Organic buffers

ND-74 3 White Chemical inorganic Salts Organic Buffer Nondurable... 

Buffers (pH 4.5, 6.8) Potential interference from UV-absorbing organic buffers Potential interference Significant interference due to ion suppression... 

As a result, various excipients (from small molecules to polymers) have been added to the aqueous solution prior to lyophilization. Some of the most common are carbohydrates [86], polymers [87], organic buffer [81], competitive inhibitors [42], or nonbuffer salts [88]. 

For high-pH operation of any silica-based stationary phase, temperature should not exceed 40°C, organic buffers should be used instead of phosphate or carbonate, and methanol instead of acetonitrile should be the organic solvent. 

Buffer Bicarbonate or phosphate buffers are suitable for biotinylation. Organic buffers, sttch as Tris, which contain atnin.es, should be avoided, because they react with aminodabding reagents or interfere with the reaction between aldehydes and hydrazides However, HEPES and iiPPS, winch contain tertiary amines, are suit-... 

Organic buffer 50 voM NH4HC03/acetonitrile 1 1—make fresh weekly. 

Joule heating is minimised by using low ionic strength buffers, low voltages, organic buffers, low column temperatures and narrow internal diameters. Decompression is avoided by low voltages or applying an external pressure to the capillary. It is... 

Zawaideh LI, Zhang TC. The effects of pH and addition of an organic buffer (HEPES) on nitrate transformation in Fe°-water systems. Water Sci Technol 1998 38 107-115. 

As discussed above a certain buffer concentration is required to perform optimal analyses. The minimum ionic strength required determines the current and Joule heating. This effect can be measured as a deviation from Ohm s law. With organic buffers the conductivity is much smaller for a given ionic strength. Consequently organic zwitterionic buffers, or at least buffers with counterions of low mobility, should be preferred especially when long capillaries have to be used. 

At pH greater than 7, phosphate buffers accelerates the dissolution of silica and severely shortens the lifetime of silica-based HPLC columns. If possible, organic buffers should be used at pH greater than 7. Ammonium bicarbonate buffers usually are prone to pH changes and are usually stable for only 24 to 48 hours. The pH of this mobile phase tends to become more basic due to the release of carbon dioxide. 

Ampholyte An amphoteric electrolyte. In proteomics, this term is used to describe small multicharged organic buffers used to establish pH gradients in isoelectric... 

Another alternative and far more efficient procedure is to employ an organic buffer, such as methane sulfonic acid and a short length of reversed phase column subsequent to the analytical column. After the separation has been achieved and the individual ions are eluted from the column, the methyl sulfonate that is eluted with them is absorbed, virtually irreversibly, on to the revered phase leaving the ions of interest to enter the detector in the absence of any buffer ions. As the suppresser column is, itself, a high efficiency LC column, little or no dispersion occurs and consequently no loss of resolution. If a basic buffer is required, then a tertiary butyl ammonium salt can be used which would be removed equally effectively by the reversed phase suppresser column. 

There has been a recent increase in the popularity and application of non-aqueous CE buffers. These buffers are useful for the analysis of water-insoluble ionisable compounds. In addition they offer different separation selectivity to aqueous buffers and they are highly appropriate for use in CE-MS studies. A range of solvents have been utilised with acetonitrile and methanol being especially popular due to their relatively low UV absorbance activity at the low UV wavelengths frequently employed in CE. Use of pure solvents requires the use of organic buffers such as acetate as the inorganic buffers such as borate and phosphate are insoluble in non-aqueous solvents. 

When using MS, the actual CEC conditions never really need to be fully optimized because the MS accomplishes the additional resolution and specific identification, as needed. The specific mobile-phase conditions in CEC-MS may be quite different than for CEC-UV/FL or HPLC, and thus optimization of CEC-MS conditions will be somewhat different than for CEC-UV/FL. This would include, just as for LC-MS, the use of volatile organic solvents and organic buffers, low flow rates, no void volumes, or loss of resolution in the CEC-MS interface and the usual interfacing requirements already developed and optimized for CE-MS [10,13-23]. 

Noteworthy toxicity (toxscreef II pro organic buffer) tctor)... 

Figure 4.4.7 Indication of the distribution of toxicity found by using ToxScreen II (pro organic buffer) and Metal Detector in the River Ribble estuary during the ebb tide. No toxicity was found with either ToxScreen II pro-metal buffer or with the standard Microtox test (Roig el al., 2007)...

Error in the pH of the standard buffer. Any inaccuracies in the preparation of the buffer used for calibration or any changes in its composition during storage cause an error in subsequent pH measurements. The action of bacteria on organic buffer components is a common cause of deterioration. 

When using this technique, the most appropriate wavelength is selected from the UV spectrum of the pure compound and that of the system suitability sample. Usually, the A ax is chosen however, in order to remove unwanted interference, it may be necessary to move away from this value. Where possible, the use of wavelength <250 nm should be avoided because of the high level of background interference and solvent adsorption. In practical terms, this requires the use of far-UV grade solvents and the avoidance of organic buffers. 

Also, the organic buffers can interact with surface amino groups of the enzyme, - R-COO Na+ + -NH3+ CF R-COOR + E- NH -f NaCl (8.7)... 

Buffering of the medium is usually achieved with phosphate, although excessive concentrations should be avoided since they cause problems of precipitation during sterilization by autoclaving. A number of organic buffers have been used effectively in different applications. In studies employing organic phosphorus compounds as P-sources, phosphate has been replaced by, for example, FIEPES (Cook et al. 1978) and MOPS has been incorporated into... 

Organic buffer additives such as acetic, adipic, acrylic, and sulfosuccinic acid enhance the rate of calcite dissolution by providing for mass transfer of acidity to the limestone surface. 

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