Single Bead String Reactor Research Articles

Generation of a square wave inductively coupled plasma scanning mass spectrometry signal using electrothermal vaporization sample introduction

A device was designed to convert the typical skewed gaussian shaped signal from an inductively coupled plasma mass spectrometer (ICP-MS) using electrothermal vaporization (ETV) into a square wave signal. The basis for such a transformation is centered on the assumption that the aerosol particles produced from ETV are aerodynamically small, and thus, have diffusive properties similar to gases, which makes them easy to mix and resistant to loss by settling. The ETV square wave signals were generated through the use of a stainless steel cylinder equipped with a motor driven piston assembly, which was used to trap the transient ETV signal and deliver a uniform density aerosol to the ICP-MS. The length of the signal was controlled by the rate of travel of the piston during expulsion of the sample aerosol. A constant flow rate was achieved and maintained using a pressure sensor feedback to the motor driving the piston. The system was evaluated by quantitative full mass scans on a variety of signal shapes including square wave signals, normal ETV signals, and broadened ETV signals generated with the use of a single bead string reactor (SBSR). The square wave signals yielded precisions for quantitative full mass scans of better than 10% RSD for most metals compared to approximately 15% for SBSR broadened signals and 40% for normal signals. The improved precision was attributed to an increased duty cycle, but the increase did not become significant until more than 100 masses were monitored due to the relatively small amount of “temporal overhead time” (fly-back time, amplifier settling time, etc.) relative to data collection periods. Because the ETV generated aerosol consists of aerodynamically small particles, there was only a minimal decrease (<2–11%) in the integrated signal area as a result of using the square wave generator.

Application of the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation assay to a flow injection system for the evaluation of antioxidant activity of some pure compounds and beverages.

The 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS(*)(+)) assay was adapted to a flow injection (FI) system to obtain a sensitive and rapid technique for the monitoring of antioxidant activity of pure compounds and complex matrixes, such as beverages and food extracts. The FI system includes a HPLC pump that flows the mobile phase (a solution of ABTS(*)(+) in ethanol) through a 20 microL loop injector, a single bead string reactor filled with acid-washed silanized beads, a delay coil and a photodiode array UV-visible detector. The technique was very sensitive, with limits of detection and of quantification of 4.14 and 9.29 micromol of Trolox/L, respectively, and demonstrated high repeatability and reproducibility. The proposed technique was then applied to the evaluation of the antioxidant activity of some pure compounds, demonstrating good agreement with published data obtained by the original spectrophotometric ABTS(*)(+) assay. Finally, the total antioxidant activity of 10 beverages was determined by both the proposed and the original method. The values ranged from 0.09 mmol L(-)(1) for cola to 49.24 mmol L(-)(1) for espresso coffee and did not result significantly different from those obtained by the original spectrophotometric ABTS(*)(+) assay (Student's paired t-test: t = 1.4074, p = 0.1929). In conclusion, the proposed FI technique seems suitable for the direct, rapid and reliable monitoring of total antioxidant activity of pure compounds and beverages and, due to the ability to operate in continuous, it allows the analysis of about 30 samples h(-)(1) making the assay particularly suitable for large screening of total antioxidant activity in food samples.

Flow injection spectrophotometric determination of europium using chlortetracycline

A flow injection (FI) spectrophotometric determination of europium (III) is described, based on the complexation between europium (III), and chlortetracycline (CTC) in a Tris–buffer pH 8.0 medium. The resulting yellow-coloured complex is measured at its absorption maximum of 400 nm after 100 μl of sample or standard solution containing europium (III) are injected into the merged streams of CTC and Tris–buffer solutions. Optimum conditions for determining μg amounts of europium (III) are achieved by univariate method. Various types of reactors are also investigated. It is shown that the use of a single bead string reactor gives rise to the enhancement of peak height. A linear calibration curve over the range of 0.10–0.60 μg ml −1 europium (III) is established with the regression equation ( n=6) Y=34.93 X+0.01 and the correlation coefficient of 0.9994 is obtained. A detection limit (3σ) of 0.01 μg ml −1 of europium (III) and the relative standard deviation (R.S.D.) of 4.32% for determining 1.0 μg ml −1 of europium (III) ( n=7) are obtained. The recommended method has been applied to the quantitation of europium (III) in spiked water and stream sediment samples with average recoveries of 99.9 and 97.5%, respectively. The sampling rate is found to be 85 h −1.

