ph of aqueous mixtures of potassium dihydrogen phosphate and disodium hydrogen phosphate at 0 degrees to 60 degrees C

Bates, Roger G.; Acree, S. F.

doi:10.6028/jres.034.020

Cited by 76 publications

(43 citation statements)

References 20 publications

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“…The values used for th e three ionization constants of H3P04 were KJ, 7.108 X 10-3 [35] ; K2 , 6.3ls X 10-8 [36]; K3 , 4.73 X 10-13 [37]; and for Kw, 1.012 X 10-14 [38]. The association constants used in this paper are defined by with values [17] Kx, 244.0; and Ky , 8.20.…”

Section: Appendixmentioning

confidence: 99%

Preparation and solubility of hydroxyapatite

Moreno¹,

Grégory²,

Brown³

1968

J. RES. NATL. BUR. STAN. SECT. A.

248

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Two portions of a syntheti c hydroxyapatite (HA), Ca" OH(PO'}J, full y characte rize d by x-ray , infrared, pe trograp hi c, and c he mi cal anal yses , were heated at 1,000 °C in a ir and steam atmosp heres, respective ly. Solubility isoth erm s for th ese two sam ples in t he syste m Ca(OH}2 -H3PO, -H20 were determin ed in the pH ran ge 5 to 7 by equilibratin g th e so lids with dilute H3 PO. solutions. Both sa mples of HA dis so lved stoichiometrically. The activity produ cts (Ca+ +)'(OH -)(pO~f' and th eir standard errors-obta ined by a least squa res adju stme nt of th e meas urements (Ca and P concentration s and pH of th e saturated solutions) subj ec t to the co ndition s of e lec trone utralit y, constancy of the activit y product, a nd stoic hiometri c dissolution -we re 3.73 ± 0.5 x 10-58 for the stea m-h eated HA and 2_5, ± 0.4 x 10-55 for th e air-heated HA. Allowa nce was made in the calculations for the prese nce of the ion pairs [CaHPO. lo and [CaH2P041 + The hi gher so lubility produ ct for the air-heated HA is ascribed either to a cha nge in th e heat of formati on brou ght abo ut by pa rtial dehydration or to a state of fine subdivision res ulting from a disproportionation reac ti on_ The so lubility produ ct co nsta nt s were used to c al culate the points of inte rsection (i.e_, sin gula r points) of the two HA solubility isot herms with the isotherms of CaHPO. ·2H20 and Ca HPO.; it was found th at the pH's of the sin gul ar points for the air-heated HA were a full unit hi gher th an th ose of th e steam -heated pre paration_ Con ditions are described for th e precipitation of HA c rystals s uitabl e for so lubilit y meas ure men ts_ Key W ords: Apatite; hydroxya patite; calcium phosphates; so lub ili ty; olubilit y isoth e rm s; solubilit y product.

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Section: Appendixmentioning

confidence: 99%

Preparation and solubility of hydroxyapatite

Moreno¹,

Grégory²,

Brown³

1968

J. RES. NATL. BUR. STAN. SECT. A.

248

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“…The first factor is related to diluting stock solutions of buffer to a lower biorelevant concentration and the second factor is related to the addition of salts to adjust the osmotic pressure of the buffered media. First, an example showing the effect of dilution: 50 mM phosphate buffer, initial pH 6.772, increases to pH 7.018 when diluted to 5 mM at 25 °C (28). Therefore, the pH of USP 50 mM phosphate buffer can be expected to change when diluted for use as a surrogate buffer (6).…”

Section: August 2017mentioning

confidence: 99%

Physicochemical Properties of Buffers Used in Simulated Biological Fluids with Potential Application for In Vitro Dissolution Testing: A Mini-review

Mauger¹

2017

Dissolution Technol.

