Simultaneous determination of thallium,silver and gold in urine by flame and graphite-furnace atomic absorption spectrometry after extraction of the iodide complexes as ion-pairs with tri-n-octylamine

A simple, rapid and sensitive atomic absorption spectrometric method is described for the determination of thallium, silver and gold in urine. The metals are extracted as their iodide complexes with tri-n-octylamine into n-butyl acetate and are determined either by direct nebulization of the extract into an air/acetylene flame, or by graphite-furnace atomic absorption spectrometry with the L'vov platform. Detection limits for thallium, silver and gold in urine by flame and graphite-furnace spectrometry are: 65, 1.5; 15, 0.3; 30, 0.6×10 ^?9 M, respectively. The graphite-furnace method is suitable for the detection of thallium, silver and gold in the urine of occupationally exposed and unexposed persons.     

An automated method for the simultaneous determination of salicylic acid and salicylazoiminopyridine in commercial salicylazosulphapyridine.

A technique for estimating nanogram quantities of mercury in sediment samples is described. Samples are heated at 870°C in an oxygen atmosphere, and the released mercury is collected on a gold-coated glass bead trap. The trap is then heated to 500°C in a helium stream; mercury is swept through a d.c. discharge cell and measured by emission spectrometry. Recoveries of mercury added to sediment samples were quantitative. Comparison of five separate samples by the proposed method and by a conventional cold-vapor atomic absorption technique showed similar results. The proposed method gives linear calibration plots up to 1700 ng Hg; the detection limit is 10 ng Hg, so that the sensitivity is 0.005 ppm for a 2.0-g sample.     

Use of a filter in atomic-fluorescence spectroscopy

A detecting system incorporating an interference filter is described for use in atomic-fluorescence spectroscopy analysis in the 200.0-300.0 nm spectral region. Results obtained by using this system are compared with those from a detecting system incorporating either a monochromator or a solar-blind photomultiplier. Improvements of approximately 700-fold and 10-fold respectively in the limits of detection for zinc and mercury result from replacing the monochromator with the filter, while results with the filter are similar to those from a solar-blind photomultiplier. Limits of detection of 10(-5) ppm for zinc and 2.5 x 10(-4) ppm for mercury, both in aqueous solutions aspirated into an air-town-gas flame, are an improvement on other published results for these elements, obtained by atomic-fluorescence flame spectroscopy.     

The reduction and elimination of matrix interferences in graphite furnace atomic absorption spectrometry

The approaches to reduction or elimination of matrix interferences encountered in graphite furnance atomic absorption spectrometry is reviewed. These techniques include matrix modification, application of active gas, and coating tubes with metallic compounds. The research work carried out in the author's laboratory is emphasized. A more universal matrix modifier, palladium, is proposed for the determination of mercury, lead, tellurium, bismuth, arsenic, thallium and indium in environmental samples.     

Laser atomic absorption spectrometry of excited Hg in a discharge applying sum frequency mixing of two diode lasers (preliminary results)

Wavelength modulation diode laser atomic absorption spectrometry is applied to the detection of atomic mercury. Transitions from metastable energy levels highly populated in a radio-frequency discharge are induced with laser diodes by use of nonlinear techniques. The wavelength of one strong transition at 365.119 nm with a high oscillator strength is obtained by sum frequency generation of two diode lasers. The cold vapor technique is used to transfer ionic into atomic mercury. The mercury in the vapor phase is transported by an argon stream into the discharge tube. From the time-dependent absorption signals detection limits of 100 ng/L are achieved at this state of research.     

Laser atomic absorption spectrometry of excited Hg in a discharge applying sum frequency mixing of two diode lasers (preliminary results)

Wavelength modulation diode laser atomic absorption spectrometry is applied to the detection of atomic mercury. Transitions from metastable energy levels highly populated in a radio-frequency discharge are induced with laser diodes by use of nonlinear techniques. The wavelength of one strong transition at 365.119 nm with a high oscillator strength is obtained by sum frequency generation of two diode lasers. The cold vapor technique is used to transfer ionic into atomic mercury. The mercury in the vapor phase is transported by an argon stream into the discharge tube. From the time-dependent absorption signals detection limits of 100 ng/L are achieved at this state of research.     

Determination of trace metals as n-butyl-2-naphthylmethyldithiocarbamates by high-performance liquid chromatography with a fixed-wavelength absorbance detector

The determination of traces of metals by high-performance liquid chromatography of their n-butyl-2-naphthylmethyldithiocarbamate complexes, with a fixed-wavelength absorbance detector, is described. Metal complexes of this ligand are thermodynamically stable and kinetically inert towards dissociation. Various metal complexes, including those of nickel(II), iron(III), mercury(II), thallium(III), platinum(II), palladium(II), copper(II), and cobalt(II) are readily determined. The practical aspects of their separation on various nonpolar stationary phase columns are discussed. The detection limits compare very favorably with those of atomic spectrometry and are about 0.1 ng or approximately 10nM.     

