Multifunctional substances ? Determination of pKa-values by various methods

Sistovaris, N.; Hamachi, Yozo; Kuriki, Takeo

doi:10.1007/bf00321579

Cited by 13 publications

(6 citation statements)

References 4 publications

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“…The determination of the pK a of a substance with multiple deprotonation steps and low solubility is not easy to perform [3]. Values have been given for deprotonation involving the successive reactions:…”

Section: Influence Of Ph and Mechanistic Studiesmentioning

confidence: 99%

“…1 for the structure of the neutral form H 2 A). Experimental values obtained by different techniques estimate pK 1 % 0.5 from octanol/water partition measurements [3] and pK 2 ¼ 3.9; 3.8; 3.65 or 3.6, determined by aqueous solution titration; mixed solvents titration; octanol/ water partition and solubility methods respectively [3]. Using liquid chromatography a 3.9 value has been assigned to the carboxylic acid dissociation [4].…”

Section: Influence Of Ph and Mechanistic Studiesmentioning

confidence: 99%

“…The structure of the neutral form of furosemide is shown in Figure 1; the protonated form has four ionizable acid groups [3,4]. It is soluble in alkaline media, as well as in organic solvents such as acetone and methanol; however, it has a very low solubility in water and acidic aqueous solutions [2].…”

Section: Introductionmentioning

confidence: 99%

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A Graphite‐Polyurethane Composite Electrode for the Analysis of Furosemide

et al. 2008

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A graphite-polyurethane composite electrode has been used for the determination of furosemide, a antihypertensive drug, in pharmaceutical samples by anodic oxidation. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the electrooxidation process at þ 1.0 V vs. SCE over a wide pH range, with the result that no adsorption of analyte or products occurs, unlike at other carbon-based electrode materials. Quantification was carried out using cyclic voltammetry, differential pulse voltammetry, and square-wave voltammetry. Linear ranges were determined (up to 21 mmol L À1 with cyclic voltammetry) as well as limits of detection (0.15 mmol L À1 by differential pulse voltammetry). Four different types of commercial samples were successfully analyzed. Recovery tests were performed which agreed with those obtained by spectrophotometric evaluation. The advantages of this electrode material for repetitive analyzes, due to the fact that no electrode surface renewal is needed owing to the lack of adsorption, are highlighted.

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Section: Influence Of Ph and Mechanistic Studiesmentioning

confidence: 99%

Section: Influence Of Ph and Mechanistic Studiesmentioning

confidence: 99%

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A Graphite‐Polyurethane Composite Electrode for the Analysis of Furosemide

et al. 2008

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“…Furosemide has pKa values of ∼3.8 and ∼10. In the stomach pH of around 2.0, furosemide is expected to be mainly unionized allowing the molecule to be more lipophilic (Sistovaris et al, 1991, Klausner et al, 2003). This explains why furosemide shows significant permeability across stomach membrane.…”

Section: Introductionmentioning

confidence: 99%

In vitro dissolution and bioavailability study of furosemide nanosuspension prepared using design of experiment (DoE)

Shariare

Altamimi

Marzan

et al. 2019

Saudi Pharmaceutical Journal

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BackgroundNanotechnology can offer the advantages of increasing solubility and bioavailability of delivering drugs like Furosemide. The aim of the current study is to investigate the in vitro and in vivo performance of furosemide nanosuspensions.MethodsFurosemide nanosuspensions were prepared by antisolvent precipitation method using full factorial experimental design. Four factors were employed namely; Stirring time, Injection rate, antisolvent: solvent ratio & stabilizer: drug ratio (at two levels = high & low). The in vitro dissolution experiments were conducted to compare the representative formulation with raw drug powder. The bioavailability of nanosuspension was, also, evaluated in mice as an animal model.ResultsSolid state characterization (PXRD, DSC and FESEM) did show physical changes during preparation and optimization of the furosemide nanosuspensions. Individual material attributes showed more significant impact on the average particle size of the nanocrystals compared to process parameters. Two-way interactions between material attributes and process parameters significantly affected nanosuspension particle size distribution. Dissolution rate of furosemide nanosuspemsion was significantly higher than that observed for raw furosemide powder. The in vivo pharmacokinetics parameters of nanosuspension in comparison to pure drug showed significant increase in Cmax and AUC(0-t), about 233% and 266%, respectively. The oral bioavailability of furosemide from nanosuspension was about 2.3 fold higher as compared with the bioavailability from pure drug.ConclusionsFurosemide nanosuspensions prepared using antisolvent precipitation method enhanced the dissolution rate and oral bioavailability compared to raw furosemide powder.

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“…The plot shows two linear segments which is accordance with other reports. 9,29 Coulometry was performed in PBS containing 1 mM furosemide at 0.98 and 1.12 V, corresponding to the potentials of I and II peaks using the Fe 3 O 4 -GO-SO 3 H-GC electrode. Electrolysis progress was carried out using CV.…”

Section: Preparation Of Modied Fe 3 O 4 -Go-so 3 H Electrodesmentioning

confidence: 99%