953 resultados para Determination method
Resumo:
Polygala cyparissias is a plant widespread in Southern Latin America. Recently, we demonstrated the gastroprotective activity of the extract, as well as for one of the isolated metabolites-1,7-dihydroxy-2,3-methylenedioxyxanthone (MDX). In this study, a HPLC method for the quantification of MDX was validated. The HPLC method was linear (0.5-24 µg mL-1 of MDX) with good accuracy, precision and robustness. The content of MDX in the extracts from whole and different parts of the plant ranged from 0 to 5.4 mg g-1 and the gastroprotective index ranged from 72.1 to 99.1%. Thus, the method might be used for the standardization of the extracts based on the MDX marker.
Resumo:
A stability-indicating RP-HPLC method is presented for determination of gatifloxacin and flurbiprofen in binary combination. Gatifloxacin, flurbiprofen and their degradation products were detected at 254 nm using a BDS Hypersil C8 (250 X 4.6 mm, 5 µm) column and mixture of 20 mM phosphate buffer (pH 3.0) and methanol 30:70 v/v as mobile phase. Response was linear over the range of 15-105 mg mL-1 for gatifloxacin (r² > 0.998) and of 1.5-10.5 mg mL-1 for flurbiprofen (r² > 0.999). The developed method efficiently separated the analytical peaks from degradation products (peak purity index > 0.9999). The method developed can be applied successfully for determination of gatifloxacin and flurbiprofen in human serum, urine, pharmaceutical formulations, and their stability studies.
Resumo:
A simple procedure is described for the determination of scopolamine by square-wave voltammetry using a cathodically pretreated boron-doped diamond electrode. Cyclic voltammetry studies indicate that the oxidation of scopolamine is irreversible at a peak potential of 1.59 V (vs. Ag/AgCl (3.0 mol L-1 KCl)) in a 0.50 mol L-1 sulfuric acid solution. Under optimized conditions, the analytical curve obtained was linear (r = 0.9996) for the scopolamine concentration range of 1.0 to 110 µmol L-1, with a detection limit of 0.84 µmol L-1. The method was successfully applied to the determination of scopolamine in pharmaceutical formulations with minimum sample preparation.
Resumo:
In this research, scanometry was used as a new, simple, fast and inexpensive method for a colorimetric determination of Mn2+ ion in water samples and thermocouple wire through the use of periodate reagent in an acidic medium. The results showed the oxidization of colorless Mn2+ ion by periodate and the formation of a purplish MnO4- ion. The system had a linear range of 1.0 to 70.0 µg mL-1 Mn2+ ion with a detection limit of 0.314 µg mL-1 and a relative standard deviation of 2.77% for G color value. This method has the capability to determine low levels of Mn2+ ion in thermocouple wire and water samples.
Resumo:
Bioorganic and biological chemistry have been found to be highly motivating to undergraduate students and in this context, biochemical blood parameter analysis emerges as highly attractive content. In this proposal, several aspects related to analyses of glucose, cholesterol and triglycerides using the enzymatic colorimetric method were involved, and the findings have at least two relevant implications: i) introducing students to connections between organic chemistry and biology based on enzymatic processes, including reactivity and mechanistic aspects; ii) performing a micro scale bioassay analysis. The proposal requires two theoretical classes (2 h per class) and one practical class (4 h).
Resumo:
The microencapsulation of palm oil may be a mechanism for protecting and promoting the controlled release of its bioactive compounds. To optimize the microencapsulation process, it is necessary to accurately quantify the palm oil present both external and internal to the microcapsules. In this study, we developed and validated a spectrophotometric method to determine the microencapsulation efficiency of palm oil by complex coacervation. We used gelatin and gum arabic (1:1) as wall material in a 5% concentration (w/v) and palm oil in the same concentration. The coacervates were obtained at pH 4.0 ± 0.01, decanted for 24 h, frozen (−40 ºC), and lyophilized for 72 h. Morphological analyzes were then performed. We standardized the extraction of the external palm oil through five successive washes with an organic solvent. We then explored the best method for rupturing the microcapsules. After successive extractions with hexane, we determined the amount of palm oil contained in the microcapsules using a spectrophotometer. The proposed method was shown to be of low cost, fast, and easy to implement. In addition, in the validation step, we confirmed the method to be safe and reliable, as it proved to be specific, accurate, precise, and robust.
