Ammonia buffer containing

The electrochemical behavior of nimodipine was studied in ammonia buffer containing 10% (v/v) ethanol [8]. A single-sweep oscillopolaro-graphic method was then developed for nimodipine in tablets. The calibration graph (peak current at —0.73 V vs. concentration) was linear from 0.2 to 70 pM, and the detection limit was 10 pM. The same authors applied linear sweep voltammetry for the determination of nimodipine in tablets [9]. A reduction peak at —0.62V vs. the Ag/ACl reference... 

Figure 11.3 Typical features and behavior of traditional or new carbon pastes and the respective electrodes in current flow measurements, (a-d) Cyclic voltammetry of [Fe(CN)g]3/ - in 0.1 M KCI, c(Fe) = 5mM, lighter line, GCE (a,b) or GC-IL (c,d), hitherto unpublished records (e) Adsorptive stripping voltammetry of Ni" at the low parts per billion level in 0.1 M ammonia buffer containing 10 iM DMG (dimethyl glyoxime)H-Hg". Legend curve (1) blank, (2) c(Ni") = 5ppb, and (3) c(Ni") = 10 ppb. Note symbol Oj denotes the reductive response of oxygen...

Note All Erlenmeyer and volumetric flasks used in this experiment must be rinsed thoroughly with distilled water prior to use. Ordinary tap water contains hardness minerals that will contaminate. The pH = 10 ammonia buffer required can be prepared by dissolving 35 g of NH4C1 and 285 mL of concentrated ammonium hydroxide in water and diluting to 500 mL. The EBT indicator should be fresh and prepared by dissolving 200 mg in a mixture of 15 mL of triethanolamine and 5 mL of ethyl alcohol. 

Let s try another one. What is the pH of a buffer containing 0.25 M ammonia and 0.75 M ammonium chloride Well, the weak acid in this case is the ammonium ion. The chloride ion is a spectator to be ignored. Ammonia is a weak base, and the conjugate base of the ammonium ion. So, since this solution contains a weak conjugate acid-base pair, it is a buffer, and we can calculate the pH using the Henderson-Hasselbach equation. The Henderson-Hasselbach equation calls for the pKa of the acid so in this case, we need the pfor the ammonium ion. The pKh for ammonia is 4.74, so the pKa for the ammonium ion is 9.26. If we substitute this value and the values for the concentrations into the buffer equation, we find the pH of this solution is 8.78. 

Determination of Cd. Re-extract Cd from the extract obtained above by shaking (30 s) with 5 ml of the ammonia buffer, and then with 5 ml of water. To these aqueous solutions (in a 25-ml standard flask) containing not more than 15 pg of Cd, add 10 ml of ethanol, 2 ml of 5-Br-PADAP solution, dilute with water to the mark, mix well, and measure the absorbance of the solution at 556 nm vj. a reagent blank solution. 

A solution hydrazine (100 mM) in 0.2 M CH3COONa buffer containing 1 mM of [Ru "(HL)(H20)] was electrolyzed at -0.05 V vs SCE in order to estimate the catalytic activity of Ru -EDTA through its hydrazinium complexes for the reduction of hydrazine to ammonia. As expected, hydrazine was only reduced to NH3 justifying the first step as a multi-electron reduction wave. The plot of moles of NH3 produced per mole of complex vs the electrolysis time was linear (Figure 4a). From the slope of the plot, the turnover rate was calculated tmd found to be 18.4 moles of ammonia per mole of catalyst per hour. While phenylhydrazine was electrolyzed under identical conditions at -0.200 V vs SCE, it reduced to equimolar ratio of ammonia and aniline The plot of moles of ammonia produced per mole of catalyst (Figure 4b) was linear and the turnover number was found to be 5.98. In both cases, 100% coulombic efficiency was observed. 

As a first example, let us consider the kinds of information that are contained in the sampled-current voltammogram for the reversible reduction of a complex ion, such as Zn(NH3)4 in an aqueous ammonia buffer at a mercury drop electrode, ... 

