Study on Chemiluminescence Reactions of L ucigenin and Reductants by Flow Injection Analysis

The chemiluminescence reactions between lucigenin and reductants such as Mo(LII),V( II), U(III), W(III), Cr(II), Ti(III) and Fe( II), which were produced on-line by passing Mo(VI),V(V),U(VI), W(VI), Cr(VI,III),Ti(IV) and Fe(III) through a micro Jones column, are studied in detail. Results show that the reactions can be used directly for the determination of these substances. The mechanism of the reactions is also investigated.

Analysis of Mechanical Properties of Injection Molded Short Glass Fibre (SGF)/Calcite/ABS Composites

Acrylonitrile-butadiene-Styrene (ABS), with and without calcium carbonate (calcite) particles,was used as the matrix for reinforcement with as-received short-glass fibres (were originallytreated by the manufacturer) and sized short-glass fibres with two amino-silane coupling agents.The calcite particle content is 0, 11.7 and 23.5 vol. pct for the matrices. The glass fiber contentis 0, 10 and 15 vol. pct. The matrix materials and corresponding composites were compoundedusing a twin screw extruder and dumbbell-shaped tensile bars were prepared with an injectionmolding process. The tensile and flexural properties as well as the unnotched and notchedCharpy impact energies of short glass fibre/calcite/ABS composites were studied in this paper.The effects of fibres, fibre surface treatments and particles on these mechanical properties ofthe composites were discussed in detail. An importarit information was obtained, which is thatthe tensile and flexural strengths of hybrid SGF/calcite/ABS composites are the same as thoseof corresponding fibre composites when the ratio of the interfacial adhesion strength betweenparticles and matrix to that between fibres and matrix is higher than certain value. otherwise theformer are lower than the latter.

Flow Injection Analysis of Histidine with Enhanced Electrogenerated Chemiluminescence of Luminol

A simple and sensitive flow injection method is presented for the determination of histidine based on its enhancement of electrogenerated chemiluminescence (ECL) of luminol. After optimization of the experimental parameters, the working range for histidine was in 1.0 x 10-6 to 1.0 x 10 -3 mol/L with a detection limit (S/N = 3) of 0.56 mmol/L. The relative standard deviation was 1.6% for 11 measurements of 5 x 10 5 mol/L histidine solution. The proposed method has been successfully applied to the determination of histidine in real pharmaceutical preparation.

SELECTIVE SULFUR DIOXIDE DETERMINATION BY GAS DIFFUSION FLOW INJECTION ANALYSIS WITH CHEMILUMINESCENT DETECTION

Sulfur dioxide has been found to decrease the chemiluminescence of luminol-iodine system.A new determination method for sulfur dioxide in atmosphere is developed by applying this reaction to a flow injection gas diffusion separation system.This permits the determination of sulfur dioxide selectively and rapidly.

Flow Injection Analysis Technique for Online Preconcentration of Lead Ions in Airborne Particulate Matter Using Imprinted Polymer as the Sorbent

This work reported a simple and sensitive flow injection analysis(FIA)technique coupled with a Flame Atomic Absorption Spectrophotometer(FAAS)for online preconcentration of lead(Ⅱ)ions in the airborne particulate matter samples(PM_(2.5))using ion-imprinted polymers as adsorbent packed in minicolumn.A bulk polymerization method was chosen to synthesize the polymer based on a ternary complex of lead ions with 4-2-pyridilazo resorcinol and 4-vinyl pyridine with methacrylic acid as a functional monomer.The optimum pH for sorption was 6,and other variables for the FIA system were optimized,including breakthrough volume,eluent concentration,and eluent volume.The optimum conditions were reached with a breakthrough volume of 4.45 mL,calculated as a dynamic retention capacity of 5.20 mg/g of Pb(II)40 mg/L,with a 1.5 mL/min flow rate.The eluent used for the FIA system was 0.5 mL HNO_(3)of 3 mol/L.Linearity,precision,and limits of detection of the FIA system were determined before being applied to preconcentration and analysis of lead ions in PM_(2.5)samples.The precision of the method was determined to be 3.09%by calculating the coefficients of the variant.Linearity of the method in the concentration range of 50-1000μg/L gave a coefficient correlation of 0.9925,showing a good response,and the limit of detection of the system was 5.11μg/L,better than that of the FAAS method.Performances of the FIA system were evaluated and showed good results with an enrichment factor of more than 20 times higher and a concentration efficiency of 11.65 min^(-1)with a consumptive index of 4.5 mL.Preconcentration and analysis of the PM_(2.5)samples in Bandung City showed the concentrations of Pb(II)were 26.67μg/L and 33.3μg/L with the accuracy of the method for each sample of104.75%and 107.86%.

