Indirect Determination Of Ascorbic Acid Research Articles

Application of column solid phase extraction of chromium for indirect determination of ascorbic acid by flame atomic absorption spectrometry

Application of column solid phase extraction of chromium for indirect determination of ascorbic acid by flame atomic absorption spectrometry

Construction of an Optical Sensor for the Determination of Ascorbic Acid Using Ionic Liquids as Modifier

An optode was designed for an indirect determination of ascorbic acid by using neocuproine, which has been coated on transparent triacetylcellulose film as a membrane. The proposed method is based on the oxidation of ascorbic acid to dehydroascorbic acid with the Cu(II) and neocuproine reagent. The increase in the absorbance value of the optode at the maximum wavelength of 455 nm was related to the ascorbic acid concentration in aqueous samples. The sensitivity of the method was improved by using room-temperature ionic liquid, [C(8)MIM][PF(6)]. The linear dynamic range for the determination of ascorbic acid was 7.4 × 10(-5) - 3.5 × 10(-3) mol L(-1) with a limit of detection of 2.2 × 10(-5) mol L(-1) (n = 10) and a response time range of 6.0 - 8.0 min. The optode was successfully applied for the determination of ascorbic acid in orange juice.

Reverse-FIA with spectrophotometric detection method for determination of vitamin C

Simple reverse flow injection analysis (rFIA) manifold with spectrophotometric detection was developed for an indirect determination of ascorbic acid. Parameters such as stability, accuracy and precision were established for the method and evaluated statistically to assess the applications of the method. Ascorbic acid in this procedure accelerates dediazoniation reaction of formed diazonium ions; hence its quantity can be determined by monitoring the derivatization product from coupling unreacted diazonium ion with phenol to give an azo dye (coupling reaction). The rFIA design was based on the injection of sodium nitrite into an acidic p-aminoacetophenon carrier stream in which diazonium ion was formed. This ion was inhibited by ascorbic acid stream before coupling with the phenol-Na2CO3 stream. Under optimum conditions, ascorbic acid acts in accordance with the Beer’s law at two concentration ranges 0.4–6.5 μg ml−1 (R = 0.9995) and 7.0–20.0 μg ml−1 (R = 0.9949), with detection limits of 0.25 μg ml−1. The developed method was applied to the determination of vitamin C in pharmaceutical formulations which produced satisfactory results compared with the standard methods reported in the British Pharmacopoeia.

Indirect fibre‐optic colorimetric determination of ascorbic acid using 2‐(5‐bromo‐2‐pyridylazo)‐5‐diethylaminophenol and cloud point extraction

A new method has been developed for the indirect determination of ascorbic acid (AA) in commercial syrup preparations based on cloud point extraction (CPE) separation and preconcentration, and determination by molecular absorption spectrometry. The colorimetric method was based on the reduction of Fe(III) to Fe(II) and complexation of Fe(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP), followed by its extraction into Triton X-114. Selectivity of the method was increased with the use of EDTA as a masking agent. The absorbance was measured at 742 nm. Various influencing factors on the separation and preconcentration of AA have been investigated systematically, and the optimized operation conditions were established. The proposed method allows the determination of AA in the range 5-200 µg L(-1) with a relative standard deviation of 3.0%. The detection limit was found to be 0.9 µg L(-1) for AA. This method has been applied to the determination of ascorbic acid in commercial pharmaceutical preparations.

Indirect determination of ascorbic acid (vitamin C) by spectrophotometric method

SummaryA novel spectrophotometric method is described. The procedure involves the use of Cu (II) as vitamin C oxidant. After completion of oxidation reaction, excess of Cu (II) is determined by complexation with alizarin red s (ARS). Thiocyanate ion is used as stabilising agent for Cu (I) which is the product of oxidation reaction. This method is used for determination of vitamin C in fruits and pharmaceutical products. Linearity was found to be perfect in the range 3.5 × 10−6–4.8 × 10−5 m (0.6–8.2 ppm). The detection limit and relative standard deviation of method are 2.0 × 10−6 m (0.35 ppm) and 1.03%, respectively. The proposed method is simple, safe, inexpensive and rapid.

Atomic Absorption Spectrometry for the Automatic Indirect Determination of Ascorbic Acid Based on the Reduction of Manganese Dioxide

A new and simple flow injection method followed by atomic absorption spectrometry has been developed for the indirect determination of ascorbic acid. The proposed method is based on oxidation of ascorbic acid to dehydroascorbic acid using a solid-phase manganese dioxide (30% m/m suspended on silica gel beads) reactor. The flow of the sample through the column reduces the MnO2 to Mn(II) in an acidic carrier stream of 6.3 mM HNO3 (pH 2.2) with flow rate of 4.0 ml/min at room temperature; Mn(II) is measured by atomic absorption spectrometry. The absorbance of Mn(II) is proportional to the concentration of ascorbic acid in the sample. The calibration curve was linear up to 30 mg/L, with a detection limit of 0.2 mg/L for a 220 microL injected sample volume. The developed procedure was found to be suitable for the determination of AsA in pharmaceuticals and foods with a relative standard deviation better than 1.09% and a sampling rate of about 95 h(-1). The results exhibit no interference from the presence of large amounts of organic compounds. The reliability of the method was established by parallel determination against the 2,6-dichlorophenol-indophenol methods.

