Takahiro Kumamaru

Trace metal enrichment by automated on-line column preconcentration for flow-injection atomic absorption spectrometry

An on-line column preconcentration technique for flow-injection atomic absorption spectrometry was developed. Diverse metal ions (Cd2+, Zn2+, Cu2+, Mn2+, Pb2+, Fe3+ and Cr3+) in solution were concentrated quantitatively by a microcolumn (7-mm × 4-mm i.d.) packed with Muromac A-1, which is an iminodiacetate chelate resin, in a flow-injection system. From the pH dependence of the uptake of the ions, all the divalent metals examined were recovered quantitatively in the pH range 3–5 and the trivalent metals were recovered at a maximum pH of 1. Enrichment factors using 20-ml samples were in the range 90–180-fold for the seven elements and the sampling rate was 13 h−1. The 3σ detection limits were in the range 0.14–2.1 μg l−1 and the relative standard deviations for replicate measurements (n=3–4) were in the range 0.7–1.7%. The method was compared with flame and graphite furnace atomic absorption spectrometry. Application to the determination of cadmium and copper in several standard reference materials is described.

Comparative Study of Zinc Tablet and Sodium Borohydride Tablet Reduction Systems in the Determination of Arsenic, Antimony, and Selenium by Atomic-Absorption Spectrophotometry via Their Hydrides

ZusammenfassungEin atomabsorptionsspektralphotometrisches Verfahren zur raschen und empfindlichen Bestimmung von Arsen, Antimon und Selen über ihre Hydride unter Verwendung der Argon-Wasserstoff-Flamme wurde im Hinblick auf die Reduktionssysteme untersucht. Die Verwendung von Zinktabletten in Kombination mit Zinn(II)-chlorid und Kaliumjodid sowie von Natriumborhydridtabletten wurde geprüft und gefunden, daß in bezug auf Empfindlichkeit und Reproduzierbarkeit keine nennenswerten Unterschiede bestehen. Das Zinksystem bietet jedoch eine bessere Selektivität, besonders im Falle von Arsen.SummaryAn atomic-absorption spectrophotometric method for the rapid and sensitive determination of arsenic, antimony, and selenium with the hydride-argon/hydrogen flame system has been studied. The comparison of the zinc tablet combined with stannous chloride and potassium iodide, and the sodium borohydride tablet reduction systems are described. The sensitivities and precisions of both reduction systems are estimated to be nearly the same. From the results of the comprehensive study on interferences, the zinc system is concluded to be more selective than the sodium borohydride system, which is especially true for arsenic.

Sensitivity enhancement for inductively-coupled plasma atomic emission spectrometry of cadmium by suction-flow on-line ion-exchange preconcentration

Abstract A column of iminodiacetate chelating resin is used to preconcentrate cadmium by a factor of 25-fold for a 5-ml sample. The sampling rate was 25 h −1 , and the detection limit 0.05 ng Cd 2+ ml −1 . The r.s.d. for 0.1 μg Cd 2+ ml −1 was 2.2% ( n = 10). This technique was applied to the determination of cadmium in certified biological reference materials and waste-water samples.

Low-temperature electrothermal vaporization of refractory elements as 8-hydroxyquinolinate complexes in inductively coupled plasma atomic emission spectrometry. Part 2. Determination of trace amounts of chromium in aluminium alloy and rock samples

A method, based on low-temperature vaporization of an 8-hydroxyquinolinate complex from a tungsten boat cuvette, is proposed for introducing trace amounts of chromium present in a digested aluminium alloy and rock samples into an inductively coupled plasma for atomic emission spectrometric detection. The operating conditions were optimized and the effect of foreign ions was investigated. Aluminium ions were found to improve the sensitivity and precision of the proposed method. The presence of aluminium ions in the sample solutions was also effective in suppressing the interferences from other foreign ions. The detection limit in the presence of 2.5 µg of aluminium (III) was determined to be 0.05 ng of chromium and that in the absence of aluminium (III), 0.07 ng. The precisions as relative standard deviation (RSD%) for 2.5 ng of chromium under the conditions described above were 2.2 and 4.6%(n=6), respectively. The chromium contents in some standard materials and reference samples determined by the proposed method were in good agreement with the certified or reference values.

