Spectral features of atomic magneto-optical rotation spectroscopy (the atomic Faraday effect) and Zeeman splittings of various elements

Spectral features of atomic magneto-optical rotation spectroscopy (AMORS) or the atomic Faraday effect of various elements are described. As a stable atomizer, an air-hydrogen flame is located between the pole pieces of the electromagnet. The dependence of the transmitted intensity on the magnetic field strength was recorded on an X-Y recorder by scanning the magnetic field. For most of the analytical lines of elements, the maximum energy was transmitted through the optical system in the Faraday configuration at magnetic field strengths of up to a few kilogauss. The theoretically calculated Zeeman splitting patterns are successfully related to the experimental results.     

A New Highly Sensitive Preconcentrating Sampling Technique for Flameless Atomatic Absorption Spectroscopy

Abstract

A new technique for sampling metal ions in solution for flameless atomic absorption has been developed. A tungsten alloy wire loop is soaked in the sample solution for a specified period of time. Metal ions are concentrated on the surface of the wire loop apparently by an ion exchange mechanism. The wire loop is then used as an electrically heated atomizer for atomic absorption spectroscopy. Detection limits of 4 × 10^?14 grams for cadmium and 2 × 10^?11 grams for lead have been achieved.     

Evaluation of a hydride generation-atomic fluorescence system for the determination of arsenic using a dielectric barrier discharge atomizer

A new atomizer based on atmospheric pressure dielectric barrier discharge (DBD) plasma was specially designed for atomic fluorescence spectrometry (AFS) in order to be applied to the measurement of arsenic. The characteristics of the DBD atomizer and the effects of different parameters (power, discharge gas, gas flow rate, and KBH₄ concentration) were discussed in the paper. The DBD atomizer shows the following features: (1) low operation temperature (between 44 and 70 °C, depending on the operation conditions); (2) low power consumption; (3) operation at atmospheric pressure. The detection limit of As(III) using hydride generation (HG) with the proposed DBD-AFS was 0.04 μg L⁻¹. The analytical results obtained by the present method for total arsenic in reference materials, orchard leaves (SRM 1571) and water samples GBW(E) 080390, agree well with the certified values. The present HG-DBD-AFS is more sensitive and reliable for the determination of arsenic. It is a very promising technique allowing for field arsenic analysis based on atomic spectrometry.     

The determination of germanium by atomic absorption spectrometry with a graphite tube atomizer

A carbon filament atom reservoir and a graphite tube atomizer are compared as methods for the determination of germanium by atomic absorption spectrometry. It is shown that the filament technique is not applicable, probably because of loss of the sample as a volatile oxide species which results in inefficient atomization. The design of a small graphite tube atomizer is described; with this, a limit of detection for germanium of 3·10^-10 g was found. For a 20-μl sample, this corresponds to a concentration of 0.015 p.p.m. The interfering effect of 13 anions and cations is studied.     

Determination of cadmium,zinc, and lead by non-dispersive atomic fluorescence spectrometry with a new graphite furnace atomizer

A new graphite furnace atomizer has been developed and applied to the determination of cadmium, zinc, and lead by non-dispersive atomic fluorescence spectrometry. A solar-blind photomultiplier, a lock-in amplifier, and microwave-excited electrodeless discharge lamps are used. The detection limits for cadmium, zinc, and lead in the non-dispersive atomic fluorescence mode are 1·10^?13g, 2·10^?13g, and 2·10^?11g, respectively, which are 20-, 10-, and 2-fold better than those in the atomic absorption mode. The analytical working curves are linear over about three decades of concentration from the detection limits.     

Shadow spectral imaging of absorbing layers in a transversely heated graphite atomizer: Part 1. Analyte atoms

The technique of shadow spectral imaging was used to investigate dynamics of formation and dissipation of Ag, In, Ga, Bi, Mn, Cu and Tl atomic layers in a transversely heated graphite tube atomizer (THGA) with and without integrated platform under gas-stop and gas-flow conditions. It is shown that non-uniform heating of the tube walls and platform surface in the radial cross section is the main reason for analyte transfer from atomizer bottom to less heated sides of the tube and platform before atomization temperature is reached. This transfer in the atomizer transverse cross section can be an additional factor that reduces matrix interferences in the THGA. In all the investigated cases, the atomic absorbing layers are not spatially uniform. Absorbance gradients grow up to 0.2 mm^− 1 even in the case of chemically inert silver atomization. Inverse atomization of In, Bi, Ga and Tl when atoms first appear in the atomizer's upper part was detected in THGA with platform. The effect of the internal gas flow on the spatial structure of analyte atoms is less pronounced in the transversely heated atomizer as compared to the end-heated furnaces.     

