Determination Of L-ascorbic Acid Research Articles

Kinetic spectrophotometric assay for the determination of vitamin C in cosmetics following ultrasound-assisted emulsification.

In this work, a new analytical approach based on ultrasound-assisted emulsification followed by a photoreaction with methylene blue (MB) and kinetic analysis by UV-vis spectrophotometry has been developed for the determination of L-ascorbic acid (AA) in cosmetic samples. The emulsification of cosmetic samples results in a transparent solution that allows an easy and rapid quantitation by UV-vis spectrophotometry. The emulsified sample is mixed with a MB aqueous solution and this mixture is subjected to irradiation with a tungsten lamp for 5 min (fixed-time kinetic assay). A reduction in the MB absorbance intensity at 664 nm occurs as the concentration of AA increases. The observed change in absorbance intensity was used for calibration and further quantitation using the relationship of absorbance logarithm vs. AA concentration (μg mL-1). In order to achieve an optimal response, different parameters involved in the reaction between AA and MB were fully investigated. Under optimal conditions, the limits of detection and quantification were 0.04 μg mL-1 and 0.15 μg mL-1, respectively. Repeatability and reproducibility, expressed as relative standard deviation, were in the range of 0.4-0.6% and 0.6-1.5%, respectively. Finally, the proposed method was applied to the analysis of 15 cosmetic samples, namely, (i) 12 samples without AA, which were used to carry out recovery studies, obtaining results in the range of 97.5-100.7%; (ii) 3 serum samples containing pure AA among their ingredients, which were used for AA stability studies.

Nafion assisted preparation of prussian blue nanoparticles and its application in electrochemical analysis of l-ascorbic acid

Due to the high sensitivity, simplicity and low cost, electrochemistry methods based on nanoparticles have been considered as an attractive technique for l-ascorbic acid. Herein, prussian blue nanoparticles (PBNPs) were synthesized by a fast and convenient synthesis strategy with Nafion and K4[Fe (CN)6] 3H2O. The PBNPs have uniform grain size of about 11.9 nm. PBNPs modified glassy carbon electrode (GCE) was used to construct electrochemical sensor for l-ascorbic acid (AA) detection and the optimization condition was studied. The electrochemical results indicate that PBNPs/GCE sensor shows a linear response to l-ascorbic acid in the range of 1–1100 μM with a detection limit of 0.47 μM and sensitivity of 22.9 μA·mM−1·cm−2 at a working potential of 0.24 V (vs. SCE). The stability and reproducibility of the same PBNPs/GCE are RSD = 0.7% and RSD = 1.3%, respectively. The excellent characteristics of this sensor demonstrates it is a useful tool for accurate determination of l-ascorbic acid in medicine samples such as a vitamin C tablet and for Vitamin C chewable tablets.

Development and Validation of HPTLC-Densitometric Method Compared to Titrimetric Method for Determination of L-ascorbic Acid in Citrus Fruits

Aims: The aim of this study is to develop and validate an efficient method for the specific determination of L-ascorbic acid in citrus fruits and to compare it with a usual method, method using 2,6-dichlorophenolindophenol
 Methodology: The research for a specific method for determination of L-ascorbic acid has led to development and validation of High Performance Thin Layer Chromatography – Densitometric (HPTLC-D) method. The validation criteria evaluated are response function, determination reading wavelength, limit of detection, precision of the technique, limit of quantification and recovery rate. The validated method was applied to citrus juice samples for quantification of L-ascorbic acid. Then a 2,6-dichlorophenolindophenol titrimetric assay of L-ascorbic acid in the same sample was performed for comparison of method results.
 Results: HPTLC-D method showed improved sensitivity on 360 ​​nm scanner and a good linearity relationship between standard concentrations and absorbance responses. The regression coefficient obtained is R2 = 0.99. The limit of detection (LOD) and the limit of quantification (LOQ) are respectively 3 ng and 9.5 ng per deposit. The method also exhibited good repeatability and precision, with intra-day (n = 3) and inter-day (n = 4) coefficients of variation (CV) of less than 6%.
 Application of the HPTLC-Dmethod to citrus juices yielded a recovery rate ranging from 97% to 99%.
 Conclusion: Comparison of results of the two methods shows that the contents obtained by titrimetry are greater than those obtained by HPTLC-D by 42.25%. This is explained by the presence of other redox compounds which are dosed at the same time as L-ascorbic acid. HPTLC-D makes it possible to specifically dose L-ascorbic acid.

