Carbon Furnace Atomic-emission Spectrometry Research Articles

A square-wave wavelength modulation system for automatic background correction in carbon furnace atomic emission spectrometry

A square-wave wavelength modulation system, based on a rotating quartz chopper with four quadrants of different thicknesses, has been developed and evaluated as a method for automatic background correction in carbon furnace atomic emission spectrometry. Accurate background correction is achieved for the residual black body radiation (Rayleigh scatter) from the tube wall and Mie scatter from particles generated by a sample matrix and formed by condensation of atoms in the optical path. Intensity modulation caused by overlap at the edges of the quartz plates and by the divergence of the optical beam at the position of the modulation chopper has been investigated and is likely to be small.

A study of spectral line profiles in carbon furnace atomic emission spectrometry

Carbon furnace atomic emission line profiles of eight elements have been studied using an echelle spectrometer, incorporating a wavelength modulation system. Furnace emission line widths were observed to increase with analyte concentration and in some cases may be of the order of 0.1 nm at 1000 μg ml −1. At low μg ml −1 concentrations, furnace atomic emission line widths for calcium, sodium, chromium, manganese and iron appear to be similar to the corresponding flame emission line widths measured using the same instrument system. Atomic absorption line widths measured for both furnace and flame atomisers are found to be comparable to the emission line widths. The effect of instrumental broadening was estimated by the measurement of hollow cathode lamp line widths to be approximately 0.002–0.003 nm. Self-reversal of atomic emission line profiles has been observed for a number of elements in the concentration range 1–1000 μg ml −1. Calibration graph curvature is attributed to selfabsorption at relatively low concentrations and to self-reversal at concentrations in excess of 1000 times the detection limit. For the spectrometer system used in the present studies, calibration graph linearity is shown to be limited only by line broadening across the modulation interval.

Determination of copper in urine by carbon-furnace atomic-emission spectrometry

A method is described for the direct determination of copper in urine at normal (10–30 μg l .) levels by carbon-furnace atomic-emission spectrometry. Wavelength modulation is used to achieve automatic background correction for scatter-signals produced by the furnace and matrix. The accuracy of the method has been assessed by comparison with continuum-source atomic-fluorescence and carbon-furnace atomic-absorption methods. Relative standard deviations of about 4–5% can be achieved for either the platform or probe atomization techniques.

Carbon Furnace Atomic Emission Spectrometry with a Constant Temperature Atomizer

Abstract A constant temperature Woodriff type furnace is used as an excitation source in carbon furnace atomic emission spectrometry. Instrumental response is limited by blackbody background emission from the heater tube and can only be partially corrected for by the optical system employed. Sensitivity at various excitation temperatures represents a tradeoff between the temperature related population of the excited state and intensity of background emission. Absolute detection limits obtainable for selected transition metals are generally in the ng range and vary from 0.05 ng for Mn to 8.6 ng for Ni. Reproduci-bility at 50 times the detection limit is ± 5% RSD or better. No matrix interferences are noted for the peak area emission obtained at concentrations of 1% (v/v) chloride, nitrate, phosphate or sulfate.

Investigation of graphite-probe atomisation for carbon-furnace atomic emission spectrometry

A new method of sample introduction for carbon furnace atomic emission spectrometry is described. The sample is deposited on a graphite probe which is inserted into the furnace along its length, after the tube has attained its maximum temperature. The heating rate experienced by the sample in an HGA-72 furnace is considerably increased by use of probe atomisation. Improved detection limits for a number of elements are reported, and the interference of magnesium chloride on the emission signals for lead and cadmium is substantially reduced.

Simultaneous multi-element analysis by carbon furnace atomic-emission spectrometry

The application of carbon furnace atomic-emission spectrometry (CFAES) to simultaneous multi-element analysis has been investigated using a direct-reading spectrometer system. A computer-controlled wavelength modulation system employing a quartz refractor plate is used to provide automatic background correction in both the single and multi-element modes. Detection limits obtained using a three-step square-wave modulation waveform with this system are comparable to those previously obtained using the rotating sector method of modulation. The linear range of calibration graphs has been extended to 4–5 orders of magnitude by measurement of emission intensities off the centre of the line profile. The potential of CFAES as a technique for simultaneous multi-element analysis is demonstrated by the determination of trace elements in NBS standard reference materials and orange and pine-apple juice samples.

Furnace atomisation with non-thermal excitation—Experimental evaluation of detection based on a high-resolution échelle monochromator incorporating automatic background correction

The analytical potential that could be derived from the combination of a FANES source with a high-resolution wavelength-modulated echelle monochromator has been investigated. Detection limits for elements of high excitation potential are improved using the non-thermal excitation process compared with the thermal excitation processes available in carbon furnace atomic-emission spectrometry. For some other elements of lower excitation potential detection limits are impaired owing to the increased complexity of the background spectrum in the FANES source.

Platform atomisation in carbon furnace atomic-emission spectrometry

The design and operational characteristics of platforms used in carbon furnace atomic-emission spectrometry are described. Platforms made of graphite and coated with pyrolytic graphite give significant improvements in the sensitivity and detection limits achieved for 23 out of 24 elements investigated. The delay in atomisation allows the production of the atomic vapour at a time when the vapour phase inside the furnace atomiser has reached higher temperatures. Improvements in signal to noise ratio have also been achieved through use of a high-resolution echelle spectrometer, a novel square-wave wavelength modulation system and the better separation of the analyte signals from blank signals.

