Flow injection spectrophotometric determination of ascorbic acid in soft drinks and beer (original) (raw)
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Talanta, 1995
Two flow injection systems for the spectrophotometric determination of ascorbic acrid at 245 nm have been described. On treatment with sodium hydroxide a fraction of the ascorbic acid was decomposed into substances, which do not absorb in UV region, and the decrease in signal measured. This was directly related to the amount of ascorbic acid present. The calibration graph was linear over the range 1-25 and 1-50 ~g/ml in the two methods with a correlation coefficient of 0.9981 and 0.9994, respectively. The detection limit (2or) was 0.5 and 0.2 9g/ml, respectively. The RSD for l ~g/ml standard was 2.5 and 1,8% (n = 6) in the two methods, and the sampling throughput 30/hr. The methods permitted the use of 6 #g/ml of 2-mereaptoethanol as an anti-oxidant and stabilizer for ascorbic acid, which is difficult to handle at its ~g/ml level. Upon matrix absorbance correction, spiked samples that are known to contain UV-absorbing substances produced an average recovery of 101% with a RSD of 1.2%. The methods were used for the rapid and simple determination of ascorbic acid in soft drinks, preserved fruit juices and pharmaceuticals and the results thus produced compared with those obtained by previously checked methods involving titration with iodine, chloranil 2,6-dichlorophenolindophenol, and HPLC. When there was a disagreement between the results, this was traced to the presence of substances which are known to interfere in comparison methods.
Fluorimetric determination of total ascorbic acid by a stopped-flow mixing technique
The Analyst, 2001
A simple, rapid and automatic fluorimetric method for the determination of total ascorbic acid is described. The method makes use of the stopped-flow mixing technique in order to achieve the rapid oxidation of ascorbic acid by dissolved oxygen to dehydroascorbic acid, which then reacts with o-phenylenediamine to form a fluorescent quinoxaline. The initial rate and fluorescence signal of this system are directly proportional to the ascorbic acid concentration. The calibration graph was linear over the range 0.1-30 µg ml 21 (kinetic method) and 0.25-34 µg ml 21 (equilibrium method). The precision (% RSD) was close to 0.5%. The method has been used for the determination of ascorbic acid in pharmaceutical formulations, fruit juices, soft drinks and blood serum.
2019
Ascorbic acid is a white crystalline powder with a molecular formula of C6H8O6 and a formula weight of 176.12 g/mol. It is a water-soluble, antioxidant vitamin, important in forming collagen, a protein that gives structure to bones, cartilages, muscles, and blood vessels. It prevents tissue damage & used in treatment of certain diseases such as scurvy, anemia, diabetes, common cold, hemorrhagic disorders, wound healing, cough, influenza, sores, gingivitis, skin diseases, diarrhea, malaria, bacterial infections, plug poisoning, liver disease, allergic reactions, arteriosclerosis as well as infertility in males. Therefore it is important to develop a method for the determination of it in different samples. A method was developed for assessing Ascorbic acid concentration in Ethiopian soft drinks such as Fanta orange, Mirinda, Pepsi and Cocacola & wines including: Gouder, Kemila and Aksumite by cyclic voltametry and square wave voltammetry. The oxidation peak for Ascorbic acid occurs at...
Food Research International, 2010
A rapid, easy to handle and low cost assay of ascorbic acid was developed, which consists in miniaturization on microplate of a redox reaction monitored spectrophotometrically, the signal being directly related to the concentration of ascorbic acid in the sample. This method was investigated in accordance with the prerogative of regulation covering food additives in terms of linear range/linearity, limits of detection and quantification, accuracy (including trueness and precision), robustness and selectivity. The application of the method was tested to determine ascorbic acid diffusivity in agar gel used as an aqueous food simulant. The diffusivity value obtained was 0.31 Â 10 À9 m 2 s À1 , with a confidence interval of 20% at 95% level. Accuracy of the assay and of the point's location on ascorbic acid profiles were examined by Monte-Carlo method to assess their influence on accuracy of diffusivity value obtained. Assay uncertainty was clearly demonstrated to be a critical parameter.
