Search results for "Ph range"
showing 10 items of 13 documents
The impact of the EMA change in definition of "dose" on the BCS dose-solubility ratio: a review of the biowaiver monographs.
2013
The Biopharmaceutics Classification System (BCS) defines the solubility characteristics of an active pharmaceutical substance based on its dose-solubility ratio: for highly soluble drugs this ratio is less than 250 mL over a defined pH range. Prior to the revision of the European Medicines Agency (EMA, formerly EMEA) guideline in 2010, the "dose" in this ratio was consistently defined by the US FDA, the EMA, and the WHO biowaiver guidelines as the highest dosage strength. However, in the revised EMA guideline, the dose is defined as the highest single dose administered according to the Summary of Product Characteristics. The new EMA criterion for highly soluble may be closer to the actual c…
Speciation of Al3+ in fairly concentrated solutions (20 to 200 mmol L-1) at I = 1 mol L-1 (NaNO3), in the acidic pH range, at different temperatures.
2011
AbstractThe hydrolysis of Al3+ was studied in aqueous 1 mol L−1 NaNO3 solution at different concentrations (20–200 mmol L−1) and temperatures (283.15–343.15 K) by potentiometry (ISE-H+, glass electrode). Many different speciation models were considered in the calculations and it was found that the best model is represented by the following species: Al(OH)2+, Al(OH)45+, Al13(OH)327+. Hydrolysis constants and enthalpy changes at different temperatures are reported.
Upconversion nanoparticles with a strong acid-resistant capping
2016
Water-dispersible upconversion nanoparticles (β-NaYF:Yb,Er, UCNP) coated with a thin shell of a biocompatible copolymer comprising 2-hydroxyethylmethacrylate (HEMA) and 2-acrylamido-2-methyl-1-propanesulphonsulphonic acid (AMPS), which we will term COP, have been prepared by multidentate grafting. This capping is remarkably resistant to strong acidic conditions as low as pH 2. The additional functionality of the smart UCNP@COP nanosystem has been proved by its association to a well-known photosensitizer (namely, methylene blue, MB). The green-to-red emission ratio of the UC@COP@MB nanohybrid exhibits excellent linear dependence in the 7 to 2 pH range as a consequence of the release of the d…
Gas-chromatographic elemental analysis via di(trifluorethyl)dithiocarbamato-chelates
1986
The capillary-gas-chromatographic conditions for the determination of trace metals after extraction from aqueous solution are optimized by coupling of capillaries and improvement of injection technique. Different detectors (FID and ECD) are tested. pH range and buffer systems for extraction of metal chelates are discussed.
Chromatographic retention–activity relationships for prediction of the toxicity pH-dependence of phenols
2007
Abstract An investigation of the use of the chromatographic retention (log k ) as an in vitro approach for modeling the pH-dependence of the toxicity to Guppy of phenols is developed. A data set of 19 phenols with available experimental toxicity–pH data was used. The importance of the mechanism of toxic action (MOA) of phenols was studied. log k data at three pH values were used for the phenols classification and two groups or ‘MODEs’ were identified. For one ‘MODE’ a quantitative retention–activity relationship (QRAR) model was calculated. Finally, the model was used to assess the toxicity to Guppy of phenols at different pH values. The results of this investigation suggest that chromato…
Gold nanoclusters for ratiometric sensing of pH in extremely acidic media.
2019
AuNCs capped with β-nicotinamide adenine dinucleotide phosphate exhibit an outstanding performance as fluorescent pH sensors; specifically they exhibit a high emission in strongly acidic media and linear dependence on pH in extremely acidic media (0.6–2.7) as well as in the 7.0–9.2 pH range, while they are unresponsive at intermediate pH values. Remarkably, these AuNCs make ratiometric sensing possible in extremely acidic media with a single fluorophore, specifically the nanocluster itself.
Die pH-Statik als Hilfsmittel der Korrosionsforschung
1977
Die pH-Statik ist ein verhaltnismasig einfaches Verfahren zur Untersuchung von Korrosionsablaufen im pH-Bereich 2 – 9. Sie beruht darauf, das die Menge des verbrauchten Sauerstoffs (bei der Oxidation von Metallen) aquivalent der Menge der entstandenen Hydroxylionen ist. Bei dieser Arbeitsweise wird im oben erwahnten pH-Bereich ein bestimmter Wert eingestellt und durch Zugabe definierter Sauremenge konstant gehalten. Diese Korrelation wird am Beispiel von Kupfer in NaCl-Losung bestatigt, wobei der pH- Wert (4, 1) durch Zusatz von Salzsaure konstant gehalten wird. Die Reproduzierbarkeit der Messung ist abhangig von Temperatur, Sauerstoffpartialdruck und Ruhrgeschwindigkeit sowie von der Grose…
Mono- and polynuclear hydroxo complexes of monophenylthallium(III)
1974
Summary The hydrolysis of PhTl(OH)ClO4 has been studied in a medium 0.3 M in NaClO4 by a potentiometric technique. The complexes formed by the hydrolysis reactions together with their formation constants have been determined by the general minimizing computer programme LETAGROP. The hydrolysis species observed in the pH range 3–5 are the mononuclear [(PhTlOH)(OH)], the dinuclear [(PhTlOH)2(OH)]+ and the dimer [(PhTlOH)2(OH)2]. The formation constants are log *β11=−4.92±0.2, log *β21=−1.52±0.03 and log *β22=−6.11±0.05. Stepwise reactions are then postulated whose formation constants are respectively log (*β21/*β11)=3.40±0.25, log (*β22/*β21)=−4.59±0.08 and log (*β22/*β112)=3.73±0.09.
Considerations on the modelling and optimisation of resolution of ionisable compounds in extended pH-range columns
2005
Abstract The problems associated to the modelling and optimisation of the chromatographic resolution of mixtures involving ionisable solutes at varying pH and acetonitrile content are discussed. Several retention models that separate the contributions of solute, column and stationary phase, were used. The retention was predicted with low errors in large pH domains (2–12), which was an essential requirement to face the optimisation of resolution. The selected mixture was particularly problematic under the viewpoint of resolution, owing to the excessively diverse acid–base behaviour of solutes. This variety led to sudden drops in retention at different pH for each solute, yielding numerous pe…
DC polarographic reduction of chloroguanide hydrochloride.
1984
Chloroguanide hydrochloride, an antimalarial drug, shows one well-defined DC polarographic wave in Britton-Robinson buffered media. In the pH range 3–9 the observed reduction wave is related to the reduction of the two azomethine centers on the monoprotonated biguanide group (BH+). The effects of pH and other experimental variables on the limiting current and half-wave potentials as well as the reduction mechanism are discussed.