A Novel Enhancer for Fe^(2+)-Catalyzed Light Emission Reaction of Luminol and Dissolved Oxygen

EDTA was used as an enhancer for Fe 2+ catalyzed light emission from luminol oxidation by dissolved oxygen. As a result, the limit of detection for ferrous ion with flow injection analysis was improved by a factor of 160 by addition of EDTA to the luminol solution. Fe 2+ and Fe 3+ were determined simultaneously with a novel copper-coated zinc reductor minicolumn installed in one of the shunt after sample splitting in the manifold. The reductor minicolumn can be used for 3000 determinations at least. The dynamic range of determination was 1×10 -9 ～1×10 -5 mol·L -1 , with the limit of detection of 2.7×10 10 and 3.5×10 10 mol·L 1 ,for Fe 2+ and Fe 3+ , respectively. The preci sion for determination of 2×10 7 mol·L 1 of Fe 2+ and Fe 3+ was 2.3% and 4.0% (n=8), respectively, at a sampling rate of 60 h -1 . Cr 3+ and Co 2+ interfere. Fe 2+ and Fe 3+ in mixture were determined with satisfactory results. Samples of Fe 2+ and Fe 3+ were determined simultaneously and the results in good agreement with the standard spectrophotometric method. Indications were shown that EDTA functions as an enhancer, Fe 2+ as a catalyst, and oxygen is the oxidant of the chemiluminescent reaction, and the mechanism of the reaction was discussed.

A novel thermal biosensor based on enzyme reaction for pesticides measurement

A novel thermal biosensor based on enzyme reaction for pesticides detection has been developed. This biosensor is a flow injection analysis system and consists of two channels with enzyme reaction column and identical reference column, which is set for eliminating the unspecific heat. The enzyme reaction takes place in the enzyme reaction column at a constant temperature(40℃) realized by a thermoelectric thermostat. Thermosensor based on the thermoelectric module containing 127 serial BiTe-thermocouples is used to monitor the temperature difference between two effluents from enzyme reaction column and reference column. The ability of this biosensor to detect pesticides is demonstrated by the decreased degree of the hydrolytic heat in two types of thermosensor mode. The hydrolytic reaction is inhibited by 36% at 1 mg/L DDVP and 50 % at 10 mg/L DDVP when cell-typed thermosensor is used. The percent inhibition is 30% at 1 mg/L DDVP and 42% at 10 mg/L DDVP in tube-typed thermosensor mode. The detection for real sample shows that this biosensor can be used for detection of organophosphate pesticides residue.

Flow-injection Spectrophotometric Determination of Uric Acid in Urine via Prussian Blue Reaction

A simple and sensitive flow injection（FI） spectrophotometric method was reported for the determination of uric acid based on the reduction of Fe（III）/ferricyanide in the presence of uric acid. The in situ reduced ions reacted with unreduced portion of ferricyanide/Fe（III） to form soluble Prussian blue, which was monitored at an absorption wavelength of 735 nm. The optimized conditions allow a linear calibration graph in a concentration range of 1―100 μmol/L. The relative standard deviation was in a range of 0.5%―2.5%, with a detection limit（3σ blank） of 0.3 μmol/L and a sampling frequency of 60 injection/h was obtained. The effect of common substances present in human physiological fluids on the determination of uric acid was examined. The method was applied to determining uric acid in human urine samples with the recoveries in a range of 96%―105%. The results agree well with those by spectrophotometric reference method at a confidence level of 95%. Spectrophotometric procedures for uric acid determination in clinical samples were reviewed briefly.

