C Buffer Solutions

It has become fairly common to adopt the manufacture of combinations of internal reference electrode and its inner electrolyte such that the (inner) potential at the glass electrode lead matches the (outer) potential at the external reference electrode if the glass electrode has been placed in an aqueous solution of pH 7. In fact, each pH glass electrode (single or combined) has its own iso-pH value or isotherm intersection point ideally it equals 0 mV at pH 7 0.5 according to a DIN standard, as is shown in Fig. 2.11 the asymmetry potential can be easily eliminated by calibration with a pH 7.00 0.02 (at 25° C) buffer solution. 

Fig.l. Schematic diagram of the flow-through biosensor for the determination of H202 (a) sample (b) luminol (c) buffer solution P peristaltic pump V injection valve F flow cell immobilized HRP and Au nanoparticles D detector PC ... 

Figure 5. Experimental measurement of porous silicon waveguide resonance after several functionalization steps and exposure to either (a) complimentary DNA, (b) non-complimentary DNA, or (c) buffer solution. The small shift due to DNA hybridization is easily within the resolution of the prism coupler rotation stage of0.002°. (d) Histogram summarizing the selectivity of the porous silicon waveguide sensor to 24 base pair DNA. DNA hybridization (complimentary DNA shift) can be clearly distinguishedfrom the low level of non-specific binding (mismatch DNA shift) and the noise floor of the measurement system...

Table 8.18 pH Values for Buffer Solutions in Alcohol-Water Solvents at 25°C 8.109... 

To prepare the standard pH buffer solutions recommended by the National Bureau of Standards (U.S.), the indicated weights of the pure materials in Table 8.15 should be dissolved in water of specific conductivity not greater than 5 micromhos. The tartrate, phthalate, and phosphates can be dried for 2 h at 100°C before use. Potassium tetroxalate and calcium hydroxide need not be dried. Fresh-looking crystals of borax should be used. Before use, excess solid potassium hydrogen tartrate and calcium hydroxide must be removed. Buffer solutions pH 6 or above should be stored in plastic containers and should be protected from carbon doxide with soda-lime traps. The solutions should be replaced within 2 to 3 weeks, or sooner if formation of mold is noticed. A crystal of thymol may be added as a preservative. 

Weber, P. L. Buck, D. R. Capillary Electrophoresis A Past and Simple Method for the Determination of the Amino Acid Composition of Proteins, /. Chem. Educ. 1994, 71, 609-612. This experiment describes a method for determining the amino acid composition of cyctochrome c and lysozyme. The proteins are hydrolyzed in acid, and an internal standard of a-aminoadipic acid is added. Derivatization with naphthalene-2,3-dicarboxaldehyde gives derivatives that absorb at 420 nm. Separation is by MEKC using a buffer solution of 50 mM SDS in 20 mM sodium borate. 

Aqueous solutions of citric acid make excellent buffer systems when partially neutralized because citric acid is a weak acid and has three carboxyl groups, hence three p-K s. At 20°C pifj = 3.14, pi 2 4.77, and = 6.39 (2). The buffer range for citrate solutions is pH 2.5 to 6.5. Buffer systems can be made using a solution of citric acid and sodium citrate or by neutralizing a solution of citric acid with a base such as sodium hydroxide. In Table 4 stock solutions of 0.1 Af (0.33 N) citric acid are combined with 0.1 Af (0.33 N) sodium citrate to make a typical buffer solution. 

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). 

Distribution of benzodiazepines in I-octanol - water system was investigated by a direct shake flask method at the presence of the compounds used in HPLC mobile phases the phosphate buffer with pH 6,87 (substances (I) - (II)), acetic and phosphate buffer, perchloric acid at pH 3 (substances (III) - (VI)). Concentrations of substances in an aqueous phase after distribution controlled by HPLC (chromatograph Hewlett Packard, column Nucleosil 100-5 C, mobile phase acetonitrile - phosphate buffer solution with pH 2,5, 30 70 (v/v)). 

