Non-dispersive atomic-fluorescence spectrometric determination of lead by the hydride-generation technique

Non-dispersive atomic-fluorescence spectrometry combined with hydride-generation has been developed for lead determination. A radiofrequency-excited electrodeless discharge lamp was used as light-source and a small argon-hydrogen flame as atomizer. The detection limit was 0.06ng/ml and the linear calibration graph was linear up 300ng/ml, with a precision of 5-6% over the dynamic range. Interference studies and optimization of the experimental parameters are reported. Severe suppression of the lead signal was observed in presence of Cu, Se or Te. An empirical equation was obtained for predicting the effect of copper on the lead signal at various concentration ratios. The strong effect of complexing agents such as EDTA was removed by addition of zinc salts.     

Determination of ultratrace bismuth in milk samples by atomic fluorescence spectrometry

A sensitive procedure was developed for determination of bismuth (Bi) in milk samples by hydride generation atomic fluorescence spectrometry (HG-AFS) after microwave-assisted sample digestion with HNO3 and H2O2. The method provides a sensitivity of 1832 fluorescence units (ng/mL) with a detection limit of 0.01 ng/mL, which corresponds to 20 pg absolute limit of detection, equivalent to 0.50 ng/g in the original sample. Application of the methodology to cow milk samples from the Spanish market showed the presence of Bi at a concentration of 11.8-28.8 ng/g, which compared well with data obtained after dry ashing of samples and with data obtained by inductively coupled plasma-mass spectrometry after microwave-assisted digestion.     

Spectroscopy in separated flames-IV: application of the nitrogen-separated air-acetylene flame in flame-emission and atomic-fluorescence spectroscopy

The primary and secondary combination zones of an air-acetylene flame have been separated by a stream of nitrogen flowing parallel to the flame to prevent access of atmospheric oxygen to its base. The flame is very stable over a wide range of fuel-air mixture strengths, and organic solvents may be aspirated without difficulty. The low flame background enables thermal-emission and atomic-fluorescence measurements to be made with high sensitivity. Bismuth, for example, has been determined in the range 5-200 ppm by its thermal emission at 306.8 nm, with a detection limit of 2 ppm in aqueous solution, and in the range 1-10 ppm with a detection limit of 0.3 ppm in 50% ethanolic solution. Zinc and cadmium have been determined at 213.9 nm and 228.8 nm by atomic-fluorescence spectroscopy in this flame with detection limits of 2 x 10(-4) ppm and 5 x 10(-4) ppm respectively, vapour-discharge lamps being used as sources of excitation. The results obtained represent a considerable improvement over those available by the same methods in a conventional air-acetylene flame.     

Hydride generation atomic absorption spectrometric determination of bismuth after separation and preconcentration with modified alumina

A simple and sensitive method has been developed for the trace determination of bismuth in aqueous samples by a combination of solid‐phase extraction and hydride generation atomic absorption spectrometry. The method is based on the use of a column packed with 2‐mercaptobenzothiazole immobilized on sodium dodecyl sulfate coated alumina. Different parameters influencing the separation and preconcentration of bismuth such as pH, sample volume, type, and concentration of eluent, and the flow rate of sample and eluent were studied. A sample volume of 500.0 mL resulted in a preconcentration factor of 100. The precision (relative standard deviation, N = 10) at the 300 ng/L level and the limit of detection (3s) were found to be 2.3% and 12 ng/L, respectively. The developed method was successfully applied to the determination of bismuth in natural water samples and two certified reference materials.     

On-line preconcentration system for bismuth determination in urine by flow injection hydride generation inductively coupled plasma atomic emission spectrometry

An on-line bismuth preconcentration and determination system implemented with hydride generation inductively coupled plasma atomic emission spectrometry (HG-ICP-AES) associated to flow injection (FI) was studied. Quinolin-8-ol and Amberlite XAD-7 were used for the retention of bismuth, at pH 4.5. The bismuth complex was removed from the micro-column with nitric acid. The detection limit value for the preconcentration of 100 ml of aqueous solution was 0.02 ng ml(-1) with a relative standard deviation (R.S.D.) of 3.5%, calculated from the peak heights obtained. The calibration graph using the preconcentration system for bismuth was linear with a correlation coefficient of 0.999 at levels near the detection limits up to at least 100 ng ml(-1). The method was successfully applied to the determination of bismuth in human urine samples.     