Resumo:
In this study, dispersive liquid-liquid microextraction based on the solidification of floating organic droplets was used for the preconcentration and determination of thorium in the water samples. In this method, acetone and 1-undecanol were used as disperser and extraction solvents, respectively, and the ligand 1-(2-thenoyl)-3,3,3-trifluoracetone reagent (TTA) and Aliquat 336 was used as a chelating agent and an ion-paring reagent, for the extraction of thorium, respectively. Inductively coupled plasma-optical emission spectrometry was applied for the quantitation of the analyte after preconcentration. The effect of various factors, such as the extraction and disperser solvent, sample pH, concentration of TTA and concentration of aliquat336 were investigated. Under the optimum conditions, the calibration graph was linear within the thorium content range of 1.0-250 µg L-1 with a detection limit of 0.2 µg L-1. The method was also successfully applied for the determination of thorium in the different water samples.
Resumo:
A simple spectrophotometric method for the determination of cefotaxime, ceftriaxone, cefadroxil and cephalexin with variamine blue is presented. The determination is based on the hydrolysis of β-lactam ring of cephalosporins with sodium hydroxide which subsequently reacts with iodate to liberate iodine in acidic medium. The liberated iodine oxidizes variamine blue to violet colored species of maximum absorption at 556 nm. The absorbance is measured within the pH range of 4.0-4.2. Beer's law is obeyed in the range of 0.5-5.8 µg mL-1, 0.2-7.0 µg mL-1, 0.2-5.0 µg mL-1 and 0.5-8.5 µg mL-1 for cefotaxime, ceftriaxone, cefadroxil and cephalexin respectively. The analytical parameters were optimized and the method is successfully applied for the determination of cefotaxime, ceftriaxone, cefadroxil and cephalexin in pharmaceuticals.
Resumo:
A simple, rapid and sensitive spectrophotometric method has been developed for the determination of methyldopa in pharmaceutical formulations. The method is based on the reaction between tetrachloro-p-benzoquinone (p-chloranil) and methyldopa, accelerated by hydrogen peroxide (H2O2), producing a violet-red compound (λmax = 535 nm) at ambient temperature (25.0 ± 0.2 ºC). Experimental design methodologies were used to optimize the measurement conditions. Beer's law is obeyed in a concentration range from 2.10 x 10-4 to 2.48 x 10-3 mol L-1 (r = 0.9997). The limit of detection was 7.55 x 10-6 mol L-1 and the limit of quantification was 2.52 x 10-5 mol L-1. The intraday precision and interday precision were studied for 10 replicate analyses of 1.59 x 10-3 mol L-1 methyldopa solution and the respective coefficients of variation were 0.7 and 1.1 %. The proposed method was successfully applied to the determination of methyldopa in commercial brands of pharmaceuticals. No interferences were observed from the common excipients in the formulations. The results obtained by the proposed method were favorably compared with those given by the Brazilian Pharmacopoeia procedure at 95 % confidence level.
Resumo:
A novel sensitive and relatively selective kinetic method is presented for the determination of V(V), based on its catalytic effect on the oxidation reaction of Ponceau Xylydine by potassium bromate in presence of 5-sulfosalicylic acid (SSA) as activator. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of Ponceau Xylydine at 640 nm between 0.5 to 7 min (the fixed time method) in H3PO4 medium at 25ºC. The effect of various parameters such as concentrations of H3PO4, SSA, bromate and Ponceau Xylydine, temperature and ionic strength on the rate of net reaction were studied. The method is free from most interferences, especially from large amounts of V(IV). The decrease in absorbance is proportional to the concentration of V(V) over the entire concentration range tested (1-15 ng mL−1) with a detection limit of 0.46 ng mL-1 (according to statistical 3Sblank/k criterion) and a coefficient of variation (CV) of 1.8% (for ten replicate measurement at 95% confidence level). The proposed method suffers few interferences such as Cr(VI) and Hg(II) ions. The method was successfully applied to the determination of V(V) in tap water, drinking water, bottled mineral water samples and a certified standard reference material such as SRM-1640 with satisfactory results. The vanadium contents of water samples were also determined by FAAS for a comparison. The recovery of spiked vanadium(V) was found to be quantitative and the reproducibility was satisfactory. It was observed that the results of the SRM 1640 were in good agreement with the certified value.