Reverse flow injection spectrophotometric determination of iron(III) using norfloxacin

A reversed flow injection colorimetric procedure for determining iron(III) at the μg level was proposed. It is based on the reaction between iron(III) with norfloxacin (NRF) in 0.07 mol l −1 ammonium sulfate solution, resulting in an intense yellow complex with a suitable absorption at 435 nm. Optimum conditions for determining iron(III) were investigated by univariate method. The method involved injection of a 150 μl of 0.04% w/v colorimetric reagent solution into a merged streams of sample and/or standard solution containing iron(III) and 0.07 mol l −1 ammonium sulfate in sulfuric acid (pH 3.5) solution which was then passed through a single bead string reactor. Subsequently the absorbance as peak height was monitored at 435 nm. Beer's law obeyed over the range of 0.2–1.4 μg ml −1 iron(III). The method has been applied to the determination of total iron in water samples digested with HNO 3–H 2O 2 (1:9 v/v). Detection limit (3 σ) was 0.01 μg ml −1 the sample through of 86 h −1 and the coefficient of variation of 1.77% ( n=12) for 1 μg ml −1 Fe(III) were achieved with the recovery of the spiked Fe(III) of 92.6–99.8%.

Automated in situ preparation of Azomethine-H and the subsequent determination of boron in fertilizer process and water effluent streams with sequential injection analysis

A sequential injection system for the automated in situ preparation of Azomethine-H and the on-line monitoring of boron in water effluents and fertilizer process streams is described. Azomethine-H, a condensation product of salicylaldehyde and H-acid (8-amino-1-naphthol-3,6-disulfonic acid) is used as the chromogenic reagent. The Azomethine-H is prepared in situ by mixing salicylaldehyde and H-acid in the presence of boron. A single bead string reactor is used to promote the mixing process. In solution the chromogenic reagent exists as its two constituents. When boron is added to the solution, Azomethine-H is formed and measured at 420 nm. The proposed system is fully computerised and is able to monitor boron at a rate of 30 samples per hour with a relative standard deviation of <1.4%. The calibration graph is linear up to 100 mg l−1. The system has a detection limit of 0.61 mg l−1.

Influence of Single Bead String Reactors on Zone Penetration and the Isodispersion Point in Sequential Injection Analysis

A non-reactive dye was used to investigate the effect, that a single bead string reactor (SBSR) has upon the isodispersion point and the degree of zone penetration of the “sample” and “reagent” zones in a simple sequential injection system. The length of SBSR, the pump speed (flow rate) and the volume ratios of both the sample and reagent zones in a total constant volume were parameters that were studied with the SBSR at one of two positions, either before the detector or between the selection valve, and the holding coil.

Micro-scale determination of glucose by capillary flow injection with an immobilized enzyme reactor

Capillary flow injection was combined with an immobilized enzyme reactor to determine glucose in various juice and soft drink samples. Glucose oxidase was successfully immobilized onto open tubular capillary reactors by covalent bonding. The glucose oxidase catalyzed oxidation of glucose to gluconic acid and hydrogen peroxide was coupled with the Trinder reaction in which the hydrogen peroxide reacts to form a quinoneimine dye. The dye product was monitored spectrophotometrically. Quantitative determinations showed improved sensitivity and reproducibility over determinations using conventional flow injection and glucose oxidase immobilized in a single bead string reactor. The use of capillary flow injection reduced reagent consumption to 320 μl/h, only 1.4% of that consumed with conventional flow injection.