Non-dispersive atomic fluorescence spectrometry with a carbon filament atom reservoir

The non-dispersive atomic fluorescence spectrometric determination of Bi, Cd, Hg, Te, Tl and Zn on a carbon filament atom reservoir with electrodeless discharge lamp sources and reflecting microscope objective lenses is described. The non-dispersive system shows distinct advantages for an element such as tellurium whose principal fluorescence lines fall within the useful range of the solar-blind photomultiplier detector, and marginal advantages for mercury, cadmium and zinc where only one line is within the detector range. It is inferior for bismuth, thallium and lead where lines lie at the extremes of the useful detector range. The technique was applied successfully to the determination of cadmium (0.012%) in a copper-base alloy.     

Plasmas for lab-on-the-chip applications

Two small-size plasmas used as detectors of halogenated hydrocarbons and suitable for miniaturized instrumentation are discussed. A reduced pressure dielectric barrier discharge was integrated in a diode laser atomic absorption spectrometer and the already reported chlorine detection limits of 5 ppm (v/v) can be improved with one order of magnitude by spatially resolved measurements. A microstructured electrode discharge at atmospheric pressure was coupled with a miniaturized Échelle spectrometer and detection limits were found to be 20 ppb for chlorine as well as for fluorine.     

A rapid,simple method for the determination of total mercury in fish and hair by cold-vapour atomic absorption spectrometry

Fuming nitric acid and acidified potassium permanganate are used to pre-digest fish or hair samples in Pyrex culture tubes. Cold-vapour atomic absorption spectrometry is used to detect the elemental mercury which is generated by reduction in a syringe. The absolute detection limit of the method is 0.66 ng Hg, and at levels of 0.14 and 0.60 parts per million (ppm) the standard deviations are ± 0.009 and ±0.008 ppm, respectively. One person can handle batches of 50–100 samples per day including standards and blanks.     

Capacitive Discharge Graphite Furnace Laser-Excited Atomic Fluorescence of Thallium

For the first time, an anisotropic graphite furnace heated by capacitive discharge was used for laser-excited atomic fluorescence spectrometry. A detection limit of 5 fg for thallium was obtained with a laser repetition rate of 500 Hz and a peak integration time of 80 ms. The use of a capacitive discharge furnace allows for a shorter integration time, which in turn should allow for integration of less background noise, and improved detection limits. Theoretically, the magnitude of the shot noise should be proportional to the square root of the integration time, and inversely proportional to the square root of the laser repetition rate. Experimental data illustrated the effect of laser repetition rate, but were inconclusive with respect to integration time. The linear dynamic range of the calibration curve was six orders of magnitude, which was comparable to that normally obtained for laser-excited atomic fluorescence in modern commercial graphite furnaces. Thallium was accurately determined in NIST biological samples at levels one to two orders of magnitude below the detection limit of electrothermal atomic absorption spectrometry, with an analytical precision between 8 and 20%. The interference effects of calcium, sodium chloride, and potassium chloride on the thallium signal were investigated and shown to be similar to both laser-excited atomic fluorescence in a conventional furnace and capacitive discharge furnace atomic absorption results reported in the literature.     

The determination of neon and argon in helium by atomic absorption spectrophotometry

An atomic absorption spectrophotometric technique is described for the determination of neon and argon, respectively, in helium. The accuracies obtained for nanomoles of neon and argon, respectively, were +2.1 and -1.5%. Two Geissler-type discharge tubes containing neon and argon, respectively, were used as emission sources; the absorption source was a quartz cell which contained the sample and related standards that were excited by a high-frequency oscillator. The spectral lines that were employed were neon 6402 Å and argon 8115 Å. Because the spectral lines used had transitions to metastable energy levels, instead of ground levels, a conventional monochromator was suitable.     

Electrochemiluminescence determination of heavy metals in aqueous solutions using a wall-jet detector

The use of a wall-jet detector for determining heavy metals by their intrinsic electrochemiluminescence at an aluminum electrode is described. The possibility of rapidly determining tin, lead, mercury, and thallium with detection limits from 1 μg/L for Pb(II) to 5 ng/L for Hg(II) by the intensity of luminescence that appears during cathodic pulses is demonstrated.     

Determination of thallium in soils by differential pulse anodic stripping voltammetry by means of a mercury film electrode

Trace amounts of thallium can be determined in soils by differential pulse anodic stripping voltammetry with a mercury film electrode. The mercury film is plated ex situ on a glassy carbon surface. By using a supporting electrolyte of ascorbic acid and EDTA at pH 4.5 and the optimum electrolysis potential, interferences from lead and other metal ions can be eliminated. The method does not require any separation of thallium from the matrix. The results are in satisfactory agreement with those obtained by graphite furnace atomic absorption spectrometry.     

