聚(3,4-乙烯二氧吩)修飾網版印刷電極的電化學分析應用

Standard additions in flow injection analysis with atomic absorption spectrometry

A flow injection analysis (FIA) system for evaluation of the antioxidant activity of a compound capable of scavenging a hypochlorite anion (OCl⁻), one of the reactive oxygen species (ROS), was developed. Aminophenyl fluorescein (APF), a fluorescence indicator of ROS, was mixed manually with the test compounds and the mixed solution was injected into the FIA system. The injected solution was reacted in-line with OCl⁻, that was produced by using sodium dichloroisocyanurate in the presence of 0.1 M CH3CO2Na in H2O. The fluorescence intensity of fluorescein generated from non-fluorescent APF was significantly attenuated in compounds that had a scavenging effect on OCl⁻. The precision obtained by the FIA system was satisfactory (relative standard deviation < 5.0%) and a rapid assay within 0.5 min per sample was achieved. The proposed FIA system was used to demonstrate that reduced glutathione, dithiothreitol, and 3-methyl-1-phenyl-5-pyrazolone (edaravone) showed a significant scavenging effect on OCl⁻. Therefore, the proposed FIA system can be used as a screening assay for OCl⁻-scavenging compounds.

Aflatoxins (AFs), an important category of pollutants, are formed in many foods and adversely affect human health. Therefore, their determination is critical to ensuring human food health. An efficient dispersive solid-phase microextraction technique was developed as a simple and straightforward sample preparation technique for determination of four aflatoxins using a high-performance liquid chromatography (HPLC) fluorescence detector. A novel efficient, green sorbent for extracting AFs was synthesized based on hydrothermal and chemical strategies. The amounts of three sorbent components were optimized using a mixture design (simplex lattice design), including 14 experiments. The optimal amount of amino-bimetallic Fe/Ni-MIL-53 nanospheres, chitosan, and magnetic Fe3O4 nanoparticles as sorbent components was 0.87, 0.67, and 0.47 g, respectively. Also, various factors affecting the process of AF determination were studied and optimized in two successive experimental designs, including the definitive screening design and the Box-Behnken design. Under optimal conditions, the linear ranges for measuring aflatoxin B1, aflatoxin B2, aflatoxin G1, and aflatoxin G2 were 0.05-82.6, 0.07-86.4, 0.08-85.7, and 0.07-89.5 ng mL-1, respectively. The relative standard deviations under inter-day and intra-day conditions for measuring AFs at three analyte concentrations were determined in triplicate analysis and were in the ranges of 3.7-4.6% and 4.9-6.1% for water sample analysis, respectively. The qualitative detection limits for determining AFs were between 0.01 and 0.05 ng mL-1. The pre-concentration factor of the method for measuring AFs ranged from 739.7 to 802.1. The proposed method was used for determining AFs in several real samples, including herbal distillate, black tea, corn, and real water samples. The relative recovery and standard deviation were 87.8-97.8% and 4.10-6.82%, respectively.

In order to improve the quality control of dehydrated broth, a new automated method was developed to determine total creatinine in dehydrated broths. The sample pretreatment was coupled on‐line with the Flow Injection Analysis (FIA) system for analyte determination by the classical Jaffé reaction, stopped flow methodology, and spectrophotometric detection. The time consumed was reduced from 7 h, which is necessary with the official method, to 25 min. The calibration graph is linear between 0.342–1.368 mg creatinine/100 mL. The relative standard deviation (RSD%) was 1.7%, the sample throughput was 7 h−1, and the detection limit was 0.185 mg creatinine/100 mL. The validation of the proposed method was carried out with real samples. The obtained results were compared with those obtained from the Association of Official Analytical Chemists (AOAC) reference method.

