The determination of trace amounts of heavy metals in waters by a flow-injection system including ion-exchange preconcentration and flame atomic absorption spectrometric detection

The flow-injection system combines on-line ion-exchange preconcentration with atomic absorption spectrometry (a.a.s.) for the determination of traces (μg l^?1) of heavy metals in water samples. Miniature columns packed with 60–100 mesh chelating resin (122) with a salicylic acid functional group are used for preconcentration. A multifunctional rotary sampling valve which incorporated two parallel sampling columns allows sampling, exchange, elution and a.a.s. to be achieved sequentially. The increases in sensitivity for nickel, copper, lead and cadmium were 20–28-fold at a sampling rate of 40 h^?1 with 5-ml samples. Relative standard deviations were 1.5–4.1%. The recoveries of these four metals added to tap, sea and polluted waters were generally satisfactory, except for cadmium in polluted water. The effects of column diameter and elution flow rates on sensitivity are discussed. Possible interferences are described.     

Chemiluminescence determination of carbofuran at trace levels in lettuce and waters by flow-injection analysis

A simple, fast chemiluminescence (CL) flow-injection (FI) method based on the reaction of luminol with KMnO₄ in alkaline medium has been described for the direct determination of carbofuran. The method is based on the enhancing effect in the emission light from the oxidation of luminol produced in presence of carbofuran. The optimisation of instrumental and chemical variables influencing the CL response of the method has been carried out by applying experimental design, using the proposed flow-injection manifold. Under the optimal conditions, the CL intensity was linear for a carbofuran concentration over the range of 0.06-0.5 μg ml⁻¹, with a detection limit of 0.02 μg ml⁻¹. The method has been successfully applied to the determination of carbofuran residues in spiked water and lettuce samples.     

Simultaneous determination of traces of heavy metals by solid-phase spectrophotometry

A coupling sensitive solid phase spectrophotometric (SPS) procedure for determination of traces of heavy metals (Me-SPS) and multicomponent analysis by multiple linear regressions (MA), a simple methodology for simultaneous determination of metals in mixtures was inaugurated. The Me-SPS procedure is based on sorption of heavy metals on PAN-resin and direct absorbance measurements of colour product Me-PAN sorbed on a solid carrier in a 1-mm cell. This methodology (Me-SPS-MA) was checked by simultaneous determination of metals in synthetic mixtures with different compositions and contents of metals important in pharmaceutical practice: Zn, Pb, Cd, Cu, Co, and Ni. Good agreement between experimental and theoretical amounts of heavy metals is obtained from the recovery test (78.3–110.0%). The proposed method enables determination of particular metal ion at the ng mL⁻¹ level and it was successfully applied to the determination impurities from heavy metal traces in pharmaceutical substances (Cu in ascorbic acid, Pb in glucose, and Zn in insulin). The proposed procedure could be possible contribution to the development of pharmacopoeial methodology for a heavy metals test.     

Determination of some heavy metals in sea water by atomic absorption spectrophotometry

Summary Direct determination of trace metals in sea water by flame atomic absorption technique suffers from serious interferences caused by the high salt content. Separation of the metals from the matrix has been effected by chelation and extraction with ammonium pyrrolidine dithiocarbamate and methyl-isobutyl-ketone. Besides a separation preconcentration and increased sensitivity is achieved with this extraction. Organic substances and metal-organic complexes are destroyed with UV-radiation before extraction is carried out. Flameless atomic absorption has been tried using the Heated Graphite Furnace combined with a) a selective volatilization procedure, b) removing of sodium from the samples using hydrated antimon pentoxide (HAP). Both methods were used to remove the interfering substances (mainly sodium salt). All the techniques have been compared by analysing the same sea water samples, some of which were also analysed by other laboratories.

