Buffers, borate

Students determine the concentrations of caffeine, acetaminophen, acetylsalicylic acid, and salicylic acid in several analgesic preparations using both CZE (70 mM borate buffer solution, UV detection at 210 nm) and HPLC (C18 column with 3% v/v acetic acid mixed with methanol as a mobile phase, UV detection at 254 nm). 

Catechin and epicatechin are two flavanols of the catechin family. They are enantiomers. The capillary zone electrophoresis (CE) methods with UV-detection were developed for quantitative determination of this flavanols in green tea extracts. For this purpose following conditions were varied mnning buffers, pH and concentration of chiral additive (P-cyclodextrin was chosen as a chiral selector). Borate buffers improve selectivity of separation because borate can make complexes with ortho-dihydroxy groups on the flavanoid nucleus. 

Electrophoretic condition 60 cm (effective length of 50 cm)x75 p.m I.D. fused capillary column, run buffer borate buffer pH 9,0, P-cyclodextrin, electrophoresis voltage 20 kV, detection at 254 nm. 

If the reaction proves difficult the TLC plate should first be dipped in 1 % solution of triethylamine in acetone or in a solution of 1 to 2 drops sodium hydroxid solution (c = 10 mol/1) in methanol to optimize the pH for the reaction. This effect can also be achieved by employing borate buffer, pH = 11, instead of acetone in the spray reagent [10,11]. 

On the other hand, metals such as Ta, Nb, Ti, Zr, Al, etc. (the valve metals ) do not exhibit transpassive behaviour, and in appropriate electrolyte solutions film growth at high fields rather than corrosion and/or oxygen evolution is the predominant reaction thus aluminium can be anodised to 500 V or more in an ammonium borate buffer titanium can be anodised to about 400 V in formic acid and tantalum can be anodised to high voltages in most acids, including hydrochloric acid. 

Acetone powder (1.5 g) was extracted 4 times with 0.1 M sodium borate buffer (pH 7.6) at 4°C, homogenizing each time with a glass grinder equipped with a Teflon pestle. The first extraction was carried out with 80 ml of the buffer, followed by 3 times with 70 ml each of the buffer. Each homogenate was centrifuged at 16,000 g for 5 min. All supernatants were combined. 

Cox et al. (1981) found, as expected, that the trianion of 2,3-dihydroxynaph-thalene-6-sulfonic acid has a higher reactivity than the dianion. They observed a specific catalytic effect of borate buffers, but unfortunately they did not investigate it further. 

Figure 5. Thickness of the anodic passivating film formed on iron at various potentials.6 9 Lbl and Lr, are the thicknesses of the barrier layer and the precipitated layer, respectively. Temperature is 25°C. , in a 150 mol m 3 phosphate buffer solution at pH 1.85 O, in a 300 mol m 3 borate buffer solution at pH 8.2. (From N. Sato, K. Kudo, and T. Noda, Z Phys. Chem. N. F. 98,271,1975, Fig. 5, reproduced with permission and N. Sato, K. Kudo, and R. Nishimura, / Elec-trochem. Soc, 123,1420,1976, Fig. 1. Reproduced with permission of the Electrochemical Society, Inc.)...

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 ... 

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