Bismuth as a general internal standard for lead in atomic absorption spectrometry

Bismuth was evaluated as internal standard for Pb determination by line source flame atomic absorption spectrometry (LS FAAS), high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS) and line source graphite furnace atomic absorption spectrometry (LS GFAAS). Analysis of samples containing different matrices indicated close relationship between Pb and Bi absorbances. Correlation coefficients of calibration curves built up by plotting A^Pb/A^Biversus Pb concentration were higher than 0.9953 (FAAS) and higher than 0.9993 (GFAAS). Recoveries of Pb improved from 52–118% (without IS) to 97–109% (IS, LS FAAS); 74–231% (without IS) to 96–109% (IS, HR-CS FAAS); and 36–125% (without IS) to 96–110% (IS, LS GFAAS). The relative standard deviations (n = 12) were reduced from 0.6–9.2% (without IS) to 0.3–4.3% (IS, LS FAAS); 0.7–7.7% (without IS) to 0.1–4.0% (IS, HR-CS FAAS); and 2.1–13% (without IS) to 0.4–5.9% (IS, LS GFAAS).     

The oscillator strength in atomic absorption spectroscopy

The role of the oscillator strength, f, in the theory of atomic absorption is investigated. For a pure natural broadened absorption line, the peak absorption coefficient α_o is independent of the oscillator strength. The peak absorption coefficient becomes dependent on f only through additional broadening processes such as Doppler or collisional broadening. The peak cross section for resonance absorption, α₀/N₁, for a closed transition with equal statistical weights is given by σ₀ = 2πXXX² = ( )/[cn(ω₀)] (where XXX = and n(ω₀) is the spectral mode density of the radiation field at the resonance frequency ω₀) and physically represents the cross-sectional area per allowed mode of the radiation field per unit time per unit frequency interval, multiplied by a lineshape factor 2/π.A summary is presented of some recent determinations of oscillator strengths of atomic absorption lines, based on lifetime measurements made in this laboratory. The results are used to revise values of the theoretical characteristic mass for Ag, Al, Au, Ca, Cu, Mo, Na, Ti and V used in absolute analysis by graphite furnace atomic absorption spectroscopy.     

Study of the hyperfine structure of Titanium atom by laser induced fluorescence on an atomic beam

Within the framework of systematic hyperfine structure (hfs) investigation of titanium atom the hfs splitting of 3d ³4s ³H_4,5,6 levels for two stable isotopes ⁴⁷Ti and ⁴⁹Ti have been measured by laser induced fluorescence. Experimental hfs constants A _exp and B _exp have been determined. The hfs measurements confirm an existence of a significant spin-dependent interaction effect on hfs structure of the level 3d ³ 4s ³H₄.     

Determination of macro- and micronutrients in plant leaves by high-resolution continuum source flame atomic absorption spectrometry combining instrumental and sample preparation strategies

A method for determination of B, Ca, Cu, Fe, K, Mg, Mn, Mo, P, S and Zn in plant tissues by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS) is proposed. This method is based on special features of HR-CS-AAS, such as side pixel registration, wavelength integrated absorbance, and molecular absorption bands, for determining macro- and micronutrients in foliar analysis without requiring several different strategies for sample preparation and adjustment of the analytes concentration ranges. Plant samples were analyzed and results for certified materials were in agreement at a 95% confidence level (paired t-test) with reference values. Recoveries of analytes added to plant digests varied within the 82–112% interval. Relative standard deviations (n = 12) were lower than or equal to 5.7% for all analytes in all concentration ranges.     

The application of a piezoelectric scanning Fabry-Perot Interferometer to the study of atomic line sources—III: Use of the channeled spectra produced with a continuum source for studies of the absorption line-width for calcium atoms in flames

An instrumental arrangement has been developed for the interferometric study of the half-width of atomic lines in absorption using a spectral continuum source. The variation of observed half-width of the calcium absorption line at 422·67 nm with calcium concentration has been examined in air-acetylene and nitrous oxide-acetylene flames supported as cylindrical flames with and without flame shielding and at long path burners. Extrapolation of the curves obtained to zero added calcium concentration in the flame may allow for correction for self-absorption and flame characteristics and calculation of collisional broadening half-widths and damping constants (a-parameters).     

