Sodium citrate buffer

Sodium benzoate is used as a broad-spectrum antimicrobial, inhibiting bacteria, molds, and yeasts. The high acid content of the soft drink is necessary for the preservative action. Sodium citrate buffers the acids, so the pH stays low (acidic). It also emulsifies any fats or fat-soluble compounds in the flavorings, keeping them in solution. 

Figure 17.7 Electrocatalysis of O2 reduction by Pycnoporus cinnabarinus laccase on a 2-aminoanthracene-modified pyrolytic graphite edge (PGE) electrode and an unmodified PGE electrode at 25 °C in sodium citrate buffer (200 mM, pH 4). Red curves were recorded immediately after spotting laccase solution onto the electrode, while black curves were recorded after exchanging the electrochemical cell solution for enzyme-fiiee buffer solution. Insets show the long-term percentage change in limiting current (at 0.44 V vs. SHE) for electrocatalytic O2 reduction by laccase on an unmodified PGE electrode ( ) or a 2-aminoanthracene modified electrode ( ) after storage at 4 °C, and a cartoon representation of the probable route for electron transfer through the anthracene (shown in blue) to the blue Cu center of laccase. Reproduced by permission of The Royal Society of Chemistry fi om Blanford et al., 2007. (See color insert.)...

Figure 6 Separation of amino acids on conventional ion exchange Beckman 120B Amino Acid Analyzer. Column 15 cm. Eluent 0.35 M sodium citrate buffer, pH 5.28. Flow rate 30 ml/hr. Temperature 50°C. Note that the separation requires approximately 6 hours. Compare to a modern separation shown in Figure 7. (Reproduced with permission from Beckman Instruments Fullerton, CA.)...

Immerse the tissue blocks in a retrieval solution (distilled water or 10 mM sodium citrate buffer, pH 6.0) at 4°C overnight. 

Fig. 2 PL spectra of II with complementary SSDNA3-FI/SSDNA4 (red) and noncomplementary ssDNA3-F1/ssDNA5 (black) in saline-sodium citrate buffer. The spectra were normalized to the polymer emission [50]...

However, it is not only the pH of the eluting buffer that determines the relative elution position of the amino acids, but also the cation concentration of the buffer. Sodium citrate buffer solutions are commonly used and the positive sodium ions compete with the positively charged amino acids for the sul-phonic acid sites on the resin ... 

Sulfur Dioxide Vapor Pressure and pH of Sodium Citrate Buffer Solutions with Dissolved Sulfur Dioxide... 

Heat of Reaction of H+ with Concentrated Sodium Citrate Buffers... 

Temperature dependence of pH and PsO / HoO over sodium citrate buffer solutions is insignificant. 

Thioanisole (6.2 mg, 50 /imol) and CPO (67.4 U) were magnetically stirred at room temperature in a 10 mL test tube for 5 min in 2 mL of a mixture of ionic liquid-sodium citrate buffer solution (0.1 m, pH 5). A 1 1 mixture was used in the case of [Nni20H][Citr] and [mmimHCHsSOJ, whereas a 0.6 1.4 mixture was employed in the case of [Nni20H][OAc]. Hydrogen peroxide solution (7 wt%) was added in two portions initially 50 pmo and then an additional 25 /imol after 2 h. After 4 h the reaction was quenched by the addition of excess Na2S203. 

The reaction performed in the 1 1 mixture of [mmim][CH3S04]/sodium citrate buffer has been scaled up 50 times without any change in chemo- and enantio-selectivity. The crude reaction mixture was purified by chromatography on silica gel (hexane/ethyl acetate 6 1-1 1) to give pure phenyl methylsulfoxide (yield 70 %, ee 99 %). 

The observation that improved remote loading of ciprofloxacin could be achieved using ammonium sulfate solutions rather than sodium citrate buffers highlighted the need for further investigation and development of drug-loading methodologies. In this section, we examine an approach in... 

Scheme 10.3 Ceramide glycanase mediated release by transglycosylation. a) Pd/C, MeOH b) (8), EEDQ, EtOH-CgHe c) MeONa d) CH2=CHCONH2, TMEDA, APS, DMSO-H2O, 50"C, CMP-NeuAc, a-2,3-sialyltransferase, BSA, MnCb, CIAP, 50 nM sodium cacodylate buffer, pH 7.49, ceramide, Triton CF-54, sodium citrate buffer, pH 6.0, 37°C, 61%.

