Boric acid-borate buffer

When a pH meter was standardized with a boric acid-borate buffer with a pH of 9.40, the cell emf was +0.060 V. When the buffer was replaced with a solution of unknown hydronium ion concentration, the cell emf was +0.22 V. What is the pH of the solution ... 

SvERRE Stene has measured the pH of a number of phosphate buffer mixtures, biphthalate solutions, and borate buffers with the hydrogen electrode at 150 . He found that the pH of biphthalate-hydrochloric acid solutions at 150° was about 0.2 unit greater than at 20°, the pH of biphthalate-sodium hydroxide mixtures was 0.7 greater than at 20°, while that of boric acid-borate buffers diminished with increasing temperature. Solutions of the latter system with pH s up to 9.0 were 0.5 unit less at 150°, 0.6 unit less for pH 9.2, 0.8 unit less for 9.6, and a whole unit for pH 10.0. Because certain assumptions introduced in his calculations were not entirely justified, these data must be accepted with reserve. Thus the boric acid-borate solutions behave differently from other buffers consisting of a weak acid and one of its salts. Walbum (table, page 250) also has found this diminution of pH with temperature. 

Our buffer preference in kinetic studies has been either 60 toM carbonate-bicarbonate buffer or 12.6 xaM boric acid-borate buffer. The kinetic data have been identical with the use of both buffers. In addition, the pH of the complete digest is the same at the end of the incubation period as when the mixture was put in the incubator, and there is no inhibition detectable at the recommended buffer concentrations. 

Buffers commonly used in clinical and molecular diagnostic laboratories include acetate, boric acid-borate, carbonate-bicarbonate, citrate diethanolamine, glycine-glycinate, phosphate, phthalate, tris(hydroxymethyl) aminomethane, and veronal-sodium veronal, and the so-caUed Good buffers (Table 1-15). 

It is often preferable for physiological purposes to use buffer systems other than the boric acid-borate mixtures. L. Michaelis has found that mixtures of veronal (diethylbarbituric acid) with its sodium salt show a satisfactory buffer action in the neighborhood of pH = 8.0. Pure commercial samples of the sodium salt of veronal are readily available, and may be used frequently without previous recrystallization. Buffer mixtures can be prepared by adding hydrochloric acid to the salt. This compound is water-free, and should suffer no loss in weight when dried at 100°. A 0.1 N solution in water requires exactly an equivalent quantity of 0.1 N hydrochloric acid when neutralized against methyl red. A stock solution should contain 10.30 g. of the sodium salt per 500 c.c. Only carbon dioxide free water should be used. 

At room temperature, the pH of a sodium borate solution is 9.3. The buffering capacity of boric acid-borate solutions was evaluated at 350°C and 3500 psia by measuring the pH change during titrations with sodium hydroxide and hydrochloric acid[13]. The borate buffer titration experiments were conducted at 350°C and 24.1 MPa (3500 psia) where the water density is 0.622 g/mL and the pKa of boric acid is approximately 9.6. The concentration of sodium borate in the feed solutions was fixed at 6.25 X 10 m, which corresponded to a total boron concentration of 0.025 m. At 350°C, the measurable pH ranges of the various optical indicators are 9.0-11.0 for 2-naphthol, 7.0-9.0 for 2-naphthoic acid, 3.0-5.0 for collidine, and 2.0-4.0 for acridine. The indicator 2-naphthol was used to measure pH for the titration of the borate buffer with NaOH which began at pH of 9.5 and ended at 10.5. For the titration with HCl, 2-naphthol, 2-naphthoic acid, and collidine were used in series to measure pH values between 9.5 and 3.0. 

From this material, samples are cut and swelled to constant weight in a buffered saline solution prepared from 8.43 g sodium chloride (NaCl), 9.26 g boric acid (H3BO3), 1.0 g sodium borate (Na3B03), and 0.1 g of the disodium salt of the dihydrate of ethylenediaminetetraacetic acid [Na2 EDTA -(/ 0)21 ini L of distilled water. 