Dissolved primary amine measurement by flow injection analysis with o-phthaldialdehyde: Comparison with high-performance liquid chromatography

Pungency evaluation of onion cultivars from the Venezuelan West-Center region by flow injection analysis–UV–visible spectroscopy pyruvate determination

Microporous gold electrodes are described for use as flow-through biosensor/electrochemical detectors in both flow injection analysis (FIA) as well as postcolumn detection in HPLC. Electrodes prepared by the covalent immobilization of tyrosinase onto the electrode surface (via a chemisorbed layer of thioctic acid and poly-lysine) are used to demonstrate the utility of the electrode. Such electrodes are shown to respond to a variety of substituted phenols under FIA conditions at applied potential of only −50 mV (vs. Ag/AgCl). Detection limits of 0.5 μM catechol and 3.4 μM phenol were achieved with a sample throughput rate of 38 samples/h. The electrode is shown to be stable for up to 14 days of use. The porous bioelectrode is shown to be useful as a postcolumn detector for substituted phenols following their separation by HPLC. Various techniques for immobilization of the enzyme onto the electrode surface (covalent and noncovalent) as well as factors affecting sensitivity and through-put (buffer ionic strength and addition of organic modifier) are discussed.

A novel flow injection procedure has been developed for the determination of tannic acid based on the inhibition of the chemiluminescences in luminol-H2O2-Manganese tetrasulfonatophthalocyanine (MnTSPc) system by tannic acid. The method is simple, rapid and sensitive with a detection limit of 8 × 10−10 mol·L−1 and a linear range of 7 × 10−9–5 × 10−6 mol·L−1. The relative standard deviation is 1.9% for eleven measurements of 5 × 10−7 mol·L−1 tannic acid. The method has been successfully applied to the determination of tannic acid in real Chinese gall and hop pellets samples.

Background: A new modified electrode based on the poly(chromotropic acid) (4,5-dihydroxynaphthalene- 2,7-disulfonic acid) film was developed by electrochemical polymerization to explore its voltammetric behavior. The electrochemical synthesis of poly(chromotropic acid) was accomplished by applying an aqueous solution of sodium hydroxide as a supporting electrolyte (0.1 M). The electrochemical behaviors of bisphenol A (BPA) on poly(chromotropic acid) modified glassy carbon electrode (poly(CTA)/GCE) were researched by cyclic voltammetry, square wave voltammetry, and chronoamperometry. Methods: The analytical performances of the developed method were carefully examined. When the concentration of BPA changed from 0.1 µM to 20 µM, the current response of BPA was linearly related to the concentration over the range of 0.1–2 µM and 2.0–20 µM, respectively and the detection limit of the suggested method was found to be 0.06 µM. The feasibility of the detector was successfully demonstrated for BPA detection in various real samples. Results: The suggested methodology was applied for the detection of BPA in different real samples (bottled water, tap water and honey sample). The samples were prepared as described above and these aforesaid samples were analyzed directly. Since no BPA was detected in these samples, standard addition method was employed. The percent recovery tests were also investigated by measuring the current responses to the samples in which the known concentrations of BPA standard solution were spiked. Thus, the spikes are subjected to similar matrix effects. The percent recoveries in the range of 94.0%– 103% were obtained. These consequences indicated that the poly(CTA)/GCE has adequate electroanalytical efficiency and it can be a feasible sensor for detection of BPA in different samples. Conclusion: A new voltammetric sensor for the detection of BPA was developed based on a very simple preparation scheme consisting in the direct electropolymerization of poly(CTA) films on GCE. The proposed poly(CTA)/GCE displays a helpful and easy method for observing of BPA in real aqueous samples exhibiting an adequate electroanalytical performance (linearity, detection limit, sensitivity, and selectivity) due to its stability and reproducibility associated with an effortless and speedy fabrication, and low cost. This new method could offer a charming approach for on-site detection of trace BPA contamination in aqueous samples. Keywords: Bisphenol A, determination, voltammetry, chromotropic acid, food analysis, water analysis.

