Buffer solutions applications

Troconiz, J.I. Lopez-Bustamante, L.G. Fos, D. High-performance liquid chromatographic analysis of piroxicam and tenoxicam in plasma, blood and buffer solution. Application to pharmacokinetic studies in small laboratory animals. Arzneimittelforschung, 1993, 43, 679-681... 

Concentration limits of the diphosphate-ion, admissible to determination of magnesium and cobalt, manganese and cobalt, zinc and cobalt by spectrophotometric method with application of the l-(2-pyridylazo)-resorcinol (PAR) are presented. Exceeding maintenance of the diphosphate-ion higher admissible supposes a preliminary its separation on the anionite in the H+-form. The optimum conditions of cobalt determination and amount of the PAR, necessary for its full fastening are established on foundation of dependence of optical density of the cobalt complex with PAR from concentration Co + and pH (buffer solutions citrate-ammoniac and acetate-ammoniac). 

Buffer solutions find many applications in quantitative analysis, e.g. many precipitations are quantitative only under carefully controlled conditions of pH, as are also many compleximetric titrations numerous examples of their use will be found throughout the book. 

The poor solubility of coelenterazine in neutral aqueous buffer solutions often hampers the use of this compound in biological applications. The simplest way to make an aqueous solution is the dilution of a methanolic 3 mM coelenterazine with a large volume of a desired aqueous buffer solution. If the use of alcoholic solvents is not permitted, dissolve coelenterazine in a small amount of water with the help of a trace amount of 1 M NaOH or NH4OH, and then immediately dilute this solution with a desired aqueous buffer solution. However, because of the rapid oxidation of coelenterazine in alkaline solutions, it is recommended that the procedure be carried out under argon gas and as quickly as possible. 

The common-ion effect is quite general. The chemistry of buffer solutions is another important application of this principle. A buffer solution relies on the common-ion effect to suppress the concentration of hydronium ions and maintain a steady pH ... 

An IL solvent system is applicable to not only lipase but also other enzymes, though examples are still limited for hpase-catalyzed reaction in a pure IL solvent. But several types of enzymatic reaction or microhe-mediated reaction have been reported in a mixed solvent of IL with water. Howarth reported Baker s yeast reduction of a ketone in a mixed solvent of [hmim] [PFg] with water (10 1) (Fig. 16). Enhanced enantioselectivity was obtained compared to the reaction in a buffer solution, while the chemical yield dropped. 

The rationale of validation experiments with fatty matrices is the high amount of fat extracted with many organic solvents. If analytes are not fat soluble and extraction is performed with water or aqueous buffer solutions, the troublesome fat is not extracted together with the analyte. Such extractions are typical for, e.g., the class of sulfonylurea herbicides. Examples exist where in such cases the applicability of an analytical method to fatty matrices was accepted by the authority without particular validation. 

Before releasing a process column for chromatography, it is advisable to perform some test to measure efficiency, such as calculating height equivalent theoretical plates (HETP), both to forestall any problems in the column bed and to provide a benchmark by which to measure column reproducibility and predict degradation of the bed or material. Examples of compounds that are relatively innocuous for use in pharmaceutical applications are 1% NaCl (for gel filtration), concentrated buffer solutions (for ion exchange), and benzyl alcohol and parabens for reverse phase LC.10... 

A 10 mM ionic strength universal buffer mixture, consisting of Good zwitterio-nic buffers, [174] and other components (but free of phosphate and boric acid), is used in the pION apparatus [116,556], The 5-pKa mixture produces a linear response to the addition of base titrant in the pH 3-10 interval, as indicated in Fig. 7.53. The robotic system uses the universal buffer solution for all applications, automatically adjusting the pH with the addition of a standardized KOH solution. The robotic system uses a built-in titrator to standardize the pH mapping operation. 

