Construction and performance of a time-multiplex multiple-slit flame atomic fluorescence spectrometer for multi-element analysis

The design and performance characteristics of a new multi-element flame atomic fluorescence spectrometer are presented. Radiation from four hollow-cathode tubes is directed onto an unsheathed air—hydrogen flame. The resulting atomic fluorescence is viewed by a special monochromator with a separate exit slit for each element. The light exiting from all slits is directed to a single photomultiplier tube. The fluorescence signals from different elements are distinguished by a time multiplex approach. Single-element detection limits for ten elements and multi-element detection limits for four elements are presented. The degradation of detection limits by flame background emission noise and effect of flame composition on performance are discussed. Better than 1% precision is obtained for moderate analyte concentrations.     

Atomic fluorescence and atomic emission measurements with an image dissector echelle spectrometer

This paper deals with the investigation of an image dissector echelle spectrometer as an analytical instrument for flame atomic fluorescence spectrometry and for flame atomic emission spectroscopy. The fluorescence was induced by high-pressure xenon arc lamps, which emitted continuum spectra and had higher power ratings, i.e. 1.6 and 2.5 kW, than those normally used for the same purpose. The experimental set-up included two different types of premix burners and one type of total consumption burner. A spherical reflector was applied to improve the utilization of the fluorescence radiation. Two different coatings were tested. None gave the expected enhancement.Detection limits and growth curves were measured for 8 different elements (Ca, Co, Cu, Fe, K, Mg, Na and Ni) in a non-separated air/acetylene flame. The attained detection limits were found to be equally good or somewhat better in flame atomic fluorescence excited with continuum sources than previously reported in the literature, i.e. using similar flames. In flame atomic emission spectroscopy better detection limits have been reported before.     

Tungsten coil devices in atomic spectrometry: absorption, fluorescence, and emission.

In this work, tungsten coil (W-Coil) devices are used as atomizers for electrothermal atomization atomic absorption spectrometry (ETAAS), electrothermal atomization laser excited atomic fluorescence spectrometry (ETA-LEAFS), and electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES). For most cases in ETAAS and ETA-LEAFS, limits of detection (LODs) using the W-Coil are within a factor of ten of those observed with commercial graphite furnace systems. LOD for Cd by W-Coil AAS is 10 pg, while LODs for As, Se, Cr, Sb and Pb by W-Coil LEAFS are 950, 320, 1400, 330, and 160 fg, respectively. The compact W-Coil device makes it an ideal atomizer for portable atomic spectrometry instrumentation, especially when coupled with a miniature charge coupled device spectrometer. Alternatively, the atomizer can be used as an inexpensive, modular add-on to an existing commercial ICP-AES system; and the thermal separation of Pb with interference elements Al, Mn, and Fe is demonstrated.     

Comparative study of atomic fluorescence spectroscopy and inductively coupled plasma mass spectrometry for mercury and arsenic multispeciation

Mercury and arsenic are two elements of undoubted importance owing to their toxic character. Although speciation of these elements has been developed separately, in this work for the first time the speciation of As and Hg using two atomic fluorescence detectors in a sequential ensemble is presented. A coupling based on the combination of high-performance liquid chromatography (where mercury and arsenic species are separated) and two atomic fluorescence detectors in series, with several online treatments, including photooxidation (UV) and hydride generation, has allowed the determination of mercury and arsenic compounds simultaneously. The detection limits for this device were 16, 3, 17, 12 and 8 ng mL^–1 for As^III, monomethylarsinic acid, As^V, Hg²⁺ and methylmercury, respectively. This coupling was compared with an analogous one based on inductively coupled plasma–mass spectrometry (ICP-MS) detection, with detection limits of 0.7, 0.5, 0.8, 0.9 and 1.1 ng mL^–1, respectively. Multispeciation based on ICP-MS exhibits better sensitivity than the coupling based on tandem atomic fluorescence, but this second device is a very robust system and exhibits obvious advantages related to the low cost of acquisition and maintenance, as well as easy handling, which makes it a suitable system for routine laboratories.     