STRUCTURE PARAMETERS DESIGN AND PERFORMANCE TEST OF FUEL INJECTION SYSTEM

Based on the numerical simulation analysis, structure parameters of the high pressure fuel pump and common rail as well as flow limiter are designed and the GD-1 high pressure common rail fuel injection system is self-developed. Fuel injection characteristics experiment is performed on the GD-1 system. And double-factor variance analysis is applied to investigate the influence of the rail pressure and injection pulse width on the consistency of fuel injection quantity, thus to test whether the design of structure parameters is sound accordingly. The results of experiment and test show that rail pressure and injection pulse width as well as their mutual-effect have no influence on the injection quantity consistency, which proves that the structure parameters design is successful and performance of GD-1 system is sound.

Electrochemical behavior of paclitaxel and its determination at glassy carbon electrode

The electrochemical behavior of paclitaxel drug was studied at a glassy carbon electrode in phosphate buffer solutions using cyclic and differential-pulse voltammetric techniques.The oxidation process was shown to be irreversible over the pH range(3.0e10.4)and was diffusion controlled.Effects of anodic peak potential(E_(p)),anodic peak current(Ipa),scan rate,pH,heterogeneous rate constant(k^(0)),etc have been discussed.A possible electrooxidation mechanism was proposed.An analytical method was developed for the determination of paclitaxel in phosphate buffer solution at pH¼7.0 as a supporting electrolyte.The anodic peak current varied linearly with paclitaxel concentration in the range 1.0×10^-(6)M to 1.0×10^-(5)M with a limit of detection(LOD)of 1.23×10^(-8)M and limit of quantification(LOQ)of 4.10×10^(-8)M.The proposed method was successfully applied to the determination of paclitaxel in pure and real samples.

Study on Chemiluminescence Reaction between Lucigenin and Four Rare Metal Ions

The chemiluminescence (CL) reactions between lucigenin and four rare metal reductants were studied systematically using a flow injection system.The results show that the reactions can be used for determination of rare metals.The probable mechanism of the CL reactions involves the reduction of dissolved oxygen to the superoxide radical O - 2·by the reductant,followed by the O - 2·reacting with alkaline Lu to generate CL.The pathway involves a dioxetane intermediate.

Flow-injection spectrophotometric determination of vanadium with malachite green oxalate by bromate in acidic and micellar medium

A flow injection method is proposed for determining vanadium（V）. The method is based on its catalytic effect on the oxidation of malachite green oxalate by bromate. The reaction was monitored spectrophotometrically by measuring malachite green oxalate absorbance at λmax = 625 nm. The reagents and manifold variables, which have influences on the sensitivity, were investigated and the optimum conditions were established. The optimized conditions made it possible to determine vanadium in the ranges of 10-140 ng/mL with a detection limit of 5.2 ng/mL and a sample rate of 20 ± 5 samples/h.

On-line coupling of derivatization with pre-concentration to determine trace levels of methotrexate

A new simple, sensitive and precise green analytical procedure using an automated packed-reactor derivatization technique coupled with on-line solid-phase enrichment （SPEn） has been developed and evaluated to determine trace levels of methotrexate （MTX）. The method was based on injection of MTX into a flowing stream of phosphate buffer （0.04 M, ptt 3.4）, carried through the packed oxidant reactor of Cerium （IV） trihydroxyhydroperoxide for oxidative cleavage of the drug into highly fluorescent product, 2,4-diaminopteridine- 6-carboxylic acid, followed by SPEn on a head of short ODS column （10mm x 4.6 mm i.d., 5 I＋tm particle size）. The flow rate was 0.25 mL/min and packed reactor temperaturc was 40 ~C. The trapped product was back-flush eluted from the ODS column to the detector by column-switching with an environmentally friendly mobile phase consisting of ethanol and phosphate buffer （0.04 M, pH 3.4） in the ratio of 5：95 （v/v）. The eluent was monitored at emission and excitation wavelengths of 460 and was linear over the concentration range of 1.25-50 360 nm, respectively. The calibration curve ng/mL with a detection limit of 0.08 ug/ml..The method was successfully applied to determine MTX in pharmaceutical formulations with mean percentage recovery ranging from 99.48 to 99.60.

