Spectral interferences using the Zeeman effect for furnace atomic absorption spectroscopy

Using a transverse, a.c. Zeeman system, with the magnet on the analyte, background correction is performed at the exact analyte wavelength. As a result, nearly all of the spectral interferences associated with continuum correction are eliminated. Errors may occur, though, using Zeeman correction if coincident or nearby absorption lines or molecular absorption bands exhibit Zeeman splitting.We have found an example of overcorrection in the determination of Cd at the alternate 326.1-nm line that we believe is due to splitting of PO bands. We have also confirmed errors from Ft in the determination of Fe at the alternate 271.9-nm line and from Co in the determination of Hg at 253.6 nm.     

Zeeman atomic absorption spectrometry

The shift of atomic spectral lines in a magnetic field (the Zeeman effect) forms the basis for three novel developments in atomic absorption spectrometry: (i) greatly improved background correction; (ii) the use of forward scattering techniques as an analytical tool; (iii) the determination of small gaseous molecules.     

Theory of Zeeman atomic absorption spectrometry

A theoretical analysis is presented of the signals observed with different systems that employ the Zeeman effect for background correction in analytical atomic absorption spectrometry.Magnetic modulation of the primary source of radiation offers basically the same possibilities as the deuterium background correction system. Correction for wavelength dependent background absorption is possible only when the magnetic field is applied to the absorbing vapour. Similar expressions are obtained for constant or variable magnetic fields directed either perpendicular or parallel to the optical axis. However, mere magnetic modulation of either the source or the atomizer cannot correct for non-absorbed lines.It is demonstrated that simultaneous correction for non-absorbed lines and background absorption can be attained with a variable magnetic field applied to the atomizer, by taking measurements at three discrete, different field strengths.     

Zeeman atomic absorption spectrometry using high frequency modulated light polarization

This paper reports the novel use of Zeeman atomic absorption spectrometry using high frequency modulated light polarization (ZAAS-HFM), its theoretical basis and experimental validation. Due to the high frequency modulation of the analytical and reference signals, the temporal background correction error is reduced below 10⁻⁵ absorbance units. In addition, the use of ZAAS-HFM enables the operator to increase the apparatus transmittance and therefore to reduce the detection limits and to broaden the dynamic range of the analytical curves.     

Polarized Zeeman effect atomic absorption spectrophotometry using a flame atomizer

A static magnetic field at 10 kG$\text{\$}\text{?}$was applied to a 10cm laminar flame produced by a premix type burner, and absorptions were observed for the polarized components of the radiation from a hollow cathode lamp. The dynamic range of the measurement was 10⁴–10⁵ for typical elements.The results showed that (1) the optimal conditions for double beam measurement and accurate correction of background absorption are achieved at the same time, (2) even if the flame conditions and the light intensity are changed, the baseline is not shifted, (3) the flame fluctuation noise and the lamp flicker noise are reduced, and (4) background absorption is corrected exactly at the same wavelength as the atomic absorption line.We thus concluded that the feasibility of flame atomic absorption spectrophotometry is much improved with this technique.     

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.     

Water analysis by Zeeman atomic absorption spectrometry

Summary The determination of trace element concentrations in fresh and marinewaters presents many difficulties because the quantities generally found are below ppb. It is possible to achieve such low detection limits by extraction followed by atomic absorption spectrometry with electrothermal atomization, provided errors due to non-specific absorption are eliminated as completely as possible. The employment of the Zeeman effect gave a mean for effective correction.The techniques selected for the determination of trace metallic elements are based on the analysis of dry residues for fresh waters and on extraction by organic solvents or ion-exchange resins for fresh and marine waters. In the case of brines, some elements are determined directly, making the Zeeman correction and employing a modifier of the matrix.

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Wasseranalyse mit der Zeeman-AAS

Zusammenfassung Die Bestimmung von Elementspuren in Süß- und Meereswasser bietet Schwierigkeiten, da die Konzentrationen unter dem ppb-Bereich liegen. Solche niedrigen Nachweisgrenzen lassen sich durch Extraktion mit nachfolgender AAS mit elektrothermischer Atomisierung erreichen, vorausgesetzt, daß Fehler durch nicht-spezifische Absorption möglichst eliminiert werden. Dazu wurde der Zeeman-Effekt benutzt. Das beschriebene Verfahren beruht auf der Analyse von Trockenrückständen bei Süßwasser bzw. der Extraktion mit organischen Lösungsmitteln oder Ionenaustauschern bei Süß- und Meereswasser. Im Falle von Solen können einige Elemente direkt mit Hilfe von Zeeman-Korrektur und Matrixmodifizierung bestimmt werden.

