Capillary zone electrophoresis in non-aqueous solutions: pH of the background electrolyte

Porras, Simo P.; Kenndler, Ernst

doi:10.1016/j.chroma.2003.07.018

Cited by 80 publications

(66 citation statements)

References 73 publications

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“…Using nonaqueous based mobile phases and/or running buffers, suitable analytical methods enable analyzing highly hydrophobic analytes or compounds that exhibit restricted stability in aqueous media. 1 Addition of the second organic solvent to aqueous solutions alters the solubility of the analyte, the resolution of analytes, or determine other relevant analytical parameters like pK a values, partition coefficients or electrophoretic mobilities. 2,3 In addition to these applications, the solubility data of TRIS is also required in solubilization/crystallization studies.…”

Section: ■ Introductionmentioning

confidence: 99%

Solubility of Tris(hydroxymethyl)aminomethane in Methanol + 1-Propanol Mixtures at Various Temperatures

Jouyban-Gharamaleki

Soleymani

et al. 2014

J. Chem. Eng. Data

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Solubility of tris(hydroxymethyl)aminomethane (TRIS) in various mass fractions of binary solvent mixtures of methanol and 1-propanol [at (293.2, 298.2, 303.2, 308.2, and 313.2) K] was measured and mathematically represented using the Jouyban-Acree model. The correlated mole fraction solubilities are in good agreement with the corresponding experimental values with an overall mean percentage deviation of 1.7%. Densities of saturated solutions of TRIS in pure methanol and 1-propanol at various temperatures were measured and employed to predict the density of saturated solutions of TRIS in their binary solvent mixtures. ■ INTRODUCTIONBuffer solutions composed of binary solvents are used as mobile phases and/or background electrolytes in analytical separation methods such as liquid chromatography or capillary electrophoresis, where the low solubility of the buffering agents at higher concentrations of the low polar solvent may cause practical problems. Using nonaqueous based mobile phases and/or running buffers, suitable analytical methods enable analyzing highly hydrophobic analytes or compounds that exhibit restricted stability in aqueous media. 1 Addition of the second organic solvent to aqueous solutions alters the solubility of the analyte, the resolution of analytes, or determine other relevant analytical parameters like pK a values, partition coefficients or electrophoretic mobilities. 2,3 In addition to these applications, the solubility data of TRIS is also required in solubilization/crystallization studies. The common method for obtaining a solute's solubility is the trial and error approach which is a time-consuming and costly method. Any predictive tool to estimate the best solvent composition for solubilization/ crystallization of Tris(hydroxymethyl)aminomethane (TRIS) is obviously in demand.TRIS (chemical abstract service number 77-86-1) is a common buffering agent in chemical and biochemical areas. It is used in nonaqueous solvents for analytical and separation purposes. Available solubility data of TRIS in various solvent mixtures is reviewed in a recent publication 4 along with reporting TRIS solubility in water + methanol (MeOH) 2 and water + 1-propanol (1-PrOH) 5 mixtures at 293.2 to 313.2 K. A quick survey on the published pharmaceutical analysis methods showed that MeOH + 1-PrOH has been used in some developed analytical methods. 6 To continue our systematic investigations on the solubility of solutes in solvent mixtures, the solubility of TRIS in MeOH + 1-PrOH mixtures at different temperatures [(293.2, 298.2, 303.2, 308.2, and 313.2) K] was measured using a validated labmade setup. 4,7 The trained version of a mathematical model is presented to provide a predictive tool for calculation of the solubility of TRIS at any composition of MeOH + 1-PrOH solvent mixture and at any temperature in the range mentioned.■ EXPERIMENTAL SECTION Materials. TRIS (with the stated purity of 0.999 in mass fraction) and MeOH (mass fraction purity of 0.999) were purchased from Merck (Germany). 1-PrOH (ma...