Enzymatic methods for the determination of α-glycerophosphate and α-glycerophosphate oxidase with an automated FIA system

A procedure for the enzymatic determination of α-glycerophosphate ( α-GP) has been developed, using an automated in-house FIA system, with immobilized glycerol-3-phosphate oxidase (GPO) on non-porous glass beads, following optimization of the immobilization and analytical parameters. Fabricated single bead string reactors (SBSR) were used in connection with the FIA system, following optimization of its parameters. The half-life of GPO-SBSR regarding reduction of the enzyme activity was found to be 110 days for its use in 20 triplicate measurements daily and storage at 4°C in the appropriate buffer. The regression equation of the calibration graph for the determination of α-GP was: A max=(10±2)×10 −4+(22 134±12)×10 −4 (mmol l −1 α-GP). The lower limit of quantitation was 0.74 μmol l −1 α-GP and the RSD of the method 0.05% ( r=0.9999). The same FIA system and procedure can be also used for the determination of the GPO activity, with the α-GP as substrate. The regression equation for this calibration graph was: A max=(23±18)×10 −4+(190±1)×10 −4 (μg ml −1 GPO), the lower limit of quantitation was 0.782×10 −3 mg ml −1 (0.782 ppm) GPO and the RSD of the method 0.53% ( r=0.9999). Serum samples obtained from hospitalized patients were deproteinized by gel filtration and analyzed under pseudo-first order conditions, at various concentrations of α-GP. A kinetic study of the reduction of α-GP in serum versus time is given and an observed reaction rate constant k ob=106.5×10 −4 min −1 was determined.

An Enzymatic Method for the Determination Of ATP and Glycerol with an Automated FIA System

ABSTRACT A method for the enzymatic determination of adenosine triphosphate (ATP) and glycerol has been developed, using an automated FIA system. The enzymes Glycerophosphate Oxidase (GPO) and Glycerol Kinase (GK) have been immobilized on non-porous glass beads following optimization of the immobilization parameters. The fabricated Single Bead String Reactors (SBSR) were used in connection with a FIA system, following optimization of its parameters. The half-life of GK SBSR, regarding enzyme activity, was found to be 45 days for 90 measurements of daily use and storage at 4°C in the appropriate buffer. The linear dynamic ranges of the working curves for the enzymatic determinations of ATP and Glycerol, were 4–70 μmol.l−1 and 2–160 μmol.l−1 respectively. Glycerol was determined in white and red wines after a 1:5,100 dilution. Glycerol was also determined in human serum, following deproteinization of the samples by gel filtration. The low limits of quantification (4μmol.l−1 ATP and 1 μmol.l−1 glycerol) and accuracies better than 2% for ATP and 1% for glycerol, show that the proposed method offers many significant improvements over the conventional methods.

Flow injection determination of glutamate in human serum and rat brain samples with immobilized glutamate oxidase and glutamate dehydrogenase reactors.

Two methods are proposed for the determination of regional concentrations of glutamate in the rat brain as well as in human serum. Glutamate oxidase was immobilized on non-porous glass beads and glutamate dehydrogenase was immobilized on glass derivatives. These supports were employed for the construction of Single Bead String Reactors and Packed Bed Reactors, respectively, which in turn were linked to Flow Injection Analysis systems with either photometric or fluorometric detection. Analytical working curves are linear in the range 1-200 mumol/l for packed bed reactors and 10-500 mmol/l for single bead string reactors. The samples were pretreated depending on their origin and the applied measuring system. Optimal dilution factors were established for the two techniques. Optimal dilution ratios were established and the influence of several added substances was investigated. Recovery and method comparison studies including high performance liquid chromatography verified the accuracy of the proposed methods. Results from within-day and between-day measurements gave relative standard deviations of 4.7 and 5.9% for serum samples and 2.5 and 4.0% for brain samples, respectively.