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Lecture given at the Collogium on the Analysis of Solids by AAS, Wetzlar, October 8–10, 1984     

The atomic absorption spectroscopy of selenium

Selenium can be determined in aqueous solution by atomic absorption spectroscopy at 1960, 2040,2063 or 2075 Å; the sensitivities for these lines with a Techtron 10-cm air-acetylene burner are in the ratio of 1:9:60:93. When a Beckman tripleburner (air-hydrogen) and a triple-pass optical system are used, the most sensitive1960 Å line provides a sensitivity of 0.5 p.p.m. and a detection limit of 1.0 p.p.m. The performence in air-hydrogen and air-acetylene flames is described,and optimum experimental conditions determined.With the Se 1960 Å line and a Techtron 10-cm air-acetylene burner, selenium extracted into methyl isobutyl ketone as its diethyldithiocarbamate complex gives a sensitivity of 0.30 p.p.m.,which is a 2.4-fold increase over that found in aqueous solution.     

The atomic absorption spectroscopy of lead

Lead can be determined by atomic absorption spectroscopy at 3 wavelengths. The relative sensitivities are 1:1.5:300. No interferences were found from the cations studied. Anionic interferences were numerous and extensive, but were removed by adding EDTA. The use of a “T” -piece increased the sensitivity of atomic absorption when flame atomizers were used. However, extreme care was necessary in controlling flame conditions both with respect to oxygen-fuel ratio and the type of solvent used. The absorption by combustion products in the flame was high, and in many cases, much greater than that of the lead itself.The most sensitive conditions for the determination of lead appeared to be as follows: wavelength, 2170 A; solvent, aqueous or organic; flame, oxy-hydrogen, with the hydrogen atomizing the sample (reversed from normal). Aflame adapter enabled detection limits of 0.013 p.p.m. to be reached.     

The atomic absorption spectroscopy of Tellurium

Telluiium can be determined by atomic absorption spetroscopy at 2143, 2359, and 2386 A The sensitivities for these lines are in the ratio of 1.9.9 187 With aqueous solutions, a Beckman triple-buiner (air-hydrogen) and a 5-pass optical system, the line 2143 Å has a sensitivity of 0.23 p.p.m , and a detection limit ot 0.076 p.p.m The sensitivities for this line in acqueous and organic solvents, and in air-hydrogen and air-acetylene flames were studied and the optimum conditions determined Where necessary, preconcentration of tellurium by coprecipitation with elemental arsenic, 01 by extraction of K₂Tel₆ or tellurium diethyldithiocarbomate with MIBK can be applied, the latter gives a two-fold enhancement in sensitivity compared with aqueous solutions.     

The atomic absorption spectroscopy of chromium

Conditions were studied for the determination of trace amounts of chromium by atomic absorption spectroscopy. Solution matrix, flame composition, and extraction procedures were the variables studied. A detection limit of 0.006 p.p.m. of chromium was observed with an air-hydrogen flame and methyl isobutyl ketone as the solvent.     

Measurement of relative atomic transition probabilities using flame atomic absorption spectroscopy

A simple and straightforward technique has been developed to measure relative atomic transition probabilities (A_ji) using flame atomic absorption spectroscopy (FAAS). A_ji values for Cu, Ag, Mn and Mo are calculated from absorption measurements in an air—acetylene flame using both line emission (AAL) and continuum excitation (AAC) sources. For Mn and Mo, large discrepancies for A_ji are found between AAL and AAC, which may be attributed to hyperfine structure (hfs). For continuum source measurements the absorbance is independent of the absorption line profile thus eliminating the problems associated with hfs. Therefore, AAC provides a more accurate method for relative A_ji measurements, with determinations of better than 10% relative standard deviation for all elements.     

Serum lithium determinations using flameless atomic absorption spectroscopy

The use of lithium salts and lithium carbonate in particular, in the control and treatment of certain types of psychiatric patients requires a means of monitoring lithium levels in serum. The currently accepted theraputic concentrations cover the range 0.5–1.5 milliequiv-alents of lithium per liter (mEq/l.) of serum with toxic symptoms reported above 1.5–2.0 mEq/l. Atomic absorption spectroscopy has been the method of choice for this analysis for several years and with the development of flameless methods the smaller samples may be used and multiple determinations made in about the same time required for a single determination using an air-acetylene flame and aspiration technique. The standard deviation of the flameless method is approximately 5% relative over the range of interest, 0.5–2.0 mEq/l. A comparison of results is made using a Perkin-Elmer Model 303 AA unit and a Varian Model AA5 with Model 63 Carbon Rod Atomizer.     

