Spectrophotometric determination of iron with ferrozine by flow-injection analysis

Two methods for the determination of iron by normal FIA and reversed FIA were developed using sodium 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine-4',4'-disulphonate (ferrozine). The reagent formed a chelate with Fe(II) in hexamethylentetramine buffered medium at pH 5.5. In one previous reaction coil Fe(III) was reduced to Fe(II) by ascorbic acid and in the other reaction coil the complexation reaction was developed. The linear range of the determination was 0.5-6 and 0.1-5 mug ml(-1) of iron for normal FIA and reversed FIA respectively. The proposed method was sensitive (detection limit 0.012 and 0.010 mug ml(-1)), rapid and reproducible (RSD 0.3 and 0.28%). The method was satisfactorily applied to the determination of iron in waste water, toadstool tissue, potato leaves, human hair and bauxites at a sampling rate of 90 and 50 samples h(-1) for normal FIA and reversed FIA respectively.     

Sequential determination of iron(II) and iron(III) in pharmaceutical by flow-injection analysis with spectrophotometric detection.

A flow injection procedure for the sequential spectrophotometric determination of iron(II) and iron(III) in pharmaceutical products is described. The method is based on the catalytic effect of iron(II) on the oxidation of iodide by bromate at pH = 4.0. The reaction was monitored spectrophotometrically by measuring the absorbance of produced triiodide ion at 352 nm. The activating effect for the catalysis of iron(II) was extremely exhibited in the presence of oxalate ions, while oxalate acted as a masking agent for iron(III). The iron(III) in a sample solution could be determined by passing through a Cd-Hg reductor column introduced in the FIA system to reduce iron(III) to iron(II), which allows total iron determination. Under the optimum conditions, iron(II) and iron(III) could be determined over the range of 0.05 - 5.0 and 0.10 - 5.0 microg ml(-1), respectively with a sampling rate of 17 +/- 5 h(-1). The experimental limits of detection were 0.03 and 0.04 microg ml(-1) for iron(II) and iron(III), respectively. The proposed method was successfully applied to the speciation of iron in pharmaceutical products.     

Sequential determination of glucose and fructose in foods by flow-injection analysis with immobilized enzymes

A sequential method for determination of glucose and fructose involving the use of enzymes (hexokinase and glucose-6-phosphate dehydrogenase) immobilized on controlled-pore glass is proposed. The flow is selected so as to determine glucose or both sugars by fluorimetric determination of the NADH formed. The method is applied to the determination of these compounds in fruit juices, yoghourt and dessert powder with good results.     

Simultaneous differential rate determination of iron(II) and iron(III) by flow-injection analysis

Flow-injection procedures for the simultaneous spectrophotometric determination iron(II) and iron(III), relying on the different kinetic-catalytic behaviour of iron(II) and iron(III) in the redox reaction between leucomalachite green and peroxodisulphate with and without the presence of the activator 1,10-phenanthroline, are described. Exploiting the fact that one of the chemical reactions is very rapid whereas the other one is comparatively slower, two experimental procedures are presented. In the first, two individual zones of sample solution are injected simultaneously into separate carrier streams of reagent in a two-line system. Taking advantage of the different residence times of the samples in the manifold lines, the resulting colour formation is measured by a single optical detector with two separate flow cells aligned within the same optical path. The second approach is based on the use of a single-line flow-injection system, exploiting the formation of a double peak as a result of injecting a large sample zone, sandwiched between reagent zones of appropriate composition. In this manner two time-resolved signals for the kinetically governed processes can be obtained and thus used for quantification of the individual species.     

