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.     

High frequency excitation of vapours produced by hollow cathode sputtering

Using a hollow cathode discharge for producing a suitable atomic vapour, the spectral lines of elements were excited by a high frequency discharge of 2450 MHz. These lamps were used as primary light sources for atomic absorption spectroscopy and were compared with conventional hollow cathode lamps. Higher intensity of radiation as well as higher sensitivity was obtained with the high frequency discharge. The interaction of the microwave field with the hollow cathode discharge limits the ultimate intensity. The stability of radiation from these sources is good. Measurements of line halfwidths indicate gas temperatures of approximately 500°K for both the high frequency and conventional hollow cathode discharges.     

Experimental characteristics of direct current and high frequency boosted hollow cathode lamps

Two types of boosted output hollow cathode lamps, viz. direct current and high frequency boosted lamps, were investigated and the characteristics compared. Both lamps are demountable and use the same water-cooled cathode holder. Remarkably similar results were obtained for both types of booster discharges with respect to intensity enhancement of various spectral lines of a number of elements, and with respect to line widths, which were measured with a Fabry-Perot interferometer for strontium only. The interferometer measurements also revealed that although the gain in total intensity for Sr is only about a factor of 8, the gain in intensity at line centre is approximately a factor 40. Although the intensity enhancement caused by the booster discharges is relatively small (～ a factor of 10) for resonance lines in the visible region, the absolute intensities of these lines are much higher than those of lines in the ultraviolet.     

Distribution of metastable argon atoms in the modified Grimm-type electrical discharge

The absorbance by metastable argon atoms of the Ar 696.543 nm line in the modified Grimm-type electrical discharge source was measured at different discharge conditions and at distances varying from 0.25 to 6 mm from the cathode. A uranium/argon hollow cathode lamp was used as primary source, which gave an argon gas temperature of 850 K when run at 12 mA. A maximum absorbance of 0.57 was found 3 mm from the cathode at 600 V, 80 mA. The magnitude of absorbance increases with discharge current while the position of maximum absorbance shifts away from the cathode with increase in discharge voltage. The quenching of metastable atoms by nitrogen is demonstrated.The spatial distribution of the intensity of four different types of spectral lines is shown. The approximate number densities of the different particles are 10¹²cm^?3 for metastable argon atoms, 10¹⁶cm^?3 for neutral argon atoms, 10¹³ cm^?3 for sputtered copper atoms and 10¹⁴cm^?3for electrons.     

Investigation of a high-intensity spectral lamp for atomic absorption spectrometry—I: High-intensity combined-discharge spectral lamps

The design of lamps with a combined discharge is described in this work. The lamps reveal high emission intensity and small resonance line width, in comparison with conventional hollow cathode and high-intensity Walsh-type lamps. The performance and operating lifetime of the lamps for 26 elements have been investigated. The design also realizes some significant advantages for creating multielement spectral light sources. The paper further describes the design of a high-intensity lamp with a selective modulator providing a modulation depth of 50–70%. The modulator-signal to modulated-signal ratio is shown to be 5–6%. It is demonstrated that application of lamps with selective modulation leads to an increase in the linear range in the high absorbance region of the analyte.     

An application of the Zeeman elect to atomic absorption spectrometry: Development of spectral-line sources stable in magnetic field

A new atomic-absorption spectrophotometer using the Zeeman effect, in which the magnetic field is applied to the light source, is described. A steady magnetic field of 3.8 kG was applied to conventional hollow-cathode lamps, which were operated using a high frequency power of 100 MHz.The π-and σ-components of the Zeeman split atomic lines were observed alternatively after traversing a flame. The absorbance difference between of the two Zeeman components was proportional to the atomic-absorption and was not influenced by background absorption. Dependences of atomic absorption signals on magnetic field strengths which were in close relation to profiles of absorption lines were measured for elements Cd, Mg, Pb, Cr, Cu and Mn by scanning of magnetic field strength.     

Further studies on the influence of pressure on spectral line overlaps in electrothermal atomic absorption spectrometry

The purge gas nature and pressure determines the shift, shape and width of absorption lines in graphite furnaces. Depending on the nature of the gas, red or blue shifts will occur. Absorption line shifts may be used to advantage in several analytical situations. Atomization in argon or nitrogen causes a red shift and broadening of absorption lines. Atomization under pressure enhances these effects. The commercial graphite furnaces are non-isobar in space and time. It is speculated that using Ar/He or Ar/H₂; mixtures, a better overlap is possible between the analyte emission line from a hollow cathode lamp and the absorption line from a graphite furnace. The consequence would be an improvement in sensitivity.     