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Bestimmung einiger Schwermetalle in Meereswasser durch Atomabsorptions-Spektralphotometrie

Zusammenfassung Die direkte Bestimmung der Spurenmetalle in Meereswasser durch Flammen-Atomabsorption wird durch den hohen Salzgehalt behindert. Die Abtrennung der Metalle von der Matrix wurde durch Komplexierung und Extraktion mit Ammoniumpyrrolidindithiocarbamat und Methylisobutylketon erreicht, wodurch außerdem eine Anreicherung und Steigerung der Empfindlichkeit erzielt wird. Organische Substanzen und metallorganische Komplexe können durch UV-Bestrahlung vor der Extraktion zerstört werden. Die flammenlose Technik mit Hilfe des erhitzten Graphitrohres wurde in Kombination mit a) einer selektiven Verdampfungsmethode und b) der Entfernung des Natriums mit hydratisiertem Antimonpentoxid eingesetzt. Alle Verfahren wurden an Hand der gleichen Wasserproben verglichen. Tests wurden auch von anderen Laboratorien durchgeführt.

This work was made possible by substantial grants from International Atomic Energy Agencies (IAEA) and from the Royal Norwegian Council for Scientific and Industrial Research.     

On-line preconcentration and GFAAS determination of trace metals in waters

An on-line separation preconcentration system coupled to electrothermal (graphite furnace) atomic absorption spectrometry was developed. A miniature column packed with iminodiacetic acid ethyl cellulose (IDAEC) was inserted into the loop. A peristaltic pump was used to deliver solutions. A flow of air was driven into the packed column, evacuating it between sample loading, washing and elution. The retained analyte was introduced on-line to graphite furnace using countercurrent elution with HNO₃. The system was applied for the determination of V, Co and Pb in medicinal mineral water samples, and nickel in sea water samples. The detection limits (3σ) were 0.058, 0.022, 0.067, 0.062 μg/l for Co, Pb, V, and Ni, respectively. The R.S.D. (n=5) was <5% at 0.4–1.0 μg/l concentration range.     

Determination of N-acetyl-L-cysteine by flow-injection potentiometry

A multi-purpose tubular flow-through sensor was constructed with an AgI-based membrane. The membrane was prepared by pressing silver salts (AgI, Ag₂S) and powdered Teflon. This membrane was incorporated in the tubular flow-through sensor body. A 2-mm diameter hole was drilled through the center of the tubular sensor and the membrane, thus determining the active sensor volume of about 4 μL. The tubular sensor with reference electrode was placed into a complex flow-injection system and used for the flow-through determination of N-acetyl-L-cysteine, (NAC), in perchloric acid medium, pH = l. Linear dependence was established between the recorded signal height and the concentration of NAC in the injected sample. The recorded change in potential for a decade change in concentration, 62 mV {p (NAC)}^–1, in the concentration range from 1 × 10^–4 to 1 × 10^–1 mol L^–1, was based on the formation mechanism of the sparingly soluble deposit between silver and NAC on the surface of the sensitive part of the membrane. Received: 7 July 1997 / Revised: 22 September 1997 / Accepted: 26 September 1997     

An efficient flow-injection system with on-line ion-exchange preconcentration for the determination of trace amounts of heavy metals by atomic absorption spectrometry

A flow-injection system with on-line ion-exchange preconcentration on dual columns is described for the determination of trace amounts of heavy metals at μg l^?1 and sub-μg l^?1 levels by flame atomic absorption spectrometry. The degree of preconcentration ranges from 50- to 105-fold for different elements at a sampling frequency of 60 s h^?1. The detection limits for Cu, Zn, Pb and Cd are 0.07, 0.03, 0.5, and 0.05 μg l^?1, respectively. Relative standard deviations were 1.2–3.2% at μg l^?1 levels. The behaviour of the different chelating exchangers used was studied with respect to their preconcentration characteristics, with special emphasis on interferences encountered in the analysis of sea water.     

Simultaneous determination of formaldehyde and methanol by flow-injection catalytic spectrophotometry

A flow-injection method is proposed for the simultaneous catalytic determination of formaldehyde and methanol on the basis of the catalytic action of formaldehyde upon the redox reaction between crystal violet and potassium bromate in a phosphoric acid medium and on-line oxidization of methanol into formaldehyde using a lead dioxide solid-phase reactor. The indicator reaction is monitored spectrophotometrically by measuring the decrease in the absorbance of crystal violet at the maximum absorption wavelength of 610 nm. A technique based on three sampling loops with a single injection valve is developed. The flow-injection system produces a signal of main peak with two shoulders of the same height. The height of the shoulders corresponds to the formaldehyde concentration, and the height difference between the shoulders and the main peak corresponds to the methanol concentration. The detection limit is 0.1 μg/mL for formaldehyde and 1.0 μg/mL for methanol with the sampling rate of 10 samples per hour. The relative standard deviations for 11 replicate determinations of formaldehyde (1.0 μg/mL) and methanol (10 μg/mL) are 1.1 and 2.1%, respectively. The method has been successfully applied to the simultaneous determination of formaldehyde and methanol in some gas samples. The text was submitted by the authors in English.     