Resumo:
The goal of this work was to develop a simple and rapid preparation method for patulin analysis in apple juice without previous clean-up. This method combined sonication and liquid extraction techniques and was used for determination of patulin in 37 commercial apple juices available on the market in the South of Brazil. The method performance characteristics were determined using a sample obtained in a local market fortified at five concentration levels of patulin and done in triplicates. The coefficient of variation for repeatability at the fortification level of 20.70µg.L-1 was 3.53 % and the recovery 94.63 %, respectively. The correlation coefficient was 0.9996 and agrees with the requirements for a linear analytical method value. The detection limit was 0.21µg.L-1 and the quantification limit 0.70 µg.L-1. Only three of the analyzed samples were upper the allowed level of 50.00 µg.L-1 recommended for the World Health Organization.
Resumo:
A simple, sensitive and reproducible spectrophotometric method was developed for the determination of sitagliptin phosphate in bulk and in pharmaceutical formulations. The proposed method is based on condensation of the primary amino group of sitagliptin phosphate with acetyl acetone and formaldehyde producing a yellow colored product, which is measured spectrophotometrically at 430nm. The color was stable for about 1 hour. Beer's law is obeyed over a concentration range of 5-25 µg/ml. The apparent molar absorptivity and Sandell sensitivity values are 1.067 x 10(4) Lmol-1cm-1 and 0.0471 µgcm-2 respectively. All the variables were studied to optimize the reaction conditions. No interference was observed in the presence of common pharmaceutical excipients. The validity of the method was tested by analyzing sitagliptin phosphate in its pharmaceutical preparations. Good recoveries were obtained. The developed method was successfully employed for the determination of sitagliptin phosphate in various pharmaceutical preparations.
Resumo:
A simple, rapid and sensitive spectrophotometric method for the determination of captopril (CPT) in pharmaceutical formulations is proposed. This method is based on the reduction reaction of ammonium molybdate, in the presence of sulphuric acid, for the group thiol of CPT, producing a green compound (λ max 407 nm). Beer's law is obeyed in a concentration range of 4.60 x 10-4 - 1.84 x 10-3 mol l-1 of CPT with an excellent correlation coefficient (r = 0.9995). The limit of detection and limit of quantification were 7.31 x 10-6 e 2.43 x 10-5 mol l-1 of CPT, respectively. The proposed method was successfully applied to the determination of CPT in commercial brands of pharmaceuticals. No interferences were observed from the common excipients in the formulations. The results obtained by the proposed method were favorably compared with those given by the official reported method at 95 % confidence level.
Resumo:
A simple, rapid, accurate and inexpensive spectrophotometric method for the determination of tetracycline and doxycycline has been developed. The method is based on the reaction between these drugs and chloramine-T in alkaline medium producing red color products with absorbance maximum at the Λ = 535 and 525 nm for the tetracycline and doxycycline, respectively. The best conditions for the reactions have been found using multivariate method. Beer´s law is obeyed in a concentration ranges 1.03 x 10-5 to 3.61 x 10-4 mol L-1 and 1.75 x 10-5 to 3.48 x 10-4 mol L-1 for the tetracycline and doxycycline, respectively. The quantification limits were 5.63 x 10-6 mol L-1 and 7.12 x 10-7 mol L-1 for the tetracycline and doxycycline, respectively. The proposed method was successfully applied to the determination of these drugs in pharmaceutical formulations and the results obtained were in good agreement with those obtained by the comparative method at the 95% confidence level.