Determination of atenolol in pharmaceutical formulations by diffuse reflectance spectroscopy

A simple analytical method for quantification of atenolol in pharmaceutical formulations by diffuse reflectance spectroscopy is described. The method is based on the reaction, on the filter paper surface, between the drug and p-chloranil producing a colored compound. The best reaction conditions were obtained with 20 μL of atenolol solution and 20 μL of p-chloranil. All reflectance measurements were carried out at 550 nm and the linear range was from 1.13×10-2 to 7.88×10-2 mol L-1 (r = 0.9992). The limit of detection was 2.80 × 10-3 mol L-1. The proposed method was successfully applied to analysis of different commercial brands of pharmaceutical formulations and the results obtained by the proposed method were in good agreement with those obtained using the British Pharmacopoeia method.

Determination of calcium and magnesium in hydroethanolic extracts of propolis by atomic absorption flame spectrophotometry

Propolis is a natural product collected by honeybees and has a large range of pharmacological activity, including antimicrobial, antitumoral, antioxidant and anti-inflammatory. Its use as a popular medicine is increasing all over the world, creating a need for quality control of the commercial products. In this study the levels of calcium and magnesium in commercial hydroalcoholic propolis extracts from varies states of Brazil were determined by atomic absorption flame spectrophotometry and different values were obtained for northern and southern states. This study can be extended to the analysis of metals that are harmful to health. The results showed that the calibration curves were linear over a wide concentration range (0.5-4.0 μg.mL -1 for calcium and 0.05-0.4 μg.mL -1 for magnesium) with good correlation coefficients (0.999 and 0.988, respectively). Good analytical recovery (94%) was obtained. The proposed method showed adequate precision and relative standard deviation lower than 2 %. The method is accurate and precise as well as having advantages such as simplicity and speed.

Electrochemical behavior and voltammetric determination of pyrazinamide using a poly-histidine modified electrode

Pyrazinamide (Pyrazinecarboxamide-PZA) is a drug that is used to treatment tuberculosis. In the present work, the voltammetric behavior of PZA was studied using a screen-printed modified electrode (SPCE). The modified electrode was constructed using poly-histidine films, and it showed an electrocatalytic effect, thus promoting a decrease in PZA reduction potential and improving the voltammetric response. Cyclic voltammetry and electrochemical impedance spectroscopy techniques have been employed in order to elucidate of the electrodic reaction. The results allowed the proposal that in the PZA reduction, a further chemical reaction occurs that corresponds to a second-order process which is subsequent to the electrode reaction. In addition, a sensitive voltammetric method was developed, and it was successfully applied for PZA determination in human urine samples. The best response was found using SPCE modified with poly-histidine prepared by histidine monomer electropolymerization (SPCE/EPH). The electroanalytical performance of the SPCE/EPH was investigated by linear sweep (LSV), differential pulse (DPV), and square wave voltammetry (SWV). A linear relationship between peak current and PZA concentrations was obtained from 9.0 × 10-7 to 1.0 × 10-4 mol L-1 by using DPV. The limit of detection at 5.7 × 10 -7 mol L-1 was estimated, and a relative standard deviation of the 5.0 × 10-6 mol L-1 of PZA of 10 measurement was 3.7%. © 2012 Elsevier B.V. All rights reserved.

Validation of a stability-indicating RP-LC method for the determination of tigecycline in lyophilized powder

A reversed-phase liquid chromatography (RP-LC) method was validated for the determination of tigecycline in lyophilized powder. The LC method was conducted on a Luna C18 column (250 × 4.6 mm i.d.), maintained at room temperature. The mobile phase consisted of buffer containing sodium phosphate monobasic (0.015M) and oxalic acid (0.015M) (pH 7.0)-acetonitrile (75:25, v/v), run at a flow rate of 1.0 mL/min and using ultraviolet detection at 280 nm. The chromatographic separation was obtained with a retention time of 8.6 min, and was linear in the range of 40-100 μg/mL (r2 = 0.9997). The specificity and stability-indicating capability of the method was proven through forced degradation studies, which also showed no interference of the excipients. The accuracy was 99.01% with a bias lower than 1.81%. The limits of detection and quantitation were 1.67 and 5.05 μg/mL, respectively. Moreover, method validation demonstrated satisfactory results for precision and robustness. The proposed method was applied for the analysis of the lyophilized powder formulation, contributing to improve the quality control and to assure the therapeutic efficacy. © The Author [2012]. Published by Oxford University Press. All rights reserved.