Preconcentration of trace lead by adsorption onto a tantalum wire for electrothermal atomization atomic absorption spectrometry with a tungsten tube atomizer

A preconcentration method of lead in waters by adsorption on a tantalum wire was developed for electrothermal atomization atomic absorption spectrometry with a tungsten tube atomizer. After the preconcentration, the tantalum wire was directly inserted into the tungsten tube atomizer. In the preconcentration (adsorption) process for lead, the optimal immersing time was 90 s and the best pH was 4. Under the optimal conditions, the detection limit for lead by the tantalum wire preconcentration method was 6.0 pg mL^− 1 (3S/N) and the relative standard deviation was 6.1%. The influences of large amounts of concomitants on the preconcentration of lead were evaluated. Even though 10³ to 10⁴-fold excess of matrix elements existed in aqueous solution, the lead absorption signal was not significantly affected by the matrix elements. The method with preconcentration on a tantalum wire was applied to the determination of lead in river waters and proved to be sensitive, simple, and convenient. Because this preconcentration method can be utilized in the in-situ treatment of trace lead in environmental water samples, it was unnecessary to carry the water samples to the analytical work place. The present technique was shown to be useful for the determination of lead in environmental water samples at 0.1−1 μg L^− 1.     

Determination of Se,Pb, and Sb by atomic fluorescence spectrometry using a new flameless,dielectric barrier discharge atomizer

A flameless atomizer for atomic fluorescence spectrometry (AFS), based on an atmospheric pressure dielectric barrier discharge, has been developed for the atomization of hydride-forming elements, such as Se, Sb and Pb. The atomizer (8 mm o.d, 35 mm length) was operated at a power less than 50 W. The discharge was sustained with argon at the flow rate of 0.85 L min^− 1 after optimization. The characteristics of the atomizer and the effects of different parameters (power, gas flow rate, and KBH₄ concentration) are investigated. The most attractive feature of this atomizer is its low operation temperature (~ 52 °C, detected at the outlet of the atomizer by a thermocouple), allowing both the radiation source and the detector to be placed in close proximity with the atomizer. The analytical performance of the atomizer has been evaluated, and detection limits for Se, Sb and Pb obtained with the present technique were 0.08, 0.11 and 0.27 μg L^− 1, respectively. The accuracy of the system was verified by the determination of Se, Sb and Pb in reference material of spinage GBW 10015. The concentrations of Se, Sb, and Pb determined by the present technique agreed well with the reference values (Se: 92 ± 24 mg kg^− 1, Sb: 43 ± 14 mg kg^− 1, Pb: 11.1 ± 0.9 mg kg^− 1). This detector is very promising for field elements detection with portable AFS.     

Application of atmospheric pressure dielectric barrier discharge plasma for the determination of Se,Sb and Sn with atomic absorption spectrometry

The atomization of hydride-forming elements, Se, Sb and Sn, has been studied with an atmospheric pressure dielectric barrier discharge atomizer. The elements were first converted to hydride through the reaction with NaBH₄. Then the hydride were atomized in the atomizer and detected by atomic absorption spectrometry. The effects of operational parameters such as power, gas flow rate and concentrations of HCl and NaBH₄ were investigated. Compared with other hydride atomization methods, the proposed atomizer shows the following features: (1) small size, which is preferable for the miniaturization of the total analytical system; (2) low temperature, which would be helpful for further improvement in the compactness of the total analytical system; (3) low power consumption, which is also necessary for the development of analytical instrumentation for in situ detection of environmentally important elements. The analytical performance of the atomizer has also been investigated. The detection limits of Sb, Se and Sn obtained with the present method were 13.0, 0.6 and 10.6 μg l^− 1. This detector is a very promising technique for hydride detection.     

On-line coupling of electrochemical preconcentration in tungsten coil electrothermal atomic absorption spectrometry for determination of lead in natural waters

A flow injection system was coupled to a tungsten coil electrothermal atomizer (150 W) for on-line separation and preconcentration of lead based on its electrochemical reduction on the atomizer surface. The electrochemical cell is built up inside the furnace by using a Pt flow-through anode and the atomizer itself as the flow-through cathode. The manifold and the tungsten coil power supply were controlled by a computer running a program written in Visual Basic, which was utilized in synchronism with the original software of the atomic absorption spectrometer. The flow-through anode (50 mm long, 0.7 mm i.d.) was inserted in tip of the autosampler arm by replacing the last section of the PTFE sample delivering tube. The tungsten coil atomizer and the counter electrode were easily connected to a d.c. power supply. An enrichment factor of 25 was obtained for lead after a 120-s electrodeposition for a sample flowing at 1.0 ml min⁻¹. The method detection limit was 0.2 μg l⁻¹ Pb and the R.S.D.<5% (n=10 for 5 μg l⁻¹ Pb). Up to 2% m/v NaCl or KCl and 5% m/v CaCl₂ or MgCl₂ did not interfere on the separation and atomization of 5 μg l⁻¹ Pb.     