Stray light effects in Zeeman atomic absorption spectrometry

A transverse Zeeman atomic absorption spectrometer has been modeled using a polychromatic, optical calculus simulation software program. The models were found to be realistic and greatly facilitated the study of the effects of various Zeeman spectrometer parameters and their interactions. The behavior of the Zeeman spectrometer calibration curves, in the presence of three different types of stray light, was modeled. From the initial results, it seems most likely that the major stray light source in real Zeeman experiments is due to polychromaticity of the light source, even when the source profile is relatively narrow in spectral bandwidth.     

Rubidium isotope measurements in solid samples by laser ablation-laser atomic absorption spectroscopy

Laser atomic absorption was used to measure the rubidium isotopes in a laser-induced plasma. An ⁸⁵Rb/⁸⁷Rb isotope ratio of 2.7±0.2 was determined in solid calcium carbonate samples. A Nd:YAG laser was used to produce the plasma on the surface of solid samples placed inside a low pressure chamber with a controlled atmosphere of 150 mtorr to 10 torr. The plasma conditions were optimized in order to provide the best sensitivity and resolution. A narrowband Ti:Sapphire laser was scanned across the 780.02-nm transition of the rubidium isotopes. The resolved isotope spectrum is shown, as well as the isotope selective calibration plots. A detection limit of 25 ppm for the individual isotopes was obtained. The optimization studies and the likely mechanisms of line broadening are discussed.     

Construction and performance of an a.c. modulated magnet for Zeeman atomic absorption spectroscopy

A Zeeman atomic absorption spectroscopy system has been constructed utilizing a 50 Hz sine wave modulated magnetic field that can be directed either parallel or perpendicular to the optical axis. The amplitude of the magnetic field strength is adjustable up to 10 kG at a maximum power consumption of 0.7 kW.The readout system allows normal atomic absorption as well as d.c. and a.c. Zeeman atomic absorption measurements. Plots of experimental sensitivity vs magnetic field strength and analytical curves are in agreement with theoretical predictions.Experiments in the presence of filter simulated and real background absorbance show that the described Zeeman instrument is capable of correcting background absorption up to two absorbance units.     

The oscillator strength in atomic absorption spectroscopy

The role of the oscillator strength, f, in the theory of atomic absorption is investigated. For a pure natural broadened absorption line, the peak absorption coefficient α_o is independent of the oscillator strength. The peak absorption coefficient becomes dependent on f only through additional broadening processes such as Doppler or collisional broadening. The peak cross section for resonance absorption, α₀/N₁, for a closed transition with equal statistical weights is given by σ₀ = 2πXXX² = ( )/[cn(ω₀)] (where XXX = and n(ω₀) is the spectral mode density of the radiation field at the resonance frequency ω₀) and physically represents the cross-sectional area per allowed mode of the radiation field per unit time per unit frequency interval, multiplied by a lineshape factor 2/π.A summary is presented of some recent determinations of oscillator strengths of atomic absorption lines, based on lifetime measurements made in this laboratory. The results are used to revise values of the theoretical characteristic mass for Ag, Al, Au, Ca, Cu, Mo, Na, Ti and V used in absolute analysis by graphite furnace atomic absorption spectroscopy.     

Blood volume measurement of newborn using stable isotope 50Cr

A technique for the blood volume measurement of newborns was established in which nonradioactive 50Cr was used in patients for whom radioactive labels were not advisable. The red blood cells (RBC) in the newborn's blood withdrawn from umbilical cord after birth were tagged with enriched stable isotope 50Cr (96%, normal abundance 4.3%) and reinjected into the newborn. Blood samples (0.5 ml) were withdrawn at 30 min and thereafter at 6, 12, 24, 48, 72 and 120 hours old. Samples were centrifugalized and portion of RBC was then freeze-dried, weighed and sealed into polyethylene sheet bag together with 50Cr standard. Neutron irradiation was performed in the reactors of the JAERI with thermal neutron flux 5 X 10(13), 2 X 10(13), 8 X 10(13) cm-2s-1 at JRR-2, -3 and -4 respectively for 20 min and samples were left for about two weeks after irradiation. Induced radioactivity (51Cr, 59Fe) of the sample was measured with a Ge(Li) gamma-ray detector system and 4096 channels pulse height analyzer. Analysis of activity data was carried out by BOB-76 code. The RBC and total blood volume of the newborn was calculated using an isotopic dilution technique. We have investigated on tagging efficiency of 50Cr to RBC, washing effect and dilution rate by 50Cr content or 51Cr/59Fe ratio. Significant difference was observed in the total blood volume of newborns depending on the delivery style and in addition, it changed dynamically along the time elapsed after birth.