A line profile study of the 193.76 nm arsenic emission line from lamps used in atomic absorption spectroscopy

The width of the 193.7 nm line of arsenic has been measured for a commercial hollow cathode lamp (HCL), a pumped hollow cathode lamp and a commercial electrodeless discharge lamp (EDL). The measurements were made using an echelle spectrometer and operating the lamps under a wide range of conditions. The line widths for the commercial HCL and for the EDL were found to be 0.91 pm (9.10 mÅ) and 0.895 pm (8.95 mÅ) respectively when operated under the recommended unpulsed operating conditions, and the EDL line was seven times as intense as that from the HCL. When the lamps were pulsed, the widths of the lines increased to 1.009 pm (10.09 mÅ) in the case of the HCL and to 0.904 pm (9.04 mÅ) for the EDL. The arsenic HCL, with neon as a carrier gas, suffers from severe spectral interference which arises from the presence of the 193.89 nm and 193.01 nm Ne II lines. This could account for most of the curvature of the absorbance-vs-concentration calibration curve.     

Line profiles emitted by Cu and Ca hollow cathode lamps pulsed to one ampere

Interferometrically measured emission resonance line profiles are presented for commercial copper and calcium hollow cathode lamps, pulsed at frequencies from 10 to 300 Hz with pulses having a constant current-duration product. Pulses ranged from 7.8 mA at 1280 μs to 1000 mA at 10 μs. Time integrated profiles show that self-reversal increases with repetition frequency and that the lines broaden with increased current. Time resolved profiles show that self reversal developes during a pulse. A simple transport model is proposed to account for the observed blue shifts in the emission profile and in the self-reversal dip of the copper resonance line. The analytical significance of the results is briefly discussed.     

Analytical and spectral features of atomic magneto-optical rotation spectroscopy (the atomic Faraday effect) of Sb,Bi, Ag and Cu with a hollow cathode lamp operated in a pulse mode

In order to increase source intensity, hollow cathode lamps were operated in a pulse mode and combined with instrumentation for Faraday or atomic magneto-optical rotation spectroscopy. The analytical and spectral features of this method were studied for the trace determination of elements Sb, Bi, Ag and Cu. Novel line crossings between the σ^±-components in the analytical line Bi I 306.772 nm were found from the dependence of the transmitted intensity on the magnetic field strength. This is related to the theoretically calculated Zeeman splitting pattern. The enhancement in the source radiance by the pulse mode gave an increase in the detection power by a factor of ten.     

Observation of spectral line profiles emitted by an inductively coupled plasma—I.: On the wavelength shift of spectral lines

Profiles of 16 spectral lines stemming from 8 elements (Ar, Na, Cu, Sr, Cd, Ba, Mg and Li) emitted by an inductively coupled plasma (ICP) have been observed and measured with a pressure-scanning Fabry-Perot interferometer. In the process of profile observations, we have found wavelength shifts of spectral lines in an ICP and for the first time studied this phenomenon quantitatively and systematically in a spectrochemical source. The profiles of spectral lines emitted by the ICP have been compared with those emitted by hollow cathode lamps. The magnitude of the wavelength shift to the red or the blue varied more or less with the plasma conditions, observation position and the concentration of a concomitant, cesium. In the present work the observed line profiles were not deconvoluted for the apparatus profiles. Typically the order of magnitude of the wavelength shift measured for spectral lines that show large shifts at an observation height of about 4 mm in an “analytical” ICP is n × 10^?3 nm, where n is about 4 for Ar I 427.2 nm and about 1 for Cu I 521.8 nm and Sr II 430.5 nm. With regard to the wavelength shift, several trends and/or regularities were found. The Stark effect is considered as the main cause of the phenomena.     

Experimental observation of line hyperfine structure with a plane grating spectrograph

For observing the hyperfine structure (HFS) of spectral lines it is required that the spectral bandwidth is smaller than or equal to both the physical widths of the HFS components and the wavelength distances between these components. The paper discusses how these conditions can be fulfilled for a 2.1-m plane grating spectrograph equipped with a 1200 grooves/mm grating. Using such a spectrograph observations were made of the HFS of lines emitted by hollow cathode lamps or an arc. Typical results for lines of Bi, Cu and In are reported. Wavelengths and relative intensities of HFS components are given.     

The performance of boosted output hollow cathode lamps in flame atomic absorption spectrometry

A study has been made of boosted output hollow cathode lamps, including (a) the relative increase in the intensity of the resonance line on boosting, (b) the effect of boosting on the spectrum of the emitted radiation, (c) the shape of the calibration graphs in flame atomic absorption spectrometry, and (d) the characteristic concentrations and detection limits found using boosted and unboosted lamps. The relative increases in the intensities of the various resonance lines on boosting is much less for modern lamps than was previously reported for early lamps, and reasons for this are discussed. For flame atomic absorption spectrometry the most useful effects of boosting appear to be a sharpening of the resonance line and a reduction in its background. The chief benefit to the analyst of using boosted output lamps is the increased linearity of the calibration graphs and the consequent extension of the range of concentrations that can be measured accurately.     