Determination of vanadium and titanium in steel by inductively coupled plasma atomic emission spectrometry with modified use of a tungsten boat furnace atomizer for atomic absorption spectrometry

Abstract For electrothermal sample introduction, a commercially available tungsten boat atomizer for atomic absorption spectrometry (AAS) was transferred to a vaporizer for inductively coupled plasma atomic emission spectrometry (ICP-AES). The modification retained as much of the original design of the atomizer as possible, so that the apparatus could be switched easily between conventional tungsten boat furnace (TBF)-AAS and TBF-ICP-AES. By using this system, a procedure for the determination of vanadium and titanium in steel was investigated. The detection limits (S/N=3) of vanadium and titanium were 3.9 and 1.5 ng ml−1, respectively. The relative standard deviations for five replicate determinations were ca. 3% for both elements. The calibration graphs were linear up to 100 μg ml−1 vanadium(V) and 10 μg ml−1 titanium(IV). Results of analyses of some low-alloy steel samples are given.

Enhancement of Sensitivity for Selenium Determination in Atomic Absorption Spectrophotometry by Introducting Hydrogen Selenide into an Argon-Hydrogen Flame

Abstract The sensitivity for selenium determination with atomic absorption spectrophotometry is enhanced to a large extent by introducing hydrogen selenide gas into an argon-hydrogen flame. As a reducing agent, zinc granular and stannous chloride is successfully used for quantitative and rapid productions of hydrogen selenide from selenium(IV) solution. The sensitivity for 1 % absorption of the signal is estimated to be about 0.02 ppm of selenium.

Determination of ultra-trace levels of cobalt by ion chromatographic separation and chemiluminescence detection

Abstract A luminol chemiluminescence detection/flow injection analysis technique coupled with ion chromatography (IC) has been examined for the selective determination of cobalt (II) at pg ml−1 levels. A barium chloride solution was used as an eluent in the IC to separate cobalt(II) from interferents. When a 100-μ1 sample injection volume was used, the detection limit was 1.0 pg ml−1 cobalt; the minimum detectable amount of cobalt was 100 fg. The calibration graph was linear above 10 pg ml−1 and the linear dynamic range extended over six orders of magnitude. The relative standard deviation for ten replicate measurements of 30 pg ml−1 cobalt was 3.8%. The results of the analysis of a synthetic sample corresponding to a boiling-water reactor coolant and some commercially available copper(II) standard solutions are given.

Microporous polytetrafluoroethylene tube separator for the determination of beryllium by flow injection-or suction-flow-solvent extraction followed by inductively coupled plasma atomic emission spectrometry

A dual-tube separator was constructed for the purpose of flow injection-or suction-flow-solvent extraction followed by inductively coupled plasma atomic emission spectrometry. It consisted of an inner microporous polytetrafluoroethylene (PTFE) tube (1 mm i.d., 10 cm long, porosity 70%) and an outer PTFE tube (3 mm i.d.). This system was used for the determination of beryllium in alloys by extraction as the acetylacetonate into carbon tetrachloride. The phase separation was complete at an organic flow-rate of 0.2–6.2 ml min–1 and an aqueous flow-rate of up to 6.2 ml min–1. With a sample volume of 0.5ml (50 p.p.b. Be) and sample and organic flow-rates of 1.2 and 0.7 ml min–1, respectively, the relative standard deviation (n= 10) was 1.3% and the sampling rate was 25 h–1. The sensitivity was enhanced about 2.6-fold compared with that obtained by the direct nebulisation of an aqueous solution.

New method for the determination of pentachlorophenol by atomic absorption spectrophotometry

A new application of atomic absorption is reported for the determination of pentachlorophenol. The method is based on solvent extraction into nitrobenzene of the ion-pair formed between tris(1,10-phenanthroline) iron(II) and the anion of pentachlorophenol, and the subsequent determination of the iron concentration m the extract by atomic absorption at the 2483 A iron line.

Low-Temperature Electrothermal Vaporization of 8-Hydroxyquinolinate Complex for Determination of Trace Vanadium by ICP-AES

A trace amount of vanadium was vaporized as 8-hydroxyquinolinate complex by using a low-temperature tungsten boat furnace for sample introduction in ICP-AES. Experimental results suggest that vanadium was vaporized as vanadium(III) 8-hydroxyquinolinate complex. Vanadium(V) and vanadium(IV) were reduced in the heating process before vaporization. The operating conditions were optimized, and the effects of foreign ions were investigated. The existence of tin(II) ion in sample solution was found to enhance the emission intensity of vanadium, improve the precision of the proposed method, and also suppress the interferences from other foreign ions. The detection limit in the presence of 5 μg tin(II) was determined to be 4 pg, and in the absence of tin(II), 7 pg, of vanadium. Sub-μg L−1 levels of vanadium in sample solution could be determined by the proposed method. The precisions in relative standard deviation (% RSD) for 100 pg of vanadium under the same conditions described above were 1.9% and 4.1%, respectively. The contents of vanadium in some standard steel and rock samples determined by the proposed method were in good agreement with their certified values.