Evaluation and application of internal standardization in atomic absorption spectrometry with electrothermal atomization

A new dual-channel system developed for use in atomic absorption spectrometry is used to assess the internal standard technique for electrothermal atomization. Cobalt was found to be a suitable internal standard for iron determinations, and is used for determination of 7—330 ng Fe ml^-1 in water samples. With use of the internal standard technique, fluctuations caused by atomizer variables are reduced and interferences from many cations are also decreased.     

Separative column atomizer for the direct determination of trace amounts of volatile elements by atomic absorption spectrometry

A novel atomizer effective for direct analysis was developed using a new type separative column atomizer (SCA) module. The SCA module incorporated an atomization part, a separation column and/or reaction column part and observation windows for atomic spectroscopic measurement. This module was applied to the direct analysis of trace amounts of mercury and cadmium in practical samples. No background absorption was observed on the thermal decomposition of synthesized samples in a starch matrix and human hair at the wavelengths of the analytical lines of Hg and Cd. The effectiveness of the technique for the determination of elemental compositions is evaluated.     

Gas-phase atomization in analytical atomic spectrometry

Summary The most important problems of analytical atomic spectrometry are introduction of the sample into the atomizer and atomization of the sample. To solve these problems gas-phase atomization is suggested. This consists of preliminary isolation of the elements to be determined in the form of gaseous (volatile) compounds with subsequent gas-chromatographic separation. Separated compounds are fed into the atomizer individually in a stream of inert gas. This technique is the basis of development of dispersionless modes of atomic emission, atomic fluorescence and atomic absorption multielement analysis using non-selective detection.

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Gasphasen-Atomisierung in der analytischen Atomspektrometrie

     

Evaluation of a carbon-rod atomizer for routine determination of trace metals by atomic-absorption spectroscopy applications to analysis of lubricating oil and crude oil

A carbon-rod atomizer (CRA) fitted with a 'mini-Massmann' carbon rod was evaluated for routine analysis of petroleum and petroleum products for trace metal content by atomic-absorption spectroscopy. Aspects investigated included sensitivity, detection limit, effect of solvent type, and interferences. The results of analysis of oil samples with this technique were compared with those obtained by other techniques. Metals studied were silver, copper, iron, nickel, and lead. Sensitivity and detection limit values obtained with the CRA were similar to those obtained with the carbon-filament atomizer. Strong 'solvent effects' were observed as well as interference by cations. On the basis of this study, design changes for the CRA are suggested, with the object of minimizing 'solvent effects' and interferences, increasing the atomization efficiency, and increasing the residence time of the atomic vapour in the optical path of the instrumental system.     

Direct analysis of solid samples by graphite furnace atomic absorption spectrometry with a transversely heated graphite atomizer and D2-background correction system (SS GF-AAS)

An instrumental design for the analysis of heavy metals in solid samples (certified reference materials, river sediments, cements) by direct graphite furnace atomic absorption spectroscopy (SSGF-AAS) is presented and outlined. A high performance atomic absorption spectrometer with a D₂-background corrector and a transversely heated graphite atomizer was modified. Solid sampling was achieved by a mechanical module combined with an ultra microbalance. Cadmium, lead and chromium in different samples (sample weights between 20–400 μg) have been determined in the μg/g- to ng/g-range with the graphite-platform technique. Different ways of calibration and inhomogeneity problems are discussed. The precision of SSGF-AAS is equal to the precision of the conventional AAS-technique with chemical digestion (microwave digestion system, Zeeman-AAS). It is shown that SSGF-AAS is a reasonable alternative to the conventional technique for selected analytical problems.     

Comparative Study of the Effect of Sample Matrix on the Atomic Absorption of High-Volatile Elements in Two-Step and Conventional Atomizers

The space–time dynamics of absorbing atomic layers of cadmium and lead and molecular layers of zinc chloride in a commercially produced transverse-heated graphite atomizer and a newly developed two-step atomizer was studied. It was shown that the limiting temperature of cadmium pyrolysis in the two-step atomizer without the use of modifiers may be as high as 1000°C, whereas in the commercial analyzer is it not higher than 300°C. Levels of nonselective absorption due to sodium chloride were compared. It was found that, for a two-step atomizer, the maximum allowable mass of sodium chloride for which the background at lead and cadmium lines can be adequately compensated is 17–30 times higher than that for the commercial atomizer. The atomization of cadmium in the presence of sodium chloride was studied using time, space, and spectral resolution. It was shown that the effect of the chloride matrix in the two-step atomizer is suppressed because of sample fractionation and distillation in the course of its evaporation and condensation.     