Study on the Flow Injection Micro-Column Pre-Separation System Coupled With High Performance Liquid Chromatography for the Determination of Ecdysterone in Traditional Chinese Medicine

A flow injection (FI) micro-column system coupled with high performance liquid chromatography (HPLC) was proposed for the pre-separation and determination of active organic component (ecdysterone) in traditional Chinese medicine, Loulu. The factors influencing separation performance were investigated and optimized. Under the optimal conditions, the contents of ecdysterone in Loulu were determined by HPLC system using MeOH-H_2O (40: 60,V/V) as the mobile phase at a flow rate of 1. 0 mL/min. The calibration curve was linear in the range of 0. 5~ 100 mg/L of ecdysterone concentrations. The detection limit of the analyte was 0. 11mol/L(3) with a precision of 0. 38% RSD (n=7 f c= 10. 0 mg/L). The average recovery of the method was 98. 7%. The proposed method has been applied to determine ecdysterone in practical samples, and the determined values by both external standard method and standard addition method were in good agreement. Compared to the traditional solid extraction method, the system proposed has the advantages of simple procedure, good reproducibility, minimum volume requirement, reduction of matrix interference and low contamination risk.

Differential Electrolytic Potentiometric, a Detector for FIA Determination of Procainamide in Pharmaceutical Preparations

Differential electrolytic potentiometry （DEP） was coupled with Flow injection analysis （FIA） technique for the determination of Procainamide in pharmaceutical preparations. Platinum electrodes were used as an indicating system to follow the oxidation of Procainamide with cerium（IV）, and permanganate in an acidic medium. The oxidation reactions of Procainamide with Ce（IV） and/or permanganate are fast enough to permit its determination by flow injection in sulfuric acid media. The univariate method was employed to optimize the variables such as the current density, the flow rate, the oxidant concentration and the concentration of sulfuric acid. The proposed method was linear in the range 20-100 μg.mL^-1 , the DL and R2 values were 12 μg.mL^-1 and 0.995 respectively. The procedure was applied successfully to the determination of Procainamide in commercial tablets. The results of this study were favorably compared statistically with those obtained with official methods.

Determination of ribavirin by flow injection chemiluminescence

Objective： To establish a rapid and precise continuous flow-injection chemiluminescence （CL） method to determine ribavirin. Methods： The ribavirin could restrain strongly CL reaction of luminol in sodium hydroxide （NaOH） solution with potassium chlorate （KClO3）. The different experimental parameters affecting the CL intensity were studied carefully. Results： Under optimum conditions （The concentrations of luminol, KClO3, and NaOH were at 0.1 mmol/L, 0.5μmol/L, and 0.2 mol/L, respectively）, the linear range of the working curves was 0.01-7.00μg/ml with a detection limit of 0.004μg/ml. Conclusion： The method is simple, rapid and sensitive, and successfully applied to the determination of ribavirin in pharmaceutical preparations and biological fluids.

Hydralazine Hydrochloride:An Alternative Complexometric Reagent for Total Iron Spotometric Determination

An alternative spectrophotometric method has been developed for total iron determination using flow injection analysis (FIA). The procedure is based on the coordination reaction between hydralazine and Fe2+ ions, which results in the formation of a purple complex monitored at 538 nm. For determination of total iron, Fe3+ ions were reduced using ascorbic acid. Under optimized conditions, a linear calibration graph (0.1 - 6.0 ?g?ml–1;n = 6) was obtained. The method allows LOD (3? of blank/slope = 0.06 ?g?ml–1) and LOQ (10? of blank/slope = 0.22 ?g?ml–1). The RSD ((s/ ) × 100) for a mixed standard containing 0.60 ?g?ml–1 Fe2+ and Fe3+ was 0.10% (n = 10). Recoveries of spiked samples were 94.3% - 106.0%. The analytical frequency was 60 h–1. The effect of possible interferences has been studied. The procedure was successfully applied for analysis of environmental samples. The real samples results were comparable with those obtained by the official method considering a paired t-test and 95% of confidence level.