Atomic-fluorescence characteristics and analytical determination of manganese in an air-acetylene flame

The atomic-fluorescence characteristics of manganese atoms in a premixed nitrogen-shielded air-acetylene flame are described. Excitation is obtained at 280 nm from a microwave-excited electrodeless discharge tube. A detection limit of 0-001 ppm for the determination of manganese by atomic-fluorescence spectroscopy is obtained by measurement of the resonance fluorescence observed at this wavelength. In addition to several other weaker atomic-fluorescence signals observed from manganese atoms in the flame, weak resonance fluorescence at 258 and 260 nm from manganese ions stimulated by ion line-emission from the source has been recorded. Linear calibration graphs for atomic-fluorescence measurement at 280 nm are obtained over the range 0.0025-10 ppm of manganese in aqueous solution. Of 26 foreign anions and cations examined for interference at the 1000-fold weight excess level only four produced interference. Large amounts of Si, Th and V interfere by scattering of the incident radiation, while Mg causes depression of the atomic fluorescence by a chemical effect.     

氢化物发生-原子荧光光谱法测定钢铁中的痕量铋

采用氢化物发生-原子荧光光谱法测定钢铁中的痕量铋。考察了观察高度、负高压、灯电流、载气流速、屏蔽气流速、介质酸度、载流酸度和硼氢化钾浓度等因素对测定结果的的影响,并优化了测定条件,研究了钢铁材料中常见元素对铋测定的影响。结果表明,用硫脲和抗坏血酸作抑制剂可以消除大量元素的干扰。铋浓度在0～100ng/mL与荧光强度呈良好的线性关系,方法的检出限为0.187ng/g。对20ng/mL的铋标准溶液平行测定10次,相对标准偏差为2.5%。用该方法对国家标准钢样品进行了测定,测定结果与标准值相符合。     

Determination of trace bismuth by flow injection-hydride generation collection-atomic absorption spectrometry

Bismuth hydride gas was collected on-line and determined via a new flow injection-hydride generation collection-flame atomic absorption spectrometry system. The performance of the gas-liquid separator, hydride gas collection time, acidity of the sample solution, NaBH(4) concentration, and the effects of concomitant interferents were investigated to optimize the conditions of this new method. Interferences from concomitant elements were investigated, and recoveries of 94.7-105.3% for 10 ng mL(-1) Bi were obtained after the addition of 0.2% ascorbic acid-thiourea masking reagents. The sensitivity of this new method was one order of magnitude higher than the continuous flow-hydride generation-flame atomic absorption method with a detection limit of 0.25 ng mL(-1) and a precision of 2.3%. The method was evaluated by determining trace bismuth in standard biological reference material human hair GBW07601, and the results were consistent with the certified value. The proposed method was then employed to determine trace bismuth in ten colored gelatin samples; recoveries of 94.2-105.8% were obtained.     

氢化物发生电加热石英管原子吸收法测定包头铁矿中的砷、锑、铋

研究了氢化物发生原子吸收法测定包头矿中痕量砷、锑、铋的分析方法,试验确立了反应条件,建立了以KI、抗坏血酸、硫脲为还原体系,消除试样中共存元素的干扰,利用KMnO4消除锑对砷的干扰.砷、锑、铋的检出限可分别达到:0.15,0.28,0.15 ng/mL.方法已用于包头矿分析.     

Determination of zinc in copper by atomic-fluorescence flame spectroscopy

The application of atomic-fluorescence flame spectroscopy to the determination of trace quantities of zinc in copper is described. A limit of detection of 10(-5)% zinc in copper has been established. The scatter of primary radiation from within the flame determined the limit of detection, but it is suggested that scatter is not a serious limitation to the practical application of the technique.     