A Potentiometric Sensor Based on a Copper(II) Ion Composite for Vitamin C Determination in Urine

We developed an all-solid-state sensor for monoascorbate ion based on a composite containing copper(II) ions (5 wt %), graphite and epoxy resin. The sensor presented super-Nernstian response at room temperature under continuous bubbling of oxygen gas in sample. The detection limit of the sensor was 0.02 mM and its linear range was between 0.05 and 1.5 mM with upper limit of quantification equal to 3 mM. The leaching out effect of the active component from composite was estimated less than 11 µg of copper(II) sulfate per day under continuous diffusion process in deionized water. Photomicrographs of the electrode surface did not show the presence of salt particles on the surface indicating that copper(II) ions could be intercalated in graphene layers. Attenuated total reflectance infrared spectrum demonstrated this possibility. The sensor was successfully applied to the in vitro determination of L-ascorbic acid in urine.

An amperometric biosensor based on poly(l-aspartic acid), nanodiamond particles, carbon nanofiber, and ascorbate oxidase–modified glassy carbon electrode for the determination of l-ascorbic acid

An amperometric L-ascorbic acid biosensor utilizing ascorbate oxidase (AOx) immobilized onto poly(L-aspartic acid) (P(L-Asp)) film was fabricated on carbon nanofiber (CNF) and nanodiamond particle (ND)-modified glassy carbon electrode (GCE). Effects of AOx, ND, and CNF amounts were investigated by monitoring the response currents of the biosensor at different amounts of AOx, ND, and CNF. The electropolymerization step of L-aspartic acid on CNF-ND/GCE surface was also optimized. Scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) techniques were used to enlighten the modification steps of the biosensor. The effects of pH and applied potential were studied in detail to achieve the best analytical performance. Under optimized experimental conditions, the AOx/P(L-Asp)/ND-CNF/GCE biosensor showed a linear response to L-ascorbic acid in the range of 2.0 × 10-7-1.8 × 10-3M with a detection limit of 1.0 × 10-7M and sensitivity of 105.0μAmM-1cm-2. The novel biosensing platform showed good reproducibility and selectivity. The strong interaction between AOx and the P(L-Asp)/ND-CNF matrix was revealed by the high repeatability (3.4%) and good operational stability. The AOx/P(L-Asp)/ND-CNF/GCE biosensor was successfully applied to the determination of L-ascorbic acid in vitamin C effervescent tablet and pharmaceutical powder containing ascorbic acid with good results, which makes it a promising approach for quantification of L-ascorbic acid. Graphical abstract.

A novel mıcrobıal bıosensor system based on C. tropicalis yeast cells for selectıve determınatıon of L-Ascorbıc acid

In this study, a novel microbial biosensor was developed for the selective determination of L-Ascorbic acid. In the construction of the microbial biosensor, lyophilized Candida tropicalis yeast cells were immobilized with o-aminophenol by forming a film layer on a platinum electrode surface using electropolymerization. L-Ascorbic acid was quantified on the basis of both amperometric and differential pulse voltammetry (DPV) methods using the biosensor. The measurements were made at +0.24 V (vs Ag/AgCl) for amperometric studies and between 0.0 V and +0.7 V for DPV studies based on the oxidation of L-Ascorbic acid to dehydro-L-Ascorbic acid by ascorbate oxidase which takes place within the catabolic metabolic pathway of C. tropicalis yeast cells. According to the results obtained from the two methods, the response of the biosensor depends linearly on L-Ascorbic acid concentration between 100 and 1500 μM. The detection limit was 62 μM and 59 μM for amperometric and DPV measurements, respectively. The response time of the microbial biosensor was 14 s and 5 s for DPV and amperometric measurements, respectively. In the optimization studies of the biosensor, some parameters such as the optimum amount of the microorganism, o-aminophenol concentration, pH and temperature were determined. For the characterization of the biosensor, reproducibility, storage stability and the effect of interferences were determined.

