Buffer Standards for the Physiological pH of N-[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]glycine (TRICINE) from T = (278.15 to 328.15) K.

The pH values of two buffer solutions without NaCl and seven buffer solutions with added NaCl, having ionic strengths (I = 0.16 mol·kg(-1)) similar to those of physiological fluids, have been evaluated at 12 temperatures from T = (278.15 to 328.15) K by way of the extended form of the Debye-Hückel equation of the Bates-Guggenheim convention. The residual liquid junction potentials (δE(j)) between the buffer solutions of TRICINE and saturated KCl solution of the calomel electrode at T = (298.15 and 310.15) K have been estimated by measurement with a flowing junction cell. For the buffer solutions with the molality of TRICINE (m(1)) = 0.06 mol·kg(-1), NaTRICINE (m(2)) = 0.02 mol·kg(-1), and NaCl (m(3)) = 0.14 mol·kg(-1), the pH values at 310.15 K obtained from the extended Debye-Hückel equation and the inclusion of the liquid junction correction are 7.342 and 7.342, respectively. These are in excellent agreement. The zwitterionic buffer TRICINE is recommended as a secondary pH standard in the region for clinical application.

Buffer standards for the physiological pH of the zwitterionic compound of 3-(N-morpholino)propanesulfonic acid (MOPS) from T = (278.15 to 328.15) K.

This paper reports the pH values of five NaCl-free buffer solutions and eleven buffer compositions containing NaCl at I = 0.16 mol·kg(-1). Conventional pa(H) values are reported for sixteen buffer solutions with and without NaCl salt. The operational pH values have been calculated for five buffer solutions and are recommended as pH standards at T = (298.15 and 310.15) K after correcting the liquid junction potentials. For buffer solutions with the composition m(1) = 0.04 mol·kg(-1), m(2) = 0.08 mol·kg(-1), m(3) = 0.08 mol·kg(-1) at I = 0.16 mol·kg(-1), the pH at 310.15 K is 7.269, which is close to 7.407, the pH of blood serum. It is recommended as a pH standard for biological specimens.

Buffer Standards for the Biological pH of the Amino Acid N-[2 hydroxyethyl]piperazine-N'-[3-propanesulfonic acid], HEPPS, From (278.15 to 328.15) K.

For the HEPPS buffer under investigation, there are seven buffer solutions without NaCl and eight buffer solutions that contain Cl(-) and have an ionic strength (I = 0.16 mol·kg(-1)), which is similar to that of blood plasma. These buffer solutions have been evaluated in the temperature range of (278.15 to 328.15) K using the extended Debye- Hückel equation and the Bates-Guggenheim convention. The previously determined E(j) values have been used to determine the operational pH values of HEPPS buffer solutions at (298.15 and 310.15) K. These are recommended as secondary standard reference solutions for pH measurements in saline media with an isotonic ionic strength of I = 0.16 mol·kg(-1).

Buffer standards for the physiological pH of N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid (BES) from (278.15 to 328.15) K.

This paper reports the results for the pH of six buffer solutions free of chloride ion with compositions: (a) BES (0.03 mol·kg(-1)) + NaBES (0.09 mol·kg(-1)); (b) BES (0.02 mol·kg(-1)) + NaBES (0.04 mol·kg(-1)); (c) BES (0.04 mol·kg(-1)) + NaBES (0.08 mol·kg(-1)); (d) BES (0.04 mol·kg(-1)) + NaBES (0.04 mol·kg(-1)) (e) BES (0.05 mol·kg(-1)) + NaBES (0.05 mol·kg(-1)); and (f) (0.06 mol·kg(-1)) + NaBES (0.06 mol·kg(-1)). The remaining eight buffer solutions (g) to (n) have saline media of the ionic strength I = 0.16 mol·kg(-1), matching closely to that of the physiological sample. Conventional pa(H) values, designated as pH(s), for all six buffer solutions (a) - (f) without the chloride ion and eight buffer solutions with the chloride ion (g) - (n) at I = 0.16 mol·kg(-1) from (278.15 K to 328.15) K have been calculated. The operational pH values for five buffer solutions at T = 298.15 K and T = 310.15 K have been determined based on the difference in the values of the liquid junction potentials between the blood phosphate standard and the experimental buffer solutions. Five of these buffers are recommended as secondary standards for the physiological pH range 7.5 to 8.5.

Buffer Standards for the Physiological pH of the Zwitterionic Compound, DIPSO from 5 to 55 degrees C.

The values of the second dissociation constant, pK(2), and related thermodynamic quantities of 3-[N,N-bis (2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid (DIPSO) have already been reported over the temperature range 5 to 55 degrees C including 37 degrees C. This paper reports the pH values of four NaCl-free buffer solutions and four buffer composition containing NaCl salt at I = 0.16 mol.kg(-1). Conventional pa(H) values are reported for all eight buffer solutions. The operational pH values have been calculated for four buffer solutions recommended as pH standards, at 25 and 37 degrees C after correcting the liquid junction potentials with the flowing junction cell.

Buffer Standards for the Biochemical pH of 3-(N-morpholino)-2-hydroxypropanesulfonic Acid from (278.15 to 328.15) K.

