technique using specific diluents, columns and detectors while the most referred colorimetric method requires a few processing steps with concentration up to 7.5 ppm by using UV spectrophotometer. In this work, a newly modified colorimetric method was established to conduct a simple measurement for a membrane's MWCO. The newly modified method has an excellent linearity for the calibration curves which R 2 values are closed to 1 with concentration of up to 150 ppm. A MWCO determination test conducted using different commercial membranes for confirming this newly modified method found that similar MWCO values were obtained as given by the membrane' manufacturers. In conclusion, this newly modified method is simpler than the formerly used colorimetric method, reliable and applicable for determining the MWCO of membranes ranging from UF to NF at a higher range of PEG concentrations (>150 ppm).