Fluorimetric determination of aflatoxins by flow-injection analysis

Summary A fast and inexpensive fluorimetric method for the determination of total aflatoxins (B₁, B₂, G₁, and G₂) in food of use in screening numerous samples suspectedly containing these substances is proposed. The sensitivity of the method (determination range between 0.5 and 200.0 ng ml^–1) allows these analytes to be detected at concentrations well below legal limits; hence, separation-detection techniques such as HPLC need only be used with samples in which these compounds are found to occur. The method has been applied to maize, peanut and tapioca samples, obtaining average recoveries of 100.9 with deviations of ±5% with respect to 100% recovery.

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Fluorometrische Bestimmung von Aflatoxinen durch Fließinjektionsanalyse

     

Sequential flow-injection spectrophotometric determination of iron(II) and iron(III) by copper(II)-catalyzed reaction with Tiron

A flow injection method for the sequential determination of iron(II) and iron(III) was developed. It is based on the differential reaction kinetics of iron(II) and iron(III) with Tiron in a double-injection FI system. The proposed method employs the accelerating action of copper(II) for the oxidation of iron(II) in the presence of Tiron. A linear calibration graph is obtained for iron (II) and iron(III) in the concentration range 1.8 × 10^–5– 1.8 × 10^–4 mol/L; the throughput of samples is 30 injections/h.     

Fluorometric determination of diphenhydramine by flow-injection analysis

A sensitive, rapid and simple flow injection procedure for the determination of diphenhydramine has been designed based on a fluorometric approach. An aqueous solution of diphenhydramine is injected into a carrierreagent stream containing Ce(IV) in dilute sulphuric acid and the fluorescence intensity of the Ce(III) produced is monitored. Chemical, FIA and instrumental variables were optimized. Analytical features of the method are: linear range 0.2–2 ppm, precision 0.7%, sample throughput 80/h. The influence of some foreign substances which can be found in typical pharmaceutical samples containing diphenhydramine was also investigated. The diphenhydramine content of a pharmaceutical preparation was determined.     

Sequential flow-injection spectrophotometric determination of iron(II) and iron(III) by copper(II)-catalyzed reaction with Tiron

A flow injection method for the sequential determination of iron(II) and iron(III) was developed. It is based on the differential reaction kinetics of iron(II) and iron(III) with Tiron in a double-injection FI system. The proposed method employs the accelerating action of copper(II) for the oxidation of iron(II) in the presence of Tiron. A linear calibration graph is obtained for iron (II) and iron(III) in the concentration range 1.8 × 10^–5– 1.8 × 10^–4 mol/L; the throughput of samples is 30 injections/h. Received: 22 October 1996 / Revised: 4 December 1996 / Accepted: 10 December 1996     

Sequential and differential catalytic-fluorimetric determination of manganese and iron by flow injection analysis

Two methods for the determination of manganese iron (40–600 and 40–500 ng ml^?1 respectively) in mixtures are suggested based on their catalytic action on the oxidation of salicylaldehyde thiosemicarbazone by hydrogen peroxide. One method uses a diverting valve to select the most suitable carrier for the determination of one in the presence of the other cation. The other method uses a configuration with splitting and confluence points to obtain two different residence times for the two portions of the sample into which the sample is divided. Simplex optimization is used to establish the best conditions.     

流动注射结合化学发光法测定没食子酸

基于没食子酸与铬 (Ⅵ )的氧化还原反应 ,产生的铬 (Ⅲ )催化鲁米诺 H2 O2 化学发光体系的研究 ,结合流动注射技术 ,优化反应条件 ,建立了一种高灵敏度的快速测定没食子酸的新方法。方法的线性范围为 2 .0× 1 0 - 9～ 5 .0× 1 0 - 6g/mL ,检出限为 1 .2× 1 0 - 9g/mL ,对 1 .0× 1 0 - 7g/mL的没食子酸进行了 1 1次平行测定 ,相对标准偏差为 2 .1 %。方法成功地用于健民咽喉片中没食子酸的测定。     

Simultaneous catalytic-fluorimetric determination of copper and mercury by flow-injection analysis

Summary A catalytic-fluorimetric method is presented for the simultaneous determination of copper(II) and mercury(II) based on their catalytic effects on the oxidation of dipyridyldiketone phenylhydrazone and 2,2-dipyridylketone hydrazone, respectively, using the FIA/ stopped-flow mode. The errors in the determination of these cations are less than 10%, with a sampling rate of 45 samples per hour and the r.s.d. is 0.91% and 1.6% for Cu(II) and for Hg(II), respectively.

