Molecullar weigh cut-off using dextran or polyethylene glycol (PEG) rejection. The pore size is determine as the molecular weigh of particle that can be rejected 90% by membrane. The filtration is conducted by filtering the serries of differend dextran MW solution. The rejection profile than defined by the linearization of the rejection-MW curve. Normaly the concentration of the dextran is less than 2% w/w. 

Procedure of PEG rejection test (A. D. Sabde et al. [1997]):

Reagents:  

1. 5% w/v BaCl2 in 1 N HCl (100 ml)
2. 100 ml of 2% KI (w/v)  + 1.27 g I2 –> This mixture than dilluted 10 times.

Procedure:

1. Add 1 ml reagen 1 to 4 ml sample —>  (I)
2. Add 1 ml reagen II to  solution I —> (II)
3. Allow the color development for 15 minutes at room temperature
4. Read the absorbtion using spectrophotometer at 535 nm againt reagent blank

Note: To get the concentration value, the calibration curve is required.

Bubble