Pore size, filter membrane

Membrane pore size rating refers to the size of a specific particle to be retained by the filter with a specific degree of efficiency. Pore size will affect the flow rate, back pressure, and life of the filter. Membrane pore size is outlined in Table 9 and selected on the basis of the applications requirements. The size and amount of particles to be filtered from the sample can also affect the pore size selection. Most applications in the isolation of drug impurities and degradants would either require prefiltration to remove large clumps of insoluble excipients or a filtration/clarification step prior to FIPLC, and would be chosen on these bases.71... 

This deposit is composed of suspended particles similar to conventional filter cakes, and more importantly, a slime that forms as retained solutes exceed their solubility. The gel concentration 6 is a function of the feed composition and the membrane-pore size. The gel usually has a much lower hydrauHc permeabihty and smaller apparent pore size than the underlying membrane (27). The gel layer and the concentration gradient between the gel layer and the bulk concentration are called the gel-polarization layer. 

As RO membranes become looser their salt rejection falls (see Section 31.8.1). Eventually a point is reached at which there is no rejection of salts, but the membrane still rejects particulates, colloids and very large molecules. The membrane pore size can be tailored to a nominal molecular weight cut-off. The resulting filtering process is called ultra-filtration. 

Grade 2 water to reverse osmosis or de-ionisation, followed by filtration through a membrane filter of pore size 0.2 jum to remove particulate matter. Alternatively, Grade 2 water may be redistilled in an apparatus constructed from fused silica. 

To 1.0 g of niclosamide add 15 mL of water, boil for 2 min, cool, filter through a membrane filter (nominal pore size 0.45 pm), wash the filter and dilute the combined filtrate and washings to 20 mL with water. To 10 mL of this solution, add... 

Matrixes Three types of paper filters (i). Filtrak, Germany, the filter Number 388 [(0.025) - soft, wide pores] filters No. 90 (0.15) and No. 90 (0.25) - dense, narrow pores) (ii). chromatographic papers FN-5, FN-11 (Germany) the kapron membrane (pore size 0.2 microns) and (iii). the membrane Vladipor MFA-MA No. 6 (Kazan industrial associations Tasma )] were applied to matrixes for biotests. The circles (6 -10 mm dia) are cut out from the matrixes materials by special instrument. The most stable results are received with use of matrixes of chromatographic papers FN-5, FN-11. 

A choice of a filter with the correct membrane pore size can prevent the shift in polish rate. The pore size chosen must be significantly larger than the slurry particle sizes. For example, if the mean of the slurry particle size is 1000 A, the pore size should be a few microns, so that no normal sized particles will be filtered out. Frequent filter changes can prevent filter clogging. 

Pass the solution through a membrane filter of pore size 0.22 microns. 

The principle of microfiltration is the application of hydrostatic pressure on a microporous filter membrane, so that the pressure difference forces solutes, water molecules, and particles smaller than the membrane pore size to flow across the pores, retaining and concentrating the larger particles in the suspension. 

Membrane pore size/density, generally 1.0-8.0 pm, with smaller pore size filters having greater pore density ... 

Modifications of the method include manual or automated cell feeding in 24-well plates, media modifications, possible coating of filter surfaces, pore size of filter membranes. Other modifications include quality assurance criteria (TEER, permeability values). 

The choice of a filter is dependent on four parameters the membrane material, the material used to house the membrane, the membrane pore size,... 

Filters CM, diameter 30 mm, pore size 0.4 pm, Millicell-CM, Millipore Corporation, or Transwell, diameter 24 mm, polyester membrane, pore size 0.4 pm, Ref 3450, Costar, Corning Incorporated... 

Place the gel between 2 sheets of welted nitrocellulose membrane (pore size 0.45 /im or, preferably, 0.2 m), avoiding any air bubbles. Cover each membrane with filter paper, foam pad and rigid screen, all previously wetted and attach with rubber bands. 

The filtration of these primary colloid systems was described in section 5.5. The colloids of a size closest to the membrane pore size resulted in the greatest flux decline, as this was attributed to pore plu ng. In contrast, the smaller colloids were too small to fill up pores effectively at the volumes filtered, and the larger colloids formed a cake on the membrane surface. These su esrions were confirmed with electronmicrographs (see Figure 5.6). 

---