Ng Of Pb Research Articles

Compact integration of gas chromatographer and atomic fluorescence spectrometer for speciation analysis of trace alkyl metals/semimetals

Gas chromatographic separation was coupled with atomic fluorescence spectrometry (GC–AFS) directly via argon-hydrogen flame for integrated GC–AFS instrumentation, i.e., the outlet end of the GC column was directly put into the bottom of the Ar-H2 flame atomizer without any transportation interface. This laboratory-constructed GC–AFS instrument was preliminarily characterized by its application for the speciation analysis of dimethyl selenide ((Met)2Se) and dimethyl diselenide ((Met)2Se2) as well as the two-channel simultaneous determination of tetramethyl tin (Sn(Met)4) and tetraethyl lead (Pb(Et)4). Under the optimized experimental conditions, the absolute limits of detection of 9.4pg for (Met)2Se, 3.8pg for (Met)2Se2, 0.23ng for Sn(Met)4 and 0.39ng for Pb(Et)4 were obtained. The coupling is simple, and the whole instrument is compact.

Application of Small-Spot Energy Dispersive X-ray Fluorescence Instrumentation in Phytoremediation Activities around Metal Mines

In view of the considerable number of analyses necessary in phytoremediation and plant biology studies, it is important that the analytical procedures used for elemental determination in plant tissues should be fast and cheap, with simple sample preparation, and of adequate accuracy and precision. The aim of the present work was focused on the possibilities and drawbacks of a low-cost benchtop energy dispersive X-ray fluorescence (EDXRF) instrument to be used as an analytical technique for studying the potential use of sunflowers (Helianthus annuus) for the phytoremediation of an abandoned Pb/Zn mining area. The simplicity and the ability to operate at room temperature and open air conditions provides a flexible setup for the rapid analysis of vegetation material without complicated previous sample pretreatments. With the help of different collimator caps, a modest lateral resolution (from 200 mum to 1 mm) was achieved and it was thought to be small enough to study the accumulation of Pb and Zn and its distribution between parts of the vegetation specimens (roots, stems, and leaves); the limits of detection achieved (0.6 ng for Zn and 3.0 ng for Pb) proved to be suitable for the intended purpose. Therefore, obtained data revealed that EDXRF spectrometry could be a useful tool to better understand the metal uptake, translocation, and tolerance mechanisms in vegetation species related to biomonitoring and phytoremediation studies.

Availability of Lead and Cadmium in Farmland Soil and Its Distribution in Individual Plants of Dry‐Seeded Rice

Availability of lead (Pb) and cadmium (Cd) in farmland soils and its distribution in individual plants of dry‐seeded rice were investigated utilizing graphite furnace atomic absorption spectrometry (GFAAS) with a matrix modification technique. Five extractants were compared, and the operating conditions for GFAAS were optimized. The detection limits were 4.2 ng for Pb with the precision of 1.54% and 0.1 ng for Cd with the precision of 2.38%. The contents of the extractable Pb and Cd in soils were determined with the five extractants, and availability of Pb and Cd in farmland soil was discussed. The contents of Pb and Cd in different parts of dry‐seeded rice were lower than those in dry‐seeded rice soil. The contents of Pb and Cd in rice were lower than in other parts. The end top leaves accumulated the highest amounts of Pb and Cd.

Precise determination of Pb isotope ratios by simple double spike MC-ICP-MS technique without Tl addition

