Ascorbic Acid In Pharmaceuticals Research Articles

Determination of Ascorbic Acid in Pharmaceuticals and Food Supplements with the New Potassium Ferrocyanide-Doped Polypyrrole-Modified Platinum Electrode Sensor

This paper reports the results obtained from the determination of ascorbic acid with platinum-based voltammetric sensors modified with potassium hexacyanoferrate-doped polypyrrole. The preparation of the modified electrodes was carried out by electrochemical polymerization of pyrrole from aqueous solutions, using chronoamperometry. Polypyrrole films were deposited on the surface of the platinum electrode, by applying a constant potential of 0.8 V for 30 s. The thickness of the polymer film was calculated from the chronoamperometric data, and the value was 0.163 μm. Cyclic voltammetry was the method used for the Pt/PPy-FeCN electrode electrochemical characterization in several types of solution, including KCl, potassium ferrocyanide, and ascorbic acid. The thin doped polymer layer showed excellent sensitivity for ascorbic acid detection. From the voltammetric studies carried out in solutions of different concentrations of ascorbic acid, ranging from 1 to 100 × 10−6 M, a detection limit of 2.5 × 10−7 M was obtained. Validation of the analyses was performed using pharmaceutical products with different concentrations of ascorbic acid, from different manufacturers and presented in various pharmaceutical forms, i.e., intravascular administration ampoules, chewable tablets, and powder for oral suspension.

A highly sensitive switch-on spectrofluorometric method for determination of ascorbic acid using a selective eco-friendly approach

Ascorbic acid has recently been extensively used due to its role in the management of COVID-19 infections by stimulating the immune system and triggering phagocytosis of the corona virus. The currently used spectrofluorometric methods for determination of ascorbic acid require using derivatizing agents or fluorescent probes and suffer from a number of limitations, including slow reaction rates, low yield, limited sensitivity, long reaction times and high temperatures. In this work, we present a highly sensitive spectrofluorometric method for determination of ascorbic acid by switching-on the fluorescence of salicylate in presence of iron (III) due to a reduction of the cation to iron (II). The addition of ascorbic acid resulted in a corresponding enhancement in the fluorescence intensity of iron (III)-salicylate complex at emission wavelength = 411 nm. The method was found linear in the range of 1–8 µg/mL with a correlation coefficient of 0.9997. The limits of detection and quantitation were 0.035 µg/mL and 0.106 µg/mL, respectively. The developed method was applied for the determination of ascorbic acid in the commercially available dosage form; Ruta C60® tablets. The obtained results were compared with those obtained by a reported liquid chromatographic method at 95% confidence interval, no statistically significant differences were found between the developed and the reported methods. Yet, the developed spectrofluorometric method was found markedly greener than the reference method, based on the analytical Eco-scale and the green analytical procedure index. This work presents a simple, rapid and sensitive method that can possibly be applied for determination of ascorbic acid in pharmaceuticals, biological fluids and food samples.

A novel voltammetric platform composed of poly(aminopyrazine), ZrO2 and CNTs for a rapid, sensitive and selective determination of ascorbic acid in pharmaceuticals and food samples

An electrochemical platform based on a composite of poly(aminopyrazine) (PAP), zirconium oxide nanoparticles (ZrO2NPs) and carbon nanotubes (CNTs) was prepared. A GCE was first modified with CNTs and ZrO2NPs via a drop-casting technique. Then, the ZrO2NPs/CNTs/GCE system was immersed into an aqueous solution of 1 mM aminopyrazine (AP) containing 10 mM LiClO4 in a potential range of −1.5 V–1.5 V for 20 cycles to carry out the polymerization step. The composite layer was characterized by energy dispersive X-ray (EDX), X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The proposed voltammetric platform (PAP/ZrO2NPs/CNTs on GCE) was applied for the electrooxidation of ascorbic acid (AA). Compared with ZrO2NPs/CNTs/GCE, CNTs/GCE and GCE, the proposed novel system (PAP/ZrO2NPs/CNTs/GCE) presented an effective catalytic activity for the oxidation of AA with a large enhancement in the current response. The procedure has also enabled a large peak to peak separation between AA and tryptophan (TRP). A linear dynamic current response was obtained for the concentrations of AA in the range of 1.0 × 10−6 - 2.95 × 10−4 M with a detection limit of 3.5 × 10−7 M. The quantification of AA in pharmaceuticals and mixed fruit juices has successfully been performed by PAP/ZrO2NPs/CNTs/GCE.