The values of the second dissociation constant pK(2) and related thermodynamic quantities of the ampholyte 3-(N-morpholino)-2-hydroxypropanesulfonic acid (MOPSO) have been previously determined at temperatures from (278.15 to 328.15) K. In this study, the pH values of two buffer solutions without NaCl and three buffer solutions with NaCl having ionic strengths (I = 0.16 mol·kg(-1)) similar to those in blood plasma, have been evaluated at 12 temperatures from (278.15 to 328.15) K using an extended form of the Debye-Hückel equation, since the Bates-Guggenheim convention is valid up to I = 0.1 mol·kg(-1). The liquid junction potentials (E(j)) between the buffer solutions of MOPSO and saturated KCl solution of the calomel electrode at (298.15 and 310.15) K have been estimated by measurement with a flowing junction cell. These values of E(j) have been used to ascertain the operational pH values at (298.15 and 310.15) K. Three buffer solutions of MOPSO are recommended as useful reference solutions for pH measurements in saline media of ionic strength I = 0.16 mol·kg(-1).

Buffer Standards for the Physiological pH of the Zwitterionic Compound, ACES from 5 to 55°C.

The values of the second dissociation constant pK2 and related thermodynamic quantities of [N-(2-acetamido)-2-aminoethanesulfonic acid] (ACES) have already been reported over the temperature range 5 to 55°C including 37°C. This paper reports the paH values of four chloride ion free buffer solutions and eight buffer solutions with I = 0.16 mol·kg -1, matching closely to that of the physiological sample. Conventional paH values for all twelve buffer solutions from 5 to 55°C, are reported. The residual liquid junction potential correction for two widely used temperatures, 25 and 37°C, has been made. The flowing-junction calomel cell method has been utilized to measure Ej , the liquid junction potential. The operational pH values for four buffer solutions at 25 and 37°C are calculated using the physiological phosphate buffer standard based on NBS/NIST convention. These solutions are recommended as pH standards in the pH range of 6.8 to 7.2 for physiological fluids.

Buffer Standards for pH Measurement of N-(2-Hydroxyethyl)piperazine-N'-2-ethanesulfonic Acid (HEPES) for I = 0.16 mol.kg from 5 to 55 degrees C.

The values of the second dissociation constant, pK(2) of N-(2-hydroxyethyl) piperazine-N'-2-ethanesulfonic acid (HEPES) have been reported at 12 temperatures over the temperature range 5 to 55 degrees C, including 37 degrees C. This paper reports the results for the pa(H) of eight isotonic saline buffer solutions with an I = 0.16 mol*kg(-1) including compositions: (a) HEPES (0.01 mol*kg(-1)) + NaHEPES (0.01 mol*kg(-1)) + NaCl (0.15 mol*kg(-1)); (b) HEPES (0.02 mol*kg(-1)) + NaHEPES (0.02 mol*kg(-1)) + NaCl (0.14 mol*kg(-1)); (c) HEPES (0.03 mol*kg(-1)) + NaHEPES (0.03 mol*kg(-1)) + NaCl (0.13 mol*kg(-1)); (d) HEPES (0.04 mol*kg(-1)) + NaHEPES (0.04 mol*kg(-1)) + NaCl (0.12 mol*kg(-1)); (e) HEPES (0.05 mol*kg(-1)) + NaHEPES (0.05 mol*kg(-1)) + NaCl (0.11 mol*kg(-1)); (f) HEPES (0.06 mol*kg(-1)) + NaHEPES (0.06 mol*kg(-1)) + NaCl (0.10 mol*kg(-1)); (g) HEPES (0.07 mol*kg(-1)) + NaHEPES (0.07 mol*kg(-1)) + NaCl (0.09 mol*kg(-1)); and (h) HEPES (0.08 mol*kg(-1)) + NaHEPES (0.08 mol*kg(-1)) + NaCl (0.08 mol*kg(-1)). Conventional pa(H) values, for all eight buffer solutions from 5 to 55 degrees C have been calculated. The operational pH values with liquid junction corrections, at 25 and 37 degrees C have been determined based on the NBS/NIST standard between the physiological phosphate standard and four buffer solutions. These are recommended as pH standards for physiological fluids in the range of pH 7.3 to 7.5 at I = 0.16 mol*kg(-1).

Decreasing reliance on mineral nitrogen--yet more food.

Higher crop production normally demands higher nutrient application rates and consequently increased mineral nitrogen use. With food demand for 2030 estimated around 2800 mill. tonnes (t) yr-1, the corresponding mineral N consumption figure is 96 mill. t (78 mill. t yr-1 in 1995/1997). Global-level mineral N losses to the environment from mineral fertilizer use are currently 36 mill. t yr-1, worth USD 11,700 mill. and with adverse environmental impacts. However, innovative fertilizer-use efficiency (FUE) technologies enable increased production with a less than a proportionate increase in mineral-N use. Moreover, nitrogen-nutrient supplies can be augmented through improvements in agricultural production systems and in the exploitation of alternative sources such as biological nitrogen fixation (BNF). By 2030, with adequate policy, technology transfer, research and investment support, the on-farm adoption of BNF and FUE technologies could generate savings of 10 mill. t yr-1 of mineral N, worth USD 3300 mill.