Inductively coupled plasma-mass spectrometry: Capabilities and applications

Researchers in the field of trace elements analysis are continuously in search of new instrumental solutions for obtaining better results in terms of analysis speed, precision, accuracy, detection power, and applicability to a wider range of analytical problems. One of the more recent innovations in this field is the inductively coupled plasma (ICP) source coupled with a mass spectrometry (MS). An ICP-MS system consists of an ICP torch which ionizes the species present and a mass spectrometer for the separation under vacuum of the different species. The main advantages of this technique with respect to graphite furnace atomic absorption spectrometry (GFAAS) and to ICP atomic emission spectrometry (ICP-AES) are: (a) detection limits better than those obtained with graphite furnace, i.e., down to the ng g⁻¹ level, due to the high sensitivity of the channel electron multiplier, which transforms the mass of each ion into an electric signal; (b) the possibility of detecting refractory elements, lanthanides, and all the other elements including halogens, C, and S; (c) high analysis speed (up to 90 elements in 5 min) due to the velocity of the quadrupole mass spectrometer in selecting different masses with respect to the speed necessary to scan different wavelengths; (d) spectral simplicity, because spectra have peaks only at the mass of each isotope and all elements have at least one isotope free from spectral overlap of other analytes; (e) capability of determining individual isotopes of each element. The instrument, therefore, allows not only quantitative elemental analyses to be carried out, but also semiquantitative assays of all the elements present and isotopic ratio analyses to determine quantitatively two or more isotopes of the same element. The most interesting application fields of this technique are in environmental chemistry, geochemistry, oil chemistry, technology of semiconductors, and biochemistry.     

Comparison of atomic fluorescence power efficiencies for the helium-oxygen-acetylene and air-acetylene flames

Power efficiencies for five elements have been measured for the helium-oxygen-acetylene and air-acetylene flames. The increased power efficiencies found in this study for the helium-diluted flame, coupled with its enhanced atom-formation capabilities, suggest that lower atomic fluorescence detection limits should exist. However, in a comparison study with an air-acetylene flame using identical experimental conditions, a decreased atomic fluorescence signal-to-noise ratio was found for most elements in the helium-diluted flame. This decrease is ascribed to greater background emission noise in the hotter helium-diluted flame and decreased nebulization efficiency caused by the low density of the helium-containing nebulizer gas. A comparison of flame emission detection limits for the two flames confirms the increased sensitivity of the hotter helium-oxygen-acetylene flame, despite its lower nebulization efficiency.     

Evaluation of the detection capability of a U-shaped d.c. arc for spectrometric analysis of solutions

A gas-stabilized arc with aerosol supply, originally designed for atomic absorption studies, has been used for emission spectrometric analysis of solutions. A characteristic of the arc is a fairly long horizontal part of the arc column which makes possible “end-on” observation of the spectral emission and selection of a well-defined region of the arc column for analysis. The most intense emission of continuum is at the arc column axis while the emission maxima of the nebulized elements are located at different distances from the axis, which mainly depend on the ionization potential of the corresponding element.The presence of alkali elements in the arc plasma enhance considerably the spectral emission of the elements with medium and low ionization potentials. The effect depends mainly on the first ionization potential of the element and its extent is approximately the same for atom and ion lines. In the case of potassium chloride the intensity increase approaches a plateau at a concentration of 2.5 mg ml^?1. The magnitude of the effect justifies the use of potassium chloride as a spectroscopic buffer.Detection limits obtained with this source on 60 spectral lines are compared with those found in inductively coupled plasmas and in an inverted V-arc echelle spectrometer system. Comparison reveals that inductively coupled plasmas yield consistently lower detection limits with the ion lines used, while with the atom lines it retains the advantage only for elements having a high ionization potential.     

Atomic fluorescence spectrometry with laser excitation

A laser atomic fluorescence spectrometry for the detection of trace concentrations of the elements is described. The detection limits for Pb, Fe, Na, Pt, Ir, Eu, Cu, Ag, Co and Mn in aqueous solutions obtained at present are the best ones for the rapid spectral analytical methods. The analytical potentials of the laser spectrometer are exemplified by the analysis of real samples of different chemical composition.     

Evaluation of tungsten coil electrothermal vaporization-Ar/H2 flame atomic fluorescence spectrometry for determination of eight traditional hydride-forming elements and cadmium without chemical vapor generation

A tungsten coil electrothermal vaporizer (W-coil ETV) was coupled to an Ar/H(2) flame atomic fluorescence spectrometer for the determination of eight traditional hydride-forming elements (i.e., As, Bi, Ge, Pb, Sb, Se, Sn, and Te) as well as cadmium without chemical vapor generation. A small sample volume, typically 20muL, was manually pipetted onto the W-coil and followed by a fixed electric heating program. During the vaporization step, analyte was vaporized off the coil surface and swept into the quartz tube atomizer of AFS for further atomization and excitation of atomic fluorescence by a flow of Ar/H(2) gas, which was ignited to produce the Ar/H(2) flame. The tungsten coil electrothermal vaporizer and Ar/H(2) flame formed a tandem atomizer to produce reliable atomic fluorescence signals. Under the optimal instrumental conditions, limits of detection (LODs) were found to be better than those by flame atomic absorption spectrometry (FAAS) or inductively coupled plasma optical emission spectrometry (ICP-OES) for all the nine elements investigated. The absolute LODs are better or equivalent to those by hydride generation atomic fluorescence spectrometry (HG-AFS). Possible scattering interferences were studied and preliminary application of the proposed method was also reported.     