Nitrogen dozen carbon quantum dots as one dual function sensing platform for electrochemical and fluorescent detecting ascorbic acid

A novel amine-modified carbon quantum dots (NH2-CQDs), which can act as a dual-detection probe for the ascorbic acid (AA) response, was synthesized. The product was obtained via facile and green hydrothermal carbonization of L-histidine. The high nitrogen to carbon ratio of L-histidine warrants a high nitrogen content of these CQDs, and thus to have more free electron pairs. This results in good electron transport capability. The NH2-CQDs with an average diameter of 3.67 ± 0.78 nm display blue fluorescence, with excitation/emission maxima at 340/420 nm, and a quantum yield of 15.9%. The fluorescence can be quenched by AA. Moreover, the NH2-CQDs can selectively detect AA with electrochemical detection. On the basis of the electrochemical and fluorescent properties of the NH2-CQDs, the electrochemistry method and fluorescence analysis for the detection of AA with a detection limit of 2.7 μM and 57 nM are developed. This finding may provide a dual-detection platform, which can be used as a potential candidate for more selective to detect AA in pharmaceuticals, clinics, and food industries.

Determination of Ascorbic Acid in Pharmaceuticals and Biological Fluids by the Quenching of Europium Luminescence

Here we present a novel strategy for the quantification of ascorbic acid (AA) (vitamin C). The developed method is based on the quenching effect produced by AA on the time-resolved luminescence signal of europium ions using excitation and emission wavelengths of 388 nm and 617 nm. The method presents a linear dynamic range from 0.2 to 2 µg mL−1 with a detection limit of 0.06 µg mL−1 and a relative standard deviation lower than 6%. The method was applied to the determination of AA in pharmaceutical preparations, human serum and human urine. The obtained results in pharmaceuticals were compared with a reference method; the recovery yields were close to 100% in all cases. The accuracy of the method was statistically assessed, demonstrating the suitability of this alternative method for the determination of AA in pharmaceuticals and biological samples, requiring no sample treatment except for a dilution step.

Flow Systems with MnO2-coated Open Tubular Reactors for Spectrophotometric Determination of Ascorbic Acid in Pharmaceutical Products

ABSTRACTA novel strategy for preparing polyethylene open tubular reactors coated with MnO2(s) was pioneered for flow analysis in order to minimize the inherent drawbacks of packed solid reagents. As an application, the determination of ascorbic acid in pharmaceuticals was selected. The method involved reduction of Mn(IV) by ascorbic acid, release of the formed Mn2+ ion, reaction with formaldoxime, and spectrophotometric monitoring. The influence of flow pattern was investigated by using two similar flow systems relying on constant or pulsed flow delivered by peristaltic or solenoid pumps. With pulsed flow, system versatility and ruggedness were improved, and the analytical sensitivity (0.01143 L mg−1 ascorbic acid), detection limit (0.6 mg L−1 ascorbic acid), and sampling rate (60 h−1) evaluated compared to constant flow were improved by 2.1%, 40.0%, and 6.5%, respectively. At the same time, the reagent consumption (2.8 mg per determination) and analytical precision (relative standard deviation of approximately 2.5%) were maintained. One can conclude that the mixing conditions did not limit the analyte/reagent interaction. The results were in agreement with the British Pharmacopoeia method.

Simultaneous determination of iron (II) and ascorbic acid in pharmaceuticas based on flow sandwich technique.