A Spectrophotometric Determination of Ascorbic Acid

A new, simple and sensitive method for the spectrophotometric indirect determination of ascorbic acid in fruits, beverages, and pharmaceuticals is described. In this method, the ascorbic acid reduces Cu2+ to Cu+ and reacts with 2,9-dimethyl-1,10-phenanothroline (neucoproine) to form Cu (neucoproine)+ complex, and it was extracted with N-phenylbenzimidoylthiourea (PBITU) in chloroform. The apparent value of molar absorptivity of the complex in terms of ascorbic acid is (3.52) × 104 L mole−1 cm−1 at λmax, 460. The detection limit of ascorbic acid is 40 μg L−1 and the method obeys Beer's law over the concentration range of 0.1–4.0 μg mL−1. The proposed method was successfully applied for the determination of ascorbic acid in various samples. The validity of the present method was checked by the flow injection analysis (FIA) method.

Evaluation of a PVC‐Based Thionine‐Zeolite and Zeolite Free Membranes as Sensing Elements in Ion Selective Electrode

AbstractThe construction and performance characteristics of thionine electrodes based on the ion‐pair complex thionine‐tungstophosphate and thionine‐mordenite zeolite embedded in a polyvinyl chloride (PVC) matrix is described. Thionine electrode based on the ion‐pair is used for the indirect determination of ascorbic acid by standard addition method.

Automatic determination of ascorbic acid by flame atomic absorption spectrometry

A continuous flow procedure is proposed for the indirect determination of ascorbic acid based on its reducing properties. Chromium(VI) in acid medium was injected into a ascorbic acid stream, and the Cr(VI) was reduced to Cr(III). This Cr(III) formed was retained on-line, proportionally to the ascorbic acid concentration in the sample, on a poly(aminophosphonic acid) chelating resin, which is only selective for this oxidation state, while non-reduced Cr(VI) was determined by flame atomic absorption spectrometry. The proposed method allows the determination of ascorbic acid in the range 0.4–20 μg ml −1 with a relative standard deviation of 2.0% at a rate of ca. 90 samples per hour. This method has been applied to the determination of ascorbic acid in pharmaceutical preparations and fruit juices.

Flow-injection, on-line concentrating and flame atomic absorption spectrometry for indirect determination of ascorbic acid based on the reduction of iron(III)

A flow-injection flame atomic absorption spectrometry is proposed for indirect determination of ascorbic acid based on its reducing action to Fe(III). The Fe(II), produced by the reduction of Fe(III), is on-line adsorbed on a mini-column filled with cation-exchange resin to concentrate, then is eluted reversely by 3 mol l −1 nitric acid to nebulizer and is measured by flame atomic absorption spectrometry, while the excessive Fe(III) reacts with NH 4F to form anion [FeF 6] 3− and passes through the mini-column to be waste. When reaction and concentrating time is 60 s, the absorbance of Fe(II) is proportional to the concentration of ascorbic acid in the range from 0.1 to 50 mg l −1. The analytic frequency is 30 samples per hour. This method has been applied to the determination of ascorbic acid in Vitamin C tablets, Vitamin C injection, vegetables and fruit juice. The results obtained in the analysis agreed well with those provided by iodimetry.

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.

Indirect determination of ascorbic acid by solid-phase spectrophotometry

Solid-phase spectrophotometry (SPS) technique, in the visible region, was used for the spectrophotometric determination of ascorbic acid based on the reducing effect on iron(III) ion, followed by formation of the iron(II)-ferrozine chelate. The chelate is easily sorbed on a dextran-type anion-exchange gel and the absorbance of the resin at 567 and 800 nm, packed in a 1 mm cell, is measured directly. The apparent molar absorptivity using 100 ml of sample was 2.1×10 7 l mol −1 cm −1 and it allowed the determination of ascorbic acid in the range 5–90 ng ml −1; the detection limit was 0.91 ng ml −1 and the RSD 0.91% for a concentration of 50 ng ml −1 of ascorbic acid ( n=10). The proposed method permits a highly sensitive and selective determination of ascorbic acid without any preconcentration and it has been satisfactorily applied for its determination in fruit juices, pharmaceuticals, urine and conservative liquids.

Indirect flow-injection determination of ascorbic acid by flame atomic absorption spectrometry

A continuous-flow procedure is proposed for the indirect determination of ascorbic acid, based on its reducing properties because of the oxidation of its 1,2-enediol group. Iron(III) was injected into a 1,10-phenanthroline stream, which was mixed with a sample carrier and then with a sodium picrate solution stream. In these conditions the iron(III) was reduced to iron(II) by the ascorbic acid. Thus, the iron(II) formed reacts with 1,10-phenanthroline to form a charged red complex, which with picrate ion forms a stable red-orange uncharged ion-association complex that is adsorbed “on-line” on a non-ionic polymeric adsorbent (Amberlite XAD-4), proportionally to the ascorbic acid in the sample. The unadsorbed iron was determined by flame atomic absorption spectrometry. The proposed method allows the determination of ascorbic acid in the range 0.5–25 μg ml−1 with a relative standard deviation of 2.9% at a rate of ca. 90 samples h−1. This method has been applied to the determination of ascorbic acid in pharmaceutical preparations, fruit juices and sweets. The results obtained in the analysis are compared with those provided by the 2,6-dichloroindophenol method.

Extraction spectrophotometric method for the determination of ascorbic acid in pharmaceutical preparations, urine and fruit juices with potassium iodate

An indirect determination of ascorbic acid is based on extraction of the iodine produced by reduction of potassium iodate. Beer's law is obeyed over the range 0.02–0.36 mg/ml ascorbic acid.