Fig. 2-19 Time to failure vs. potential for X70 pipeline steel in pH 5.5 buffer solution containing 150 mg L sulfide ions at various loads, 15°C = -0.53 V...

Apply indole derivatives dissolved in sodium bo- [105] rate buffer solution (c = 0 2 mol/1, pH 9 0) — ethanol (1 -I-1) Dip TLC plate in fluorescamine solution to just above starting zone (15 s) Then dry at room temperature and develop In case of indole amines followed by spraying with 40% perchloric acid... 

Citrate buffer solution Dissolve 210 g citric acid in 400 ml caustic soda solution (c = 5 mol/1) and make up to 11 with water. Mix 530 ml of this solution with 470 ml caustic soda solution (c = 1 mol/1) and adjust to pH 6.6 with caustic soda solution or citric acid [1]. 

Note The pre- and post-treatment of the chromatograms with the basic tri-ethylamine solution, which can be replaced by an alcoholic solution of sodium hydroxide [1,4] or a phosphate buffer solution pH = 8.0 (c = 0.2 mol/1) [5], serves to stabilize the fluorescence of the amino derivatives [2]. A final spraying with methanolic hydrochloric acid (chci = 5 mol/1) or 70% perchloric acid renders the detection reaction highly specific for histamine [4] and for catecholamines and indolamines [5]. 

FIGURE l.l Hydrophobic interaction and reversed-phase chromatography (HIC-RPC). Two-dimensional separation of proteins and alkylbenzenes in consecutive HIC and RPC modes. Column 100 X 8 mm i.d. HIC mobile phase, gradient decreasing from 1.7 to 0 mol/liter ammonium sulfate in 0.02 mol/liter phosphate buffer solution (pH 7) in 15 min. RPC mobile phase, 0.02 mol/liter phosphate buffer solution (pH 7) acetonitrile (65 35 vol/vol) flow rate, I ml/min UV detection 254 nm. Peaks (I) cytochrome c, (2) ribonuclease A, (3) conalbumin, (4) lysozyme, (5) soybean trypsin inhibitor, (6) benzene, (7) toluene, (8) ethylbenzene, (9) propylbenzene, (10) butylbenzene, and (II) amylbenzene. [Reprinted from J. M. J. Frechet (1996). Pore-size specific modification as an approach to a separation media for single-column, two-dimensional HPLC, Am. Lab. 28, 18, p. 31. Copyright 1996 by International Scientific Communications, Inc.. Shelton, CT.]... 

An amount of enzyme preparation equivalent to 900 mg of wet cells was made up to 25 ml with the above potassium phosphate buffer solution. 150 mg (1.15 mmol) of 5-fluorouracil and 1.0 gram of thymidine (4.12 mmol) were dissolved in 15 ml of the above potassium phosphate buffer solution. The mixture was incubated at 37°C for 18 hours. After this time, enzyme action was stopped by the addition of four volumes of acetone and one volume of peroxide-free diethyl ether. The precipitated solids were removed by filtration, and the filtrate was evaporated under nitrogen at reduced pressure until substantially all volatile organic solvent had been removed. About 20 ml of aqueous solution, essentially free of organic solvent, remained. This solution was diluted to 100 ml with distilled water. 

A) A solution of (SMI (320 mg) in trifluoroacetic acid (7 ml) was kept under nitrogen at room temperature for 15 minutes. Ether (100 ml) was added and the precipitate filtered, washed thoroughly with ether and dried. This material (280 mg) was added to concentrated sulfuric acid (20 ml), cooled at -20°C. The solution was kept in the dry ice-acetone bath at -20°C for 75 minutes. The sulfuric acid solution was poured into ice water (80 ml). The precipitate was centrifuged, resuspended in ice water (30 ml) and 4N sodium hydroxide was added until a clear solution was obtained. After reacidification to pH 4 with dilute sulfuric acid, the precipitate formed was centrifuged, washed twice with ice water and dried. Yield 155 mg. Chromatograph of DEAE Sephadex (with ammonium carbonate buffer) yielded the desired octa-peptide sulfate ester 30 mg. 