Chemiluminescent Determination of Cyromazine in Milk Samples Using Copper（III） Chelate-Triton X-100 by Flow Injection Analysis

Cyromazine（CYR） was determined in milk samples using copper（HI） chelate-Triton X-100 chemiluminescence（CL） system associated with flow-injection（FI） in KOH medium. The relative CL intensity for CYR concentration was linear over the range of 5×10^-4-10μg/mL（R2=0.9990, n=11） with injection rate of 160 h-1 and the relative standard deviation（RSD, n=4） of 1.2%-2.6%. The limit of detection（LOD） for signal-to-noise ratio of 3 was 1.5×10^4μg/mL. The influences of key chemical and physical parameters, some major fresh water ions at their maximum admissible concentrations and a number of pesticides were examined as potential interferences. The concentrations of CYR in spiked milk samples were successfully determined by the proposed method and the results were in good agreement with that of the previously reported HPLC method, having recovery range of （92% a=4%）-（106% a：2%）. The possible CL reaction mechanism for copper（m） chelate-Triton X-100-CYR was also briefly discussed.

Integration of microfluidic injection analysis with carbon nanomaterials/gold nanowire arrays-based biosensors for glucose detection

Carbon nanotubes(CNTs) and reduced graphene oxide(r GO) nanosheets were utilized to construct glucose biosensors in combination with gold nanowire arrays(Au NWAs), and microfluidic injection analysis driven by gravity force was used to investigate the performances of as-prepared glucose biosensors. The results demonstrated glucose biosensors based on carbon nanomaterials/Au NWAs presented excellent performance at low working potential of-0.2 V versus Ag/Ag Cl(3 mol/L KCl), such as high sensitivity, good anti-interference ability and high throughput(45 h^(-1)). The glucose biosensor based on glucose oxidase(GOx)–CNT–Au NWAs showed a wide linear range from 100 to 3,000 lmol/L with a sensitivity of 4.12 l A/cm^2 mmol/L. Furthermore, the linear range and sensitivity of GOx–r GO–Au NWAs-based glucose biosensor were 50–4,000 lmol/L and 8.59 l A/(cm^2 mmol/L), respectively, which were better than those of glucose biosensor based on GOx–CNT–Au NWAs,suggesting r GO nanosheets in combination with Au NWAs being a good platform for the construction of glucose biosensors.

Electropolymerized poly(Toluidine Blue)-modified carbon felt for highly sensitive amperometric determination of NADH in flow injection analysis

Poly（pheniothiazine） films were prepared on a porous carbon felt（CF） electrode surface by an electrooxidative polymerization of three phenothiazine derivatives（i.e.,Tthionine（TN）,Toluidine Blue（TB） and Methylene Blue（MB）） from 0.1 mol/L phosphate buffer solution（pH 7.0）.Among the three phenothiazies,the poly（TB） film-modified CF exhibited an excellent electrocatalytic activity for the oxidation of nicotinamide adenine dinucleotide reduced form（NADH） at ＋0.2 V vs.Ag/AgCl.The poly（TB） film-modified CF was successfully used as working electrode unit of highly sensitive amperometric flow-through detector for NADH.The peak currents（peak heights） were almost unchanged,irrespective of a carrier flow rate ranging from 2.0 to 4.1 mL/min,resulting in the measurement of NADH（ca.30 samples/hr） at 4.1 mL/min.The peak current responses of NADH showed linear relationship over the concentration range from 1 to 30 μmol/L（sensitivity：0.318 μA/（μmol/L）;correlation coefficient：0.997）.The lower detection limit was found to be 0.3 μmol/L（S/N = 3）.