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.     

Simultaneous determination of trace metals in sewage and sewage effluents by inductively coupled argon plasma atomic emission spectrometry

Inductively coupled plasma excitation sources are adapted for the simultaneous determination of multiple elements in sewage and sewage effluents by atomic emission detection. Digestion with aqua regia in test tubes is recommended for sample preparation. A typical comparison of lead in sewage by atomic emission (x) and atomic absorption (y) gave a least-squares fit of x = 0.98 y + 0.03 with a standard error of 0.5 mg l^-1 and a correlation coefficient of 0.996. More complete comparison data by the atomic emission and absorption techniques are presented for other elements.     

Comprehensive analytical figures of merit for fluorimetry of polynuclear aromatic hydrocarbons

The analytical figures of merit for fluorescence of sixty polynuclear aromatic hydrocarbons are presented. The limits of detection for most of the compounds are below 50 ng ml^-1 and the average relative standard deviation at 1 μg ml^-1 for each compound is 1.4%. The fluorescence excitation and emission peak wavelengths are listed. These results confirm the excellent detection limits and precision offered by this technique for quantification of polynuclear aromatic hydrocarbons.     

Simultaneous determination of Cr,Ga, In and V in soil and water samples by tungsten coil atomic emission spectrometry

Tungsten coil atomic emission spectrometry is employed for the simultaneous determination of Cr, Ga, In, and V. Both V and In are detected by this technique for the first time. The atomizer is a simple, inexpensive tungsten filament extracted from a mass-produced, commercially-available 150 W, 15 V microscope bulb. A 25 µl sample aliquot is placed directly on the coil and a small constant-current power source is used to carefully dry, ash and atomize the sample. Analytical signals are detected with a Czerny-Turner spectrograph and a charge coupled device detector. Multiple emission lines from all 4 elements are monitored simultaneously in a 54 nm spectral window. Concentration limits of detection are in the µg l^− 1 range for all elements, and the absolute limits of detection are 0.2, 2, 0.5, and 10 ng for Cr, Ga, In, and V, respectively. Even lower values may be obtained by combining the signals for the multiple emission lines of a single element. The method precision is typically better than 5.0% relative standard deviation, and sometimes as good as 0.95% (Ga). Standard reference materials of soil and water are used to check the method accuracy. After a simple acid extraction, the values determined by the method presented no significant difference from the reported values at the 95% confidence level.     

Electrothermal atomic absorption spectrometry with two-step probe atomization and primary absorption signal feedback

A method is proposed to reduce the relative detection limits for elements in an atomic absorption spectrometer with a graphite furnace and two-step probe atomization, based on using feedback between the absorption impulse of primary sample atomization and probe fixation in the position for vapor fractionation. Deposition of sample fractions on the probe, which interferes with measuring the analytical signal, is reduced. The relative limits of the direct detection of Pb, Cd, and Tl in NaCl and K₂SO₄ are lowered by more than one order of magnitude in comparison to the atomization of such salts under the conditions of a temperature-stabilized furnace with a platform. The detection limits are 10^?7 to 10^?8 wt %. The relative standard deviation of the analytical signals does not exceed 5%, which is appropriate for the measurement of concentration.     

Developing electrodeposition techniques for preconcentration of ultra-traces of Ni, Cr and Pb prior to arc-atomic emission spectrometry determination

Electrodeposition is known to be proper for separation and preconcentration of extremely low concentrations of analytes from the bulk sample which is instrumentally very simple. In the present research, a combination of electrodeposition with arc atomic emission spectrometry (ED-AAES) method has been developed in order to improve the analytical performance of this spectrometry technique. The results show that sensitivity and detection limits by using ED-AAES were improved 1000–2000 folds over those of normal arc atomic emission spectrometry in determination of the selected elements. The detection limits for measurement of Ni, Cr and Pb were 2.56, 3.05 and 2.11 µg L^{− 1} for monodeposition and 3.31, 3.72 and 3.25 µg L^{− 1} for simultaneously deposition, respectively. The precision of determination was in the range of 2–4% RSD. Typical calibration graphs for these elements were linear up to 100 µg L^{− 1}, depending on the element and matrix.Application of this technique was also tested on determination of the studied elements in an electroplating plant's waste water. The accuracy of technique was verified by comparing the results of the waste water analysis with those of electrothermal atomic absorption spectroscopy as a reference standard method.The obtained results show that the combined technique (ED-AAES) has been progressed substantially toward the ultimate goal of direct interference-free determination of trace analysis in complex samples by AAES.     

