Acetic acid buffer solutions

Reagents. In view of the sensitivity of the method, the reagents employed for preparing the ground solutions must be very pure, and the water used should be re-distilled in an all-glass, or better, an all-silica apparatus the traces of organic material sometimes encountered in demineralised water (Section 3.17) make such water unsuitable for this technique unless it is distilled. The common supporting electrolytes include potassium chloride, sodium acetate-acetic acid buffer solutions, ammonia-ammonium chloride buffer solutions, hydrochloric acid and potassium nitrate. 

Reverse phase HPLC describes methods that utilize a polar mobile phase in combination with a nonpolar stationary phase. As stated above, the nonpolar stationary phase structure is a bonded phase—a structure that is chemically bonded to the silica particles. Here, typical column names often have the carbon number designation indicating the length of a carbon chain to which the nonpolar nature is attributed. Typical designations are C8, C18 (or ODS, meaning octadecyl silane), etc. Common mobile phase liquids are water, methanol, acetonitrile (CH3CN), and acetic acid buffered solutions. 

Parkash and Bansal reported the detection and determination of microgram quantities of ethylenediaminetetraacetic acid with molybdophosphoric acid by a spectrophotometric method [25]. For the detection of EDTA, 5 to 10 Amberlite IRA-400 resin beads (hydroxide form) were placed on a white spot-plate and blotted dry. One drop of sample solution was added, followed by one drop of 4% molybdophosphoric acid solution. A blue color develops if EDTA is present. For the determination, the sample solution (2 mL, containing 18.6 to 186 pg of EDTA) and 4% molybdophosphoric acid solution (3 mL) are mixed for 5 minutes and diluted to 10 mL with water or sodium acetate-acetic acid buffer solution of pH 2. The absorbance is measured at room temperature at 690 nm against a reagent blank. 

There are also a number of wet chemical approaches used to isolate NH4 including precipitation with mercuric chloride (Fisher and Morrisey, 1985). This method, however, is problematic with marine samples and generates particularly toxic waste. A newer method converts NH4 in natural waters to N02, via hypobromite, and then to N2O using a sodium azide/acetic acid buffer solution the N2O produced is than analyzed using a mass spectrometer (Zhang et ah 2007). 

Nitrate can also be converted to N02 using cadmium reduction (columns or spongy cadmium) as described above. Once the NOa" is in the form of N02, the N02 can be isolated via organic extraction (e.g., Olson, 1981) or with SPE after the N02 is converted to an azo dye (Kator et al, 1992). Nitrate can be isolated by conversion to N2O via sodium azide in an acetic acid buffer solution (Mcllvin and Altabet, 2005). Another approaches uses a genetically engineered denitrifier to convert N03 to N2O (Sigman et al, 2001) the bacteria wiU denitrify NOa" in a sample to N2O, but lacking nitrous oxide reductase the bacteria cannot take the reaction to completion and form N2. The N2O produced by either approach can then be analyzed on a mass spectrometer. A more detailed discussion of these methods is presented in Chapter 31 by Lipschultz, this volume. 

Fornstedt et al. investigated the thermod5mamics and the mass transfer kinetics of the retention of the enantiomers of R- and S-Propranolol on a system using an acetic acid buffer solution as the mobile phase and the protein CBH I immobilized on silica as the stationary phase. The single-component isotherm of each isomer fitted well to the bi-Langmuir isotherm model... 

Several tests were run to determine the eflBciency and precision of extraction of metal complexes with sodium diethyldithiocarbamate and methyl isobutyl ketone by the following procedure. A single liter solution was prepared to contain 0.25 p.p.m. of the following ferric iron, copper, zinc, cadmium, and lead in 1% hydrochloric acid (V/V). The solution was split into four 250-ml. portions. The concentration of each metal was determined in the normal manner prescribed for aqueous solutions on one portion. The remaining three portions were adjusted to pH 2.5 with an ammonium acetate-acetic acid buffer solution and transferred to 500-ml. separatory funnels. Twenty ml. of a 5% sodium diethyldithiocarbamate solution was added to each sample and shaken. Each solution was then extracted with two 20-ml. portions of methyl isobutyl ketone. The extracts were combined for each sample and diluted to 50 ml. with methyl alcohol. The absorbance of each metal was determined in the three 50-ml. organic solutions. 

The electrochemistry of triazines is well documented.Polak and Volke described a dpp procedure for the determination of symmetrical and asymmetrical triazines (desmetryne, methoprotryne, prometryne, aziprotryne, terbutryne, atrazine, cyanazine, simazine, terbuty-lazine, metribuzine) in water. The herbicides are extracted into chloroform from the sample at pH 8 to 9. The detection limit in 0.02 M H2SO4 or acetic acid buffered solution at pH 2.5 is given as 10 M. 