A double-spike multicollector ICP-MS (DS-MC-ICP-MS) technique for Pb isotope analysis without Tl addition is established and its analytical performance is examined in detail. This simple DS-MC-ICP-MS technique using 20 ng ml−1 gave averages of 16.9417, 15.4988 and 36.7196 with reproducibilities of 0.007, 0.008 and 0.009% (RSD, n = 35), respectively, for 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb in NIST 981 solution, corresponding to consumption of 4 ng of Pb in a pair of spiked and non-spiked measurements. The average is consistent with those obtained by previous studies by DS-TIMS and DS-MC-ICP-MS with Tl addition. The reproducibility (RSD %) of 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb improves from 0.26, 0.54 and 0.69% to 0.0022, 0.0030 and 0.0029% as the Pb consumption during analysis increases from 20 pg to 11 ng. The reproducibility with 11 ng is similar to or even better than those by DS-TIMS, MC-ICP-MS with Tl addition, or with DS-Tl addition. The accuracy of the simple DS-MC-ICP-MS technique for Pb, including the column chemistry, is further confirmed by analysis of actual silicate sample, JB-3.

Isotopic analysis of lead in sub-nanogram quantities by TIMS using a202Pb–205Pb spike

We present a method for isotopic analyses of Pb in sub-nanogram quantities by thermal ionization mass spectrometry with fractionation correction using a 202Pb–205Pb spike. The procedure is simple, fast, easy to automate, and requires only one analysis of Pb per sample to acquire both fractionation-corrected Pb isotopic ratios and Pb concentration. The procedure is evaluated by analysis of multiple loads of NIST Pb isotopic standards SRM-981 and SRM-982, and Pb separated from USGS standard rock BCR-1 and chondrite Bruderheim, with the amount of Pb per load between 0.05–3.0 × 10−9 g. The data have been corrected using both the double spike (DS) fractionation correction described here, as well as by conventional external normalization (EN) procedures, thus providing a direct comparison between the correction methods on exactly the same analytical runs. The enhancement in precision and reproducibility achieved by DS normalization varies with the quantity of Pb analysed. For amounts of Pb of less than 0.2 ng, the improvement in precision and reproducibility of 207Pb/206Pb ratios is small but becomes more substantial with increasing sample size: 3–10 times lower within-run errors, and 2–3 times better reproducibility are obtained for 0.5–3.0 ng loads. Even greater enhancement in precision and reproducibility is achieved for the 208Pb/206Pb ratios, at twice the relative mass difference between isotopes. The advantage of DS for the 204Pb/206Pb ratio is, however, much smaller. This indicates that factors other than fractionation control precision and accuracy of isotopic ratios measured at the ion beam levels below 2–3 × 10−13 A—the intensity typically observed for 204Pb in all samples smaller than 2–3 ng, and for all Pb isotopes in samples smaller than ca. 0.1 ng. The method described here is applicable to high-precision Pb–Pb and U–Pb dating of milligram quantities of meteorites and their components, and single, microgram-size grains of zircon and other U-bearing minerals. The technique described here had been used for dating early solar system materials (Ca–Al rich inclusions and primitive achondrites) containing 0.01–0.3 ng of Pb per fraction, and yielded Pb–Pb isochrons with the age error of 0.16–0.33 million years, which was previously unattainable for such small samples.

Solid sampling analysis by flame atomic absorption spectrometry for lead determination in seawater samples after pre-concentration using cocrystallized alizarin red - naphthalene

A device for direct solid analysis by flame atomic absorption spectrometry (DSA-FAAS) with prior solid phase extraction procedure is proposed for the determination of lead in water samples. A buffer solution (NH4Cl-NH3, pH 8.1) and alizarin red - naphthalene solid phase were added for Pb sorption. After, samples (up to 200 mL) were filtered and the naphthalene matrix was dried, ground to particle size < 80 µm and then maintained into a desiccator up to the Pb determination by DSA-FAAS. Test samples (from 0.1 to 2 mg) were weighed into small polyethylene vials. Vials were connected to a homemade device for solid introduction directly into a conventional air + acetylene flame. Test samples were carried as a dry aerosol to a T-quartz cell specially designed for DSA-FAAS. The T-quartz cell was positioned above the burner and below the optical path of the instrument. In the flame, the generated atomic vapor produced a transient signal that was totally integrated in 2 s. The effect of operating conditions on the analytical signal was evaluated. Background signals were always low (wavelength=217.0 nm) and no memory effects were observed. A characteristic mass of 1.1 ng for Pb was found. Calibration was performed using different masses of solid alizarin red-naphthalene spiked with Pb reference solution. Results were considered satisfactory, for concentration ranging from 30 and 50 µg L-1, regarding to both accuracy (recoveries from 94 to 103%) and precision (relative standard deviation less than 5%, n=6). The stability of lead in the solid phase (naphthalene + alizarin red) was evaluated up to 45 days and the results showed that the solid material could be stored during this period. The proposed device used for solid introduction into the flame atomizer may be easily fitted to conventional atomic absorption spectrometers.