Figure 2 Stability of /3-poly(L-malate) measured by its activity to inhibit purified DNA polymerase a of P. polyceph-alum. The relative degree of inhibition is shown (100 rel. units refer to complete inhibition). The DNA polymerase assay was carried out in the presence of 5 /tg/ml /S-poly(L-malate) as described [4]. The polymer was preincubated for 7 days at 4°C in the following buffer solutions (50 mM) KCl/HCl (—A—). Citrate (—V—). 2-(A/-Morpholino)-ethanesulfonic acid, sodium salt (—O—). Sodium phosphate (— —). N-(2-Hydroxyethyl)piperazine-N -(2-ethanesul-fonic acid), sodium salt (— — ). N,N-b s (2-Hydroxyethyl)-glycine, sodium salt (—T—). Tris/HCl (— —). 3-(Cyclo-hexylamino)-l-propanesulfonic acid, sodium salt (— —).

Because the ionic product of water = [H ] [OH ] = 1.04 x 10" at 25°C, it follows that pH = 14 - pOH. Thus, a neutral solution (e.g., pure water at 25°C) in which [H j = [OH ] has a pH = pOH = 7. Acids show a lower pH and bases a higher pH than this neutral value of 7. The hydrogen ion concentrations can cover a wide range, from -1 g-ion/liter or more in acidic solutions to -lO" " g-ion/liter or less in alkaline solutions [53, p. 545]. Buffer action refers to the property of a solution in resisting change of pH upon addition of an acid or a base. Buffer solutions usually consist of a mixture of a weak acid and its salt (conjugate base) or of a weak base and its salt (conjugate acid). 

Pipette 25 mL of the solution containing magnesium, manganese and zinc ions (each approx. 0.02M), into a 250 mL conical flask and dilute to 100 mL with de-ionised water. Add 0.25 g hydroxylammonium chloride [this is to prevent oxidation of Mn(II) ions], followed by 10 mL of the buffer solution and 30-40 mg of the indicator/potassium nitrate mixture. Warm to 40 °C and titrate (preferably stirring magnetically) with the standard EDTA solution to a pure blue colour. 

Procedure. Place 25 mL of an aqueous solution of the amine, 10 mL of solution C and 1 mL of buffer solution in a 100 mL stoppered conical flask the amount of amine should not exceed 10 g. After 1 minute add 10 mL chloroform and stir on a magnetic stirrer for 15-20 minutes. Transfer to a... 

APPENDIX 4 SATURATED SOLUTIONS OF SOME REAGENTS AT 20°C 829 APPENDIX 5 SOURCES OF ANALYSED SAMPLES 830 APPENDIX 6 BUFFER SOLUTIONS AND SECONDARY pH STANDARDS 830 APPENDIX 7a DISSOCIATION CONSTANTS OF SOME ACIDS IN WATER AT 25°C 832 APPENDIX 7b ACIDIC DISSOCIATION CONSTANTS OF SOME BASES IN WATER AT 25°C 833... 

Fig. 3.1.6 Effects of pH on the activity and stability of Cypridina luciferase (solid lines) and the quantum yield of Cypridina luciferin (dashed line). In the measurements of activity and quantum yield, luciferin (1 pg/ml) was luminesced in the presence of luciferase (a trace amount for the activity measurement 20 pg/ml for the quantum yield) in 20 mM buffer solutions of various pH containing 0.1M NaCl, at 20°C. In the stability measurement, luciferase (a trace amount) was left standing in 0.1 ml of the buffer solutions of various pH for 30 min at 20°C, then the activity was measured by adding 1 ml of 50 mM sodium phosphate buffer, pH 6.5, containing 0.1 M NaCl and 1 pg of luciferin, at 20°C. The activity and stability data are taken from Shimomura et al., 1961, with permission from John Wiley 8c Sons Ltd.