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Simultane katalytisch-fluorimetrische Bestimmung von Kupfer und Quecksilber durch Flow-Injection-Analyse

Zusammenfassung Mit Hilfe der FIA/stopped-flow-Technik wurde eine Simultanbestimmung von Cu(II) und Hg(II) durchgeführt, die auf der katalytischen Wirkung dieser Elemente auf die Oxidation von Dipyridyldiketon-phenylhydrazon bzw. 2,2-Dipyridylketon-hydrazon beruht. Die Fehler sind geringer als 10% mit einem Probendurchsatz von 45 Proben je Stunde. Die relative Standardabweichung beträgt 0,91% für Cu und 1,6% für Hg.

     

Simultaneous spectrophotometric determination of nitrite and nitrate by flow-injection analysis

An automatic direct spectrophotometric method for the simultaneous determination of nitrite and nitrate by flow-injection analysis has been developed. Nitrite reacts with 3-nitroaniline in the presence of hydrochloric acid (0.96-1.8 M HCl or pH 0.5-0.7) to form a diazonium cation, which is subsequently coupled with N-(1-naphthyl)-ethylenediamine dihydrochloride to form a stable purple azo dye, the absorbance of which is measured at 535 nm. Nitrate is reduced on-line to nitrite in a copper-coated cadmium column which is then treated with azo dye reagent and the absorbance due to the sum of nitrite and nitrate is measured; nitrate is determined from the difference in absorbance values. A copper column incorporated into the reaction manifold before the copperised cadmium column not only improves the long-term accuracy, but also extends the life time of the copperised cadmium column. Various analytical parameters, such as effect of acidity (pH), flow rate, sample size, dispersion coefficient, time, temperature, reagent concentration and interfering species, were studied. The calibration graphs were rectilinear for 0.1-3.5 mug ml(-1) of NO(3) and 10 ng ml(-1)-2.2mug ml(-1) of NO(2). The method is successfully applied to some food samples (meat, flour and cheese), environmental waters (inland and surface), beer and soil samples. Up to 30 samples can be analysed per hour with a relative precision of approximately 0.1-2%.     

On-line determination of sulphite in brine by flow-injection analysis

A spectrophotometric flow-injection procedure for the determination of sulphite in aqueous media over the range 0.5–20 mg 1^?1 is described. The reagent used was the organic disulphide 5,5′-dithiobis(2-nitrobenzoic acid). Results are presented for a laboratory-based method for sulphite in water and a potential on-line method for sulphite in high ionic strength potassium chloride brine. The general attractions of flow-injection-based monitors for the on-line analysis of liquid process streams are also discussed.     

Rapid determination of zinc and iron in foods by flow-injection analysis with flame atomic-absorption spectrophotometry and slurry nebulization

A rapid method of determining zinc and iron in food by flame atomic-absorption spectrophotometry with slurry nebulization into an air-acetylene flame has been developed. A V-groove, clog-free Babington-type nebulizer, coupled to a single-line flow-injection analysis (FIA) system, was employed to introduce the slurry into the spray chamber. Under the FIA conditions described, an injection frequency of 120/hr is possible, with negligible carry-over and memory effects. The calibration graphs were obtained by using various concentrations (up to 0.1 g/ml) of white bean homogenate as standards, rather than solutions. The method has been applied to various kinds of foods, including grains, vegetables, fruits and sausage. Homogenization of semi-prepared samples to form slurries took only 4 min. Relative deviations between results by the slurry and solution methods for both elements averaged 2-3%. Detection limits by the slurry method were 0.3 mug/ml Zn and 0.6 mug/ml Fe.     