The simple and easy performed flow system based on sandwich technique has been developed for the simultaneous separate determination of iron (II) and ascorbic acid in pharmaceuticals. The implementation of sandwich technique assumed the injection of sample solution between two selective reagents and allowed the carrying out in reaction coil two chemical reactions simultaneously: iron (II) with 1,10-phenanthroline and ascorbic acid with sodium 2,6-dichlorophenolindophenol. For achieving of excellent repeatability and considerable reagent saving the various parameters such as flow rate, sample and reagent volumes, reaction coil length were also optimized. The limits of detection (LODs) obtained by using the developed flow sandwich-type approach were 0.2 mg L(-1) for iron (II) and 0.7 mg L(-1) for ascorbic acid. The suggested approach was validated according to the following parameters: linearity and sensitivity, precision, recoveries and accuracy. The sampling frequency was 41 h(-1).

Surfactant media for constant-current coulometry. Application for the determination of antioxidants in pharmaceuticals

Effect of surfactant presence on electrochemical generation of titrants has been evaluated and discussed for the first time. Cationic (1-dodecylpyridinium and cetylpyridinium bromide), anionic (sodium dodecyl sulfate) and nonionic (Triton X100 and Brij® 35) surfactants as well as nonionic high molecular weight polymer (PEG 4000) do not react with the electrogenerated bromine, iodine and hexacyanoferrate(III) ions. The electrogenerated chlorine chemically interact with Triton X100 and Brij® 35. The allowable range of surfactants concentrations providing 100% current yield has been found. Chain-breaking low molecular weight antioxidants (ascorbic acid, rutin, α-tocopherol and retinol) were determined by reaction with the electrogenerated titrants in surfactant media. Nonionic and cationic surfactants can be used for the determination of antioxidants by reaction with the electrogenerated halogens. On contrary, cationic surfactants gives significantly overstated results of antioxidants determination with electrogenerated hexacyanoferrate(III) ions. The use of surfactants in coulometry of α-tocopherol and retinol provides their solubilization and allows to perform titration in water media. Simple, express and reliable coulometric approach for determination of α-tocopherol, rutin and ascorbic acid in pharmaceuticals using surfactant media has been developed. The relative standard deviation of the measurements does not exceed of 5%.

Preparation of Tetraheptylammonium Iodide-Iodine Graphite-Multiwall Carbon Nanotube Paste Electrode: Electrocatalytic Determination of Ascorbic Acid in Pharmaceuticals and Foods

The present work describes the construction of a new modified graphite-multiwall carbon nanotube paste electrode by casting the appropriate mixture of tetraheptylammonium iodide-iodine as a new modifier. The modified paste electrode was used for the determination of ascorbic acid (AA) in a phosphate buffer solution (pH 2.0). When compared to activated carbon, a graphite and multiwall carbon nanotube paste electrode containing a new modifier, the proposed modified paste electrode not only shifted the oxidation potential of AA towards a less-positive potential but also enhanced its oxidation peak current. Further, the oxidation of AA was highly stable at the modified paste electrode. The optimum analytical conditions were sought. The current response of AA increases linearly while increasing its concentration from 5.6 × 10(-5) to 1.2 × 10(-2) M with a correlation coefficient of 0.9991; the detection limit (3σ) was found to be of 3.6 × 10(-5) M. The present modified paste electrode was also successfully used for the determination of AA in the presence of common interference compounds. The present modified electrode was successfully demonstrated towards the determination of AA in pharmaceutical and food samples.

A spectroscopic study on applicability of spectral analysis for simultaneous quantification of l-dopa, benserazide and ascorbic acid in batch and flow systems

The usefulness of derivative spectrophotometry for simultaneous assay of l-dopa, benserazide and ascorbic acid in pharmaceuticals was studied. The parameters of derivatisation depends on composition of solution in which particular compound was determined. For quantification of l-dopa in mixtures with benserazide or ascorbic acid the first derivative was used. Its determination in ternary mixture ( l-dopa + benserazide + ascorbic acid) is possible by third derivative spectra. Benserazide was assayed in presence of l-dopa using first derivative while in ternary mixture by third derivative. Direct determination of ascorbic acid is possible applying first derivative only in presence of l-dopa. The elaborated derivative spectrophotometric methods were used for assaying of l-dopa and benserazide in their commercial form “Madopar”. The proposed spectrophotometric derivative method of simultaneous determination of l-dopa and benserazide was combined with FIA technique.