Eriochrome Cyanine R (C. I. Mordant Blue 3, Solochrome Cyanine R), a triphenylmethane dye, forms, in weakly acid solution, a violet lake with aluminum ions which is the basis of a spot test for the metal, One drop of the acidified sample is placed on a test plate and mixed with one drop each of Na acetate-acetic acid buffer solution (pH 5) and 1 % aqueous Eriochrome Cyanine R. The pH should be 4-6. One drop of NaHSOg solution is added. The formation of a violet color which is stable for 1 minute indicates the presence of aluminum. Iron i salts must first be reduced with ascorbic acid. Ti, Zr and Th ions form colored precipitates which must be centrifuged off. Cu must be masked with thioglycolic acid. 

Pipette an aliquot of the test and blank solutions (maximum 35 cm ) into two separate 50 cm standard volumetric flasks. If the volume added is less than 35 cm then adjust the volume to 35 cm. Add 5 cm of Tiron to each flask and neutralize to Congo red paper with 50% ammonia solution. Add 5 cm of sodium acetate-acetic acid buffer solution (pH 4.7) and dilute to 50 cm with distilled water. 

A spectrophotometric method has been described which depends upon the controlled degradation of penicillin to penicillenic acid. This is carried out by heating with sodium acetate-acetic acid buffer solution of pH 4 6 to which a trace of copper sulphate has been added. In the absence of... 

Mn . Tc. Re. The oxidation of HN3 by an equimolar amount of Mn in aqueous solution yields H, N2, and Mn . The intermediate formation of free radicals induces the polymerization of added acrylonitrile [59]. Kinetic investigations in [59 to 61] failed to completely identify the rate law of the reaction. The reaction becomes faster with increasing concentration of H and is first order in Mn [60, 61]. A second-order dependence in the concentration of HN3 was found in HCIO4 solution [60]. The first-order dependence on the total concentration of azide in an acetic-acid-buffered solution becomes more complicated at [N3]>0.225 mol/L [61]. Earlier results are given in Mangan C 3, 1975, pp. 263/4. 

Electrochemical reduction of iridium solutions in the presence azodye (acid chrome dark blue [ACDB]) on slowly dropping mercury electrode is accompanied by occurrence of additional peaks on background acetic-ammonium buffer solutions except for waves of reduction azodye. Potentials of these peaks are displaced to cathode region of the potential compared to the respective peaks of reduction of the azodye. The nature of reduction current in iridium solutions in the presence ACDB is diffusive with considerable adsorptive limitations. The method of voltamiuetric determination of iridium with ACDB has been developed (C 1-2 x 10 mol/L). 

Hydroxylammonium chloride. 10 per cent aqueous solution, or benzene-1,4-diol (quinol), 1 per cent solution in an acetic acid buffer of pH ca 4.5 (mix 65 mL of 0.1M acetic acid and 35 mL of 0.1M sodium acetate solution). Prepare when required. 

Sodium acetate-acetic acid buffer. Prepare a solution which is 0.2 M in sodium acetate and 0.8 M in acetic acid. The pH is 4.0. 

If the analyte contains either an acidic or a basic functionality, adjusting the pH of the extraction solvent to make the analyte either ionic or nonionic may be advantageous. To make an analyte that contains an acidic or basic functionality nonionic for extraction into a nonpolar solvent, a small amount (5% or less) of an organic acid (such as acetic acid or trifluoroacetic acid) or organic base (triethylamine) along with methanol (about 10%) can be added to diethyl ether or ethyl acetate. Conversely, buffered solutions can be used to control the pH precisely in such a way as to control the charge on an analyte and thus improve its extraction efficiency into polar solvents. 

Palfray and Sabetay246 added an emulsifying agent, Gardinal, to aid in the oxidation of the water-insoluble 1-0-benzylglyceritol. Aqueous solutions of methanol,247 248 ethanol,13 - 249-261 dioxane,74 - 262 266 acetic acid,230 - 266 and acetic acid buffered with lithium acetate164 have been used. The use of lithium periodate or triethylammonium periodate in aqueous alcohol solution has been suggested,267 because of the solubility of these salts in this medium. 

Fig. 8-42. Anodic and cathodic polarization curves observed for electron transfer of hydrated redox particles at an electrode of metallic niobium covered with a thick niobium oxide NbsOs film (12 nm thick) in acidic solution reaction is an electron transfer of hydrated redox particles, 0.25MFe(CN)6 /0.25M Fe(CN)g, in 0.1 M acetic add buffer solution of pH 4.6 at 25 C. =...

