Multicommutated stepwise injection determination of ascorbic acid in medicinal plants and food samples by capillary zone electrophoresis ultraviolet detection

Cubic-shaped corylus colurna extract coated Cu2O nanoparticles-based smartphone biosensor for the detection of ascorbic acid in real food samples

Ascorbic acid (AA) is a highly water-soluble organic chemical compound and plays a significant role in human metabolism. For the purpose of food quality monitoring, this study focuses on the development of a smartphone-integrated colorimetric and non-enzymatic electrochemical Corylus Colurna (CC) extract-Cu₂O nanoparticles (Cu₂O NPs) biosensor to detect AA in real food samples. The characterization of the CC-Cu₂O NPs was determined using SEM, SEM/EDX, HRTEM, XRD, FTIR, XPS, TGA, and DSC. The CC-Cu₂O NPs are cubic in shape with an approximate size of 10 nm. According to electrochemical results, the oxidation of AA at the modified electrode exhibited a LOD of 27.92 nmolL^-1 in a wide concentration range of 0.55-22 mmolL^-1. The fabricated digital CC-Cu₂O NPs sensor successfully detected AA in food samples. This strategy provides a nanoplatform to determine the detection of AA in food samples.

A reversible and dual responsive sensing approach for determination of ascorbate ion in fruit juice, biological, and pharmaceutical samples by use of available triaryl methane dye and its application to constructing a molecular logic gate and a set/reset memorized device

Since dyes are available in huge quantities and have the well-established chemistry involved in their synthesis, their use in chemosensing could be continued. In the current study, a new and reversible colorimetric and fluorometric chemosensor based on available triaryl methane dye (brilliant green (BG)) - phosphotungstic acid (PTA) complex has been designed for determination of ascorbate (AscH^-1) ion in water/DMSO (90:10v/v, 1.0mmolL^-1 HEPES, pH7.0). The "ON-OFF" fluorescence and colorimetric responses of this ion association complex to AscH^-1 were based on a displacement mechanism. For the detection of AscH^-1, the linear ranges achieved for UV-Vis absorbance and fluorescence experiments were 3.9-62.6μmolL^-1 and 1.9-85.4μmolL^-1, respectively. The limits of detection for both of them were also calculated to be 0.4 and 0.2μmolL^-1. The proposed method was also successfully utilized for rapid recognition of ascorbate in juice samples, human serum, and the formulation of supplement products. Moreover, the proposed chemosensor capability of functioning as INHIBITION-type sensor with PTA and AscH^-1 as chemical inputs was indicated by the investigation of the molecular logic behavior of this chemosensor. Eventually, a sequential memory unit displaying "Write-Read-Erase-Read" function could be integrated based on the reversible and reproducible system.

A dual-model strategy for fluorometric determination of ascorbic acid and of ascorbic acid oxidase activity by using DNA-templated gold-silver nanoclusters

Methods are described for the fluorometric and colorimetric determination of ascorbic acid (AA) and the activity of ascorbic acid oxidase (AA-Ox). The method for AA is based on AA-induced growth and aggregation of DNA-templated gold/silver nanoclusters (DNA-Au/Ag NC), which is accompanied by quenching of fluorescence emission at 605 nm upon 260 nm excitation and a visible color change of the solution from colorless transparent to yellow. The determination of the activity of AA-Ox is based on the finding that it catalyzes the oxidation of AA which results in the inhibition of growth and aggregation. AA can be determined with a 0.6 μmol·L^-1 detection limit over the 5 to 150 μmol·L^-1 concentration range. AA-Ox can be determined with a 0.0048 U·mL^-1 detection limit over the 0.01 to 0.20 U·mL^-1 range. Graphical abstract Schematic of a novel fluorometric and colorimetric platform for determination of ascorbic acid and ascorbic acid oxidase activity based on the use of DNA-templated gold-silver nanoclusters.

