Determinação da constante de dissociação (Ka) do captopril e da nimesulida: experimentos de química analítica para o curso de farmácia

Pereira, Airton Vicente; Garabeli, Aline Ansbach; Schunemann, Grazieli Delponte; Borck, Patrícia Cristine

doi:10.1590/s0100-40422011000900029

Cited by 11 publications

(12 citation statements)

References 7 publications

(9 reference statements)

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“…It is important to consider that the solution containing a compound with low solubility and high molar absorptivity may be diluted, as solution containing a compound with high solubility and low molar absorptivity may not be necessarily diluted. Thus, the dilution mainly depends on molar absorptivity of the drugs (Alves et al, 2010;Filippin, Souza, 2006;Pereira et al, 2011;Ruela, Araújo, Pereira, 2009). The cumulative quantity of dissolved drug was corrected for each sample interval according to volume collected from the each vessel.…”

Section: Intrinsic Dissolution Methodsmentioning

confidence: 99%

Equilibrium solubility versus intrinsic dissolution: characterization of lamivudine, stavudine and zidovudine for BCS classification

Dezani

Pereira

Caffaro

et al. 2013

Braz. J. Pharm. Sci.

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Solubility and dissolution rate of drugs are of major importance in pre-formulation studies of pharmaceutical dosage forms. The solubility improvement allows the drugs to be potential biowaiver candidates and may be a good way to develop more dose-efficient formulations. Solubility behaviour of lamivudine, stavudine and zidovudine in individual solvents (under pH range of 1.2 to 7.5) was studied by equilibrium solubility and intrinsic dissolution methods. In solubility study by equilibrium method (shake-flask technique), known amounts of drug were added in each media until to reach saturation and the mixture was subjected to agitation of 150 rpm for 72 hours at 37 °C. In intrinsic dissolution test, known amount of each drug was compressed in the matrix of Wood's apparatus and subjected to dissolution in each media with agitation of 50 rpm at 37 °C. In solubility by equilibrium method, lamivudine and zidovudine can be considered as highly soluble drugs. Although stavudine present high solubility in pH 4.5, 6.8, 7.5 and water, the solubility determination in pH 1.2 was not possible due stability problems. Regarding to intrinsic dissolution, lamivudine and stavudine present high speed of dissolution. Considering a boundary value presented by Yu and colleagues (2004), all drugs studied present high solubility characteristics in intrinsic dissolution method. Based on the obtained results, intrinsic dissolution seems to be superior for solubility studies as an alternative method for biopharmaceutical classification purposes.Uniterms: Drugs/solubility. Drugs/dissolution rate. Intrinsic dissolution/method/biopharmaceutical classification. Biopharmaceutical Classification System.A solubilidade e a taxa de dissolução de fármacos são de grande importância em estudos de pré-formulação de formas farmacêuticas. A melhora na solubilidade permite que os fármacos sejam candidatos potenciais à bioisenção, podendo ser uma boa maneira para desenvolver formulações dose-eficientes. O comportamento de solubilidade da lamivudina, estavudina e zidovudina em solventes individuais (sob faixa de pH 1,2 a 7,5) foi estudado pelos métodos de solubilidade em equilíbrio e dissolução intrínseca. No estudo de solubilidade pelo método do equilíbrio (método de agitação de frascos), conhecidas quantidades do fármaco foram adicionadas em cada meio até atingirem a saturação e a mistura foi submetida à agitação de 150 rpm por 72 horas a 37 °C. No ensaio de dissolução intrínseca, conhecida quantidade de cada fármaco foi comprimida na matriz do aparato de Wood e submetida à dissolução em cada meio com agitação de 50 rpm a 37 °C. No método de solubilidade em equilíbrio, a lamivudina e a zidovudina podem ser consideradas como fármacos altamente solúveis. Embora a estavudina apresente alta solubilidade nos meios pH 4,5, 6,8, 7,5 e água, a determinação da solubilidade em pH 1,2 não foi possível devido a problemas de estabilidade. Com relação à dissolução intrínseca, a lamivudina e a estavudina apresentaram alta velocidade de dissolução. Considerando o valor ...

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Section: Intrinsic Dissolution Methodsmentioning

confidence: 99%

Equilibrium solubility versus intrinsic dissolution: characterization of lamivudine, stavudine and zidovudine for BCS classification

Dezani

Pereira

Caffaro

et al. 2013

Braz. J. Pharm. Sci.

