The  Membrane Filtration Products, Inc.

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MFPI proudly presents its line of dialysis products featuring Cellu·Sep® Regenerated Cellulose Tubular Membrane. Cellu·Sep T-Series Membranes are manufactured in a broad range of molecular weight cut-offs and flat widths. Ideal for sensitive applications, Cellu·Sep H1 High Grade Membranes are specially prepared, ultra-clean and shipped wet. Try out our convenient Dialysis Accessories, designed to help lend a hand with many dialysis procedures. Use the membrane of your choice “right off the shelf” with our easy to use QuixSep® Micro Dialyzers. Please refer to the Product Part Numbers provided within each product listing.  All orders come direct from us.

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The dialysis process of a solute occurs at the membrane surface, in context to the concentration differences of two solutions on either side of the membrane. This process is affected by the variables of temperature, viscosity and mixing rate of a solution.

The movement of a solute across a semipermeable membrane is the result of random molecular motion. As the solute molecules in a solution move, they will collide from time to time with the membrane until they diffuse. (See diagram 1.)

The permeation of a given solute (Y), from a solution on the left (L) of the membrane to the right (R), and back again, will depend upon the frequency of collisions between Y molecules on either side of the membrane.

For example, if the concentration of solute-Y, in the solution L is 100 mM, and solution R is 10 mM, the probability of Y-solute colliding with the Y-solute in the solution L, will be much higher than the chance of the solute-Y colliding with the R side of the membrane. Therefore, the net rate of transfer of a given solute, (at a certain temperature, viscosity and mixing rate) will increase with greater concentration differences between the two solutions.

Permeation Rate

The rate of transport across a semipermeable membrane depends mainly on the shape, charge, and size of the solute. Speed and size are only two out of numerous interacting factors. The flux, or permeation across a semipermeable membrane of solutes in solution, is inversely related to the molecular weight.

Small molecules collide more often with the membrane, thus, their rate of molecular migration through the membrane will be high. Large molecules, moving at low velocities collide infrequently with the membrane. Therefore, their rate of migration through the semi-permeable membrane will be low (even those that fit through the membrane pores).

The size of a solute correlates highly with the molecular weight. As the molecular size approaches and exceeds the size of the membrane pores (MWCO), passage of solutes will completely or partially be prevented.

Influence on Permeation Rate




Concentration gradient

Large concentration differential

Small concentration differential

Molecular Size

Small spherical molecules

Large fibrous molecules


High temperature

Low temperature

Wall thickness

Thin (<20µm)

Thick (>20µm)

Membrane surface area



Dialysis Membrane Materials

Synthetic and natural membranes are commonly used for filtration applications. Membrane materials most often used include regenerated cellulose, cellulose acetate, polysulfone, polycarbonate, polyethylene, polyolefin, polypropylene, and polyvinylidene fluoride.

The regenerated cellulose in Cellu·Sep® is derived from cotton: Cotton linters are dissolved in a solution and spread into flat sheets or extruded into tubes. The material is treated with glycerin to prevent the pores from collapsing and air dried at a certain temperature and pressure to form a rigid membrane. Cellu·Sep regenerated cellulose membrane has a symmetric pore structure which allows small molecules to migrate in either direction, making it ideal for experimental purposes.

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Comfort & Ease

We only use original parts or parts of equivalent quality. ​We make sure you get the best quality available on the market at the best price. All our interventions are guaranteed for a period of one year.

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Fitting design

We only use original parts or parts of equivalent quality. ​We make sure you get the best quality available on the market at the best price. All our interventions are guaranteed for a period of one year.

Natural control

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