Spectrophotometric determination of catecholamines with metaperiodate by flow-injection analysis

A flow-injection Spectrophotometric method for the determination of adrenaline and isoprenaline, based on the reaction with metaperiodate, is described. The calibration graphs are linear up to 2 × 10⁻⁴ M. Flow injection allows the measurement of 120 samples per hour. The method was successfully applied to the determination of both catecholamines in pharmaceuticals.     

Spectrophotometric determination of silicon in silicates by flow-injection analysis

A flow-injection spectrophotometric method has been developed for the accurate, continuous determination of silicon in silicate rocks. A rock sample solution is prepared by fusion with a 1:1 mixture of lithium carbonate and boric acid and subsequent dissolution of the cake in 1 M hydrochloric acid. The preparation technique is the same as that used for the determination of total iron, aluminium, calcium, titanium, and phosphorus in silicate rocks by flow-injection spectrophotometry. Because of the marked polymerization of silicic acid in acid solution, silicic acid is depolymerized in alkaline medium after a simple cation-exchange column filtration of the rock sample solution and then determined by a static or an FIA spectrophotometric method. The FIA system consists of two channels which carry the carrier solution and molybdate reagent, and allows the colour reaction to proceed under controlled conditions. The FIA system permits high throughput of 70 samples per hour. The procedure has been applied to a variety of standard silicate rocks of the U.S. Geological Survey and the Geological Survey of Japan, and gave satisfactory agreement with the recommended values.     

Simultaneous determination of iron and zinc by pH gradient construction in a flow-injection system

A flow-injection method for the simultaneous determination of iron and zinc in the human hair with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) using a pH gradient technique has been developed. The linear range for the determination of iron is 0.1 approximately 1.8 mug ml(-1) and for zinc is 0.2 approximately 5.0 mug ml(-1). About 20 approximately 30 samples can be determined in 1 h. The proposed method is simple, rapid and accurate. It has been applied to the simultaneous determination of trace amounts of iron and zinc in the human hair with satisfactory results.     

Spectrophotometric determination of silicate with Rhodamine B by flow-injection analysis

A spectrophotometric flow-injection method for the determination of silicate based on the formation of an ion pair between molybdosilicic acid and Rhodamine B is proposed. It allows silicate to be determined over the concentration range 0.17–2.0 mg 1^?1 at a sampling rate of 40 h^?1, is reasonably precise and is highly tolerant to ions that commonly occur in waters. It has been applied with satisfactory results to the determination of silicate in various types of water.     

Chemiluminometric -lysine determination with immobilized lysine oxidase by flow-injection analysis

An enzymatic flow-injection procedure for the determination of -lysine was developed. A lysine oxidase reactor is combined with a fibre-optic hydrogen peroxide detector. Hydrogen peroxide detection is based on the peroxidase-catalysed luminol reaction. The chemiluminescent light is detected by a photomultiplier. -Lysine can be determined in the range 10–1000 μM. A sampling rate of up to 90 h⁻ can be achieved. The whole sensing assay works for more than 1 month. The double logarithmic graph of the peak signal height vs. the lysine concentration is linear, the slope being larger than unity (r² = 0.991, n = 4).     

Spectrophotometric determination of sulphate in sodium hydroxide solutions by flow-injection analysis

A spectrophotometric flow-injection procedure is described for the determination of sulphate in sodium hydroxide solutions. Sulphate catalyses the reaction between zirconium and methylthymol blue to form a complex measured at 586 nm. Optimal reaction conditions are discussed. The calibration graph is linear over the range 0.05–0.5 g l^?1 sulphate with a relative standard deviation of 0.02. The sample throughput is 20 h^?1. Sulphate is easily determined in 1 M sodium hydroxide; the results agree with those obtained by the conventional gravimetric method and by ion chromatography.