Kinetic spectrofluorimetric determination of trace ascorbic acid based on its inhibition on the oxidation of pyronine Y by nitrite

A highly sensitive spectrofluorimetric method is proposed for the determination of trace amount of ascorbic acid using a new indication. The method is based on the inhibition of ascorbic acid on the oxidation of pyronine Y (PRY) by nitrite. The detection limit for ascorbic acid is 0.012 μg ml −1, the linear range of the determination is 0.02–0.36 μg ml −1. Analytical parameters, such as reagent concentration, pH, reaction temperature and time, were optimized. The relative standard deviations of eleven replication determinations of 0.12 and 0.24 μg ml −1 ascorbic acid were 1.4 and 0.72%, respectively. This method has been used to determine ascorbic acid in pharmaceuticals, vegetables, fruits and soft drink with satisfactory results.

Successive determination of thiamine and ascorbic acid in pharmaceuticals by flow injection analysis

A simple and rapid fluorimetric method for the determination of mixtures of thiamine and ascorbic acid is proposed. The procedure is based on the oxidation with mercury(II) of the B 1 and C vitamins to form thiochrome (TC) and quinoxaline derivate, respectively. Both reaction products exhibit fluorescence at the same wavelengths ( λ ex=356 and λ em=440 nm). The procedure is optimised in a flow injection (FI) system and applied with excellent results in the determination of B 1 and C vitamins in commercial pharmaceutical preparations. The calibration graphs were linear over the range 2–100 μg ml −1 for thiamine and 5–100 μg ml −1 for ascorbic acid. The throughput was 25 samples per hour.

Solid-phase iodine as an oxidant in flow injection analysis: determination of ascorbic acid in pharmaceuticals and foods by background correction

A flow injection analysis (FIA)-background correction method comprising two solid-phase reactors and spectrophotometry for determination of ascorbic acid (AsA) is proposed. A polyethylene mini-column filled with solid iodine (30% m/m suspended on silica gel beads), reactor 1, and other column filled only with silica gel, reactor 2, which are then incorporated in a flow system so that solid iodine reagent in reactor 1 is affected as the sample passes through the column. The sample blank is produced by the oxidation of the AsA by iodine to form dehydroascorbic acid, insensitive to ultraviolet at 267 nm. AsA in samples is determined after injected in reactor 2; the difference in two analytical signal observed is related to amount of AsA. The linear range of the system is up to 50 μg ml −1 with a detection limit of 0.08 μg ml −1, R.S.D. of better than 1.0% and sampling frequency of 110 sample h −1. The method is successfully applied to the determination of AsA in pharmaceuticals and foods.

A New Simple and Accurate Turbidimetric Method for Determination of Ascorbic Acid in Pharmaceuticals and Fruits

AbstractAn accurate, simple, solvent free and inexpensive turbidimetric method is presented for the determination of ascorbic acid in pharmaceutical preparations and fruits. It needs no special reagents or precautions. In this method HgCl2 oxidizes ascorbic acid in citrate buffer at a pH of about 4 and produced Hg2Cl2 precipitate as monitored by turbidance measurements. The procedure is very simple and the experimental conditions such as temperature, ionic strength, stirring and time are not critical. High sensitivity and selectivity are two other advantages of this method. Linear dynamic range of the calibration curve is between 3–120 μg/mL with limit of detection (LOD) 1 μg/mL, which allows the ascorbic acid contents of most fruits and vegetables to be analyzed. On the other hand, the interference studies show that common compounds in real samples and colored substances have no considerable effect on the determination. Only filtration of some samples is necessary and other treatments, which are performed prior to determination of ascorbic acid by other analytical methods, are eliminated. Finally, ascorbic acid concentration in different samples is determined by the proposed method and obtained results are compared with the results of the official 2,6‐dichlorophenolindophenol or iodimetric methods and a good agreement is obtained. This method is very sensitive in comparison with iodimetry and is very fast relative to the 2,6‐dichlorophenolindophenol method.

