Nm For Ascorbic Acid Research Articles

Simultaneous determination of catecholamines, uric acid and ascorbic acid at physiological levels using poly( N-methylpyrrole)/Pd-nanoclusters sensor

An interesting electrochemical sensor has been constructed by the electrodeposition of palladium nanoclusters (Pd nano) on poly( N-methylpyrrole) (PMPy) film-coated platinum (Pt) electrode. Cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy were used to characterize the properties of the modified electrode. It was demonstrated that the electroactivity of the modified electrode depends strongly on the electrosynthesis conditions of the PMPy film and Pd nano. Moreover, the modified electrode exhibits strong electrocatalytic activity toward the oxidation of a mixture of dopamine (DA), ascorbic acid (AA), and uric acid (UA) with obvious reduction of overpotentials. The simultaneous analysis of this mixture at conventional (Pt, gold [Au], and glassy carbon) electrodes usually struggles. However, three well-resolved oxidation peaks for AA, DA, and UA with large peak separations allow this modified electrode to individually or simultaneously analyze AA, DA, and UA by using differential pulse voltammetry (DPV) with good stability, sensitivity, and selectivity. This sensor is also ideal for the simultaneous analysis of AA, UA and either of epinephrine (E), norepinephrine (NE) or l-DOPA. Additionally, the sensor shows strong electrocatalytic activity towards acetaminophen (ACOP) and other organic compounds. The calibration curves for AA, DA, and UA were obtained in the ranges of 0.05 to 1 mM, 0.1 to 10 μM, and 0.5 to 20 μM, respectively. The detection limits (signal/noise [S/N] = 3) were 7 μM, 12 nM, and 27 nM for AA, DA, and UA, respectively. The practical application of the modified electrode was demonstrated by measuring the concentrations of AA, DA, and UA in injection sample, human serum, and human urine samples, respectively, with satisfactory results. The reliability and stability of the modified electrode gave a good possibility for applying the technique to routine analysis of AA, DA, and UA in clinical tests.

Sodium glycylglycine as effective electrolyte run buffer for ascorbic and uric acid separation by CZE: A comparison with two other CE assays

A new CE method for ascorbic acid (AA) and uric acid (UA) detection in human plasma has been developed. Analytes were resolved in less than 4 min by employing sodium glycylglycine (Glygly) as electrolyte run buffer at pH 8.0. Using the diode array detector ability to measure multiple wavelengths simultaneously, detection was optimized by monitoring the run at 262 nm for AA and at 288 nm for UA. Electrophoretic parameters such as resolution, migration times, efficiency, and peak areas of this new method were compared to those obtained by the two CE assays described in literature, in which the analytes separation was achieved by using sodium borate (that allows faster migration times but poor resolution) or tricine (with the highest resolution but elevated migration times) as electrolyte run buffer. Sodium Glygly allows to obtain the same good resolution given by the tricine buffer but with the faster analysis times of the sodium borate run buffer. Ascorbate and urate levels were measured in 35 healthy volunteers by the three methods and the obtained data were compared by three different statistical tests (mountain plot, Passing-Bablok regression, and Bland-Altman test) in order to verify the accuracy of our proposed method.

Optimization of ascorbic and uric acid separation in human plasma by free zone capillary electrophoresis ultraviolet detection

In this paper we propose a new fast free zone capillary electrophoresis method for the simultaneous determination of ascorbic acid (AA) and uric acid (UA) in human plasma. We investigated the effect of analytical parameters, such as concentration and pH of borate running buffer, cartridge temperature, and sample treatment, on resolution, migration times, corrected peak areas, and efficiency. A good separation was achieved using a 60.2-cm × 75-μm uncoated silica capillary and 100 mmol/L sodium borate buffer, pH 8, when metaphosphoric acid was employed as protein precipitant, in less than 4 min. These conditions gave a good reproducibility of migration times (CV 0.35 and 0.34%) and peak areas (CV 3.2 and 3.1%) for ascorbate and urate, respectively. The limit of detection was 0.5 mg/L for both analytes when the detection was performed at 254 nm for AA and at 292 nm for UA. We compared the present method with a validated capillary electrophoresis assay by measuring plasma urate and ascorbate in 32 normal subjects and the obtained data were analyzed by the Passing and Bablok regression.