Slurry sampling for the determination of thallium in soils and sediments by graphite furnace atomic absorption spectrometry

The analytical conditions for thallium determination in soils and sediments by slurry sampling graphite furnace atomic absorption spectrometry were studied and optimized. Elimination of a strong background for soils rich in organic materials by application of tungsten carbides coated graphite tubes/platforms was studied in detail. Tungsten carbides increased the maximum permissible pyrolysis temperature from 300 to 900 degrees C. The mechanism of tungsten carbide formation on different graphite surfaces was proposed. Application of a strong basic anion-exchange resin for interference elimination in thallium determination in marine sediments was described. Calibration was performed directly using aqueous standards both for soil and sediment analysis. Analysis of CRM confirmed the reliability of the approach. The precision and accuracy of thallium determination by the described method for soils and sediments was acceptable. A characteristic mass of 13.8 pg was obtained and the limit of detection for the proposed method was around 0.06 microg g(-1) Tl.     

Extending the metal interface generality of surface-enhanced Raman spectroscopy: Underpotential deposited layers of mercury,thallium, and lead on gold electrodes

Surface-enhanced Raman (SER) spectra are reported for several adsorbates at underpotential deposited (upd) layers of mercury, thallium, and lead on an electrochemically roughened gold electrode. For upd mercury monolayers, SER bands were obtained for the surface-halide stretching mode, ν_M-X, of adsorbed chloride and bromide that are of comparable intensities to those observed on the unmodified gold substrate. The ν_M-X peak frequencies are downshifted by 15–24 cm⁻¹ on the former relative to the latter surface, consistent with a smaller extent of halide bond covalency on mercury. These spectral changes induced by upd formation could be reversed by anodic stripping of the mercury monolayer. Comparable results were also obtained by prior formation of the upd monolayer in a separate solution followed by electrode transfer rather than by deposition in the solution of interest. Satisfactory SER spectra at upd mercury are reported additionally for thiocyanate and pyridine, as are similar experiments for upd thallium and lead layers on gold. Of the above adsorbates, only pyridine yielded easily measurable SER spectra for these layers, having 2–3 fold smaller signal intensities than on unmodified gold. The SERS intensity decreases upon thallium, and lead upd formation exhibited both irreversible and reversible components. Differential capacitance-potential plots for upd mercury indicate some similarities to liquid mercury interfaces. The results indicate that overlayers on gold provide a means of extending SERS to metals that in themselves do not exhibit suitable Raman scattering enhancements.     

Continuous monitoring of total and inorganic mercury in wastewater and other waters

An automated continuous monitoring system for the determination of total as well as inorganic mercury by cold-vapor atomic absorption spectrometry is described. The method uses continuous flow digestion, reduction and extraction in small bore tubes at slow flow rates, and is suitable for use in the analysis of wastewater and natural waters. A detection limit of 0.1 ppb is obtained when a specially designed, complete gas—liquid separator is used with a condenser circulated with ice-chilled water for removing water vapor, and an 8-μl flow cell for detection. The response times for the determination of inorganic and total mercury are about 3 and 5 min, respectively. The amount of reagents required is about one-tenth of that in conventional Auto-Analyzer methods.     

Evaluation of new high-frequency discharge lamps for atomic absorption and atomic fluorescence spectrometry of cadmium,lead and zinc

High-frequency discharge lamps with a hollow electrode are successfully utilized as the spectral line sources for atomic absorption and atomic fluorescence spectrometry of cadmium, lead and zinc. The sensitivities for atomic absorption spectrometry are superior to those obtained with commercially available hollow-cathode lamps by factors of 1.5 (Cd), 1.4 (Pb) and l.6 (Zn). Detection limits for non-dispersive atomic fluorescence spectrometry with graphite furnace atomization are 1 × 10^-13 g (Cd), 3 × 10^-11 g (Pb) and 2 × 10^-13 g (Zn). The linear analytical range covers over four (Cd, Zn) and three (Pb) decades of concentration above the detection limits.     

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.     

Charged particle activation analysis applied to the detection of heavy elements

Trace analysis methods have been developed for determining thallium, lead and bismuth. Proton or deuteron activation is used followed by a radiochemical separation of the reaction products:²⁰³Pb from thallium,²⁰⁶Bi from lead, and²⁰⁷Po from bismuth. Activation curves are presented for different nuclear reactions occuring on the elements studied. Determinations have been carried out on high purity samples containing varying amounts of thallium, lead, and bismuth. Based on experimental data, the detection limits are estimated at 0.01 ppm for lead, and 0.001 ppm for thallium and bismuth, respectively.