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“…A concentração de NaOH foi determinada por tratamento das curvas de pH versus volume sendo os volumes de equivalência determinados pelo método de primeira derivada. A primeira derivada apresenta um valor no ponto de inflexão da curva de titulação, que inicia próximo de zero antes do ponto final até atingir o máximo no ponto final, voltando a quase zero após o ponto final (Pereira et al, 2011).…”

Section: 1reagentes E Soluçõesunclassified

DEVELOPMENT OF SULFENTRAZONE EXTRACTION PROCEDURE FROM COMMERCIAL HERBICIDE FORMULATION AND DETERMINATION OF ITS IONIZATION CONSTANT (pKa) BY POTENTIOMETRIC TITRATION

Oliveira¹,

Silva²,

Paula³

et al. 2018

PTQ

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The herbicide sulfentrazone (SFZ) is widely used in soybean and sugarcane crops, although it is classified as very dangerous to the environment. To minimize barriers to the development of research with this herbicide due to the high cost of acquisition of its analytical standard and the availability of few distributors to acquire the standard in the country, a procedure of extraction and purification of SFZ was developed from a commercial herbicide formulation available in Brazil. Using the most suitable experimental conditions established for the extraction procedure, the SFZ content in the resulting solid after extraction and drying was 97.5% (m/m), which value was determined by acid-base potentiometric titrations. To characterize the solid obtained in this procedure, the material was studied by thermal analysis (thermogravimetry and differential scanning calorimetry) and Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) to confirm the presence of functional groups present in the SFZ molecule. Thermal analysis of the solid resulting from the extraction indicated processes of melting, thermal degradation and volatilization of the SFZ during its heating. By potentiometric titrations of the purified solid dissolved in water/acetonitrile (ACN) binary mixtures, it was possible to determine the ionization constant (pKa) of SFZ in water at 25.0ºC. By this study, extrapolated value of pKa in water is 6.45 obtained from the linear correlation of pKa versus molar ACN fraction plot. The value obtained at 25.0 °C by potentiometry in this study is quite close to the literature value of 6.56 determined at 20 °C by the spectrophotometric technique. However, the pKa value determined by potentiometric titrations of dilute solutions of the SFZ commercial formulations was much higher than that of 6.56, indicating that the degree of ionization of SFZ under herbicide application conditions can be quite distinct in the presence of possible adjuvants present in the commercial formulation of the herbicide.

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“…Therefore, potenciometric titration was not able to determine the values of both pK 1 and pK 2 for HPG in water. This may be explained by the low acidity of the amine group present in HPG (Pereira et al, 2011). Capillary zone electrophoresis (CZE) and ionic mobility curves may be applied to determine pK 1 and pK 2 values of weak acids (Slampová et al, 2008).…”

Section: Brazilian Journal Of Chemical Engineeringmentioning

confidence: 99%

Solid-liquid equilibrium data of amoxicillin and hydroxyphenylglycine in aqueous media

Bezerra

Chiavone‐Filho

Mattedi

2013

Braz. J. Chem. Eng.

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-The enzymatic synthesis of amoxicillin is catalyzed by Penicillin G Acylase (PGA). As byproducts, hydroxyphenylglycine and alcohol are also formed from hydrolytic reactions and antibiotic synthesis, respectively. The design of this process should be directed to promote the synthesis reaction. At the same time, it is necessary to reduce the hydrolytic reaction of amoxicillin through its crystallization or separation from the reaction medium. This work presents measurements of solid-liquid equilibrium data for amoxicillin and hydroxyphenylglycine in water at different temperatures (283.15 -298.15 K), pH (5.5 -7.5) and ethanol composition (0 -70 wt.%). This information is relevant to determine the conditions that offer the lowest solubility for the antibiotic, favoring its separation and purification. All solubility data were obtained using an analytical method with indirect determination by UV spectroscopy. Ideal thermodynamic modeling was applied to describe the experimental solubility data sets.

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Determinação da constante de dissociação (Ka) do captopril e da nimesulida: experimentos de química analítica para o curso de farmácia

Cited by 11 publications

References 7 publications

Equilibrium solubility versus intrinsic dissolution: characterization of lamivudine, stavudine and zidovudine for BCS classification

Equilibrium solubility versus intrinsic dissolution: characterization of lamivudine, stavudine and zidovudine for BCS classification

DEVELOPMENT OF SULFENTRAZONE EXTRACTION PROCEDURE FROM COMMERCIAL HERBICIDE FORMULATION AND DETERMINATION OF ITS IONIZATION CONSTANT (pKa) BY POTENTIOMETRIC TITRATION

Solid-liquid equilibrium data of amoxicillin and hydroxyphenylglycine in aqueous media

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