Figure 11 Separation of anti-inflammatories by CZE at various pHs in a 40-cm polyacrylamide-coated (left) and a 70-cm uncoated (right) capillary Experimental conditions 275 V/cm UV = 215 nm buffers 20 mM borate-100 mM boric acid, pH 8.4 (46 pA) 30 mM phosphate-9 mM borate, pH 7.0 (70 pA) 80 mM MES-30 mM Tris, pH 6.1 (20 pA) peak identification 1 = naproxen, 2 = ibuprofen, 3 = tolmetin. (From Wainwright, A., /. Microcol Sep., 2, 166, 1990. With permission.)...

Fig. 17.11. Bottom CGE separation of components of poly U (sigma) in 25% pluronic F127. Top Note the resolution of two contaminants between each of the oligonucleotides from about 15 to 27 nucleotides long in this expanded section of the bottom electropherogram. Electrophoresis was performed in 25% pluronic F127 in tris-borate-EDTA buffer (90 mM tris, 90 mM boric acid, 2 mM Na EDTA, pH 8.3.) (25°C, 500 V cm-1, effective column length 30 cm). Reprinted with permission from Ref. [82],...

Buffers contain mixtures of weak acids and their salts (i.e., the conjugate bases of acids), or mixtures of weak bases and their conjugate acids. Typical buffer systems used in pharmaceutical dosage forms include mixtures of boric acid and sodium borate, acetic acid and sodium acetate, and sodium acid phosphate and disodium phosphate. The reason for the buffering action of a weak acid, HA (e.g., acetic acid) and its ionized salt, A" (e.g., sodium acetate) is that A" ions from the salt combine with the added hydrogen ions, removing them from solution as undissociated weak acid. 

What molar ratio of acid to salt is required to adjust the pH of a solution to 8.8 using boric acid-sodium borate buffer ... 

What molar ratio of salt/acid (sodium borate to boric acid) is required to prepare a buffer solution having a pH of 9.6 The pKa of boric acid is 9.24 at 25°C. 

Purification of murine antiheparin monoclonal antibody produced in cell culture was monitored by Malsch et al.63 using a CZE method with a borate or boric acid buffer (pH 9) in an uncoated capillary. 

Sodium borate buffer 0.2 M boric acid, 160 uiM NaCl, pH 8.5. 

The two lower pH levels were phosphate buffers whereas the 8.6 buffer consisted of a boric acid, sodium borate system. The buffers showed no reaction with pretreatment chemicals used, and had sufficient buffer capacity to maintain constant pH during experiments of long duration. 

Tris-borate-EDTA (TBE) buffer (lOx solution) 0.89 M TRIZMA base, 0.89 M H3BO3,20 mM EDTA. Per liter 108 g TRIZMA base, 55 g boric acid, 40 ml 0.5 M ethylenedi-aminetetraacetate (EDTA) solution. 

Buffers of boric acid are useful in the pH range 8.5 to 10. Borate has the major disadvantage of complex formation with many metabolites, especially carbohydrates. 

Borate buffer 0. M boric acid solution adjusted to pH 8 0 with NaOH... 

Ophthalmic Granulocyte colony stimulating factor HPLC Borate buffer (1.71 g boric acid/0.265 g borate) H20/100 ml, extract with light petroleum, residue dissolved in EtOH Silica -Hexane-EtOAc (98 2), 1 ml/min 600 nm [509]... 

Buffer (borate) solution pH 7j. Dissolve 2.5 g of sodium chloride R, 2.85 g of disodium tetraborate R, and 10 J g of boric acid R in water and dilute to 1000.0 mL with the same solvent Adjust the pH if necessary,... 

The supporting electrolyte for all free-solution separations reported here was a borate buffer (pH 8.1 or 8.26, 0.10 M or 0.20 M), prepared from reagent-grade sodium borate decahydrate and boric acid (J.T Baker). 

Electrophorese a 5 m1 sample of the above digest in parallel with 4m1 of the untreated RFI solution on a 1% agarose gel in tris-borate buffer (lOOmM-Tris base, lOOmM-boric acid, 2 mM-EDTA). Dilute each sample into 15 m1 H20 and add 3m1 loading buffer (3% bromophenol blue in 0.1M-EDTA, pH 8.3, 50%... 

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