PH drift

Add sufficient water (normally 1 % w/w) to transform anhydrides to avoid pH drift of pastes (check by Karl Fischer titration)... 

Efficient mixing of the organic acid and the alkaline phase is essential to promote the instantaneous reaction and to avoid undesired degradation reactions in isolated acid spots and pH drift occurring in the neutralized product storage... 

Add an additional 20 pi of 0.1M imidazole, pH 6.0. Mix and react for at least 2 hours at room temperature. The additional buffer prevents pH drift during the carbodiimide reaction. 

Equilibrium Dialysis Standard ED High-throughput, 96-well format. Long incubation time - compound instability and plasma degradation. Issues of pH drift and osmotic volume shifts (can be corrected for). Membrane adsorption/non-specific binding. [30-32]... 

For the calibration and evaluation of kinetic response of pH electrodes, a Milton-Roy sapphire and Hastalloy pump (capable of 6,000 psi) were built into the pressure line in order to feed acid, base, or buffered solutions through the test vessel by way of stainless capillary tubing of 0.030-in. i.d. Outflow from this system can be controlled by means of two Hoke Micro-Metering valves which, when mounted in series, can provide an "engineered leak with an outfall that can be matched by the pump to allow system flows from 0.6 cm3/min to 16 cm3/min. Such a pumpable system allows fresh reference solution to be continuously added to the system while maintaining constant pressure. This avoids a possible pH drift caused by reactions between the walls of the test chamber and the reference solution. This system also allows... 

In this study, model latexes were diluted with distilled water to 1 percent solids by weight. Individual samples were adjusted with sodium hydroxide to various pH values from 3 to 13 and allowed to equilibrate 24 to 48 hours depending on the pH drift observed. Sedimentation coefficients were determined at 30°C with a Beckman Model E analytical ultracentrifuge using a single sector cell. 

Slurry chemistry Oxidizers, pH and pH drifts, pH stabilizers, complexing agents, dispersants, and corrosion inhibitors... 

Two different approaches have been taken toward waterborne alkoxysiloxane and alkoxysilane waterproofing materials. The recent patent literature contains many references to emulsions of alkoxysilanes and silane—resin mixtures (87) that claim stabihty to hydrolysis until the emulsions are applied and allowed to dry on the masonry, at which point hydrolysis and condensation are underway. Alkoxysilane stabihty within the emulsion is obtained through judicious choice of emulsifiers and the use of buffering agents to minimize pH drift. Excellent performance in static water holdout tests may be obtained with these systems, although initial water beading by the cured coatings can be somewhat compromised by the presence of surfactant. 

The pH value of aqueous suspensions should be taken at a given temperature and only after settling equilibrium has been reached, to minimize pH drift and electrode surface coating with suspended particles. Electrolyte should not be added to the external phase of the suspension to stabilize the pH, because neutral electrolytes disturb the physical stability of the suspension. 

The analysis indicates that up to about 50% of the reagent can be added to the second tank without excessive downstream pH drift in the worst case. Provided at least 1.2% of the reagent is required to make the shift between the first and the second tank pH setpoints, the second tank should always be adding some reagent. Despite the titration curve variability of up to 10 1, there should be no difficulty in accommodating these requirements. Steady-state conversion is not likely to be problematic. 

Understanding of the metal-protein interaction between zinc and insulin has recently been enhanced by studies of titration curves. Crystalline insulin as normally prepared contains a small amount of zinc, and moreover is insoluble between pH 4 and 7, where pH drifts are also observed. Fred-ericq (1954) titrated two fractions of insulin which differed in their solubility at pH 8, and reported that two imidazole groups which dissociate near pH 7 in the soluble form are not evident in the insoluble fraction. 

Smaller and less easily interpreted pH drifts have been reported by Kearney and Singer (1951) during inactivation of partially purified i-amino acid oxidases of snake venom. Reference ivill be made later to other proteins that exhibit other less direct indications of the existence of labile masking of certain prototropic groups. 

Fig, 12. Log first-order half-period as a function of pH and temperature for COHb in formate buffers, n = 0.02 circles, spectrophotometric method crosses, precipitation method. From Zaiser and Steinhardt (1951). Broken line represents halfperiods for unmasking of groups, based on pH drifts over short times (see text). 

The titration protocol (for a selected electrolyte at a certain concentration and a fixed solid-to-liquid ratio) defines the starting and end points of titration, the distances between the data points, and the rate of titration. The distances between data points can be defined by a fixed amount of titrant added per data point or by fixed differences in pH between data points. The rate of titration can be defined by a fixed time of equilibration or by an accepted rate of pH drift (the data point is taken once the rate drops below a pre-assumed value). Even in fast titrations,... 

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