Dialysis membrane Spectra/Por® 7 MWCO 25,000 (opaque), 18 mm, 1 Piece(s)

Microvolumes of sample (5-100 μl) can also be dialysed by membrane filter discs made of cellulose mixed ester (pore size 0,025 μm, Art. No. CY35.1-CY37.1): Fill a Petri dish with dialysis buffer. Place the membrane filter disc on the surface of the solution (shiny side up, avoid bubbles under the filter) by using a stainless steel forceps. Float the membrane for ca. 5 min until it is completely soaked. Pipette the sample on the center of the filter. Due to the open pore structure of the membrane filter and the high surface-to-volume ratio the dialysis is done within a short time (mostly < 30 min). To avoid evaporation of the sample seal the Petri dish tightly during the procedure. In this way the sample volume remains nearly constant.

Do not tie knots in regenerated cellulose. Closure clips must be used to avoid any changing of membrane or MWCO.

Dry dialysis membranes have different appearances, dependent on pore size and wall thickness: Clear, opaque or even completely white.

Reason:

Larger MWCO membranes are made slightly thicker to maintain membrane strength when the pores are larger.

The thicker the membrane and larger the pores, the more opaque. So the different membranes look as follows:

Dry membranes with MWCO

100-1000: clear

3 500-5 000: mostly clear

8 000-10 000: slightly opaque

20 000-50 000: opaque

≥100 000: white.

When the membrane is wetted with water the effect dissapears and the membrane becomes more clear.