Dialysis factor

The phase transfer factor P (cf. Sec. 1.4.6) in on-line dialysis may be conveniently expressed by the dialysis factor, defined as the output concentration of the detector channel. Q, normalized by division with the initial sample channel concentration, Cs [5]. The phase transfer efficiency may also be described using dialysis percentage by multiplying the dialysis factor with 100. 

The dialysis factor Cd/Cs depends on several experimental parameters such as permeation qualities of the membranes, membrane area, channel dimensions, analyte concentration, flow-rates of the donor and acceptor streams and their ratios, the relative flow direction of the two streams and temperature. A brief summary on the effects of various factors under FIA conditions, based mainly on results and observations obtained by van Staden and Rensburg [6] using calcium and chloride ions as model anal)aes are given here. 

Dialysis factors are little influenced by differences in analyte concentrations within relatively wide concentration ranges below 5000 mg 1" However, other coexisting solutes may influence the dialysis efficiency, and interfere by changing the osmotic pressure. 

Within a practical flow>rate range of 1-4 ml min concurrent and countercurrent flow of donor and acceptor streams show no differences in dialysis factors. However, the reproducibility of results are better under concurrent flow conditions. 

The sample volume has no influence on the dialysis factor. This implies that for a fixed dialyzer, the ratio of membrane surface area to sample volume will not affect the dialysis factors. 

The dialysis factor increases with a decrease in flow-rate (equal flow-rates for donor and acceptor streams) in the range 1.0 - 3.9 ml min However, precision is better at the larger flow-rates and higher sample throughputs are feasible. 

Dialysis factor increases with a decrease in membrane thickness and an increase in pore size, the influence being more pronounced at higher flow-rates. 

Dialysis factor increases with an increase in channel length from 70 to 3(X) cm (0.5 mm wide). Obviously, this also implies an enhancement in dialysis factor with an increase in the membrane area. 

Dialysis factors may be noticeably influenced by temperature vanations. it is advisable to thermostat the dialyzer. usually at 25°, for optimum results. 

Homogeneous membranes effect transfer of a species from donor to acceptor by molecular diffusion. Therefore the dialysis factor depends on the solubility and diffusivity of the species in the membrane and not on their particle sizes. 

The seminal discovery that transformed membrane separation from a laboratory to an industrial process was the development, in the early 1960s, of the Loeb-Sourirajan process for making defect-free, high flux, asymmetric reverse osmosis membranes (5). These membranes consist of an ultrathin, selective surface film on a microporous support, which provides the mechanical strength. The flux of the first Loeb-Sourirajan reverse osmosis membrane was 10 times higher than that of any membrane then avaUable and made reverse osmosis practical. The work of Loeb and Sourirajan, and the timely infusion of large sums of research doUars from the U.S. Department of Interior, Office of Saline Water (OSW), resulted in the commercialization of reverse osmosis (qv) and was a primary factor in the development of ultrafiltration (qv) and microfiltration. The development of electro dialysis was also aided by OSW funding. 

The voltage used for electro dialysis is about 1 V per membrane pair, and the current flux is of the order of 100 A/m of membrane surface. The total power requirement increases with the feedwater salt concentration, amounting to about 10 MW per m product water per 1000 ppm reduction in salinity. About half this power is required for separation and half for pumping. Many plant flow arrangements exist, and their description can be found, along with other details about the process, in References 68 and 69. Many ED plants, as large as 15,000 vsf jd, are in operation, reducing brackish water concentration typically by a factor of 3—4. 

While it is easy to add materials to a fermentation, removal is difficult. Membrane devices have been placed in the fermenter or in external recycle loops to dialyze away a soluble component. Cells release wastes or metabolites that can be inhibitory these are sometimes referred to as staling factors. Their removal bv dialysis has allowed cell concentrations to reach ten to one hundred times that of control cultures. 

Several cytokines are in clinical use that support immune responses, such as IL-2, DFNs, or colony-stimulating factors. IL-2 supports the proliferation and effector ftmction of T-lymphocytes in immune compromised patients such as after prolonged dialysis or HIV infection. IFNs support antiviral responses or antitumoral activities of phagocytes, NK cells, and cytotoxic T-lymphocytes. Colony-stimulatory factors enforce the formation of mature blood cells from progenitor cells, e.g., after chemo- or radiotherapy (G-CSF to generate neutrophils, TPO to generate platelets, EPO to generate erythrocytes). 

Risk factors that may increase the potential for hypotension include elderly age, diabetes, autonomic neuropathy, uremia, and cardiac disease.46 The symptoms associated with hypotension during dialysis include dizziness, nausea, vomiting, sweating, and chest pain. 

Pathophysiology Muscle cramps can occur with up to 20% of dialysis sessions.48 The cause is often related to excessive ultrafiltration, which causes hypoperfusion of the muscles. Other contributing factors to the development of muscle cramps include hypotension and electrolyte and acid-base imbalances that occur during hemodialysis sessions. 

Monnier, M. Hosli, L. (1964). Dialysis of sleep and waking factors in blood of the rabbit. Science 146, 796-8. 

International travelers who plan to spend >6 months in countries with high rates of HBV infection and who will have close contact with the local population Recipients of clotting-factor concentrates Sexually transmitted disease clinic patients HIV patienVHIV - testi ng patients Drug-abuse treatment and prevention clinic patients Correctional facilities inmates Chronic dialysis/ESRD patients... 

Factors that influence drug dialyzability in chronic ambulatory peritoneal dialysis include drug-specific characteristics (e.g., molecular weight, solubility, degree of ionization, protein binding, and VD) and intrinsic properties of the peritoneal membrane (e.g., blood flow, pore size, and peritoneal membrane surface area). 

In order to evaluate the catalytic characteristics of colloidal platinum, a comparison of the efficiency of Pt nanoparticles in the quasi-homogeneous reaction shown in Equation 3.7, with that of supported colloids of the same charge and of a conventional heterogeneous platinum catalyst was performed. The quasi-homogeneous colloidal system surpassed the conventional catalyst in turnover frequency by a factor of 3 [157], Enantioselectivity of the reaction (Equation 3.7) in the presence of polyvinyl-pyrrolidone as stabilizer has been studied by Bradley et al. [158,159], who observed that the presence of HC1 in as-prepared cinchona alkaloids modified Pt sols had a marked effect on the rate and reproducibility [158], Removal of HC1 by dialysis improved the performance of the catalysts in both rate and reproducibility. These purified colloidal catalysts can serve as reliable... 

Pancreatic amylase is very labile and sensitive to its chemical environment. Its lability is accelerated by purification and by such factors as dilution of its aqueous solutions, dialysis of its aqueous solutions against water, unfavorable hydrogen ion activities and unfavorable temperatures.29-31, 36,33 The loss of amylase activity in solutions of pancreatic amylase increases with increasing temperature and is very rapid between 50° and 60°. The inactivation of pancreatic amylase in aqueous solution may be retarded by the addition of certain anions, of which the chloride ion is outstanding 37-39 by the addition of certain cations, of which... 

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