2.5.2. Quantification of residual proteins by Pierce-BCA method after soxhlet extraction
The extraction of BSA from the membranes was carried out using a method developed by Puro et al., 2002. The protein extractions from membrane samples after being fouled with BSA and after the cleaning with the tested solutions (NaOH and P3 Ultrasil 115) were carried out in a Soxhlet extractor. 350 ml of acetone–water solution (9:1) was used as a solvent and the total time for each extraction was 2 h. After that, acetone was separated by distillation with a rotary evaporator equipment. Finally, the amount of proteins in each sample was measured by Pierce BCA test. Experimental procedure of Pierce BCA test was: 1 ml of BCA working reagent was added to 1 ml of each sample, then samples were incubated at 60 C for 1 h and after cooling at room temperature, the absorbance samples were measured with the spectrophotometer
at 562 nm.