APDC-MIBK extraction system for the determination of trace elements in saline waters by atomic-absorption spectrophotometry

A technique has been developed for the determination of "soluble" cobalt, copper, iron, lead, nickel and zinc in saline waters by simultaneous extraction of their complexes with ammonium pyrollidine dithiocarbamate (APDC) into methyl isobutyl ketone (MIBK) and subsequent analysis by atomic-absorption spectrophotometry. Particulate matter is analysed separately by dissolving millipore filters in an acetone-hydrochloric acid mixture. Various analytical and instrumental parameters have been evaluated. The method is selfcompensating in that it makes allowance for any incomplete extraction of the complexes. The technique has been applied to the determination of these elements in sea-water and saline lakes.     

Fast determination of nitrate in small samples of rain and surface waters by means of uv spectrophotometry and flow-injection analysis

Summary An UV-spectrophotometric determination of NO_¯3 in small samples (0.5 ml) of rain and surface waters is described. A variant of flowinjection analysis is used in combination with an active carbon filter for removal of organic interferences. The accuracy and the reproducibility of the method are generally better than 3%. One determination takes 30 s.

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Schnelle UV-spektralphotometrische Nitratbestimmung in kleinen Proben von Regen- und Oberflächenwasser mit Hilfe der FIow-Injection-Technik

Zusammenfassung Eine Methode zur Nitratbestimmung in Proben von 0.5 ml mittels eines UV-spektralphotometrischen Verfahrens in Kombination mit der flow-injection Methode und einem Filter zur Beseitigung organischer Substanzen wird vorgeschlagen. Die Genauigkeit und Reproduzierbarkeit sind meistens besser als 3%. Eine Bestimmung fordert einen Zeitaufwand von 30 s.

     

Ion chromatographic determination of alkaline earth metals and some heavy metals

The method is described for ion chromatographic determination of Ba, Ca, Cd, Cu, Mn, Ni, Sr, Pb and Zn. Ethylenediammonium chloride or tartrate solutions are used as eluents with a suppressor column. The detection limits for the listed elements are (in μg l^?1): Ba 1.4, Ca 0.045, Cd 0.6, Cu 0.3, Mn 0.8, Ni 0.5, Pb 6.3, Sr 0.3, Zn 1.2. Relative standard deviations are 0.015–0.050 ar the 20 mg l^?1 level (n = 5, p = 0.95). Interferences are considered.     

流动注射催化动力学光度法测定碘离子

Based on catalysis of I- on the decolor reaction between potassium bromate and indigo carmine in the acid medium,and combined with flow injection analysis,a new flow-injection catalytic kinetic spectrophotometric method was found for determination of iodide in sample.The experimental results show that the determination is carried out at temperature of 80℃ and the concentration of H_2SO_4,KBrO_3,and indigo carmine is 1.2 mol/L,1.8×10~(-2) mol/L and 1.0×10~(-4) mol/L respectively,the linear range for the method is 0.50～1.8 mg/L.The detection limit is 0.0022 mg/L.The relative standard deviation is 1.92%.The proposed method was applied to the determination of iodide in troche successfully.The recovery was between 99.2% and 103.6%.     

Rapid continuous determination of aluminium in copper-base alloys by flow-injection spectrophotometry

Summary A flow-injection spectrophotometric method has been developed for the rapid, continuous determination of aluminium in copper-base alloys. The system consists of the masking of copper, zinc, iron, etc. with a combined use of thiourea, ascorbic acid and EDTA and the measurement of light absorption of aluminium-Xylenol Orange complex at 506 nm. With appropriate standardization satisfactory results are obtained in spite of sluggish reaction of aluminium and Xylenol Orange. The system allows the analysis of solutions of copper-base alloys for aluminium to be conducted at a rate of 50 determinations per hour without any carryover. The results obtained for standard brasses and aluminium bronze (Al 1.43–10.2%) agreed well with the certified values. The precision (rsd) ranges are 0.2–0.3%.