Feasibility of peak volume,side pixel and multiple peak registration in high-resolution continuum source atomic absorption spectrometry

In high-resolution continuum source atomic absorption spectrometry (HR-CS AAS) with a pixel detector, such as a charge-coupled device array for signal registration, the absorbance A not only depends on the absorption coefficient, the length of the absorbing layer and the number of absorbing atoms therein, but also on the spectral interval over which the signal is recorded, i.e., the spectral bandwidth per pixel and the number of pixels evaluated. Although the problem of different (absorption and emission) line widths is known for several decades already to exist in conventional line source AAS, it is usually disregarded. By choosing a certain number of pixels in HR-CS AAS a defined wavelength interval can be selected over which the absorbance is recorded. As the numerical values obtained this way are not directly comparable with the conventional absorbance, it is necessary to define new terms and symbols for this kind of signal evaluation. With a steady-state signal the individual pixel absorbance values can be added or integrated, resulting in the unit-free wavelength-selected absorbance (WSA, symbol A_Σ), or the wavelength-integrated absorbance (WIA, symbol A_λ) having a wavelength unit, such as picometers (pm). Similarly, with transient signals one can add-up or integrate (over wavelength) the individual integrated (in time) absorbance values of the selected pixels to obtain the volume under the absorbance peak. This results in the peak volume selected absorbance (PVSA, symbol A_Σ,int), and the peak volume integrated absorbance (PVIA, symbol A_λ,int), with the units second (s) and second times picometer (s pm), respectively. For comparison purposes, however, the integrated absorbance values, i.e., WIA or PVIA, should be used since they are instrument-independent.     

HFS and isotope shift in the atomic spectrum of205Pb

The hfs of²⁰⁵Pb in the 283.3-nm resonance line and its isotope shift (IS) have been measured in absorption with the use of dispersive spectroscopy. A new method for calibration and analysis, when internal standards are not available is described. The results are: hfs interaction constantsA=70.3(5)×10^?3 cm^?1,B=?0.6(1.1)×10^?3 cm^?1,²⁰⁵Pb-²⁰⁸Pb IS=?123.9(2.0)×10^?3 cm^?1. The derived nuclear magnetic dipole moment,μ=0.704(5)μ _N is in good agreement with values calculated with a nuclear configuration mixing model.     

Flow injection flame atomic absorption analysis of Fe and Mn in cement samples

Summary A new procedure has been developed for the determination of Fe and Mn in cements. It consists in dispersing 50 mg of the solid sample in 25 ml of 0.15 mol/l HNO₃ and 0.12 mol/l HCl solution. Acid slurries are heated at 50°C for 10 min and then different volumes of the slurry are injected into a water carrier stream. This previous acid treatment leaches the elements to be determined and permits the use of acid solutions as standards. For the Mn determination, the use of a single line flow injection manifold provides a limit of detection of 0.03 mgl^–1 and a dynamic range up to 6 mgl^–1. For the determination of Fe, the on-line dispersion of samples, using a well stirred mixing chamber, increases the dynamic range up to a concentration of 125 mgl^–1 and provides a limit of detection of 1 mgl^–1. The procedure has been applied to the analysis of real cement samples and a certified reference material. Results were in agreement with those obtained by a reference procedure involving the alkaline fusion of samples and batch analysis by flame atomic absorption spectrometry.     

Sequential voltammetric determination of trace metals in meals

An analytical procedure for the sequential determination of Zn(II), Cr(VI), Cu(II), Sb(III), Sn(II), Pb(II) by square wave anodic stripping voltammetry (SWASV) and Fe(III), Mn(II), Mo(VI) by square wave voltammetry (SWV) in matrices involved in foods and food chain as wholemeal, wheat and maize meal is described.The digestion of each matrix was carried out using a concentrated HCl–HNO₃–H₂SO₄ attack mixture, employing dibasic ammonium citrate buffer solution (pH 6.9 and 8.7) as supporting electrolytes. The analytical procedure was verified by the analysis of the standard reference materials Wholemeal BCR-CRM 189, Wheat Flour NIST-SRM 1567a and Rice Flour NIST-SRM 1568a.For all the elements in the certified matrix, the precision as repeatability, expressed as relative standard deviation (s_r) was of the order of 3–5%; the accuracy, expressed as relative error (e) was generally of the order of 3–6%.In presence of reciprocal interference, the standard addition method considerably improved the resolution of the voltammetric technique.Finally, the analytical procedure was transferred and applied to commercial meals sampled on market.A critical comparison with atomic absorption spectroscopic measurements is also discussed.     