Development and validation of a differential pulse polarography method for determination of total vitamin C and dehydroascorbic acid contents in foods

The objective of the study was to develop a new method for the determination of total vitamin C and dehydroascorbic acid contents in food using the differential pulse polarography technique, and to compare achieved results to those obtained with the proposed reference method applying HPLC with spectrophotometric detection. Dithiothreitol was used to reduce dehydroascorbic acid into l-ascorbic acid. Interference due to the presence of dithiothreitol during polarographic determination of l-ascorbic acid was efficiently eliminated by clarification of the sample solution with Carrez reagent. Validation of the polarographic method indicates its usefulness for the analysis of foods products that do not contain isoascorbic acid. The coefficient of variation for the analysis of l-ascorbic acid and total vitamin C content ranges from 1.86% to 6.98%, Horrat values from 0.41 to 0.89 and average recovery of l-ascorbic acid ranges from 98% to 104%. Results obtained using the developed method are characterised by high compatibility with those obtained with the HPLC reference method, indicating equivalence of both methods, and in conclusion, the method was deemed fit for purpose for measuring total vitamin C and dehydroascorbic acid in foods.

Determination of L-Ascorbic Acid in Milk by Ultra-High-Performance Liquid Chromatography Coupled to Tandem Mass Spectrometry Analysis

This study provides a fast, accurate and reproducible method for L-ascorbic acid (L-AA) determination in milk samples by ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). A small volume of a low toxicity organic solvent (ethanol) was used for degreasing and deproteinization steps. Ethylenediaminetetraacetic acid disodium salt (EDTA) and formic acid were used as stabilizing agents. The method was successfully validated in terms of linearity, limit of detection (LOD), limit of quantification (LOQ), accuracy, and inter/intra-day precision and applied in raw and processed milk samples. Good linearity (r2 > 0.9915) and low LOD and LOQ, 1.5 and 5.0 µg L-1, respectively, were obtained. The recoveries for 500 and 1000 µg L-1 spikes were higher than 90% and the precision values expressed in terms of relative standard deviation (RSD) were ≤ 6.8%. For the first time, the determination of L-AA in a 500 µg L-1 concentration range was reported for milk samples.

Determination of L-Ascorbic Acid Using MBs-AOX/GO/IGZO/Al by Wireless Sensing System and Microfluidic Framework

In this paper, the L-ascorbic acid (L-AA) biosensor based on magnetic beads-ascorbate oxidase/graphene oxide/indium gallium zinc oxide/aluminum (MBs-AOX/GO/IGZO/Al) membrane was integrated with the potentiometric measurement system with the microfluidic framework in order to investigate the different sensing characteristics under the static condition and the dynamic condition. The L-AA biosensor showed the average sensitivity of 78.9 mV/decade (25 °C) under the static condition, and it showed the average sensitivity of 81.7 mV/decade (25 °C) at the optimal flow rate ( $25~\mu \text{L}$ /min). Besides, the XBee module was used to apply in the remote detection for the L-AA biosensor, and the experimental results were shown the average sensitivity of 78.7 mV/decade (25 °C). Moreover, we also investigated various experiments, such as temperature effect, hysteresis effect, and lifetime. These experimental results would be beneficial to the development of the L-AA biosensor based on electrochemical detection.

Potentiometric determination of ascorbic acid in water–acetonitrile solution using pyrite and chalcopyrite electrodes

Performance characteristics of the solid-state potentiometric sensors, based on natural sulfide minerals pyrite and chalcopyrite, are assayed in aqueous and non-aqueous medium. The electrodes are simply and quickly prepared using inexpensive material that originate from natural environment. The pyrite and chalcopyrite electrodes exhibit good sensitivity and repeatability, stable potential with respect to time, short response time (less than 15 s), the sub-Nernstian response, with a slope of 48.0 mV per decade for pyrite and 41.6 mV per decade for chalcopyrite over a wide concentration range of copper(II) ion in acetonitrile, and a possibility of application without a time limit in aqueous and non-aqueous solution, as well. The practical applicability of these indicator electrodes is their utilization in potentiometric determination of L-ascorbic acid in water and water-acetonitrile, by using Cu(II) solution as the titrant, in pure compound and pharmaceutical formulations. The determination of 10.5–11.5 mg (0.50 mL) of L-ascorbic acid shows average recoveries of 98.2–101.9 %, with relative standard deviations of 0.1–0.9 %. The results show that the large potential break is obtained at the equivalence point when the titration was carried out in the presence of chelating bidentate ligand, neocuproine. This is a very simple, precise, reliable and sensitive one-step method, suitable for work in the laboratory and can be carried out directly, without any prior treatment of the investigated samples.