Microwave induced plasma atomic emission spectrometry: a suitable detection system for the determination of volatile halocarbons

Microwave induced plasma atomic emission spectrometry (MIP-AES), a highly sensitive detection system for organometal compounds, was coupled to an automated purge and trap gas chromatographic system for the determination of volatile halogenated hydrocarbons in environmental water samples. Optimisation of the parameters affecting the injection and detection system led to relative detection limits from 1 to 14 ng · L^–1 for chlorine- and bromine-compounds and from 10 to 75 ng · L^–1 for iodine-compounds, on basis of a 10 mL sample volume. A comparison of the analytical characteristics between atomic emission detection (AED) and electron capture detection (ECD) showed a lower sensitivity of the atomic emission detector for halocarbons, but the detection thresholds are low enough to use the method for the determination of volatile halocarbons in trace level concentrations. The ability of the atomic emission detector provides increased selectivity for monitoring individual halogenated compounds under simplified and rapid chromatographic conditions, within a total analysis time of only 30 min. The method was applied with gas chromatographic separation for the analysis of sea water samples. Concentrations for the different elements between 0.05 and 15.28 μg · L^–1 were determined.     

Analytical possibilities of different X-ray fluorescence systems for determination of trace elements in aqueous samples pre-concentrated with carbon nanotubes

This study was aimed to achieve improved instrumental sensitivity and detection limits for multielement determination of V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Se, Pb and Cd in liquid samples by using different X-ray fluorescence (XRF) configurations (a benchtop energy-dispersive X-ray fluorescence spectrometer, a benchtop polarised energy-dispersive X-ray fluorescence spectrometer and a wavelength-dispersive X-ray fluorescence spectrometer).The preconcentration of metals from liquid solutions consisted on a solid-phase extraction using carbon nanotubes (CNTs) as solid sorbents. After the extraction step, the aqueous sample was filtered and CNTs with the absorbed elements were collected onto a filter paper which was directly analyzed by XRF.The calculated detection limits in all cases were in the low ng mL^− 1 range. Nevertheless, results obtained indicate the benefits, in terms of sensitivity, of using polarized X-ray sources using different secondary targets in comparison to conventional XRF systems, above all if Cd determination is required.The developed methodologies, using the aforementioned equipments, have been applied for multielement determination in water samples from an industrial area of Poland.     

电热蒸发进样电感耦合等离子体原子发射光谱（ETV－ICP－AES）联用技术研究

本文采用国产部件组装了一套ＥＴＶ－ＩＣＰ－ＡＥＳ仪器体系，对装置的连接及操作参数进行优化。深入系统地考察了分析物的蒸发过程和传输过程，提出了难熔元素的蒸发和传输机理。研究了ＥＴＶ－ＩＣＰ－ＡＥＳ中基体效应，提出了以聚四氟乙烯为氟化剂，氟化辅助ＥＴＶ－ＩＣＰ－ＡＥＳ测定难熔元素的新方法，应用于环境和生物标样中痕量元素分析，获得满意结果。     

Limits of detection for an AOTF-FFP spectrometer in ICP atomic emission spectroscopy

Limits of detection for a number of elements both in air and in argon inductively coupled plasma atomic emission spectroscopy (ICPAES) have been determined using a high-resolution interferometric spectrometer (HiRIS) that consists of an acousto-optic tunable filter, a fiber-optic Fabry-Perot interferometer, and a photon-counting PMT detector. Detection limits using the HiRIS are comparable to those determined using a 1.5 m focal-length grating spectrometer, which has resolution similar to that of the HiRIS. Differences between the two spectrometer systems and the two plasma systems are discussed. The portability and versatility of the HiRIS make it a useful alternative for field or on-line measurements using ICPAES. The high-resolution capabilities allow the HiRIS to replace large grating spectrometers for resolution of isotopic and complex spectra.     

Determination of trace elements in suspensions and filtrates of drinking and surface water by wavelength-dispersive X-ray fluorescence spectrometry

An X-ray fluorescence method (XRF) is presented that allowed low detection limits (at the 0.1–23 ng mL⁻¹ level) to be obtained for Cr, Mn, Fe, Ni, Zn, Sr, Pb, Bi and Br in water. The samples were prepared using a thin layer method. Trace elements were determined via the calibration curve and standard addition. Absorption effects and inhomogenities in prepared samples were checked for using the emission–transmission method and internal standards, respectively. The results from the XRF method were compared with the results from the inductively coupled plasma atomic emission spectrometry method.