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Although aqueous buffers alone cannot be expected to fulfill all the requirements of biorelevant media, buffers will likely continue to play a central role in controlling the pH of complex formulations simulating biological fluids (3,9). The use of biorelevant dissolution media to forecast in vivo drug performance has been reviewed (9). This minireview focuses on the physicochemical factors related to buffers used in these media and not the biorelevant dissolution media, per se. This mini-review is based on a survey of the literature associated with buffers in general ABSTRACTThis literature review focuses on the physicochemical properties of buffers used in biorelevant media for in vitro dissolution testing. Because biorelevant dissolution systems have been previously reviewed, this review is primarily related to the buffers used in biorelevant media and not the media, per se. It is based on a survey of the literature in areas including analytical chemistry; biochemistry; clinical, solution, and physical chemistry; dissolution science and technology; pharmaceutical sciences; simulated biological fluids; and buffer-related articles from the National Institute of Standards and Technology with the intent of identifying challenges in formulating buffered biorelevant dissolution media and also identifying general attributes that are useful in selecting a buffer for a particular dissolution application. Other topics include: (1) key physicochemical properties of buffers that affect experimental conditions and dissolution results; (2) buffer compatibility with a diverse array of ingredients found in biorelevant media; and (3) the potential to supplement the library of traditional buffers used for in vitro dissolution testing with zwitterionic buffers that were designed for biological application.

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“…t Based on pKa 7 1976 at zero ionic strength (Bates & Acree, 1945), and corrected to 6-85 at 90 mm ionic strength using the Giintelberg approximation (Stumm & Morgan, 1970 …”

Section: Relation To Earlier Workmentioning

confidence: 99%

Heat production in chemically skinned smooth muscle of guinea‐pig taenia coli.

Lönnbro

Hellstrand

1991

The Journal of Physiology

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SUMMARY1. The rate of heat production of chemically skinned guinea-pig taenia coli smooth muscle at 25°C was measured using microcalorimetric techniques.2. Muscle strips were mounted isometrically and incubated in solutions containing MgATP (3-2 mM) and phosphocreatine (PCr, 12 mM), pH 6-9. Activation was obtained by the injection of Ca2+ into the sample compartment of the calorimeter.3. The heat production rate of the resting preparation (pCa 9) was 0-40 + 003 mW g-' wet weight (n = 23). During maximal activation (pCa 48) the heat rate increased to 1P12+0-07 mW g-1 (mean+s.E.M., n = 15). With stepwise increase in [Ca2+] from pCa 9 to 4-8 the energetic cost of force maintenance tended to increase at higher [Ca2+]. 4. After activation by Ca2 , the heat production rate reached its maximum while force was still increasing.5. Changing ionic strength from 90 to 150 mm had no effect on either basal or activated heat rate. Oligomycin, amphotericin B and the adenylate kinase inhibitor Ap5A had no effect on the basal heat rate.6. Exchanging ATP in the incubation medium for inosine triphosphate (ITP) reduced the force and heat production after injection of Ca2+. The basal heat production was not lowered when ATP was exchanged for ITP.7. The observed enthalpy change for PCr splitting at 25°C (pH 6-9, ionic strength 90 mM) was -28 + 3 kJ mol-1 (mean + S.E.M., n = 9). After correction for the phosphate equilibrium, buffer reactions, and Mg2+ binding to PCr and HP042-, the net enthalpy change is calculated to be -39 + 3 kJ mol-1. 8. Heat production in the skinned smooth muscle consists of one basal component present in relaxed muscle, and one component associated with contraction. The nature of the basal heat production is unclear but does not seem to involve turnover of phosphate on the myosin light chains. The increase in the energetic tension cost with increasing activation by Ca2+ has implications for the understanding of the contractile mechanism in smooth muscle.

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ph of aqueous mixtures of potassium dihydrogen phosphate and disodium hydrogen phosphate at 0 degrees to 60 degrees C

Cited by 76 publications

References 20 publications

Preparation and solubility of hydroxyapatite

Preparation and solubility of hydroxyapatite

Physicochemical Properties of Buffers Used in Simulated Biological Fluids with Potential Application for In Vitro Dissolution Testing: A Mini-review

Heat production in chemically skinned smooth muscle of guinea‐pig taenia coli.

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