Spectrophotometric Determination of L-Ascorbic Acid Based on Its Oxidation by Potassium Peroxodisulfate in the Presence of Cu(II) as Catalyst

A new, selective and accurate direct spectrophotometric procedure was developed for the determination of L-ascorbic acid (AA) in pharmaceuticals. Background correction was based on the oxidation of AA by potassium peroxodisulfate in the presence of Cu(II) as a catalyst. The molar absorptivity of the proposed procedure was 1.04 × 104 L/(mol cm) at 262 nm. Beer’s law was obeyed in the concentration range of 0.68–16.00 μg/mL for AA. The detection limit was 0.20 μg/mL, and the relative standard deviation was 0.91% (n = 7) for 8.00 μg/mL AA. Other compounds commonly found in pharmaceutical preparations did not interfere with the detection of AA. The proposed procedure was successfully applied to the determination of AA in pharmaceuticals, and the results obtained agreed with those obtained by iodine titration.

Spectrophotometric determination of l-ascorbic acid based on its oxidation by potassium peroxodisulfate in the presence of Cu(II) as catalyst

Spectrophotometric determination of l-ascorbic acid based on its oxidation by potassium peroxodisulfate in the presence of Cu(II) as catalyst

Ascorbate Oxidase-Based Amperometric Biosensor for l-Ascorbic Acid Determination in Beverages.

A novel biosensor for l-ascorbic acid determination in different beverages was elaborated. The ascorbate oxidase enzyme (AAO) from Cucurbita sp., EC 1.10.3.3, was immobilized on a screen-printed carbon electrode with poly(ethylene glycol) (400) diglycidyl ether (PEGDGE) as a crosslinking agent. The standards and samples were measured first with a blank electrode. An inert protein, bovine serum albumin (BSA), was immobilized on the surface of this electrode with PEGDGE. The BSA mass was equivalent to the mass of 10 U of AAO enzyme immobilized on the electrodes (0.021 mg). The linear measuring range for l-ascorbic acid was between 5 and 150 µmol/L. As l-ascorbic acid is a vital vitamin and a common antioxidant used in food industry, fruit juices and vitamin C effervescent tablets were examined. The results were compared to HPLC measurements.

Spectrophotometric Determination of L-Ascorbic Acid in Pharmaceuticals Based on Its Oxidation by Potassium Peroxymonosulfate and Hydrogen Peroxide

Spectrophotometric Determination of L-Ascorbic Acid in Pharmaceuticals Based on Its Oxidation by Potassium Peroxymonosulfate and Hydrogen Peroxide

Simultaneous determination ofl-ascorbic acid and dehydroascorbic acid in human plasma

A method combining high-performance liquid chromatography with ultraviolet detection (HPLC-UV) was developed and validated for the accurate determination ofl-ascorbic acid (AA) and dehydroascorbic acid (DHAA) concentrations in human plasma.

Peroxydisulfate Oxidation of L-Ascorbic Acid for Its Direct Spectrophotometric Determination in Dietary Supplements

A selective and accurate direct spectrophotometric method was developed for the determination of L-as cor bic acid in dietary supplements. Background correction was based on the oxidation of L-ascorbic acid by potassi um peroxydisulfate in an acidic medium. The molar absorptivity of the proposed method was 1.41 · 104 l/(mol · cm) at 265 nm. The method response was linear up to an L-ascorbic acid concentration of 12.00 μg/ml. The detection limit was 0.11 μg/ml, and the relative standard deviation was 0.9 % (n = 7) for 8.00 μg/ml L-ascorbic acid. Other compounds commonly found in the dietary supplements did not interfere with the detection of L-ascorbic acid. The proposed procedure was successfully applied to the determination of L-ascorbic acid in these supplements, and the results obtained agreed with those obtained by iodine titration.

A CdTe/CdS/ZnS core/shell/shell QDs-based “OFF–ON” fluorescent biosensor for sensitive and specific determination ofl-ascorbic acid

Herein we report a quantum dots (QDs)-based “OFF–ON” fluorescent biosensor for the sensitive and specific determination ofl-ascorbic acid.