It is difficult in practice to use ec reduction as a method of detection in hplc. Oxygen is very easily reduced, and if it is present in the mobile phase it will create a background current thousands of times larger than the current due to the solutes. To prevent this, oxygen would have to be very carefully removed. This can be done, but it certainly is not easy in practice. So most of the ec applications are oxidations. Another important consideration with ec detectors is that the mobile phase used must have fairly high conductance, so they are used with aqueous-organic mixtures containing added salts, or with buffer solutions. 

Over the last several years, the number of studies on application of artificial neural network for solving modeling problems in analytical chemistry and especially in optical fibre chemical sensor technology, has increase substantially69. The constructed sensors (e.g. the optical fibre pH sensor based on bromophenol blue immobilized in silica sol-gel film) are evaluated with respect to prediction of error of the artificial neural network, reproducibility, repeatability, photostability, response time and effect of ionic strength of the buffer solution on the sensor response. 

Methods in which the cell potential for the sample solution is compared with that for one or more standards are rapid, simple and readily automated. The measurement of pH is the most common application of this type, one or more buffer solutions serving to calibrate the pH-meter (potentiometer). In all such measurements, calibration involves the evaluation of the constant in the equation... 

Many applications for buffer solutions are found in the analytical laboratory. It is frequently required to have solutions that do not change pH during the course of an experiment. An example is cited in Section 5.3.3 and used in Experiments 11 and 12. 

The composition and pH of the buffer should be accurate to 0.001 mol l-1 and 0.01 pH units. Most methods rely on the sequential application of a series of buffer solutions of increasing pH and molarity, with the initial pH around 3.2. Sodium citrate or, preferably, lithium citrate buffers are used, which incorporate a detergent (BRH 35), an antioxidant (thiodiglycol) and a preservative... 

A typical counter electrode reaction is the electrolysis of water. Here the cathodic evolution of hydrogen is coupled with the formation of base, the anodic development of oxygen produces acid additionally. Frequently, acid and base formation at both electrodes will be balanced. Otherwise, a buffer solution or a (continuous) base/acid addition, for example, by a pH-controlling system, can enable the application of an undivided cell. 

The polarization resistance of Cu in a UDI/phosphate buffer solution was found to be four times that of bare Cu. The proven inhibitor, BTA, also increases the polarization resistance. This result indicates that UDI may have practical applications. 

Urea-formaldehyde resins are generally prepared by condensation in aqueous basic medium. Depending on the intended application, a 50-100% excess of formaldehyde is used. All bases are suitable as catalysts provided they are partially soluble in water. The most commonly used catalysts are the alkali hydroxides. The pH value of the alkaline solution should not exceed 8-9, on account of the possible Cannizzaro reaction of formaldehyde. Since the alkalinity of the solution drops in the course of the reaction, it is necessary either to use a buffer solution or to keep the pH constant by repeated additions of aqueous alkali hydroxide. Under these conditions the reaction time is about 10-20 min at 50-60 C. The course of the condensation can be monitored by titration of the unused formaldehyde with sodium hydrogen sulfite or hydroxylamine hydrochloride. These determinations must, however, be carried out quickly and at as low temperature as possible (10-15 °C), otherwise elimination of formaldehyde from the hydroxymethyl compounds already formed can falsify the analysis. The isolation of the soluble condensation products is not possible without special precautions, on account of the facile back-reaction it can be done by pumping off the water in vacuum below 60 °C imder weakly alkaline conditions, or better by careful freeze-drying. However, the further condensation to crosslinked products is nearly always performed with the original aqueous solution. 

Potassium chloride is the most important salt of potassium from the perspective of its abundant occurrence and apphcations. This salt, along with potassium sulfate, is used heavily in fertilizers as the primary source of potassium, an essential element for crops. Over 90% salt manufactured is consumed as fertilizer. Also, potassium chloride is a raw material for producing potassium metal and several important potassium salts including potassium nitrate, potassium hydroxide, and potassium sulfate. Other applications are in electrode cells photography buffer solutions and measurement of salinity in water. 

Sodium acetate is a mordant in dyeing. Other applications are in photography, as an additive to food, in purification of glucose, in preservation of meat, in tanning, and as a dehydrating agent. In analytical chemistry it is used to prepare buffer solution. 

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