Highly precise and accurate isotopic analysis of small amounts of Pb using205Pb–204Pb and207Pb-204Pb, two double spikes

A new, simple, and practical method has been developed for the accurate and precise isotopic analysis of extremely small amounts of Pb (<∼3 ng) by thermal ionization mass spectrometry. Two different types of double spikes, one consisting of 205Pb and 204Pb and another enriched in 207Pb and 204Pb, are used to reduce “204Pb error” and to correct mass fractionation during mass spectrometry. Using this technique, replicate analyses of 1.5 ng of Pb from NBS981 were performed, and an external precision of 0.02% (2σ) was attained for the 208Pb/204Pb ratio. Compared with results for 1.5 ng of Pb by the normal double spike method using a single 207Pb–204Pb double spike, the external precision for the isotopic ratios involving 204Pb is reduced by about 60–70%, simply by addition of the 205Pb–204Pb double spike. The two double spikes method was also applied to isotopic analyses of natural rock samples, and we obtained an external precision of 0.06% (2σ) for 208Pb/204Pb in ∼1.5 ng of Pb separated from fresh peridotite, in which the Pb concentration is as low as 3.2 ppb. This new technique is superior to any previous method for precise and accurate isotopic analyses of extremely small amounts of Pb, and will be a highly powerful tool in the future of earth science and environmental science.

Multicollector ICP-MS analysis of Pb isotopes using a 207pb- 204pb double spike demonstrates up to 400 ppm/amu systematic errors in Tl-normalization

Pb isotope analyses using multicollector magnetic sector inductively coupled plasma mass spectrometers (ICP-MS) may potentially be corrected for mass bias, a major source of uncertainty, by assuming that the mass bias for Tl is similar to that of Pb. Around 7 ng of Pb has been analysed in this study using a Micromass IsoProbe MC-ICP-MS. With detailed attention to backgrounds arising from instrument memory and tailing from adjacent peaks, external precision of 55–180 ppm 2sd has been achieved over a year on Pb isotope ratios normalized to constant 208Pb/ 206Pb. This involves use of a wide range of SRM981 solutions and two different nebulizers. Mean ratios are very close to multidynamic TIMS data normalized in the same way, provided that anomalous TIMS behaviour of 207Pb [Chem. Geol. Isot. Geosci. Sect. 163 (2000) 299] is corrected to the least fractionated ratios measured. Tl-normalized Pb isotope ratios vary substantially between different SRM981 solutions and between nebulizers, with external precision over the year being up to 541 ppm (2sd) on 208Pb/ 204Pb. However, a 207pb- 204pb double spike (DS) can accurately correct for mass bias on the IsoProbe, and external precision of at worst 245 ppm (2sd) on 208Pb/ 204Pb has been obtained over the year using a wide range of SRM981 solutions and two different nebulizers. Mean ratios on DS-corrected SRM981 and silicate samples are within error of DS-TIMS results, even using an independent calibration for the DS on the IsoProbe. A new 208Pb/ 206Pb value for SRM981 of 2.1677±2 is proposed, normalized to SRM982 208Pb/ 206Pb=1.00016. Use of SRM981 to optimize the 205Tl/ 203Tl normalizing ratio would give Tl-normalized sample ratios ∼400 ppm/amu higher than those calculated using the DS correction. It is shown that these problems with Tl normalization cannot result from isobaric interferences, but they appear to be due to unusual solution chemistry of Tl in the nebulizer.

