Buffer, type

How do the solution conditions including pH, ionic strength, and buffer type, affect the transport, and how can these conditions be controlled and optimized for a particular ap-phcation ... 

In the case of polyacrylamide gels, Stellwagen [367] found that buffer type (TAE vs TBE) did not affect the apparent pore size (21 mn for 10.5% T 5% C to 200 mn for 4.6% r/2% C), although more extreme variations in salt content and buffer physical properties may very likely strongly affect pore structure in polyacrylamide gels. 

Tran, A. D., Park, S., Lisi, P. J., Huynh, O. T., Ryall, R. R., and Lane, P. A., Separation of carbohydrate-mediated microheterogeneity of recombinant human erythropoietin by free solution capillary electrophoresis. Effects of pH, buffer type and organic additives,. Ckromatogr., 542, 459, 1991. 

In preformulation one task is to establish the stability of the drug substance in both solid and dissolved state. In the latter case it is important, with small samples of drug substance, to assess (a) the effect of buffer type, (b) the effect of buffer concentration, (c) the effect of pH in a practical range, (d) the effect of temperature, and (e) the kinetic salt effect. 

An interesting paper that attempted to relate dissolution of a poorly soluble acidic drug (naproxen) to simulated gastrointestinal flow in the presence of buffers was published by Chakrabarti and Southard [17]. In addition to showing that buffer type (citrate, phosphate, or acetate) had a significant impact on naproxen dissolution, these authors unexpectedly found that elevating a solid tablet into the flow channel of the flow-between-two-plates apparatus resulted in a substantial... 

Complex formation between PBA or PDBA group and the SHA group occurs in a wide range of buffer types from pH 5 to 9, and it can tolerate high salt conditions (to 1.5 M) or the... 

As electrostatic interactions exist between the HILIC zwitterionic stationary phase and charged solutes, particular attention has to be paid to the rigorous control of experimental conditions such as pH, buffer type and ionic strength. 

The composition of the aqueous phase plays a critical role in interfacial reactions too. Sah and Bahl [35] showed that critical factors such as pH, buffer type and concentration affected the destabilisation of (3-lactoglobulin towards emulsification. In particular, pHs away from the pi and low buffer/salt concentrations are beneficial for minimising the interfacial inactivation. 

Integrated multi-biosensors based on ISFET can be produced by using a photosensitive polymer which incorporates the enzyme and is spinned onto the gate [54]. The reported measuring range for glucose is 5 mM which is rather weak, and some cross sensitivities due to problems regarded with buffer type and capacity were also reported. 

The key operational parameter in free-solution capillary electrophoresis is the pH of the running buffer, as the electroosmotic flow and ionization of the analyte can be regulated by this variable. The role of buffers in capillary electrophoresis has been discussed in detail, with emphasis on buffer concentration, buffer type, and pH effects [10]. The effect of organic solvents on separation and migration behavior has been studied for dipeptides [11] and somatostatin analog peptides [12]. The order of migration as well as the selectivity may be manipulated by organic modifiers in... 

S. Heinisch and J. L. Rocca, Effect of mobile phase composition, pH and buffer type on the retention of ionizable compounds in reversed-phase liquid chromatography Application to method development,/. Chromatogr. A 1048 (2004), 183-193. 

Figure 8-71. Effect of wpH 11 buffer type on bidentate-C18P columns, 15 x 0.46 cm. Mobile phase 55% acetonitrile 45% 0.05M buffer (1-methyl-piperidine bnffer was adjusted to pH 11 with HCl and dipotassium monohydrogen phosphate bnffer was adjusted to SpH 11 with NaOH). Flow rate, l.OmL/min, temperature, 23°C UV, 215 nm. (Reprinted from reference 43, with permission.)...

There is a solvent-related pH dependence that varies with the specific reaction components and conditions (e.g., liposomes vs. membranes vs. emulsions, fatty acids vs. phospholipids, buffer type, heme compound). 

Napaporn, J. Thomas, M. Svetic, K.A. Shahrokh, Z. Brazeau, G.A. Assessment of mytotoxicity of pharmaceutical buffers using an in vitro muscle model effect of pH, capacity, tonicity, and buffer type. Pharm. Dev. Technol. 2000, 5 (1), 123-130. 

Although the use of a buffer will aid in reducing the risk of precipitation upon dilution, there are pH, concentration and buffer type limitations. Physiological compatibility will depend on factors such as the route of administration, tonicity, and contact time. Other factors such as chemical stability as a function of pH must also be considered. Table 4 lists some marketed... 

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