Removal of ascorbic acid interference in the determination of glucose and sucrose in non-alcoholic beverages

A flow-injection system with an immobilized-enzyme, single-bead string reactor has been used to study the ascorbic acid interference in the determination of glucose and sucrose. Glucose was enzymatically determined in standard solutions and in samples of non-alcoholic beverages. After the measurement of glucose, the samples were spiked with different amounts of ascorbic acid, which was found to introduce serious errors even in low concentrations. A procedure for treating the samples containing ascorbic acid with ascorbase is proposed. The treatment completely removes the interference effect and ensures the recovery of the true concentration of glucose present in the measured samples. The method was applied to determinations of glucose and sucrose in soft drinks and in natural orange juice. The relative standard deviation of the procedure is ±3%.

Determination of organophosphorous and carbamate insecticides by flow injection analysis

A flow injection system, incroporating an acetylcholinesterase (AChE) single bead string reactor (SBSR), for the determination of some organophosphorous (azinphos-ethyl, azinphos-methyl, bromophos-methyl, dichlorovos, fenitrothion, malathion, paraoxon, parathion-ethyl and parathion-methyl) and carbamate insecticides (carbofuran and carbaryl) is presented. The detector is a simple pH electrode with a wall-jet entry. Variations in enzyme activity due to inhibition are measured from pH changes when the substrate (acetylcholine) is injected before and after the passage of the solution containing the insecticide. The percentage inhibition of enzyme activity is correlated to the insecticide concentration. Several parameters influencing the performance of the system are studied and discussed. The detection limits of the insecticides ranged from 0.5 to 275 ppb. The determination of these compounds was conducted in Hepes buffer and a synthetic sea water preparation. The enzyme reactor can be regenerated after inhibition with a dilute solution of 2-PAM and be reused for analysis. The immobilized enzyme did not lose any activity up to 12 weeks when stored at 4°C.

Reductive reverse flow injection amperometric determination of nitrate at a platinum electrode after on-line reduction to nitrosyl chloride in concentrated sulphuric acid medium containing chloride

A simple method has been developed for the determination of nitrate using flow injection with amperometric detection. The nitrate sample, which is made 2 M in hydrochloric acid, is the carrier stream, and into this is injected a small volume (25 µl) of concentrated sulphuric acid. The nitrosyl chloride and chlorine formed are detected as a combined reduction signal at a platinum electrode held at +0.70 V versus Ag-AgCl. As formation of nitrosyl chloride only occurs in the initial stages of dispersion of the sulphuric acid into the sample solution (i.e., at high concentrations of sulphuric acid), incorporation of a 40-cm long single bead string reactor as the transmission tubing between the injection valve and the detector, which reduces this dispersion, increases the size of the signal and provides conditions in which gas (mainly hydrogen chloride) formed on-line, which otherwise results in a noisy base line, is re-dissolved before reaching the detector. Calibration graphs were rectilinear over the range from 9 × 10–5M(the detection limit) to 5 × 10–3M. Coefficients of variation were typically less than 4%. Other common constituents of hydroponic fluids did not interfere.

Moment analysis for evaluation of flow-injection manifolds

The applicability of the exponentially modified Gaussian (EMG) peak-shape model to a variety of flow-injection manifolds is explored. Using previously derived equations and manual calculations, the second moment (variance) is employed as the fundamental descriptor of flow-injection response curves. The applicability of the EMG model is verified over a wide range of flow rates (0.2–1.7 ml min −1 for coiled, knitted and Serpentine II manifolds, single-bead string reactors (SBSR) and a coiled reactor with a single confluence point. The Serpentine II reactor exhibits decreased dispersion at higher flow-rates. The determination of the variance of flow-injection response curves reveals that for the examined SBSR and Serpentine II manifolds, reagent consumpsion is decreased as the flow-rate is increased from intermediate (1.0 ml min −1 to high flow rates (1.7 ml min −1. Determination of peak variance is shown to yield unique information in the time domain which assists in the optimum design and evaluation of performance in flow manifolds.