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.     

Direct atomic absorption spectrometry determination of tin, lead, cadmium and zinc in high-purity graphite with flame furnace atomizer

This work described methodology of Sn, Pb, Cd and Zn impurities determination in high-purity graphite at direct atomic absorption spectrometry (AAS) with flame furnace (FF) atomizer. It was evidence that quality of AAS measurements are depended from sample amount, its homogeneity, particle size, as well as calibration procedure and operation parameters of FF atomizer. Prior to analysis the method has been developed and optimized with respect to the furnace heating temperature and flame composition of FF atomizer. Conditions of absorption peak areas (Q_A) formation to each element were studied on the basis of contribution into its value some of individual parameters of analytes, including mass-transporting process from increasing mass of graphite samples into gas phase. Because particle size and homogeneous distribution of analyte in powdered materials has an enormous influence on accuracy and precision of measurement results, graphite as well as appropriate series of powdered reference standards was previously ground and investigated. Graphite samples to be analyzed and standard reference materials with mass from 0.025 to 0.200 g was previously briquetted as pellet and insert on corresponding hole in furnace. The characteristic mass (g₀) of Sn, Pb, Cd and Zn were 0.35, 0.1, 0.008 and 0.025 ng, respectively, and relative standard deviation (S_r) not more than 20%.     

Organophosphorus acid interferences in flame atomic absorption spectrometry

The interference of the organophosphorus acids, 1-hydroxyethane-1,1-bisphosphonic acid, aminotris(methylenephosphonic acid), ethylenediaminetetrakis(methylenephosphonic acid) and hexamethylenediaminetetrakis(methylenephosphonic acid) on the determination of eighteen metal ions by flame atomic absorption spectrometry is reported. Comparisons with the effect of orthophosphoric acid reveal similarities and distinct differences in their interfering effects. In the air/acetylen flame, depressive interferences are attributed to the formation of phosphates, M₃(PO₄)₂, or hydroxynpatite-like compounds, M₅(OH)(PO₄)₃, in the flame aerosol particles for Mg, Ca, Sr, Ba, Mn, Co and Ni. Iron(III) and chromium(III) appear to form stable oxide phosphates, M₂O₃?MPO₄ or M₃O₄?MPO₄. Evidence for the formation of stable molybdenum carbides, MoC and MoC₂, is also presented. In the nitrous oxide/acetylene flame, serious interferences perssisted only for molybdenum but were eliminated by the addition of sodium sulphate.     

Sequential determination of platinum, ruthenium, and molybdenum in carbon-supported Pt, PtRu, and PtMo catalysts by atomic absorption spectrometry

A simple accurate and precise analytical method for the determination of platinum, ruthenium, and molybdenum in Pt, PtRu, and PtMo nanoparticles catalysts deposited on high-surface area carbon by flame atomic absorption spectrometry (FAAS) and graphite furnace atomic absorption spectrometry (GFAAS) is described. The complete digestion of samples (0.010-0.020 g), which contain noble metals (NMs) in the range between 0 and 30% in combination among them or with other non-NMs, is obtained under mild conditions using both concentrated HCl and HCl+HNO₃ (1+1 (v/v)) mixture to boiling for 30 min in an open vessel. Carbon is separated from the solution by filtering it. Under optimized conditions of the flame, the poor sensitivity of platinum is enhanced 50-fold in presence of 1% (m V⁻¹) ascorbic acid, whereas the analytical signal of ruthenium increased by the presence of co-existing platinum. Any kind of interference is observed on the analytical signal of molybdenum. Recovery test obtained by analyzing commercial powder catalysts ranged from 99 to 101%. The precision, expressed as relative standard deviation of five measurements, is better than 1%. Electrode catalysts, made by using the carbon-supported platinum-based powder catalysts, have been analyzed for the metal loadings onto the electrode by GFAAS after dissolution under the same conditions used for the powder catalysts. The precision, expressed as relative standard deviation of three measurements, is better than 2%.     

