Use of factorial design for the multivariate optimization of polypropylene membranes for the cleanup of environmental samples using the accelerated membrane-assisted cleanup approach
Accelerated membrane-assisted cleanup (AMAC) is a recently developed method to purify extracts from matrix rich samples such as fish tissue and sediments. In this study, we tested the applicability of cast polypropylene (CPP) membranes in AMAC and evaluated the optimized dialysis procedure for the cleanup of extracts of fish tissue. Design of experiments was used to optimize the factors temperature, solvents and static time of dialysis. Main factors influencing dialysis procedure were solvents and temperature as well as the number of cycles. For the CPP membrane the optimal parameters were a temperature of 55 °C, a solvent mixture of n-hexane:acetone (90:10, v:v), a static time of dialysis of 6 min and 20 dialysis cycles. Comparing to the LDPE membrane this was a reduction of dialysis time from 160 to 120 min, but a higher solvent use of 150 ml per sample. However, compared to LDPE membranes CPP exhibited a lower retention of fish tissue matrix and thus reduced cleanup efficiency. Compound specific structural descriptors such as the molecular weight, the van der Waals volume and a shape factor were calculated to explain differences in diffusivity of the different model compounds. We concluded that the permeation of the molecules was related to molecular shapes and the availability of free solvent cavities in the membranes.