Multicommutation in flow analysis. Part 2. Binary sampling for spectrophotometric determination of nickel, iron and chromium in steel alloys

Martelli, Patrícia Benedini; Reis, Boaventura F.; Kronka, Eloisa A.M.; F̊, Henrique Bergamin; Korn, Mauro; Zagatto, Elias A.G.; Lima, José L.F.C.; Araújo, Alberto N.

doi:10.1016/0003-2670(94)00281-p

Cited by 52 publications

(11 citation statements)

References 13 publications

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“…The flow set up consisted of a 432 Femto (São Paulo, Brasil) spectrophotometer with a flow cell (180 µL inner volume, 12 mm optical path), coupled to a REC 61 Radiometer strip chart recorder, an Ismatec IPC-8 peristaltic pump, with Tygon pumping tubes of different inner diameters, a home made automatic injector designed as described in the next section, three-way solenoid valves 5 , coiled reactors and flow lines of polyethylene tubing (0.8 mm inner diameter), a resin column (10 mm long, 4 mm i.d) machined in perspex as described elsewhere 12 , a 486 microcomputer equipped with an interface PCL-771S Advantech Corp. and other needful electronic interface 5 . The microcomputer run a software written in Quick Basic 4.5, which controlled injector and solenoid valves.…”

Section: Apparatusmentioning

confidence: 99%

“…After several analytical cycles, chloride concentration became high enough to cause competition with peroxydisulphate ions by resin active sites. As a result, a drop in analytical signal was observed, since the kinetics of the chemical reaction depends strongly on peroxydisulphate concentration 5 . In order to prevent this drawback, peroxydisulphate solution was changed after that number of analytical cycles.…”

Section: Nickel Determinationmentioning

confidence: 99%

“…Potassium peroxydisulphate has been generally used as oxidizing reagent, and should be added to the sample following the addition of the dimethylglyoxime solution 4 . In earlier work 5 , the authors observed that potassium peroxydisulphate concentration exerted a remarkable effect on the magnitude of the analytical signal. Since potassium peroxydisulphate solutions with concentrations larger than 5% are difficult to be achieved, therefore, a strategy to increase the peroxydisulphate concentration available for the oxidation process should be appreciated.…”

Section: Introductionmentioning

confidence: 95%

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The use of ion exchange resin for reagent immobilization and concentration in flow systems: determination of nickel in steel alloys and iron speciation in waters

Martelli¹,

Reis²,

Korn³

et al. 1997

J. Braz. Chem. Soc.

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Neste trabalho, foi investigado o emprego de persulfato de potássio imobilizado em resina aniônica AG1-X8, como agente oxidante, na determinação espectrofotométrica de níquel em ligas metálicas, e na especiação de Fe (III)/Fe (II) em águas de rio, utilizando-se sistema de análise em fluxo. O diagrama de fluxo foi desenvolvido para que a oxidação da espécie de interesse e o recondicionamento da resina pudessem ser efetuados em linha. A determinação de níquel baseou-se no método da dimetilglioxima, apresentando uma freqüência analítica de 80 determinações por hora. Com este sistema, obteve-se um baixo consumo de reagentes, 10 mg (200 µL) de persulfato de potássio e 8,0 µg (133 µL) de dimetilglioxima por determinação. Para uma solução de amostra contendo 21,5% (m/m) de Ni, encontrou-se um desvio padrão relativo de 1% (n = 10). Aplicando-se o teste-t pareado, obteve-se uma concordância com 95% de confiança entre os resultados do sistema proposto e os obtidos com espectrofotometria de absorção atômica com chama. Na determinação de Fe (III), utilizou-se tiocianato de potássio como reagente cromogênico, alcançando-se uma frequência analítica de 60 determinações por hora. O método apresentou um consumo de reagentes de 3,5 mg (70 µL) persulfato de potássio e de 5,4 mg (270 µL) de tiocianato de potássio por determinação. O desvio padrão relativo calculado para uma solução de amostra contendo 3,17 mg L -1 de Fe (III) foi de 1,5% (n = 10). Os resultados empregando-se o método proposto para Fe (II) foram comparados com aqueles obtidos com o método espectrofotométrico, baseado na reação com 1,10 -fenantrolina, apresentando uma concordância com nível de confiança de 95%.Flow injection systems employing potassium peroxydisulphate as oxidizing reagent, immobilized on the anionic exchange resin AG1-X8 are proposed for spectrophotometric determination of nickel in steel alloys and for the speciation of iron (III)/iron (II) in waters. The flow networks were designed to provide facilities to perform on line analyte oxidation and resin reconditioning steps. The feasibility was ascertained by determining nickel in acid solutions of steel alloys and performing speciation of iron (III)/iron (II) in waters, using as chromogenic reagents dimethylglyoxime for nickel and potassium thiocyanate for iron. Profitable features such as a throughput of 80 and 60 samples per hour, 1.0 and 1.5% (n = 10) as relative standard deviations for nickel (21.5% m/m) and iron (III) (3.17 mg L -1 ), low reagents consumption (10 and 3.5 mg of potassium peroxydisulphate, 8.0 µg dimethylglyoxime and 5.4 mg of potassium thiocyanate, for nickel and iron, respectively) were observed. The accuracy for both procedures were ascertained by applying paried t-test between results obtained with flame atomic absorption spectrophotometry (FAAS) for Ni and 1,10-phenantroline spectrophotometric method for Fe (II), and no significant difference at 95% confidence level were observed.