The preparations proved to be 98 to 99% chromatographically pure, the contaminant always being the other isomer. The various absorption maxima are reported in Table I. All solutions were 0.01 M in complex. Those designated as HC or HT were measured either in water at pH 5-6, or in O.lM sodium acetate-acetic acid buffer at pH 5.5 (no spectral differences resulted) and those designated C or T were adjusted to pH 10.5 with ethylenediamine. 

Describe how to prepare 100 mL of 0.200 M acetate buffer, pH 5.00, starting with pure liquid acetic acid and solutions containing 3 M HQ and 3 M NaOH. 

Perfetti et al. (131) described a method for the determination of ethoxyquin in milk. Milk solids were precipitated by adding acetonitrile, and the water-acetonitrile supernatant was washed with hexane to remove fat. The addition of NaCl caused the water-acetonitrile solution to separate into an aqueous phase and an acetonitrile phase, thus separating ethoxyquin from most water-soluble impurities. A large volume of water was then added to the acetonitrile layer, and ethoxyquin was partitioned into hexane and removed at reduced pressure. The residue was dissolved in the mobile phase and analyzed on a 250-mm X 4.6-mm-ID. Ultrasphere ODS column using fluorescence detection with excitation of 230 nm, and emission of 418 nm, respectively. A mixture of water and acetonitrile with a diethylamine-acetic acid buffer was the mobile phase. Recoveries from milk samples fortified at 1, 5, and 10 ng/g averaged 78%, with a coefficient of variation of 5.0%. Low concentrations (less than 1 ng/g) of apparent ethoxyquin were detected in commercial milk samples analyzed by this method. 

Samples of freeze-dried fish tissues are extracted with 25% tetramethy-lammonium hydroxide using a microwave digester. After extraction, the pH is adjusted to 4 with acetic acid buffer. A 1% solution of NaBEt4 is added, with some hexane. The solution is shaken for 5 minutes. A fresh portion of NaBEt4 is added, the shaking is repeated, and finally, a third portion is added and allowed to react. The sample is centrifuged and an aliquot of the supernatant hexane is taken for injection into the GC [132],... 

In 1947, Hudson et al. (H15) developed a method for acid phosphatase which, like the procedure of Bessey et al. for alkaline phosphatase (B16), was based upon the use of p-nitrophenyl phosphate as substrate. The buffer substrate solution consisted of equal volumes of a 0.1 M sodium acetate-acetic acid buffer, pH 5.4, and 0.001 M magnesium chloride and of a 0.4% solution of approximately 50% pure disodium p-nitrophenyl phosphate in 0.001 N HCl. To 1 ml of this solution, 0.1 ml of the serum sample was added. The final concentrations in this reaction mixture were 0.045 M acetate buffer, pH 5.4 magnesium chloride. 0.00045 ilf substrate, 0.004 M. The reaction was allowed to run for 30 minutes at 38°C, and the reaction was stopped by the addition of sodium hydroxide. The liberated yellow p-nitrophenol was read at 400 nm and the amount was... 

Sodium nonatungstosilicate is a white solid, which is slightly soluble in water. The solution is metastable at all pH values, but it changes slowly. The best characterization is polarography in 1 M sodium acetate-1 M acetic acid buffer The polarogram shows only one four-electron wave with 1/2 = — 0.80 V versus SCE. The polyanion can be characterized in the solid state by its IR spectrum (KBr pellet, cm ) 985, 940(sh), 930, 865, 848(sh), 808, 712, 552, 530, 490(sh), 435, 373, and 335. 

The potassium /33-undecatungstosilicate is a white solid, which is soluble in water. In solution it slowly converts into the a isomer. It can be characterized by polarography in M sodium acetate-IM acetic acid buffer The... 

The acid and its potassium salt are white solids, which are soluble in water. The polyanion is stable below pH 4.5. It is characterized by polarography of the fresh solution in M sodium acetate-IM acetic acid buffer The polarogram shows two one-electron and one two-electron waves at — 0.24, — 0.48, and — 0.95 V versus SCE, respectively. The UV spectrum in aqueous solution shows e" 2 58 = 47, 000, and e "232 = 19, 200. 

Another spectrophotometric determination of salicylic acid in pharmaceutical formulations using copper acetate as a color developer. Different vol. of salicylic acid solution (10 mg/ml) were mixed with an equal vol. of copper acetate solution and made up to 10 ml with Na acetate acetic acid buffer (pH 5.6 to 6.0). The absorbance of the stable, yellowish-green complex was measured within 30 h at 730 nm (24). 

---