Kinetic–spectrophotometric determination of ascorbic acid by inhibition of the hydrochloric acid–bromate reaction

A new analytical method was developed for the determination of ascorbic acid in fruit juice and pharmaceuticals. The method is based on its inhibition effect on the reaction between hydrochloric acid and bromate. The decolourisation of Methyl Orange by the reaction products was used to monitor the reaction spectrophotometrically at 510 nm. The linearity range of the calibration graph depends on bromate concentration. The variable affecting the rate of the reaction was investigated. The method is simple, rapid, relatively sensitive and precise. The limit of detection is 7.6×10 −6 M and calibration rang is 8×10 −6–1.2×10 −3 M ascorbic acid. The relative standard deviation of seven replication determinations of 8×10 −6 and 2×10 −5 M ascorbic acid was 2.8 and 1.7%, respectively. The influence of potential interfering substance was studied. The method was successfully applied for the determination of ascorbic acid in pharmaceuticals.

Indirect Determination of Ascorbic Acid with Ammonium Sulfate and Ethanol by Extraction and Flotation of Copper

AbstractA new method of indirect determination of ascorbic acid with ammonium sulfate and ethanol by extraction and flotation of copper in the presence of thiocyanate has been studied in this paper. The study shows that a small amount of Cu(II) is reduced to Cu(I) by ascorbic acid, then Cu(I) precipitates with SCN−. In the course of phase separation of ethanol from water, the precipitated CuSCN is extracted and stays in the interface of ethanol and water. A good linear relationship is observed between the extraction yield of Cu(II) and the amount of ascorbic acid. The detection limit for ascorbic acid is 1 10−5 M. Every parameter has been optimized and the reaction mechanism has been studied. The method is simple, rapid (5 min) and suffers from few interferences of common anions and cations. It has been successfully applied for the determination of ascorbic acid in pharmaceuticals and fruits.

Flow injection kinetic spectrophotometric determination of ascorbic acid based on an inhibiting effect

A rapid and sensitive flow-injection kinetic spectrophotometric method is proposed for the determination of ascorbic acid. The procedure is based on the inhibiting effect of ascorbic acid on the enhancing effect of oxalate on the potassium dichromate-potassium iodide/rhodamine 6G system. The detection limit and linear ranges are 0.08 and 0.10–4.00 μg/ml, respectively. The relative standard deviation of 11 replicate measurements is less than 2.0%. This method has been successfully used to determine ascorbic acid in pharmaceuticals, tomatoes and oranges.

Kinetic Determination of Ultratrace Amounts of Ascorbic Acid with Spectrofluorimetric Detection

A simple, fast and highly sensitive fluorimetric method is reported for the determination of ultratrace amount of ascorbic acid. The method is based on the activating effect of ascorbic acid on the oxidation of rhodamine 6G by potassium bromate in the presence of vanadium(V), which acts as a catalyst. The detection limit for ascorbic acid is 0.62ng/ml; the linear range of the determination is 1.6-28ng/ml The proposed method was used to determine ascorbic acid in pharmaceuticals, fruit juices and vegetables with satisfactory results.

Flow injection fluorimetric determination of ascorbic acid based on its photooxidation by thionine blue.

The photooxidation of ascorbic acid sensitized by Thionine Blue was studied. The Leucothionine Blue formed during the reaction is highly fluorescent. A flow injection method using merging zones is proposed for the determination of ascorbic acid over a concentration range from 8 x 10(-7) to 5 x 10(-5) mol l-1 with a throughout of 80 samples per h. The method was used for the simple and rapid determination of ascorbic acid in pharmaceuticals, fruit juices and soft drinks.

Determination of chlorine and dissolved oxygen in waters and of ascorbic acid in pharmaceuticals by iodimetric potentiometric titration using a plasticized poly(vinyl chloride) membrane electrode

The response to triiodide of an electrode based on a membrane containing poly(vinyl chloride) and 2-nitrophenyl octyl ether as plasticizer in a 1:2 ( w w ) ratio is studied. The electrode is suitable for the automatic potentiometric titration of triiodide in the concentration range 10 −5–10 −3 mol l −1 with thiosulphate. The electrode has been satisfactorily applied to the determination of chlorine and dissolved oxygen in tap waters and that of ascorbic acid in pharmaceuticals. Possible explanations for the response of the membrane to triiodide are included.