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Kontinuierliches Schnellverfahren zur Bestimmung von Aluminium in Kupferlegierungen mit Hilfe der Flow-Injection-Spektralphotometrie

Zusammenfassung Bei dem empfohlenen Verfahren werden Cu, Zn, Fe und andere Störelemente mit Hilfe von Thioharnstoff, Ascorbinsäure und EDTA maskiert und der Al-Xylenolorange-Komplex bei 506 nm gemessen. Mit Hilfe eines geeigneten Eichverfahrens werden trotz der trägen Reaktion von Al mit Xylenolorange zufriedenstellende Werte erhalten. 50 Bestimmungen können innerhalb von 1 h ohne jedes Verschleppen durchgeführt werden. Bei der Analyse von Messing und Al-Bronze (1,43–10,2% Al) wurde gute Übereinstimmung mit zertifizierten Werten erzielt. Die Standardabweichungen lagen im Bereich von 0,2–0,3%.

     

Determination of trace heavy metals in waters by atomic-absorption spectrometry after preconcentration by liquid-phase polymer-based retention

A new method for the determination of metals in waters by flame atomic-absorption spectrometry is described. The metals are retained by water-soluble polymers in a membrane filtration cell and the factors which influence their determination are discussed. The method has been applied to the determination of Ni, Cu, Zn, Hg and Cd in drinking and river water with poly(ethyleneimine) and its thiourea derivative as complexing polymers. The metals were determined in the aqueous concentrate after a 250-fold preconcentration by 2% polymer solution at pH 7. The metal recoveries were at least 92%, and the limits of detection (ng/mg) were 0.012 for Cu, 0.006 for Zn, 0.03 for Ni, 0.004 for Cd and 0.0001 for Hg (cold vapour method). When a new type of membrane filtration cell is used even higher preconcentration factors can be achieved and lower concentrations can be determined.     

Selective leaching of trace heavy metals associated with suspended matter in fresh waters

Summary River and pond waters, less than 400 ml, are filtered through 47 mm-diam. Nuclepore polycarbonate membrane filters of 12-, 5-and 0.4-m pore sizes sequentially for size fractionation of suspended matter. Each filter along with collected suspended matter (ca. 1 mg) is ultrasonically treated with 1 ml of chloroform and 0.5 ml of leaching solvent (1M ammonium acetate soln. or 0.1 M hydrochloric acid) in a test tube for 1 min. The filter is completely dissolved in the organic phase, while the suspended matter remains in the aqueous phase enabling a rapid leaching. The leaching solvent is then analyzed by graphite-furnace atomic absorption spectrometry for chromium, copper and cadmium. The proposed technique is more sensitive than the conventional leaching technique, which requires at least 4 ml of leaching solvent.

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Selektive Abtrennung von Schwermetallspuren von suspendierten Teilchen in Frischwasser

Zusammenfassung Fluß- bzw. Teichwasser wird in Mengen von weniger als 400 ml durch Polycarbonat-Membranfilter mit einem Durchmesser von 47 mm und einer Porengröße von 12, 5 bzw. 0,4m zwecks Fraktionierung der suspendierten Teilchen filtriert. Jedes Filter wird zusammen mit der darauf gesammelten Materie (ca. 1 mg) mit 1 ml Chloroform und 0,5 ml Auslaugmittel (1 M Ammoniumacetat oder 0,1 M Salzsäure) 1 min in einem Reagensglas mit Ultraschall behandelt. Das Filter löst sich in der organischen Phase vollständig, während die suspendierten Teilchen in der wäßrigen Phase rasch ausgelaugt werden. Die so erhaltene Lösung wird in einem Graphitofen durch Atomabsorptions-Spektrometrie auf Chrom, Kupfer und Cadmium analysiert. Die empfohlene Vorgangsweise ist empfindlicher als das konventionelle Auslaugverfahren, wofür wenigstens 4 ml Auslaugmittel benötigt werden.