Determination of Lead, Cadmium, Arsenic and Nickel in Atmospheric Particulate Matter by Simultaneous Multi-Element Electrothermal Atomic Absorption Spectrometry

A simple method for the determination of lead, cadmium, arsenic and nickel in atmospheric particulates by simultaneous multi-element Electrothermal Atomic Absorption Spectrometry has been developed. Due to the high concentrations of Pb and low concentrations of Cd, As and Ni found in particulate matter, lead was monitored at 261.4 nm and the other analytes at the usual wavelengths. Two approaches have been compared using aqueous standard solutions and acid extracts of particulate matter samples. First, a fast electrothermal programme, without chemical modifier, and a short pyrolysis step at 500°C for 10 s, has been developed. The omission of the pyrolysis step was not possible, because strong interference on arsenic was observed. The characteristic masses determined with this approach were 2.10 ng for Pb, 2.0 pg for Cd, 35.8 pg for As and 27.5 pg for Ni. The corresponding detection limits were 4.2 μg l−1 (Pb), 0.025 μg l−1 (Cd), 0.42 μg l−1 (As) and 1.5 μg l−1 (Ni), respectively. The second approach utilized the addition of Pd/Mg modifier (5 μg + 5 μg). The pyrolysis temperature (Tpyr) could be raised up to 650°C. The characteristic masses were 1.40 ng (Pb), 2.2 pg (Cd), 37.3 pg (As) and 27.9 pg (Ni). In the presence of Pd/Mg modifier the limits of detection were 4.3 μg l−1 (Pb), 0.020 μg l−1 (Cd), 0.26 μg l−1 (As) and 0.97 μg l−1 (Ni), respectively. These two approaches were applied in the determination of Pb, Cd, As and Ni in atmospheric particulates. Matrix matched calibration was used in order to achieve accurate and precise results. The calculated recoveries, in the absence of chemical modifiers, were 128% for Pb, 124% for Cd, 108% for As and 110% for Ni. The calculated recoveries were consistently better in the presence of the mixed Pd/Mg modifier: 101% (Pb), 99.7% (Cd), 103% (As) and 102% (Ni), respectively.

Anodic stripping coulometry with collection for absolute trace analysis of lead, using flow-through electrochemical cells with porous working electrodes

Flow-through electrochemical cells with porous working electrodes made of crushed reticulated vitreous carbon and plated with mercury were used for absolute analysis of trace amounts of lead by anodic stripping coulometry with collection (ASCWC) in a flow system. The role of mercury coating, flow rate and pH were investigated. The coulombic content of the collection peak corresponded to the theoretical values calculated by Faraday's law in a concentration range from about 10−9 to 10−6 mol/l. The relative error and the relative standard deviation was +0.15% and 0.8%, respectively for 2×10−6 mol/l analyte concentration. The absolute detection limit (3 s) was 0.1 ng of Pb, the linear response range 7×104.

Low-pressure vaporization for graphite furnace atomic absorption spectrometry

A low-pressure graphite furnace atomic absorption spectrometry technique is presented which, for aqueous Pb samples at 0.15 Torr, results in a 2 orders of magnitude reduction in sensitivity and a working range that extends to about 1 ..mu..g. The limit of detection is 5 ng of Pb. Sticking is diminished for refractory analytes (e.g., V), thus reducing memory effects and peak tailing. Solid sample analysis is demonstrated for Pb in a phosphorized Cu alloy, for which low-pressure atomization minimizes Cu vaporization while allowing for quantitative determination of Pb when compared to a calibration curve prepared from aqueous standards. In addition, the appearance of multiple peaks suggests the use of the technique for differentiating between various forms or locations of Pb within the sample. This is in contrast to atmospheric vaporization where only one broad peak is observed.

