Citric acid buffer

Testing is undertaken by several methods, including chloroform extraction and use of a sulfonphthalein dye (absorbance of yellow-colored complex using bromophenol blue and bromocresol green) or the use of eosin (sodium tetrabromofluorescein) solution in acetone and tetrachloroethane solvent. After shaking with a citric acid buffer and eosin addition, upon standing the lower layer turns pink if filmer is present. Subsequent titration with Manoxol OT (sodium dioctyl sulfosuccinate) quantifies the filmer, with loss of the pink color indicating the end point. 

Peptides Luminol and ABEI Acridinium- H202 Citric acid buffer (pH 2.7) Luminol- H202 Phosphate buffer (pH 9.9)... 

Metal ions Metals ions-catalyzed luminol- H202 Citric acid buffer (pH 4.5) Online CL detection 20 zmol Co(II) 100 amol Mn(II) 88... 

For the conversion of (15)-(+)-3-carene approximately 0.045 mg mL ( 1.2 /tm) CPO was incubated in 100 mM citric acid buffer, pH 3.5 with 25 % (v/v) tert-butanol containing 10 him (15)-(+)-3-carene (final assay concentration) and 10 him sodium chloride, sodium bromide or sodium iodide (final assay concentrations) in a 50 mL vessel on a magnetic stirrer (300 rpm) at room temperature. Hydrogen peroxide was added to a total concentration of 10 ruM over a reaction time of 60 min at a rate of 165 /iM min (165 portions every minute). 

Remove from oven and allow to cool in the citric acid buffer for 45 min (see Note 7). 

It is difficult to use proteolytic enzyme digestion with this treatment, but if needed, the sections should be digested following the microwave heating because boiling enzymatically digested tissue results in tissue loss. A milder form of this method is to boil the citric acid buffer only and incubate the sections in the preheated solution, or steam, for 15 min, or sections can be heated to 80°C in this buffer and kept overnight with similar results (11). 

The hemoglobin-catalyzed oxidation of o-phenylenediamine to 2,3-diaminophenazine (100), in phosphate-citric acid buffer at pH 5.0, shown in equation 30, is the basis for a kinetic method for determination of H2O2, in a FIA system, measuring at 425 mn by the stopped-flow method. The LOD is 9.2 nM, with RSD 2.08% at 0.5 p,M and linearity in the 50 to 3500 nM range . This colorimetric method was proposed for development as a standard procedure in the Republic of China for determination of H2O2 in foodstuffs . ... 

Citric acid Buffering agent, antioxidant synergist, chelating agent, flavor enhancer On storage, sucrose may crystallize from syrups in the presence of citric acid. Dilute aqueous solutions may ferment on standing. Tart acid taste... 

Eluants.—Citric acid buffered with ammonium citrate is the first eluant to be used in the separation of rare earths by ion exchange process. It is also the most extensively [85—89] investigated eluant. At low pH the individual rare earths move down the column at different rates. A plot of volume of eluted portion vs. concentration shows typical bell-shaped curves (Fig. 2) with widely spaced maxima characteristic of elution chromatography, although the system makes use of a chelating agent. 

The methodologies used to measure color density and polymeric color were developed for fruit juices, which naturally have an acidic pH. If the material to be measured has a pH in the neutral or alkaline range, the pH of the solution should be lowered with a weak acid. In these cases, the authors recommend the use of a 0.1 M citric acid buffer, pH 3.5, instead of distilled water to prepare the different dilutions. 

As in the SETFICS and TALSPEAK processes, the DIAMEX-SANEX/HDEHP process involves selectively back-extracting the trivalent actinides by a hydrophilic polyamino-carboxylate complexing agent, HEDTA, in a citric acid buffered solution (pH 3). However, the combination of HDEHP and DMDOHEMA at high acidity promotes the coextraction of some block transition metals, such as Pd(II), Fe(III), Zr(IV), and Mo(VI), which must be dealt with by specific stripping steps (as described on Figure 3.26) that increase the total volume of the output streams ... 

The An(III) are selectively stripped by HEDTA in a citric acid buffered solution (pH 3), while the Ln(III) are maintained extracted in the organic phase by HDEHP. 

Bulk/injection HPLC Partition between CH2Cl2/citric acid buffer, derivatize with bromo-2-acetonapthone Silica Water-1,3-butanediol- CH2C12 (0.5 7 992) 254 nm USP 23, ISTD-guaifensin, resolved from impurities 15 R-epimer and 5-trans epimer ... 

To prepare the citric acid buffer, sodium hydroxide (NaOH) (16 g) is dissolved in a minimum amount of distilled water in a beaker, cooled, transferred to a 1 1 volumetric flask, and about 900 ml water is added. Citric acid (42 g) is dissolved in this solution, the pH adjusted to 5.0 first with 10 M abd then 1 M NaOH, and the volume adjusted to 1 1 with water. The mixture is then transferred to a reagent bottle and is stored at 5°C in the dark. Ethanol water is prepared by mixing 1 1 water and 1 1 95% ethanol in a 2.5 1 brown glass bottle. 

Triplicate aliquots (0.75 ml) of standard solutions, blanks, and soil extracts are pipetted into labeled 20 ml thick-wall test tubes (15 mm diameter). Citric acid buffer (1.75 ml 0.2 M) is pipetted into each tube. Ninhydrin reagent (1.25 ml) is then pipetted slowly into each tube and vortex-mixed for two seconds. The top of each test tube is loosely covered with aluminum foil and placed in a vigorously boiling water bath for 25 minutes. There should be sufficient water in the bath so that the water level is always above the level of the solutions in the test tubes. The water should return to boiling within 2 minutes of the tubes being placed in the bath. After 25 minutes, the test tube... 

OTFLEXES Figure 3. Haptoglobin separation schematic. A schematic illustrating typical results of a Hp determination run in 8 mm, 10% starch gel prepared with tris citric acid buffer at pH = 8.6. The tank buffer is boric acid, pH — 7.9. The electrophoresis is run at 100 V for 17 hr at 4°C. The Hp-Hb complexes are stained by virtue of the peroxidase reaction of hemoglobin which gives a o color reaction with benzidine. 

Zhang et al. determined ciprofloxacin lactate in injectable solutions by acid dye biphasic titration [5]. A 200 mg dried sample was dissolved in and diluted with water to a volume of 100 mL, and then a 2 mL aliquot of the solution was mixed with 10 mL Na2HP04/citric acid buffer (pH 7) and 15 mL CHC13. This solution was titrated with 0.5 mM-bromothymol blue, with agitation, until a light-blue end-point appeared in the aqueous phase. Recoveries were 99.9-102%, with a relative standard deviation (n = 4) of 0.22-0.24. 

Identification Transfer 1 g of sample and 1 g of potassium metabisulfite to a 100-mL volumetric flask, dissolve in about 50 mL of pH 3.0 Citrate-Citric Acid Buffer (see Assay, below), and dilute to volume with the same buffer. The red color caused by anthocyanins is bleached. 

Assay The color strength (CS) expressed as the absorbance of a 1 % solution in pH 3.0 Citrate-Citric Acid Buffer in a cell of 1 -cm pathlength shall not be less than 90% of the color strength as represented by the vendor. 

Nicotinamide (118) forms the 1,6-dihydropyridine (119) and the 6,6 -dimer (120) upon polarography in aqueous solution. The 4-isomer (121 Scheme 24) generates the aldehyde (122) when reduced in 0.8 M hydrochloric acid and the alcohol (123) in an alcoholic citric acid buffer solution. The thioamides produce the 4-aminomethyl- or 4-cyano-pyridines under related conditions. The isomeric cyanopyridines... 

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