     

流动注射催化光度法测定微量Sb(Ⅲ)

基于在B-R缓冲溶液介质中,Sb(Ⅲ)对H2O2氧化孔雀石绿褪色反应具有催化作用,建立了流动注射催化动力学光度法测定微量元素Sb(Ⅲ)的新分析方法,该方法的线性范围为0.010～2.0μg/mL,检出限为7.8×10-3μg/mL,r=0.9996。对0.1μg/mL Sb(Ⅲ)测定的RSD=0.97%n=11,进样频率为22.8次/h。用于环境水样中微量Sb(Ⅲ)的测定,回收率为97.3%～97.7%。     

Catalytic determination of molybdenum in plants by flow-injection spectrophotometry with ion-exchange separation

The catalytic effect of molybdenum n the oxidation of iodide by hydrogen peroxide is utilized. A cation-exchange resin column is incorporated into the system to remove interfering ions; during sample processing, the interfering ions are eluted towards waste. Plant materials are ashed and solutions are injected. The proposed system can handle about 40 samples per hour with molybdenum contents in the 1.0–40.0 μg 1^?1 range. Results are precise (r.s.d. usually <%) and in agreement with those obtained by graphite-furnace atomic absorption spectrometry.     

Fluorimetric differential-kinetic determination of silicate and phosphate in waters by flow-injection analysis

A flow-injection analysis (FIA) method for simultaneous determination of silicate and phosphate, based on the different rates of formation of their molybdate heteropoly acids is suggested. The fluorimetrically monitored product is thiochrome, formed by oxidation of thiamine by the heteropoly acid. The FIA configurations designed allow performance of two measurements at different times on each sample injected. The method permits the determination of these anions in the range 30-600 ng ml in ratios from 1:10 to 10:1 and can be applied to samples of running and bottled water with good results. The sampling frequency achievable is 60 hr .     

Nickel and zinc determination by flow-injection solid-phase spectrophotometry exploiting different sorption rates

Flow-injection solid-phase spectrophotometry is applied for sequential determination of nickel and zinc, exploiting their different sorption rates on 1-(2-thiazolylazo)-2-naphthol (TAN) immobilized on C(18)-bonded silica. The Zn(II) sorption rate on the solid support is constant for flow rates ranging from 0.70 to 2.2 ml min(-1), but for Ni(II) the sorption rate decreases with increasing flow rate. A flow system was designed to perform sequential measurements at two different flow rates (0.85 and 1.9 ml min(-1)). The absorbance was measured at 595 nm, where both TAN-immobilized complexes showed maximum absorption. The coefficients of variation were estimated (n=10) as 1.1 and 1.7% (at 1.9 ml min(-1)) and 1.2 and 2.1% (at 0.85 ml min(-1)) for zinc and nickel, respectively. This strategy was applied to determine zinc and nickel in copper-based alloys and the results agreed with certified values at the 95% confidence level. The sample throughput was estimated as 36 h(-1).     

Particle discrimination effects in the determination of trace metals in natural fresh waters

Instrumental neutron activation analysis (i.n.a.), atomic absorption spectrometry (a.a.s.), and inductively-coupled plasma atomic emission spectrometry (i.c.p.a.e.s.) have been applied to the determination of Na, K, Mg, Ca, Al, Mn, Fe and Zn in fresh waters containing naturally occurring particles. Scattered results were obtained for the total concentrations of trace metals which were associated to some extent with particles retainable by 0.45-μm filter membranes. Particle discrimination effects are indicated and the fraction of elements included in the final result depends on the method used. For the simultaneous determination of the total concentrations of Al, Mn, Fe and Zn, i.n.a.a. is preferred, as all element fractions present are included in the result. When a.a.s. or i.c.p.a.e.s. is applied, lower results are obtained when particulate matter is present, the results referring only to the acid-soluble low-molecular-weight fraction (< 0.45 μm diameter). When particles are removed prior to the quantifying step, the results obtained on the filtrates by all methods are in good agreement. However, considering the low concentrations of several elements in the separated fractions, i.n.a.a. is most favourable for the determination of aluminium while graphite-furnace a.a.s. is most suitable for zinc. Both methods are applicable for manganese. For Ca, Fe, K, Mg and Na, i.c.p.a.e.s. is recommended.