pH control of nucleophilic/electrophilic oxidation

Freed, Anita L.; Strohmeyer, Holly; Mahjour, Majid; Sadineni, Vikram; Reid, Darren L.; Kingsmill, Carol A.

doi:10.1016/j.ijpharm.2008.01.061

Cited by 36 publications

(28 citation statements)

References 12 publications

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“…The previous studies (8) reported three macro-pKa values for cetirizine (1.52, 2.92 and 8.27), the lowest of which was attributed to the nitrogen nearest to the aromatic rings and pKa 2.9-to the carboxylic acid. The minimum of the oxidation rate at pH of 6.5 could be explained by the protection effect of protons on tertiary amine (9). According to the literature (8,10), zwitterionic form HX is predominant between pH 3 to 8 (Fig.…”

Section: Mechanism Of Cetirizine Oxidationmentioning

confidence: 84%

Isolation and Characterization of Cetirizine Degradation Product: Mechanism of Cetirizine Oxidation

et al. 2010

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Section: Mechanism Of Cetirizine Oxidationmentioning

confidence: 84%

Isolation and Characterization of Cetirizine Degradation Product: Mechanism of Cetirizine Oxidation

et al. 2010

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“…At this pH, many amines are protonated and N-oxide formation is diminished. 43 In addition, low pH can lead to the degradation of some hydroperoxides. 44 To accommodate for this, the authors suggested conducting another reaction with AIBN where low pH is unnecessary.…”

Section: Tween 80/fe (Iii)mentioning

confidence: 99%

The Use Of N-Methylpyrrolidone as a Cosolvent and Oxidant in Pharmaceutical Stress Testing

Reynolds

Galvani

Hicks

et al. 2012

Journal of Pharmaceutical Sciences

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“…This was attributed to the high electron density at the hetero N atom that was confirmed by the molecular orbital calculations reported in the literature for RLX and some related molecules. 42,43 Moreover, RLX possesses three pK a values reported as 8.95, 9.83 and 10.91. 41,43 However, in this study, the constancy of the slope of E p vs. pH plot may be attributed to the very close reduction peak potentials of the protonated and unprotonated forms (acid and base forms) of RLX.…”

Section: Cyclic Voltammetric Studiesmentioning

confidence: 99%

“…42,43 Moreover, RLX possesses three pK a values reported as 8.95, 9.83 and 10.91. 41,43 However, in this study, the constancy of the slope of E p vs. pH plot may be attributed to the very close reduction peak potentials of the protonated and unprotonated forms (acid and base forms) of RLX. Thus, in the acidic media (pH values < 7), cationic form was expected to be predominant (pK a1 of 8.95 is attributed to the dissociation of protonated basic nitrogen).…”

Section: Cyclic Voltammetric Studiesmentioning

confidence: 99%

Adsorptive stripping voltammetry determination of the hormone therapy Raloxifene HCl in formulation and human serum

Ghoneim¹,

Hassanein²,

Salahuddin³

et al. 2012

J. Braz. Chem. Soc.

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Raloxifeno HCl (RLX) adsorveu fortemente na superfície do eletrodo de mercúrio numa monocamada com cobertura superficial de 5,724 × 10 −10 mol cm -2 . Dois métodos voltamétricos de redissolução catódico adsortivo com varredura linear e onda quadrada (LS-AdCSV e SW-AdCSV, respectivamente) precisos, rápidos e livres de extração são descritos para determinação em nível de traço de RLX em solução, em formulação comercial e soro humano. Limites de quantificação (LOQ) de 2,0 × 10 -9 e 5,0 × 10 -11 mol L −1 de RLX em solução e 4,0 × 10 -9 e 1,0×10 -10 mol L −1 em soro humano enriquecido foram obtidos pelos métodos descritos LS-AdCSV e SW-AdCSV, respectivamente. Interferências de alguns excipientes comuns, íons metálicos e drogas coadministradas foram insignificantes. LOQ adquidos pelos métodos são baixos assim como oferecem boas possibilidades de determinação de drogas em preparações farmacológicas de baixa dosagem. Contudo, o método SW-AdCSV descrito é sensível suficiente em ensaios de drogas também em soro humano.Raloxifene HCl (RLX) was found to strongly adsorb onto surface of the mercury electrode in a monolayer surface coverage of 5.724 × 10 −10 mol cm -2 . Two precise, rapid and extractionfree linear sweep and square wave adsorptive cathodic stripping voltammetry (LS-AdCSV and SW-AdCSV, respectively) methods are described for trace quantitation of RLX in bulk form, commercial formulation and human serum. Limits of quantification (LOQ) of 2.0 × 10 -9 and 5.0 × 10 -11 mol L −1 RLX in bulk form and 4.0 × 10 -9 and 1.0 × 10 -10 mol L −1 RLX in spiked human serum were achieved by the described LS-AdCSV and SW-AdCSV methods, respectively. Insignificant interferences from some common excipients, metal ions and co-administrated drugs were obtained. LOQ achieved by the methods are low as well as they offer good possibilities for determination of drug in low-dosage pharmaceutical preparations. However, the SW-AdCSV method described is sensitive enough to assay the drug also in human serum.

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pH control of nucleophilic/electrophilic oxidation

Cited by 36 publications

References 12 publications

Isolation and Characterization of Cetirizine Degradation Product: Mechanism of Cetirizine Oxidation

Isolation and Characterization of Cetirizine Degradation Product: Mechanism of Cetirizine Oxidation

The Use Of N-Methylpyrrolidone as a Cosolvent and Oxidant in Pharmaceutical Stress Testing

Adsorptive stripping voltammetry determination of the hormone therapy Raloxifene HCl in formulation and human serum

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