Determination of disease biomarkers in Eucalyptus by comprehensive two-dimensional gas chromatography and multivariate data analysis

In this paper is reported the use of the chromatographic profiles of volatiles to determine disease markers in plants - in this case, leaves of Eucalyptus globulus contaminated by the necrotroph fungus Teratosphaeria nubilosa. The volatile fraction was isolated by headspace solid phase microextraction (HS-SPME) and analyzed by comprehensive two-dimensional gas chromatography-fast quadrupole mass spectrometry (GC. ×. GC-qMS). For the correlation between the metabolic profile described by the chromatograms and the presence of the infection, unfolded-partial least squares discriminant analysis (U-PLS-DA) with orthogonal signal correction (OSC) were employed. The proposed method was checked to be independent of factors such as the age of the harvested plants. The manipulation of the mathematical model obtained also resulted in graphic representations similar to real chromatograms, which allowed the tentative identification of more than 40 compounds potentially useful as disease biomarkers for this plant/pathogen pair. The proposed methodology can be considered as highly reliable, since the diagnosis is based on the whole chromatographic profile rather than in the detection of a single analyte. © 2013 Elsevier B.V..

Development and Validation of A Stability-Indicating Mekc Method for Determination of Flucloxacillin Sodium in Capsules

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Validation of an HPLC Method for the Determination of Dibucaine Encapsulated in Solid Lipid Nanoparticles and Nanostructured Lipid Carriers

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Stability-indicating LC method for the determination of cephalothin in lyophilized powder for injection

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Stability-indicating thin-layer chromatographic method for determination of darunavir in complex darunavir-beta-cyclodextrin in the presence of its degradation products

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Determination of pantoprazole in human plasma by LC-MS-MS using lansoprazole as internal standard

An analytical method based on liquid chromatography with positive ion electrospray ionization (ESI) coupled to tandem mass spectrometry detection was developed for the determination of pantoprazole (CAS 102625-70-7) in human plasma using lansoprazole (CAS 103577-45-3) as the internal standard. The analyte and internal standard were extracted from the plasma samples by liquid/liquid extraction using diethyl-ether/dichloromethane (70:30; v/v) and chromatographed on a C-8 analytical column. The mobile phase consisted of acetonitrile/water/methanol (57:25:18; v/v/v) + 10 mmol/l acetic acid + 20 mmol/l ammonium acetate. The method has a chromatographic total run time of 4.5 min and was linear within the range 5.0-5,000 ng/mL. Detection was performed on a triple quadrupole tandem mass spectrometer by Multiple Reaction Monitoring (MRM). The intra- and inter-run precisions calculated from quality control (QC) samples were 4.2% and 3.2%, respectively. The accuracies as determined from QC samples were -5.0% (intra-run) and 2.0% (inter-run). The method herein described was employed in a bioequivalence study of two tablet formulations of pantoprazole.

Flavonoid Detection in Hydroethanolic Extract of Pouteria torta (Sapotaceae) Leaves by HPLC-DAD and the Determination of Its Mutagenic Activity

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Determination of anticonvulsants in human plasma using SPME in a heated interface coupled online to liquid chromatography (SPME-LC)

A simple and sensitive method using solid phase microextraction (SPME) and liquid chromatography (LC) with heated online desorption (SPME-LC) was developed and validated to analyze anticonvulsants (AEDs) in human plasma samples. A heated lab-made interface chamber was used in the desorption procedure, which allowed the transference of the whole extracted sample. The SPME conditions were optimized by applying an experimental design. Important factors are discussed such as fiber coating types, pH, extraction time and desorption conditions. The drugs were analyzed by LC, using a C18 column (150 mm 4.6 mm 5 mm); and 50 mmol L1 , pH ¼ 5.50 ammonium acetate buffer : acetonitrile : methanol (55 : 22 : 23 v/v) as the mobile phase with a flow rate of 0.8 mL min1 . The suggested method presented precision (intra-assay and inter-assay), linearity and limit of quantification (LOQ) all adequate for the therapeutic drug monitoring (TDM) of AEDs in plasma.