Investigation of artifacts caused by deuterium background correction in the determination of phosphorus by electrothermal atomization using high-resolution continuum source atomic absorption spectrometry

The artifacts created in the measurement of phosphorus at the 213.6-nm non-resonance line by electrothermal atomic absorption spectrometry using line source atomic absorption spectrometry (LS AAS) and deuterium lamp background correction (D₂ BC) have been investigated using high-resolution continuum source atomic absorption spectrometry (HR-CS AAS). The absorbance signals and the analytical curves obtained by LS AAS without and with D₂ BC, and with HR-CS AAS without and with automatic correction for continuous background absorption, and also with least-squares background correction for molecular absorption with rotational fine structure were compared. The molecular absorption due to the suboxide PO that exhibits pronounced fine structure could not be corrected by the D₂ BC system, causing significant overcorrection. Among the investigated chemical modifiers, NaF, La, Pd and Pd + Ca, the Pd modifier resulted in the best agreement of the results obtained with LS AAS and HR-CS AAS. However, a 15% to 100% higher sensitivity, expressed as slope of the analytical curve, was obtained for LS AAS compared to HR-CS AAS, depending on the modifier. Although no final proof could be found, the most likely explanation is that this artifact is caused by a yet unidentified phosphorus species that causes a spectrally continuous absorption, which is corrected without problems by HR-CS AAS, but which is not recognized and corrected by the D₂ BC system of LS AAS.     

Systematic investigation of some metal cation interferences on the determination of molybdenum by flame atomic absorption spectrometry

The interference effects of some metal cations on the absorbance of Mo during its determination by flame AAS have been investigated, in air-acetylene flame, at a fuel flow rate of 1.8 L/min. While the interfering ion concentration was changing between 5 and 40 000 mg/L, the Mo concentration was taken as 10, 20 and 40 mg/L. It was shown that even at low concentrations of interfering ion there was a large suppression of Mo absorbance. No absorbance was observed for Mo in the presence of 50 time higher concentration of Mg, Ca, Sr, and Ba. These interference effects were suppressed by additions of 0.04% (m/v) sodium diethyldithiocarbamate (Na-DDTC), 2% (m/v) ammonium chloride, and 0.4% (m/v) sodium hydrogen phosphate. The interference from another group of elements, Mn, Fe, Al, Cd, Ni, Cr, Co, Cu and Zn, has been also investigated. In the presence of above mentioned metals, except Mn, the reproducibility of Mo absorption signal was not satisfactory. In the presence of Mn (5–40000 mg/L) the absorbance of Mo decreased significantly, however, the reproducibility was high. Molybdenum absorbance decreased under the influence of 5000–40000 mg/L of Fe, Co, Ni, 500–40000 mg/L of Cr. On the other hand, the absorption signal of Mo increased at about 20–40% in the presence of Zn and Cd. By the addition of 2% NH₄Cl the interference of these metals could be eliminated completely for all mass ratios of Mn: Mo and up to Mo: M mass ratio of 1: 10–1: 100 for the other metals, and reliable absorbance signals of Mo were obtained. The text was submitted by the authors in English.     

Coupling of ultrasonic nebulization to flame furnace atomic absorption spectrometry—new possibilities for trace element determination

The use of ultrasonic nebulization (USN) with desolvation system for sample introduction in flame atomic absorption spectrometry (F AAS) and flame furnace atomic absorption spectrometry (FF AAS) with a nickel tube is described. Polytetrafluorethylene (PTFE) adaptors were built to replace the pneumatic nebulizer for USN-F AAS measurements. For USN-FF AAS analysis, an alumina injector allowed the direct introduction of the dry aerosol into the nickel tube. The analytical performance of both systems is shown for Ag, Bi, Cd, Cr, Cu, Mn, Pb, Sb, Se, Tl and Zn. The results demonstrate that a sensitivity gain of up to 39 times can be achieved using USN-FF AAS, mainly due to the increase in residence time and to the absence of dilution of the analyte by the flame gases, as the atomization takes place inside the nickel tube. However, elements that require higher atomization temperatures, such as Cr and Mn, are more efficiently determined using USN-F AAS. To evaluate the accuracy of the proposed methods for the determination of trace elements, five certified reference samples were analyzed, and good agreement was, in general, achieved between certified and determined values at a 95% confidence level. The relative standard deviation was frequently below 5%, demonstrating good precision, particularly for USN-FF AAS. In this sense, coupling of USN with F AAS and especially with FF AAS has proved to be simple, safe, with high precision and good accuracy, also maintaining some of the most important features of F AAS, such as the high analytical frequency and the low running cost.     