Objective To study a method of detecting S-carboxymethyl cysteine in urine by high-performance liquid chromatography(HPLC) with o-phthalaldehyde(OPA) pre-column derivation. Methods Urine samples were purified and richened by small column(Sep-Pak C18).S-carboxymethyl cysteine in purified samples reacted with OPA in autosampler of HPLC,separated by column Lichrospher 100 RP-18e and detected by DAD detector at wavelengh 338 nm. Results The correlation coefficient of S-carboxymethyl cysteine standard curve(concentration 0.0～0.5 mmol/L) was 0.999 8.Detection limit of method was 0.002 mmol/L.Inner relative standard deviation(RSD) of 0.05,0.30 and 0.50 mmol/L S-carboxymethyl cysteine were 1.42%,0.78% and 1.97%(n=6),respectively.Outer RSD of 0.05,0.30 and 0.50 mmol/L S-carboxymethyl cysteine were 2.43%,4.23% and 3.89%(n=6),respectively.Recovery rates of 0.10,0.30 mmol/L S-carboxymethyl cysteine were 93%,102%,respectively. Conclusion The method has good linearity,precision and satisfactory recoveries.The program of method is also automatic and simple.Therefore,it may be used for detecting S-carboxymethyl cysteine in urine.

Cucurbit[8]uril-based electrochemical sensors as detectors in flow injection analysis. Application to dopamine determination in serum samples

A catalytic-fluorimetric method for the determination of copper(II) at the nanograms per millilitre level is proposed, based on the catalytic action of the copper(II) cation on the oxidation of 2,2′-dipyridyl ketone hydrazone (DPKH) by dissolved oxygen. In order to obtain the maximum analytical signal, two steps are necessary: oxidation of DPKH (basic medium) and development of fluorescence (strongly acidic medium). Flow injection analysis is very suitable for this determination as it is sensitive and rapid. The calibration graph shows two linear intervals, between 8 and 30 ng ml–1[relative standard deviation (r.s.d.) 2.3%] and 40 and 300 ng ml–1(r.s.d. 2.0%). The sampling frequency is 100 h–1 for an injected volume of 60 µl. A study of interferences is reported. The use of “reverse” flow injection analysis makes the method more sensitive.

A novel flow injection analysis (FIA) method with Rayleigh light scattering (RLS) detection was developed for the determination of total protein concentrations. This method is based on the weak intensity of RLS of bromothymol blue (BB) (3',3"-dibromothymolsulfonephthalein) which can be enhanced by the addition of protein in weakly acidic solution. A common spectrofluorimeter was used as a detector. It was proved that the application of this method to quantify the total proteins in real samples by using bovine serum albumin was possible. The RLS signal was detected at lambda(ex)= lambda(em)=572 nm. The linear range was 7.0-70.0 microg mL(-1), the detection limit was 3.75 microg mL(-1), the reproducibility was 5.5% (n=7), and the sample throughput was 26 h(-1).

Precise determination of dissolved phosphorus concentration in antibiotic fermentation broths is essential for microbial growth and metabolism during fermentation. The conventional method often relies on manual operations, leading to low reproducibility. Herein, we applied the phosphomolybdenum blue reaction to flow injection analysis (FIA) to create an automated approach for phosphorus quantification in antibiotic fermentation broths. Key parameters for the FIA system, including flow rate (1.75 mL/min), ammonium molybdate concentration (20 g/L), and sulfuric acid concentration (0.30 mol/L), were optimized, resulting in a reliable standard curve. Compared to the conventional method, which requires a 10-min incubation in a 50 °C water bath, the FIA method enables measurements in approximately 20 s (sample throughput = 178 h−1). Furthermore, this method offers a wider linear range (0.53–200 mg/L). With good accuracy and precision (relative standard deviation (RSD)=0.35%) and a low limit of detection (LOD, 0.16 mg/L) and limit of quantification (LOQ, 0.53 mg/L), this FIA method presents significant potential for microbial fermentation monitoring. It offers advantages such as automation, low reagents consumption, and the capacity to produce high-precision data at large scale.

New interface for coupling flow-injection and capillary electrophoresis