Fig. 3.3.2 Influence of pH on the activity of luciferase ( ) and the quantum yield of coelenterazine (o) in the bioluminescence of Oplophorus. The measurements were made with coelenterazine (4.5 pg) and luciferase (0.02 pg) for the former, and coelenterazine (0.1 pg) and luciferase (100 pg) for the latter, in 5 ml of 10 mM buffer solutions at 24° C. The buffer solutions used sodium acetate (pH 5.0), sodium phosphate (pH 6.0-7.5), Tris-HCl (pH 7.5-9.1), and sodium carbonate (pH 9.5-10.5), all containing 50 mM NaCl. Replotted from Shimomura et al., 1978, with permission from the American Chemical Society.

Fig. 4.1.4 Influence of pH on the total light emission and initial light intensity of aequorin. Buffer solutions containing 0.1 mM calcium acetate, 0.1 M NaCl, and 10 mM sodium acetate (for pH < 7) or 10 mM Tris-HCl (for pH > 7) were adjusted to various pH with acetic acid or NaOH, and then 2 ml of the solution was added to 3 pi of aequorin solution containing 1 mM EDTA to elicit luminescence, at 22°C. The data shown are a revision of Fig. 9 in Shimomura et al., 1962. The half-total time is the time required to emit 50% of total light.

Fig. 4.1.8 Influence of various calcium chelators on the relationship between Ca2 " concentration and the luminescence intensity of aequorin, at 23-25°C (panel A) in low-ionic strength buffers (I < 0.005) and (panel B) with 150 mM KC1 added. Buffer solutions (3 ml) of various Ca2+ concentrations, pH 7.05, made with or without a calcium buffer was added to 2 pi of 10 pM aequorin solution containing 10 pM EDTA. The calcium buffer was composed of the free form of a chelator (1 or 2mM) and various concentrations of the Ca2+-chelator (1 1) complex to set the Ca2+ concentrations (the concentration of free chelator was constant at all Ca2+ concentrations). The curves shown are obtained with 1 mM MOPS (A), 1 mM gly-cylglycine ( + ), 1 mM citrate (o), 1 mM EDTA plus 2mM MOPS ( ), 1 mM EGTA plus 2 mM MOPS ( ), 2 mM NTA plus 2 mM MOPS (V), and 2 mM ADA plus 2 mM MOPS (A). In the chelator-free buffers, MOPS and glycylglycine, Ca2+ concentrations were set by the concentration of calcium acetate. Reproduced with permission, from Shimomura and Shimomura, 1984. the Biochemical Society.

Fig. 4.1.14 Relationship between Ca2+ concentration and the initial light intensity of various recombinant semisynthetic aequorins and w-aequorin J (a semisynthetic natural aequorin made from isoform J). The curve number corresponds to the number of semisynthetic aequorin used in Table 4.1.4. A sample aequorin (3 (Ag) was in 3 ml of calcium-buffer solution containing 1 mM total EGTA, 100 mM KC1,1 mM Mg2+ and 1 mM MOPS (pH 7.0), at 23-24°C. From Shimomura etal., 1993a, with permission from Elsevier.

Fig. 4.5.5 Effect of pH on the luminescence of coelenterazine catalyzed by Periphylla luciferases A, B and C, and on the stability of the luciferases. The effect on light intensity (solid lines) was measured in 3 ml of 50 mM phosphate buffers, pH 4.1-7.25, and 50 mM Tris-HCl buffers, pH 7.1-9.7, all containing 1 M NaCl, 0.025% BSA, and 0.3 pM coelenterazine. To measure the stability (dotted lines), a luciferase sample (5 pi) was left standing for 30 min at room temperature in 0.1 ml of a buffer solution containing 1 M NaCl and 0.025% BSA and having a pH to be tested, and then luciferase activity in 10 pi of the solution was measured in 3 ml of 20 mM Tris-HCl, pH 7.8, containing 1M NaCl, 0.05% BSA, and 0.3 pM coelenterazine at 24°C. The amounts of luciferases used for measuring each point were luciferase A, 150 LU luciferases B and C, 170 LU. One LU = 5.5 x 108 quanta/s. From Shimomura etal., 2001.

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