Simple Determination of l-Ascorbic Acid on TLC by Visual Detection Using Autocatalytic Reaction

The L-ascorbic acid concentration in beverages was measured after separation by silica gel thin layer chromatography (TLC) by visually determining the time in autocatalytic reaction for the L-ascorbic acid spot to turn the same yellow color of the background and disappear (the end time of the induction period) after spraying the slide with a 3,6-dihydroxyxanthane solution. There was a good linear relationship between the end time of the induction period and the concentration of L-ascorbic acid for concentrations in the range of 5.0 - 20 mM (r(2) = 0.9944). In addition, there was a good relationship expressed by a quadratic equation in the concentration range of 0.1 - 5.0 mM (r(2) = 0.9975). The relative standard deviations of the L-ascorbic acid values for 3 beverages (2.2 - 8.6 mM) were less than 5% (n = 5), and the recovery of 5.0 mM L-ascorbic acid from 4 beverages (0.7 - 7 mM) was 97 - 110%. A good correlation was also observed between the L-ascorbic acid values of 23 beverages (0 - 86 mM) determined by the proposed TLC method and the colorimetric method contained in a commercially available kit for L-ascorbic acid (r(2) = 0.9945).

A rapid method for the simultaneous determination of l-ascorbic acid and acetylsalicylic acid in aspirin C effervescent tablet by ultra performance liquid chromatography–tandem mass spectrometry

In present study, a rapid and sensitive method using ultra performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) was developed for the simultaneous determination of l-ascorbic acid and acetylsalicylic acid in aspirin C effervescent tablet. The optimum chromatographic separation was carried out on a reversed phase Waters® Acquity UPLC BEH C18 column (1.7μm particle size, 100mm×2.1mm ID) with an isocratic elution profile and mobile phase consisting of 0.1% formic acid in water and acetonitrile (75:25, v/v, pH 3.5) at flow rate of 0.5mLmin−1. The influences of mobile phase composition, flow rate and pH on chromatographic resolution were investigated. The total chromatographic analysis time was as short as 2min with excellent resolution. Detection and quantification of the target compounds were carried out with a triple quadrupole mass spectrometer using negative electrospray ionization (ESI) and multiple reaction monitoring (MRM) modes. The performance of the method was evaluated and very low limits of detection less than 0.09μgg−1, excellent coefficient correlation (r2>0.999) with liner range over a concentration range of 0.1–1.0μgg−1 for both l-ascorbic acid and acetylsalicylic acid, and good intraday and interday precisions (relative standard deviations (R.S.D.) <3%), were obtained. Comparison of system performance with traditional liquid chromatography–photo diode array detector (HPLC–PDA) was made with respect to analysis time, sensitivity, linearity and precisions. The proposed UPLC–MS/MS method was found to be reproducible and appropriate for quantitative analysis of l-ascorbic acid and acetylsalicylic acid in aspirin C effervescent tablet.

Clonal differences in antioxidant activity and bioactive constituents of hardy kiwifruit (Actinidia arguta) and its year‐to‐year variability

Hardy kiwifruit (Actinidia arguta) is a new species, commercially grown in recent years. Total phenolics (TPC), vitamin C (TAA) content, antioxidant activity (AA) and their year-to-year variability in seven hardy kiwifruit clones were evaluated. TPC was determined using the Folin-Ciocalteu reagent assay. TAA was estimated by determination of l-ascorbic acid and l-dehydroascorbic acid levels using high-performance liquid chromatography. AA was measured using diphenyl-1-picryl-hydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and OH radicals. The highest content of vitamin C, in all seasons, was found in D11 (1447-2181 mg kg(-1) fresh weight) and phenolics for D11 and M1 clones (2583-3312 and 2228-3414 mg gallic acid equivalents kg(-1) fresh weight, respectively). TPC and TAA content showed significant differences between hardy kiwifruit clones and showed significant year-to-year variability. Each year, the level of AA was significantly higher for D11 (DPPH, ABTS). AA was strongly correlated with TPC and TAA content in Actinidia fruit. Hardy kiwifruit are an important source of vitamin C and phenolics, which resulted in their good antioxidant potential. A significantly higher content of these compounds was found in fruit of hybrid origin, which suggests that A. purpurea × A. arguta clones may be useful genetic resources for further interspecific hybridization.