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Section: Apparatusmentioning

confidence: 99%

Section: Nickel Determinationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 95%

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The use of ion exchange resin for reagent immobilization and concentration in flow systems: determination of nickel in steel alloys and iron speciation in waters

Martelli¹,

Reis²,

Korn³

et al. 1997

J. Braz. Chem. Soc.

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“…This drawback has been surmounted by designing flow systems based on merging zones [2,3] or on sandwich-technique approaches [4]. When analytes compound absorb radiation at the same wavelengths, the flow networks have been designed to determine each analyte at a different time [5]. On the other hand, if chemical species absorb at a different wavelength, simultaneous determination had been carried out, nevertheless equipment with the ability to sweep automatically the wavelengths have been employed [6,7].…”

Section: Introductionmentioning

confidence: 99%

Automatic flow system for simultaneous determination of iron and chromium in steel alloys employing photometers based on LEDs as radiation source

Fernandes

Reis

Campos

2003

Journal of Analytical Methods in Chemistry

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A multicommutated flow system for simultaneous determination of iron and chromium in steel alloys by photometry is described. The flow network consisted of an automatic injector and four solenoid valves assembled to form two independent analytical pathways, each one comprising reaction coils and a flow cell. The light source (LED) and detector (photodiode) were attached to the flow cells to form a compact unit. The flow system was microcomputer controlled by Quick BASIC 4.5 software, which carried out all steps of the analytical procedure. The feasibility of the system was proved by the determination of iron and chromium in steel alloys and its accuracy was accessed by comparing results with those obtained by plasma atomic emission spectrometry (ICP-AES). No significant difference at the 95% confidence level was observed.Other profitable features such as low reagent consumption (0.33 mg 1,10-phenantroline and 0.03 mg 1,5-diphenylcarbazide per determination); relative standard deviations (n ¼ 5) of 0.4% for iron and 1.2% for chromium; and an analytical throughput of 160 determinations per h were also achieved. IntroductionThe simultaneous determination of two or more analytes at a time by flow-injection analysis became very attractive after the work proposed by Stewart and Ruzicka (1976) [1]. Afterwards, a large number of flow procedures for multiparameter determination per sample using different detection techniques have been described [2][3][4][5][6].When a multidetermination flow system is implemented using UV-Vis spectrophotometry as the detection technique, the reagents' incompatibility is one difficulty that may appear. This drawback has been surmounted by designing flow systems based on merging zones [2,3] or on sandwich-technique approaches [4]. When analytes compound absorb radiation at the same wavelengths, the flow networks have been designed to determine each analyte at a different time [5]. On the other hand, if chemical species absorb at a different wavelength, simultaneous determination had been carried out, nevertheless equipment with the ability to sweep automatically the wavelengths have been employed [6,7].A light-emitting diode (LED) has been employed as a radiation source in some photometric procedures, its advantages being robustness and low current consumption [8,9]. Nevertheless, depending on the LED type, the width of the emission band can range from 30 to 100 nm [10][11][12][13]. However, by carefully selecting the methods, LEDs can became a good option as a radiation source in flow system when multidetermination is performed with photometric detection employing non-expensive instrumentation [14][15][16][17].The flow network for multicomponent determination can became complex, mainly when the selected spectrophotometric methods required two reagent solutions per analyte [3,18]. This difficulty can be minimized by employing the multicommutation approach that allowed facilities to handle several reagent solutions using a single pumping channel [19,20].In the present work, the intention ...

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“…Afterwards, a large number of flow procedures for multiparameter determination per sample using different detection techniques have been described [2][3][4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Automatic flow system for simultaneous determination of iron and chromium in steel alloys employing photometers based on LEDs as radiation source

Fernandes¹,

Reis²,

Campos³

2003

Journal of Automated Methods & Management in Chemistry

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Multicommutation in flow analysis. Part 2. Binary sampling for spectrophotometric determination of nickel, iron and chromium in steel alloys

Cited by 52 publications

References 13 publications

The use of ion exchange resin for reagent immobilization and concentration in flow systems: determination of nickel in steel alloys and iron speciation in waters

The use of ion exchange resin for reagent immobilization and concentration in flow systems: determination of nickel in steel alloys and iron speciation in waters

Automatic flow system for simultaneous determination of iron and chromium in steel alloys employing photometers based on LEDs as radiation source

Automatic flow system for simultaneous determination of iron and chromium in steel alloys employing photometers based on LEDs as radiation source

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