Pharmacokinetics of hydroxymethylnitrofurazone and its parent drug nitrofurazone in rabbits

The prodrug hydroximethylnitrofurazone (NFOH) presents antichagasic activity with greatly reduced toxicity compared to its drug matrix nitrofurazone (NF). Besides these new characteristics, the prodrug was more active against the parasite T. cruzi amastigotes. These advantages make the prodrug a possible therapeutic alternative for the treatment of both acute and the chronic phase of Chagas disease. However, the knowledge of pharmacokinetic profile is crucial to evaluate the feasibility of a new drug. In this study, our objective was to evaluate the in vivo formation of NF from the NFOH single administration and to evaluate its pharmacokinetic profile and compared it to NF administration. A bioanalytical method to determine the NF and NFOH by LCMS/MS was developed and validated to perform these investigations. Male albino rabbits (n=15) received NF intravenously and orally in doses of 6.35 and 63.5 mg / kg respectively, and NFOH, 80.5 mg / kg orally. The serial blood samples were processed and analyzed by mass spectrometry. The system operated in positive and negative modes for the analites determination, under elution of the mobile phase 50:50 water: methanol. The administration of NFOH allowed the calculation of pharmacokinetic parameters for the prodrug, and the NF obtained from NFOH administration. Using the pharmacokinetic profile obtained from the NF i.v. administration, the oral bioavailability of NF from the administered prodrug was obtained (60.1%) and, as a key parameter in a prodrug administration, should be considered in future studies. The i.v. and oral administrations of NF differ in the constant of elimination (0.04 vs 0.002) and elimination half-life (17.32 min vs 276.09 min) due to the low solubility of the drug that hinders the formation of molecular dispersions in the digestory tract. Still, there was observed no statistical differences were observed between the pharmacokinetic parameters of orally administered NF and NF obtained from NFOH. The calculated area under the curve (AUC 0-∞) showed that the exposure to the parental drug was fairly the same (844.79 vs 566.44) for NF and NF obtained from the prodrug administration. The tendency to higher NF's mean residence time (MRT) as observed in the prodrug administration (956.1 min vs 496.3 min) guarantees longer time for the action of the drug and it allows the expansion of the administration intervals. These findings, added with the beneficial characteristics of the prodrug encourage new efficacy tests towards the clinical use of NFOH.

Validation of a stability indicating capillary electrophoresis method for the determination of darunavir in tablets and comparison with the of infrared absorption spectroscopic method

Darunavir (DRV) is a protease inhibitor used in the treatment of HIV infection, which constitutes a keystone in the therapy of patients infected with this virus. There is no monograph described in official compendia. The literature provides few methods of analysis for the determination of DRV in pharmaceuticals which include TLC, IR, UPLC, HPLC, HPLC-MS, HPLC-MS/MS, but there are no reports of the use of capillary electrophoresis (CE) for the determination of this drug. Thus, this research proposed the development and validation of a CE method for the determination of DRV in tablets. The method was completely validated according to the International Conference on Harmonization guidelines, showing linearity, selectivity, precision, accuracy and robustness. The migration was achieved in less than 1 minute using fused-silica uncoated capillary with an id of 50 μm and total length of 21 cm and voltage of +20 kV. The sample injection was performed in the hydrodynamic mode. The method was linear over the concentration range of 50-200 μg mL-1 with correlation coefficient 0.9998 and limits of detection and quantification of 7.29 and 22.09 μg mL-1, respectively. The drug was subjected to acid, base, oxidation and photolysis degradation. Degradation products were found interfering with the assay of DRV, therefore the method can be regarded as stability indicating. The validated method is useful and appropriate for the routine quality control of DRV in tablets.