A Rowland Circle,multielement graphite furnace atomic absorption spectrometer

A simultaneous, multielement atomic absorption spectrometer utilizing a graphite furnace atomizer was constructed and evaluated. The optical arrangement employs a concave grating to combine the spectral output from a deuterium lamp and four hollow cathode lamps that are placed on the perimeter of a Rowland Circle. A graphite furnace atomizer is positioned on the circle at the point of convergence of the five light sources. Background correction is performed by the continuum source method. Simultaneous detection of the analyte absorption signals is accomplished with a charged-coupled device. Four test elements were used for evaluation purposes: cadmium, lead, copper and chromium. Even though the elements differ greatly in volatility, the detection limits approach the values published for single element GFAAS: 4, 12, 14 and 12 pg for Cd, Pb, Cu and Cr, respectively. The characteristic masses (integrated absorbance) for the four metals are 3, 24, 14 and 7 pg, respectively. Three drinking water reference materials are analyzed: NIST SRM #1643b (Trace Elements in Water), Fisher Scientific “Metals Drinking Water Standard,” and High Purity Standards “Drinking Water Metals Solution A and B”. The determined amounts were within 10% of the certified values for each of the four elements for all three reference materials.     

Comparison of trace analytical results obtained with different hollow cathode discharge lamps

Summary Detection limit and sensitivity of trace analysis of powdered samples have been tested using hollow cathod discharge lamps made in our laboratory. We found some special problems for trace analysis with hollow cathode excitation; such problems are the energy tuning and the pressure dependence of spectral lines. Results obtained with improved hollow cathode discharge lamp and with water cooled hollow cathode discharge lamp are compared to each other.

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Vergleich spurenanalytischer, mit verschiedenen Hohlkathodenlampen erzielter, Ergebnisse

Zusammenfassung In Pulveranalysenergebnissen wurde die mit den von uns entwickelten Entladungsröhren erzielten Nachweisgrenzen sowie die Veränderung des Nachweisvermögens geprüft. Es wurde experimentell nachgewiesen, daß bei der Hohlkathodenentladung auch spezielle spurenanalytische Probleme entstehen, wie die Energieabstimmung und die Druckabhängigkeit der Spektrallinien. Die Ergebnisse der modifizierten und die der wassergekühlten Hohlkathodenentladung wurden zusammengestellt und verglichen.

     

Trace determination of sulphide and sulphur dioxide by vapor molecular absorption spectrometry using magnesium and tellurium hollow cathode lamps

A new method has been developed in this paper for determining sulphide and sulphur dioxide simultaneously. Two emission lines, 202.6 nm and 214.3 nm which are emitted from hollow cathode lamps (HCL) of magnesium and tellurium, respectively, were used as radiation sources for measurement of absorbances of H(2)S at 202.6 nm and SO(2) at 214.3 nm or 202.6 nm. The detection limit for S(2-) was shown to be 0.01 mug/ml and the detection limits for SO(2) with 202.6 nm and 214.3 nm lines were 0.05 and 0.2 mug/ml, respectively. The method has been employed to satisfactorily analyse practical samples.     

Instrumentation for simultaneous multielement atomic absorption spectrometry with graphite furnace atomization

Graphite furnace-atomic absorption spectrometry (GF-AAS) is restricted to the determination of 4 to 6 elements simultaneously due to the limitations of hollow cathode lamps. However, a consideration of prototype continuum source instruments and recent advances in the fields of spectrometer and detector technology suggests that a multielement GF-AAS instrument, with the multielement versatility associated with atomic emission spectrometry, is possible. Such a multielement instrument would employ a continuum source and provide 1.) multielement determinations for 30 to 40 elements, 2.) wavelength and time integrated absorbance measurements which are independent of the source width, 3.) detection limits comparable to line source AAS with the potential for another order of magnitude improvement using atomization at elevated pressures, 4.) extended calibration ranges limited only by the memory of the atomizer, and 5.) high resolution inspection of the spectra surrounding the analytical wavelength. Such an instrument could provide figures of merit comparable to inductively coupled plasma-mass spectrometer with considerably less complexity.     

Instrumentation for simultaneous multielement atomic absorption spectrometry with graphite furnace atomization

Graphite furnace-atomic absorption spectrometry (GF-AAS) is restricted to the determination of 4 to 6 elements simultaneously due to the limitations of hollow cathode lamps. However, a consideration of prototype continuum source instruments and recent advances in the fields of spectrometer and detector technology suggests that a multielement GF-AAS instrument, with the multielement versatility associated with atomic emission spectrometry, is possible. Such a multielement instrument would employ a continuum source and provide 1.) multielement determinations for 30 to 40 elements, 2.) wavelength and time integrated absorbance measurements which are independent of the source width, 3.) detection limits comparable to line source AAS with the potential for another order of magnitude improvement using atomization at elevated pressures, 4.) extended calibration ranges limited only by the memory of the atomizer, and 5.) high resolution inspection of the spectra surrounding the analytical wavelength. Such an instrument could provide figures of merit comparable to inductively coupled plasma-mass spectrometer with considerably less complexity.     

An application of the zeeman effect to analytical atomic spectroscopy-I The construction of magnetically-stable spectral sources

A design is given for a d.c. discharge lamp which will maintain a stable plasma in a magnetic field. The lamp is of particular use for applications of the Zeeman effect to analytical atomic spectroscopy. Three designs of cathode are described, which cover three different temperature ranges for the m.p. of the elements concerned. The experimental behaviour of lamps at varying magnetic field strengths, filler pressures and operating currents is considered.