Determination of sulfur by molecular absorption of carbon monosulfide using a high-resolution continuum source absorption spectrometer and an air-acetylene flame

A standard air-acetylene flame, attached to a high-resolution continuum source atomic absorption spectrometer, was used to determine sulfur via measurements of selected rotational lines of carbon monosulfide (CS) formed in the flame. The lines are part of the strong molecular absorption system around 258 nm. Their half-widths in the order of a few picometers are comparable to common atomic lines. The analytical method is characterized by simplicity, rapidity, reliability, and robustness. Potential chemical and spectral interferences were tested using nitric, hydrochloric, perchloric and hydrofluoric acids at concentrations up to 5% (v/v), and solutions of Al, Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, and Pb at concentrations up to 2000 mg L⁻¹. The only serious spectral interference occurred with Pb at concentrations higher than 200 mg L⁻¹, which is due to the formation of lead sulfate in the solution. The limit of detection achieved for sulfur was 2.4 mg L⁻¹, using the CS line at 258.056 nm and a measurement time of 5 s. A linear dynamic range of more than 3 orders of magnitude was obtained. The analytical results were verified by means of standard reference materials, yielding good precision and accuracy.     

Synthesis, characterization and thermal behaviour of solid-state compounds of folates with some bivalent transition metals ions

Solid-state M–L compounds, where M stands for bivalent Mn, Co, Ni, Cu and Zn and L is folate (C₁₉H₁₇N₇O₆)_, have been synthesized. Simultaneous thermogravimetry and differential scanning calorimetry (TG–DSC), X-ray powder diffractometry, infrared spectroscopy (FTIR), TG–DSC coupled to FTIR, elemental analysis and high-resolution continuum source flame atomic absorption spectrometry technique (HR-CS FAAS) were used to characterize and to study the thermal behaviour of these compounds. The results provided information concerning the composition, dehydration, thermal stability and thermal decomposition.     

An integrated approach to the complete chemical analysis of magnesium or sodium diuranate (yellow cake) sample

A procedure for the complete chemical analysis of magnesium or sodium diuranate (yellow cake) sample is reported. Uranium is determined gravimetrically after peroxide precipitation. Optimum parameters, such as pH, quantity of hydrogen peroxide, volume of sample, temperature and complexing agent for quantitave precipitation of uranium, and effective separation of other elements were studied. Aluminum, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, and Zn were determined by flame atomic absorption spectrometer and B, Mo, SO₄, REEs and Y by inductively coupled plasma atomic emission spectrometer in the filtrates of hydroxide and peroxide precipitation separation. The proposed method is accurate and the precision is characterized by an RSD of ~0.2% for U; 2 to 6% for Mg, Na, K, Ca, Fe, SiO₂, Al, Cd, Co, Cr, Fe, Mn, Ni, Pb, and Zn and 3 to7% for REEs, Y, Mo and B     

Direct and simultaneous determination of copper and manganese in seawater with a multielement graphite furnace atomic absorption spectrometer

The direct and simultaneous determinations of Cu and Mn in seawater using a multielement graphite furnace atomic absorption spectrometer (Perkin-Elmer SIMAA6000) are described. Three kinds of chemical modifier (Mg(NO₃)₂, Pd(NO₃)₂ and a mixture of these) were tested. The matrix interferences were removed completely so that a simple calibration curve method could be used to determine Cu and Mn in seawater from the open ocean using Pd or a mixture of Pd and Mg as the chemical modifier. The relative standard deviations (RSDs) for the simultaneous determination of Cu and Mn in seawater from open ocean are 10% or less, and the detection limits were 0.07 μg 1⁻¹ for Cu and 0.10 μg 1⁻¹ for Mn, using Pd as the chemical modifier. The accuracy of the method is confirmed by analysis of four kinds of certified reference saline waters.