Talanta, 2012
A flow-injection indirect spectrophotometric method for the determination of ascorbic acid (AA) in pharmaceutical preparations is proposed. The method is based on the reduction of iron(III) to iron(II) by the AA, and by the subsequent reaction of the produced iron(II) with 2,4,6-tripyridyl-s-triazine (TPTZ) in buffered medium (pH=3.6) to form a coloured complex (λ(max)=593nm). The three-line manifold with one reaction coil was used. The linear range of the method is from 0.08 to 10μM of ascorbic acid, with the detection limit 24nM of AA. The proposed method is simple, rapid (sampling rate of 180 samples per hour), sensitive and reproducible (RSD 0.8%, n=100). The proposed method is very selective, because only the reducing substances with standard (formal) potentials lower than 0.6V would have the thermodynamic predisposition to interfere in the proposed method. Tested reducing substances (thiol compounds) did not give serious errors when present at the same concentrations as the ascorbic acid. The proposed method can be applied for the determination of AA in pharmaceutical preparations, down to picomolar quantity.
2012
This study presents a new, selective and accurate indirect spectrophotometric method for determination of L-ascorbic acid in fruit juices, pharmaceuticals and biological samples. Beer's law is obeyed by ascorbic acid (conc. range, 0.8-6.3 µg) per 25 ml of final solution (0.032-0.252 ppm). The method showed: apparent molar absorptivity, 1.56 × 10 5 l mol-1 cm-1 ; Sandell's sensitivity, 0.0024 µg cm-2 ; limit of detection, 0.0086 µg ml-1 ; and limit of quantitation, 0.01 µg ml-1. It was satisfactorily applied for determination of ascorbic acid in fruit juices, pharmaceuticals and biological samples. Reliability of method was established by parallel determination against Leuco crystal violet and Rhodamine-B method.
Indirect Determination of Ascorbic Acid in Pharmaceutical Preparations Using Reversed FIA-CL Method
2009
This paper includes a new simple, sensitive and rapid automated chemiluminescence (CL) method for the indirect determination of ascorbic acid through the reverse flow injection technique. Quenching of the titanium- luminol complex CL is caused by adding ascorbic acid, which systematically decreases the CL-intensity with increasing concentration of ascorbic acid. As a result, the CL-system is able to determine ascorbic acid in the range of (2-30 mg/l) and detection limit of (1 mg/l) with correlation coefficient of (0.9980) and a sampling frequency 515s/hr. The excipient substances do not interfere with this determination. Ascorbic acid in pharmaceutical preparations is determined and the results are of comparable accuracy as indicated by a statistical analysis of the data, using both t- and f-tests.
Sequential injection redox or acid–base titration for determination of ascorbic acid or acetic acid
Talanta, 2002
Two sequential injection titration systems with spectrophotometric detection have been developed. The first system for determination of ascorbic acid was based on redox reaction between ascorbic acid and permanganate in an acidic medium and lead to a decrease in color intensity of permanganate, monitored at 525 nm. A linear dependence of peak area obtained with ascorbic acid concentration up to 1200 mg l (1 was achieved. The relative standard deviation for 11 replicate determinations of 400 mg l (1 ascorbic acid was 2.9%. The second system, for acetic acid determination, was based on acid Á/base titration of acetic acid with sodium hydroxide using phenolphthalein as an indicator. The decrease in color intensity of the indicator was proportional to the acid content. A linear calibration graph in the range of 2 Á/8% w v (1 of acetic acid with a relative standard deviation of 4.8% (5.0% w v (1 acetic acid, n 0/11) was obtained. Sample throughputs of 60 h (1 were achieved for both systems. The systems were successfully applied for the assays of ascorbic acid in vitamin C tablets and acetic acid content in vinegars, respectively. #