Because it is based on UV absorption, the use of ninhydrin is the least sensitive method for the determination of amino acids. It also has the disadvantage that the reaction coil must be heated to 130°C in order for the postcolmnn chemistry to occur in the minimmn amovmt of time. In addition, the reagent reacts with ammonia, which leads to baseline instability if buffers containing trace ammonia are employed to make up the mobile phase. 

Polyethylene catheters were surface primed either with chromic acid solution or with oxygen plasma treatment, then dipped into a 0.6 % chitosan solution in 1 % acetic acid. After drying, the catheters were exposed to ammonia and then soaked in a pH 7.0 phosphate buffer containing 1 % heparin. About 40 yg of chitosan were deposited per square cm. The heparinization procedure added 2-3 units of heparin per square cm. This heparin can be removed by soaking in 25 % sodium chloride, however, if the heparinization is performed in the presence of sodium cyanoborohydride, the brine removes only a minor part of heparin. Negligible amounts of the coating were removed by blood at 37°C after 24 hr contact. 

In polarographic practice the most important reference electrodes are separated calomel electrodes, a mercurous sulphate electrode, or, especially for small volumes, a silver chloride electrode immersed into an electrolysed solution containing OT M chlorides. This electrode proved satisfactory over the pH-range 1-13 when sodium or potassium chloride was added to the buffer solutions. Measurements in solutions forming complexes with silver e.g. glycine, veronal or ammonia buffers are precluded. The use of this electrode eliminates the uncertainty concerning the liquid junction potential. 

Exercise 1 Calculate the curve obtained during the titration of 50 ml of a solution containing 10 mol/L of magnesium cation in a 0.10 mol/L ammonia buffer at pH = 10 with a 10 mol/L EDTA solution. Calculate the sharpness index. 

To 100 ml of a neutral solution containing about 20 mg of manganese add a small amount of hydroxylamine hydrochloride to prevent oxidation of the manganese. Then add 10 ml of ammonia buffer solution followed by 3 to 5 drops of catechol violet indicator and titrate immediately with 0 01 M EDTA until the colour changes from greenish-blue to reddish-purple. 1 ml O OIM EDTA = 0 0005493 g manganese. 

For phenols giving aminophenazone dyes insoluble in chloroform. Transfer a suitable aliquot of a prepared solution containing 0 2 to 0-4 mg of the phenol to a 50-ml graduated flask and add 1 ml of 4-aminophenazone solution. Wash in with dilute ammonia buffer to give a volume of about 45 ml, mix, add 1 ml of a freshly prepared 8 per cent solution of potassium ferricyanide and dilute to volume with the dilute buffer. IVIix and measure the extinction, as rapidly as possible, at the absorption maximum, using 1-cm cells with, in the comparison cell, a suitable aliquot of the prepared solution, diluted to 50 ml with dilute ammonia buffer. 

The examination of peanut meal extract, arachin, and conarachin in ammonia buffer, m = 0.1, pH 9.26, has been reported (81,106). The meal extract which contains about 98% of the protein is composed of one major component and two minor components. Arachin which represents about 63 % of the protein is composed of two components in a ratio of about 3 to 1. Conarachin which represents about 33% of the protein is composed of two components in a ratio of about 4 to 1. These data are summarized in Table IV. 

A buffer contains significant amounts of ammonia and ammonium chloride. Write equations showing how this buffer neutralizes added acid and added base. 

Practice Examples la. [H3 O ] = 0.018 M, [HF] = 0.482 M. [H3O+] = 0.103 M, [HF] = 0.497 M. lb. 30 drops 2a. [H3 0+ ] = 12 X Iff M, [HCOO] = 0.150 M. 2b. 15 g NaCH3COO 3a. The hydronium ion and the acetate ion react to form acetic acid. All that is necessary to form a buffer is to have approximately equal amounts of a weak acid and its conjugate base together in solution. This will be achieved if we add an amount of HCl equal to approximately half the original amount of acetate ion. 3b. HCl dissociates essentially completely in water and serves as a source of hydronium ion. This reacts with ammonia to form ammonium ion. Because a buffer contains approximately equal amounts of a weak base H3) and its conjugate acid (NH4 ), to prepare a... 

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