An automated magnetic dispersive micro-solid phase extraction in a fluidized reactor for the determination of fluoroquinolones in baby food samples

An automated magnetic dispersive micro-solid phase extraction procedure in a fluidized reactor was developed for the determination of fluoroquinolone antimicrobial drugs (fleroxacin, norfloxacin and ofloxacin) in meat-based baby food samples. A stepwise injection system was successfully combined with afluidized reactorand applied for the magnetic dispersive micro-solid phase extraction procedure automation. The developed automated procedure involved injection of the sample solution into the fluidized reactor followed by the on-line separation of the analytes from the sample matrix based on fluidized beds strategy using magnetic nanoparticles, elution and determination of the analytes using a high performance liquid chromatography system with fluorescence detection. The floating of the magnetic nanoparticles in a liquid sample phase was accomplished by air-bubbling. In the developed method Zr-Fe-C magnetic nanoparticles were used as an efficient sorbent for the determination of fleroxacin, norfloxacin and ofloxacin. Under the optimal conditions, the calibration graphs were linear over the concentration ranges of 10-1000 μg L^-1 for fleroxacin (R² = 0.996), 5-1000 μg L^-1for norfloxacin (R² = 0.998) and ofloxacin (R² = 0.998). The limits of detection, calculated from the blank tests based on 3σ, were 3.0 μg L^-1forfleroxacin, 1.5 μg L^-1for norfloxacin and ofloxacin. The limits of quantification, calculated from the blank tests based on 10σ, were 10 μg L^-1 forfleroxacin, 5 μg L^-1for norfloxacin and ofloxacin. The method was applied for the determination of fluoroquinolonesin meat-based baby food samples and the results were compared with those obtained by the reference method. The recovery values for all analytes were within of 86-122% range.

Electrochemical and analytical performance of boron-doped diamond electrode for determination of ascorbic acid

The electrochemical behavior and determination of ascorbic acid (AA) was investigated at a bare boron-doped diamond (BDD) electrode using cyclic and differential pulse voltammetry. The influence of pH of supporting electrolyte and scan rate on the current response of analyte was examined to select the suitable experimental conditions. It was found that AA provided one well-shaped irreversible and diffusioncontrolled oxidation peak at +0.87 V vs. Ag/AgCl in Britton-Robinson buffer pH 4.0. Applying differential pulse voltammetry, the peak current of AA was linearly proportional to its concentration from 5 × 10-6 to 2 × 10-4 mol L-1 (R2 = 0.999), with the limit of detection of 1.1 × 10-6 mol L-1 and the good repeatability (relative standard deviation of 2.3 %). The developed electroanalytical protocol was successfully applied to determine the content of AA in commercial pharmaceutical preparations, based on the standard additions method, with the obtained recovery of 122 %. The accomplished analytical performance indicates that BDD electrodes are promising electrochemical sensors for pharmaceutical analysis.

Cyclodextrin-assisted liquid-solid extraction for determination of the composition of jujube fruit using ultrahigh performance liquid chromatography with electrochemical detection and quadrupole time-of-flight tandem mass spectrometry

A novel, simple and environmental friendly sample preparation technique based on the use of cyclodextrin has been developed for the extraction of phenolic compounds from jujube samples, the analytes being finally determined by ultrahigh performance liquid chromatography with electrochemical detection. Quadrupole time-of-flight tandem mass spectrometry was used to characterize the composition of jujube fruit. The present method exhibited higher efficiency for extracting phenolic compositions than Pharmacopoeia heat-reflux approach in term of peak areas. Moreover, compared with traditional ultrasound-assisted extraction, the developed methodology was found without the use of toxic organic solvent, meeting the principles of green chemistry. Validation experiments showed that the proposed method presented good linearity (r(2)>0.9970), satisfactory precision (RSD<7.55%), and high recovery (85.63-105.67%). The limits of detection were from 4.92ng/mL to 142.85ng/mL for eight phenolic compounds. Eventually, the optimized approach was successfully applied to the analysis of jujube fruit.

Recent advances in flow injection analysis

A dynamic development of methodologies of analytical flow injection measurements during four decades since their invention has reinforced the solid position of flow analysis in the arsenal of techniques and instrumentation of contemporary chemical analysis.