Two derivative spectrophotometric methods for the simultaneous determination of lovastatin combined with three antioxidants

A zero crossing and an algorithm bivariate calibration derivative method for the simultaneous determination of lovastatin combined separately with three antioxidants (ascorbic acid, quercetin and gallic acid) in synthetic mixtures are described. The aqueous or methanolic solutions obeyed Beer's law in the concentration ranges of 3.20–17.36 μg/ml for lovastatin, 1.76–8.80 μg/ml for ascorbic acid, 1.41–7.04 μg/ml for gallic acid and 1.84–9.20 μg/ml for quercetin, for both methods, respectively. In the second derivative ( 2D) zero crossing method measurements were carried out at 238.4 nm for lovastatin and 265.6 nm for ascorbic acid, 247.7 nm for lovastatin and 281.1 nm for quercetin, 251.8 nm for lovastatin and 267.6 nm for gallic acid. In the first derivative ( 1D) bivariate spectrophotometric method an optimum pair of wavelengths was chosen for the determination of different binary mixtures. The proposed procedures were successfully applied to the simultaneous determination of lovastatin and different antioxidants in mixtures with high percentage of recovery, 98.3–100.4% for lovastatin, 98.3–98.6% for ascorbic acid, 99.0–99.8% for quercetin and 100.5–101.1% for gallic acid and good precision. In addition, the results from the above procedures were verified by using partial least-squares (PLS) multivariate calibration method.

Studies of sol-gel ceramic film incorporating methylene blue on glassy carbon: an electrocatalytic system for the simultaneous determination of ascorbic and uric acids.

In this work, we investigated the immobilization of methylene blue in a methyltrimethoxysilane sol-gel ceramic film on a glassy carbon electrode. Up to a certain saturation level, under our conditions, it was found that the methylene blue was tightly held and did not leach out into aqueous solutions, even with continuous immersion for up to 1 month. The electrochemical behavior of the immobilized methylene blue was then studied. pH variation revealed that there were two distinct redox couples whose existences were pH-dependent. The methylene blue/sol-gel film was also examined as an electrocatalytic system for ascorbic and uric acid oxidations. It was revealed that this system was highly sensitive for ascorbic and uric acid sensing (practical determination limits of 5.00 nM and 1.00 nM for ascorbic acid and uric acid, respectively) and also allowed simultaneous determination of these biomolecules. The simultaneous determination of these two analytes in a human urine sample was demonstrated. The stability of the methylene blue/sol-gel film/glassy carbon electrode sensing system was good, with up to at least a month of continual operation.

Spectrophotometric Determination of Ascorbic acid in Pharmaceutical Products with the Copper(II)-rhodanine Reagent

Abstract A simple method has been developed for the determination of ascorbic acid(AA) in pharmaceutical products by the copper(II)-5-(4-hydroxy-3-methoxybenzilidene) rhodanine reagent. The method is based on the oxidation of AA with the reagent and complexation of copper(I) produot with unchanged rhodanlne. The red complex soluble In dioxane-water yields an effective molar absorptivity of 2.6x104 l.mol−1. cm-1 at 473 nm for AA at an apparent pH of 3.8.Beer's law is obeyed between 6.25x10−6and 3.75x10−5 mol.dm−3 concentrations of AA with a relative standard deviation of 3.4%.The method has been successfully applied to vitamin C assay in pharmaceutical formulations. Biologically important thiols such as cysteine and glutathione could also be quantified by the same procedure with a molar absorptivity of 1.3x104 l.mol−1 cm−1.

Spectrophotometric determination of ascorbic acid and thiamine hydrochloride in pharmaceutical products using derivative spectrophotometry

Direct spectrophotometric methods for the determination of ascorbic acid (vitamin C) and thiamine hydrochloride (vitamin B1) each in the presence of its degradation product are presented. The methods are based on the use of UV derivative spectrophotometric measurements—the first derivative at 215 nm for ascorbic acid and the second derivative at 254 nm for thiamine hydrochloride. The values obtained are linearly related to the concentration of each vitamin solution and have relative standard deviations of 0.52 and 1.07%, respectively. The mean percentage recoveries for mixtures of each vitamin with their respective degradation product were found to be 101.5 and 99.4%, respectively. Graphs of log C(%m/V)versus time for ascorbic acid solution in 3 N hydrochloric acid and for thiamine hydrochloride solution in buffer at pH 10 were straight lines with slopes of –0.1044 d–1 and –0.0207 h–1, respectively. The methods have been successfully applied to monitor the stability of the vitamins.