Effectiveness of palladium plus magnesium as a matrix modifier for the determination of lead in solutions and soil slurries by electrothermal atomisation atomic absorption spectrometry

A systematic study of various amounts of Pd + Mg as a matrix modifier for the determination of Pb using platform atomisation was carried out. In aqueous solution, small amounts of Pd alone were effective in delaying analyte vaporisation until conditions in the graphite furnace were nearly isothermal. However, Pb recoveries were low unless Mg was also present. Optimum amounts were 0.6 µg of Pd plus 1.0 µg of Mg for the determination of 1.0 ng of Pb. For soil slurries, 0.6 µg of Pd alone was effective. It is thought that the organic material in soil aids the reduction of Pd and thus improves its effectiveness in delaying Pb vaporisation.

Trace element detection by forward scattering using a continuum light source

It has been demonstrated that forward scattering is feasible using a continuum light source (high pressure Xe-lamp). Detection limits of 50 pg in the case of Cd (228.8 nm) and 0.2 ng for Pb (282.3 nm) have been achieved. The method is applicable to the trace detection of any element vaporisable in a graphite furnace. Since changing the light source is not required, there is good hope for a further development of this method for simultaneous multi-element detection.

Composition Isotopique du plomb total de Roches: Méthodologie Lead Isotopic Composition in Whole Rocks: Methodology

AbstractThe different stages of the lead isotopic analysis and the determination of the Pb and U concentration in whole rocks are treated. We examine successively.the dissolution of the sample;the chemical separation of Pb and U on ion exchange resin columns.the isotopic analysis of Pb by mass spectrometry with a precision better than one per mil per atomic mass unit;the determination of Pb and U contents by isotopic dilution mass spectrometry at ±1% (on samples with 1.5 to 0.1 μg of Pb and 0.8 to 0.05 μg of U);the contamination problem for the whole chemical procedure with blank values less than 3 ng of Pb;the accuracy and reproducibility of the results at the 0.1% level (by analysis of the Pb standard NBS 981 and by repeated analysis of the same sample).

A Photoluminescence Technique for Detection of Gunshot Residue

Rapid, convenient detection of gunshot residue on the hands of a suspect, following a shooting, can be accomplished by the photoluminescence determination of the presence of lead (Pb) and antimony (Sb), which originate in the cartiridge primer. Following the firing of a gun, the backs of both hands are washed in a stream of distilled water. Each hand washing is filtered, and the residue collected on a membrane filter is dissolved in hydrochloric acid. Lead(II)and Sb(III) form chloride ion complexes with the acid, which luminesce strongly upon selective ultraviolet excitation at low temperature. Upon excitation, the Pb and Sb complexes emit light with maxima at wavelengths characteristic for the two metallic elements. By the use of this procedure, it is possible to detect as little as 1.0 ng of Pb and 10 ng of Sb. The total time for sample collection and analysis is less than 30 min.

A contribution to the problem of increasing fhe sensitivity of anodic-stripping voltammetry

A brief discussion of problems connected with increasing the sensitivity of anodic-stripping determinations is presented. A new microcell for anodic-stripping voltammetry in solution volumes down to about 0.01 ml was constructed. The effect of the solution volume, the mercury-drop electrode size, and of the pre-electrolysis time and potential on the sensitivity of determinations was studied and the reproducibility of results for determinations of lead in mineral acids is given. It was found that nanogram amounts of heavy metals can easily be determined in this way. In determination of 2 ng of Pb 2+ in 0.02 ml of solution the results were 2.00 ± 0.13 ng (95% confidence limits), the mean relative deviation being 6.3%. For determination of copper in KNO 3, stripping microanalysis was compared with atomic-absorption spectrophotometry. Advantages and disadvantages of stripping voltammetry on the macro- and micro-scales are discussed.