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Section: ■ Introductionmentioning

confidence: 99%

Solubility of Tris(hydroxymethyl)aminomethane in Methanol + 1-Propanol Mixtures at Various Temperatures

Jouyban-Gharamaleki

Soleymani

et al. 2014

J. Chem. Eng. Data

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“…As the amount of organic solvent in the system is increased, it alters the pK a of the acid in the system and hence alters the pH that is observed. It has been reported that in 100% methanol pH values can be adjusted by adding 2.3 to the observed pH measurements to get the equivalent pH value in water [17]. However, as the solvent composition changes, the amount by which the observed pH values need to be adjusted also changes [18].…”

Section: Resultsmentioning

confidence: 99%

The effect of using a methanol–water solvent mixture on pH oscillations in the palladium-catalyzed phenylacetylene oxidative carbonylation reaction

Parker

Novakovic

2017

Reac Kinet Mech Cat

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The palladium-catalyzed phenylacetylene oxidative carbonylation reaction has been shown to produce regular oscillations in pH, reaction heat, and turbidity when conducted in batch with methanol as solvent. Previous studies of the catalytic system showed that water plays an important role in the behavior of the catalytic cycle. Investigating this role further, the reaction was performed in methanol-water mixtures. Experiments demonstrated that, under the conditions studied, oscillations in pH are feasible when the water concentration in the system is increased (0-30 V%). At the same time oscillations visually changed, being transformed from regular oscillations to more stepwise behavior as the proportion of water is increased. By establishing the relationship between the recorded pH and HI concentration it was found that increased water concentration suppresses HI formation and hence slows the autocatalysis in the reaction. It was also found that oscillations begin when the HI concentration is in the region of 1 9 10 -3 mol L -1 . Additionally, as the amount of water in the system increases a slight decrease in the concentration of HI when oscillations start was noted.

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“…In methanol, pH adj is approximated by adding 2.3 pH units to the measured value of pH (pH app ) and hydrogen ion concentrations subsequently estimated using 10 -(pHapp ? 2.3) [16]. The formation of water during the PCPOC reaction could in theory change the solvent composition and affect pK a values.…”

Section: Methodsmentioning

confidence: 99%

Oscillatory carbonylation of phenylacetylene in the absence of externally supplied oxidant

Donlon

Parker

Novakovic

2014

Reac Kinet Mech Cat

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The palladium-catalyzed oxidative carbonylation of phenylacetylene (PCPOC reaction) is known to exhibit autonomous oscillations in a variety of parameters including pH, redox potential and heat of reaction. Previous studies report that external addition of both an oxidizing agent and water is required to allow production/ consumption of H ? in an oscillatory fashion. In this work we show that solutions of PdI 2 / KI dried over 3 Å molecular sieves can catalyze phenylacetylene carbonylation in the absence of an external oxidizing agent. Oscillations are readily achieved in this considerably simplified PCPOC system. Palladium-catalyzed carbonylation of methanol generates HI as a by-product, which can react with excess KI and methanol producing methyl iodide and water in situ. Methyl iodide can also undergo decomposition, generating iodine as an internally formed oxidizing agent, which accounts for recorded catalyst regeneration. Oscillations are observed in the pH range 1.5-3.5 commencing, at the earliest, 70 min after introduction of phenylacetylene. Oscillations vary in period between 1 and 3.5 h and last for several days. The onset of oscillations may be delayed via portion-wise addition of the phenylacetylene substrate.

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Capillary zone electrophoresis in non-aqueous solutions: pH of the background electrolyte

Cited by 80 publications

References 73 publications

Solubility of Tris(hydroxymethyl)aminomethane in Methanol + 1-Propanol Mixtures at Various Temperatures

Solubility of Tris(hydroxymethyl)aminomethane in Methanol + 1-Propanol Mixtures at Various Temperatures

The effect of using a methanol–water solvent mixture on pH oscillations in the palladium-catalyzed phenylacetylene oxidative carbonylation reaction

Oscillatory carbonylation of phenylacetylene in the absence of externally supplied oxidant

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