Mechanism of atom excitation in carbon furnace atomic-emission spectrometry

By consideration of electronic and vibrational excitation temperatures and the ionisation temperature, it is demonstrated that local thermal equilibrium (LTE) is established under the practical analytical conditions of interrupted gas flow in which commercial carbon furnace atomisers are used as emission sources. The electron concentration is shown to be derived from thermionic emission from the carbon tube and calculated values of 5.2 × 1010 cm–3 at 2558 K and 1.3 × 1011 cm–3 at 2766 K are reported. The processes that contribute to the establishment of LTE are considered in detail, and it is suggested that molecular collisions make the major contribution to atomic excitation under all conditions, but that radiation absorption may be significant when a monatomic gas is used as purge gas and when molecules are present as impurities at concentrations of only 0.01%.

Optimization of temperature in carbon-furnace atomic emission spectrometry with commercially available electrothermal atomizers

For instruments without automatic background emission correction, optimization of the applied temperature may be necessary to achieve the lowest analyte detection limits. Optimum temperatures of less than the maximum available are reported for most elements with commercially available instruments in which the heating rate and the final temperature are subject to independent control. Temperature optimization, however, has little effect on furnaces in which the final temperature and the rate of heating are controlled solely by the same applied voltage. Improved emission detection limits are reported for many elements as a result of temperature optimization.

Investigation of atomiser tube design for carbon furnace atomic-emission spectrometry

Modifications to a standard graphite furnace tube, designed for atomic-absorption measurements, are shown to give improved performance for atomic-emission measurements of a number of elements. Four different modified tubes are compared with a standard Perkin-Elmer HGA-72 graphite tube with respect to their thermal characteristics and the detection limits of ten selected elements of varying atom-appearance temperatures. Different elements were found to give lowest detection limits in tubes of different design. The results indicate the need for a new approach to tube design, specifically for atomic-emission measurements, in order that best detection limits can be achieved for all elements in a single graphite tube.

Determination of minor elements in steel by carbon furnace atomic emission spectrometry

Procedures are described for the determination of chromium, copper, manganese, nickel and soluble aluminium in steels by carbon-furnace atomic emission spectrometry. A single set of atomization conditions is optimum for all five elements but different dilutions of the sample solution are recommended for different analyte concentrations in the steels. Interferences from iron and nitric acid are small or insignificant and easily compensated.

Determination of barium in potable waters and sediments by carbon-furnace atomic emission spectrometry

A method is described for the determination of barium in potable waters and sediments by carbon-furnace atomic emission spectrometry. The method has been evaluated for river, reservoir and borehole water and a river sediment. Calcium does not interfere. The working range, 0.01–0.2μg Ba ml -1, is adequate to meet even the most stringent water quality regulations. The limit of detection (2σ ) for barium in deionized water is 0.0008 μg ml -1 and in potable water 0.002μg ml -1. The relative standard deviation is typically 4.7%. Results are compared with those obtained by atomic absorption spectrometry with a nitrous oxide—acetylene flame.

The Effect of Temperature on Carbon Furnace Atomic Emission Spectrometry

The effect of atomization temperature on detection limits attained in carbon furnace atomic emission spectrometry is described and discussed. Standard carbon tubes have been modified, to give a maximum tube temperature 370°K higher, by removing 1 mm of the outside of the tube at its center. The dependence of the emission signal on temperature is shown to have an exponential form, and detection limits for 25 elements are reported in both standard and modified tubes. The potential analytical advantages of a purely electrothermal energy source in emission spectroscopy are outlined.

Determination of barium in calcium carbonate rocks by carbon furnace atomic-emission spectrometry

A simple and rapid method is described for the determination of barium at 0.5–30 µg g–1 concentrations in calcium carbonate and limestone rocks. The sample is dissolved in nitric acid, caesium is added as an ionisation suppressor and the resulting solution is analysed by using carbon furnace atomic-emission spectrometry with automatic background correction using wavelength modulation. Spectral interference from CaOH band structure is low in the carbon furnace compared with flame atomisation and is removed by background correction. Other matrix interferences are negligible. The reproducibility is 5.9% at the 2.4 µg g–1 level and the detection limit is 0.036 µg g–1 of barium in rock samples.

Background emission in carbon furnace atomic-emission spectrometry

Download options Please wait... Article information DOI https://doi.org/10.1039/AN9770200553 Article type Paper Download Citation Analyst, 1977,102, 553-563 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Background emission in carbon furnace atomic-emission spectrometry D. Littlejohn and J. M. Ottaway, Analyst, 1977, 102, 553 DOI: 10.1039/AN9770200553 To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author D. Littlejohn J. M. Ottaway

Communication. Use of hydrogen to reduce molecular oxide emission interference in carbon furnace atomic-emission spectrometry

Communication. Use of hydrogen to reduce molecular oxide emission interference in carbon furnace atomic-emission spectrometry

Determination of Lithium in Copper by Carbon Furnace Atomic Emission Spectrometry

Abstract Carbon furnace atomic emission spectrometry has been used for the determination of lithium in copper. The method involves dissolution of the sample in nitric arid and direct injection into the carbon furnace. The detection limit for lithium is 0.00007 μg/ml Li in aqueous solution and 0.000014% Li in the copper samples.

Carbon furnace atomic-emission spectrometry: a preliminary appraisal

Atomic-emission signals obtained from sodium, potassium, magnesium, chromium, lithium and aluminium by using a standard carbon furnace atomic-absorption spectrometer are reported. Optimisation of the instrument for emission measurements is discussed and detection limits are compared with those obtained by flame emission and carbon furnace atomic absorption using the same instrument.