Determination of boron isotope ratios by Zeeman effect background correction-graphite furnace atomic absorption spectrometry

A new method for the determination of isotopic ratio of boron using Zeeman effect background correction-graphite furnace atomic absorption spectrometry with conventional atomizer and natural-boron hollow cathode source is described. The isotope-shift Zeeman effect at 208.9 nm is utilized for isotopic ratio determination. At a given concentration of total boron, the net absorbance decreases linearly with increasing ¹⁰B/¹¹B ratio. The absorbances are recorded at the field strength of 1.0 T. The isotope ratios measured by the proposed method were in good agreement with the results obtained by inductively coupled plasma-quadruple mass spectrometry or thermal ionization mass spectrometry. The present method is fairly fast and less expensive compared to the above techniques and is quite suitable for plant environments.     

Different platform and tube geometries and atomization temperatures in graphite furnace atomic absorption spectrometry: Cadmium determination in whole blood as a case study

In the present work the performance of different platform and tube geometries and atomization temperatures in graphite furnace atomic absorption spectrometry was investigated, using the determination of Cd in whole blood as an example. Grooved, integrated and fork platforms as well as atomization temperatures between 1200 °C and 2200 °C were investigated in a longitudinally heated graphite atomizer and compared with the performance of a transversely heated furnace. In the longitudinally heated furnace the increase of the atomization temperature in the studied range resulted in an increase of matrix effects for all platform geometries. The integrated platform exhibited slightly lower sensitivity and increased multiplicative interferences in comparison to the other two platform designs. Interference-free Cd determination was possible with all types of platforms and 1200 °C as the atomization temperature as well as with grooved and fork platforms at 1700 °C. On the other hand, lower atomization temperatures resulted in poorer limits of detection, due to the longer integration time needed. No matrix effect was observed at any atomization temperature using the transversely heated atomizer; in addition, limits of detection were better than those observed with the longitudinally heated atomizer. Best values were around 0.02 μg L^− 1 with the latter atomizer compared to values around 0.02 μg L^− 1 with the former one.     

Direct determination of lead in sweet fruit-flavored powder drinks by electrothermal atomic absorption spectrometry

A simplified method for direct determination of lead in sweet fruit-flavored powder drinks, syrups and honeys by electrothermal atomic absorption spectrometry without sample digestion is proposed. Samples were dissolved in water, acidified to 0.2% (v/v) HNO₃, and directly injected into an end-capped transversely heated graphite atomizer (THGA). Building up of carbonaceous residue inside the atomizer was effectively precluded for sugar solutions not exceeding 8.0% (m/v) when a heating program with two pyrolysis steps (600 and 1000°C) was carried out without air-ashing. Under these conditions one atomizer supported about 250 firings. Among various chemical modifiers tested, better recovery and repeatability results were obtained with a 5 μg Pd + 3 μg Mg(NO₃)₂ mixture. Tests carried out with individual concomitants containing up to 1.0 μg Na, K, Ca or Cl, and up to 10.0 μg phosphate or sulphate, and several mixtures of these six concomitants, did not reveal significant interferences on lead atomization. Characteristic mass and detection limit based on integrated absorbance were 15 and 11 pg Pb, respectively. The relative standard deviation based on 10 measurements for typical samples (20–60 ng g⁻¹ Pb) was always lower than 5.5%. The detection limit of 7.0 ng g⁻¹ Pb attained the Codex recommendation for the maximum allowed lead contents in the sugar samples. Application of t-test to the results obtained by the proposed direct analysis, and the official method adopted by Food Chemical Codex, demonstrated that there were no significant differences at the 5% probability level.     

Minimizing the effect of organic matrices in the analysis of tin-containing extracts by electrothermal atomic absorption spectrometry: Determination of Tin in rocks

The effect of the nature of the extracted complex and of the organic solvent on the sensitivity of the extraction/atomic absorption determination of tin in a graphite-furnace atomizer is investigated. It is recommended that extracts of tin as its chloride complex, or chelates with N-benzoyl-N-phenylhydroxylamine or 8-quinolinol, in organic solvents which do not contain chlorine should be used. The depressive effect of the organic matrix can be significantly decreased by using ascorbic acid as matrix modifier, by atomization from a graphite platform, and by using an atomizer coated with tungsten carbide. The procedure developed is applied to the determination of tin in rocks. For tin concentrations of 0.1–10 μg g^?1, the relative standard deviation does not exceed 10%.