Koch-Light 1887-00 oat-spelt xylan (Lot 90560) was split into soluble and insoluble fractions by dissolving it in 0.05A/, pH 6.05 sodium citrate buffer and centrifuging out Ae unAssolved material. The msoluble portion was suspended in Ae buffer in roughly 1% concentration and was assayed wiA an equal volume of Xylanase II in... 

Essentially pure xylo-oligosaccharides in 0.5% concentration were incubated with Xylanase II at 50°C in 0.05M sodium citrate buffer, pH 5.0 for X5 through X7 and pH 6.05 for Xg and X9, and samples after varying periods were submitted to HPLC. With X5, X2 and X3 were the major products, with smaller amounts of X4 and D-xylose produced. Incubation of gave X3 as the major product, followed by X4 and X2. With prolonged incubation the X4 was consumed to form X2 and smaller amounts of D-xylose and X3. Hydrolysis of X7 led to the formation of X4 and X3, with smaller amounts of X5, and X2, and a very small amount of Xg. Tlie course... 

RPC has found use in the analysis of barbiturates including the determination of drugs taken in an overdose (332). Thiopental was determined using a mobile phase comprised of methanol-0.1% sodium citrate buffer, pH 6.5 (45 55) (333). Hydantoins, along with other species which have anticonvulsant activity, have been determined with barbiturates. These include phenytoin in the presence of phenobarbital and primidone (334,335) and the related anticonvulsants ethosuximide and carbamazepine (336). 

Following intravenous injection of 0-2.8 pCi/kg (104,000 Bq/kg) thorium-227 in a solution of citric acid-sodium citrate buffer in dogs, an increase in serum alkaline phosphatase measurements and hypoalbuminemia and hyperglobulinemia were observed (Stevens et al. 1967). No effects on the levels of serum glutamic pyruvic transaminase (SGPT) or serum glutamic oxaloacetic transaminase (SGOT) were found. 

Amino Acid Analyses. Samples of native and ozonized lysozymes were hydrolyzed in evacuated, sealed tubes with 6N hydrochloric acid at 110 C for 24 hr. After being cooled to room temperature, the solution was adjusted to pH 2 with NaOH solution and brought to mark in a volumetric flask with sodium citrate buffer pH 2.3. A portion containing a suitable amount of the amino acids was applied to a Beckman 12OB amino acid analyzer. 

The mixed lanthanide (III) ions (Ln3+) can be absorbed from solution at the top of a column of a cation-exchange resin RSOsNa (Section 14.4) and then selectively eluted from it, that is, swept down the column in bands by a stream of a solution of a substance that competes with the Ln3+ for sites in the resin. An acidic tribasic chelating agent H3X (usually citric acid/sodium citrate buffer) is used so that, as in reaction 17.16, the tendency for a specific Ln3+ to form neutral LnX and so escape the electrostatic... 

Figure 3. Spinco amino acid chromatogram of H2SO4 extract of MarceUus shale run in sodium citrate buffer column 1 to right eluted 2Yz hours at pH 3.25, then 2l/s hours at pH 4.25, [Na], 0.2N column 2 to left eluted with pH...

Overall crude cellulase activity was measured using Remazol brilliant blue acid-swollen cellulose (cellulose-azure, Calbiochem.) (22). The assay consists of combining 40 mg cellulose azure, 1.0 mL of lOOmM sodium citrate buffer (pH 4.8), and 1.0 mL of enzyme solution and... 

Enzyme activity towards carboxylmethyl cellulose (CMC) was measured by combining 50 fiL enzyme with 0.5 mL of 0.5% CMC in pH 4.8 sodium citrate buffer and incubating at 50°C for 10 min. After this, the reaction was stopped by addition of 1.5 mL dinitrosalicylic acid reagent and the resultant color, which was measured at A54onm, related to the reducing sugar concentration. 

Avicel was first incubated with Cx at 50 °C for 30 min liquids were removed by centrifugation. Pretreated Avicels were then washed with high-salt buffer (0.5 Af NaCl) followed by sodium citrate buffer. The Avicels were then digested by enzymes as indicated. 

In the reversed phase system, buffers are used most often as the mobile phases with small amount of organic modifiers. The use of buffers as the mobile phases has increased the efficiency of the resolution. Ammonium nitrate, triethylammonium acetate (TEAA), and sodium citrate buffers have been used very successfully. A variety of organic modifiers have been used to alter selectivity [2,5,22], Acetonitrile, methanol, ethanol, 2-propanol, and THF have shown good selectivities for various analytes. In the reversed-phase mode, the amount of organic modifiers is typically low, usually of the order of 10-20%. The typical starting composition of the mobile phase is an organic modifier-buffer... 

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