Nominal molecular weight cutoff

Figure 1. Production of Fe(II) on irradiation of pH 4.0 solutions of distilled, deionized water and 0.1M NaCl and a pH 6.5 solution of 0.1M NaCl/2mM NaHC03 containing 3.5pM am-FeOOH. The ultrafilterability of the iron through a membrane exhibiting a nominal molecular weight cutoff of 10,000 (Amicon PM10) in the pH 4.0 study is also shown. Light source simulated solar spectrum of total intensity 300 pEinsteins cm-2 min-1. (Reproduced from Ref. 32. Copyright 1984, American Chemical Society.)...

Disposable Ultrafree-CL (Millipore) ultrafiltration cartridge units (10 kDa nominal molecular weight cutoff). 

UF and RO offer an alternative means of isolating DOM from freshwaters. With UF membranes having nominal molecular weight cutoffs of 100 kDa, lOkDa, and 1 kDa, the median recoveries of DOM are 31%, 53%, and 71%. It is possible to show by a simple calculation that the average molecular weight of DOM in freshwaters would be at least 34 kDa, if actual molecular weights of DOM fractions equaled the nominal molecular weight cutoffs of the UF... 

UF membranes can retain macromolecules such as polysaccharides, proteins, biomolecules, polymers, and colloidal particles. Generally, ultrafiltration membranes are classified by the type of material and their nominal molecular weight cutoff (MWCO), which is usually defined as the smallest molecular weight species for which the membrane has more than 90% rejection. 

The pore size of a UF membrane is described by its nominal molecular weight cutoff (MWCO), defined as the molecular weight of the smallest species for which the rejection is 90% or greater. Although the nominal... 

Because the size of the micropores is not uniform, the molecular weight cutoffs given by the manufacturer are not as sharp as would be expected. Nominal molecular weight cutoffs usually represent the particle size that will be 90% retained. In addition, ultrafiltration separates solutes according to molecular size, which will be dependent on molecular charge and configuration. 

The retention characteristics of ultrafiltration membranes are measured in Nominal Molecular Weight Cutoff (NMWCO). The NMWCO can be controlled during membrane formation and is typically available in 1,000 10,000 100,000 and 1,000,000 daltons. For cell harvesting, ultrafiltration membranes of 100,000 NMWCO and microporous membranes are generally employed. While the separation is based on size, the efficiency of the operation can be influenced by other factors. 

UF membranes are characterized by a nominal molecular weight cutoff (MWCO),... 

Membrane Pore Size (nm) Nominal Molecular Weight Cutoff (AMU) pH Range... 

Ultrafiltration membrane manufacturers frequently characterize their membranes using the cutoff concept rather than pore size. The nominal molecular weight cutoff (MWCO) is a performance-related parameter, defined as the lower limit of a solute molecular weight (e.g., dextran) for which the rejection is 95-98% (Boerlage, 2001). As the MWCO decreases, the mean pore diameter for most UF membranes has been foimd to decrease (Kim et al., 1990). However, the MWCO may be sharp or diffuse, that is, thoe is a range of MWCO, and in reality MWCO is only a rough indication of the membrane s ability to remove a given compound as molecular shape, polarity, and interaction with the membrane affect rejection (Mulder, 1996). Moreover, membrane surface characteristics (e.g., surface porosity and pore size distribution) may influence the apparent size of particles retained. 

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