A Selective Flow-Rate Independent Flow Injection Analysis Technique: Combination of a Single Bead String Reactor with Rapid Scan Square-Wave Voltammetry

A Selective Flow-Rate Independent Flow Injection Analysis Technique: Combination of a Single Bead String Reactor with Rapid Scan Square-Wave Voltammetry

Factors affecting the detection limit of a flow- injection spectrophotometric procedure

Design criteria for manifolds to obtain adequated sensitivity and freedom from certain types of noise are discussed. For the determination of chloride by the mercury(II) thiocynate method, the mergin-streams manifold, needed to eliminated negative peaks at low concentrations and refractive index effects, increased the baseline noise because of inefficient mixing at the confluence point. Packed-bed reactors and single-bead-string reactors (SBSR) significantly improved the baseline noise. Refractive index effects caused by sample concentration gradients were eliminated by the injection of large volumes (>500 μl), so that the detector could view a homogeneous central part of the sample zone. This approach maximises the signal because the dispersion is governed only by the relative flow rates of the carrier and reagent streams. The detection limits for chloride were improved to 40 ng l −1 in aqueous solutions of low ionic strength and to 1.3 mg l −1 in 5.25% (w/v) potassium sulphate.

Computer-assisted optimization of an immobilized-enzyme flow-injection system for the determination of glucose

A flow-injection system utilizing the Trinder reaction for the determination of glucose is designed and optimized. Glucose is converted to gluconic acid by passing it through a single-bead-string reactor (SBSR) onto which glucose oxidase enzyme has been immobilized. As it flows through a second SBSR, the gluconic acid reacts with a reagent stream of horseradish peroxidase, 4-aminoantipyrine and 3,5-dichloro-2-hydroxyphenyl sulfonate. The absorbance of the quinoneimine dye produced is then monitored at 510 nm in a flow-through cell. Optimum operating conditions were sought by using both univariate and Composite Modified Simplex procedures. Seven variables were considered. The performance of the system was improved by a factor of 22.5 relative to the starting conditions. A calibration curve obtainedat the optimum conditions was linear for 0–3.3 mM glucose and usable for 0–5.5 mM glucose. The optimization procedures revealed some interesting aspects of the Trinder reaction. scatter diagrams generated from the simplex data showed definite trends for each of the seven variables. These are discussed.

Flow injection determination of penicillins using immobilized penicillinase in a single bead string reactor.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTFlow injection determination of penicillins using immobilized penicillinase in a single bead string reactorR. Gnanasekaran and Horacio A. MottolaCite this: Anal. Chem. 1985, 57, 6, 1005–1009Publication Date (Print):May 1, 1985Publication History Published online1 May 2002Published inissue 1 May 1985https://doi.org/10.1021/ac00283a009RIGHTS & PERMISSIONSArticle Views90Altmetric-Citations57LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (665 KB) Get e-Alerts Get e-Alerts

Flow injection analysis of trace hydrogen peroxide using an immobilized enzyme reactor

Flow Injection Analysis of Trace Hydrogen Peroxide Using an Immobilized Enzyme Reactor Sub-part-per-billion levels of aqueous hydrogen peroxide have been determined with a flow injection analysis system employing a single bead string reactor composed of horseradish peroxidase covalently bound to an animated macroporous polymeric adsorbent with glutaraldehyde and a passive cation exchange membrane reactor to alter pH. The chemistry relies on the peroxidase mediated oxidation of nonfluorescentp-hydroxyphenylacetate to its fluorescent dimer. The advantage of the system includes rapid throughout rates (40 samples/h), excellent detection limits (0.3 ppb H2O2) and large dynamic range of linear response (1 ppb-1 ppm). However, the immobilized enzyme is not useful for the analysis of organic peroxides which act as inhibitors.

Kinetics in a single bead string reactor for flow injection analysis

Etude theorique de l'influence de cinetique chimique de premier ordre sur le phenomene de dispersion. Directives pour la conception d'un systeme d'analyse par injection en ecoulement