Improvements in the non-dispersive atomic fluorescence spectrometric determination of arsenic and antimony by a hydride generation technique

A sodium borohydride reduction, with subsequent atomization in a small argon—hydrogen—entrained air flame has been developed for the determination of arsenic and antimony by non-dispersive atomic fluorescence spectrometry. The proposed method increases the signal level and decreases the noise level in the system. The detection limits for arsenic and antimony are 0.05 ng and 0.1 ng, respectively. The analytical working curves are linear over about four decades of concentration from the detection limits. The consumption rates of hydrogen and argon are comparatively low, while the speed of hydride evolution is improved; a peak measurement requires less than 40 s. The technique has been applied to the determination of arsenic in steel samples.     

Determination of bismuth in nickel-base alloys by atomic absorption spectrometry with introduction of solid samples into an induction furnace

Atomic absorption spectrometry with an induction furnace is applicable'to the determination of bismuth at 0.02–10 μg g^-1 levels in 1–30-mg samples of nickel-base alloys dropped into the furnace. Calibration graphs of peak absorbance versus mass of bismuth are constructed by use of standardised alloys. Samples of alloys can be added to the furnace at 2.5-min intervals. Calibration graphs, accuracy, precision and limits of detection of the method are discussed for 26 alloys. Accuracy is assessed by comparing the induction furnace results with results supplied with the alloys, and with results obtained for solutions of the alloys by atomic absorption spectrometry in association with hydride generation or a mini-Massmann furnace. With alloys containing more than 0.1 μg Bi g^-1, relative standard deviations by the induction furnace method are usually < 15%. The limit of detection for bismuth is 0.02 μg g^-1     

HPLC Coupled with in-line photolysis, hydride generation and flame atomic-absorption spectrometry for the speciation of tin in natural waters

The use of an in-line photolysis coil in a continuous-flow system of high-performance liquid chromatography coupled with hydride generation and flame atomic-absorption spectrometry for the speciation of tin in natural waters is described. Irradiation with ultraviolet light is shown to convert tributyltin into organic tin(IV), from which a volatile hydride can be produced in the conventional way. The effect of various conditions on the analytical performance is discussed. A detection limit of 2 ng for tin was obtained, and the tin species could be completely separated within 6 min. Use of the technique for quantification of tributyltin compounds in local coastal waters is described.     

Optimization of dimethyltin chloride determination by hydride generation gas phase molecular absorption spectrometry using a central composite design

A factorial design is applied to the optimization of the determination of dimethyltin chloride by hydride generation gas phase molecular absorption spectrometry (HG-GPMAS). A method is described for the determination of dimethyltin chloride after conversion into gaseous dimethyltin hydride by adding a sodium tetrahydroborate (III) solution. The hydride generated is collected in a liquid nitrogen cryogenic trap. This is revolatilized, driven to the quartz flow cell and measured with gas phase molecular absorption spectrometry (GPMAS) with diode array detection. A Plackett-Burmann design is used for the study of the factors that influence the absorption signal. The optimization of these factors is performed using a central composite design. The spectra obtained over a wide range of wavelengths, 190-220 nm, allow the multivariate calibration to be studied. The parameters affecting the production and collection of the dimethyltin hydride are studied. The detection limit obtained is 3.2 ng ml(-1). The precision (RSD=4.1%) is calculated from a solution containing ten times the corresponding detection limit. The recoveries (99-108%) are satisfactory. A study is made of the influence of several interferent ions (hydride generators, transition metals and anions) in the presence of dimethyltin chloride.     

The determination of tellurium by nondispersive atomic fluorescence spectrometry using the hydride generation technique

Atomic fluorescence spectrometry with a nondispersive measuring system is combined with a hydride generation technique for the determination of tellurium. Atomic fluorescence measurement is based on the reduction of tellurium by either metallic zinc or sodium borohydride, introduction of the generated tellurium hydride into a premixed argon (entrained air)-hydrogen flame, and excitation with a tellurium electrodeless discharge lamp. The comparison of the zinc and the sodium borohydride reduction methods is discussed in terms of detection limit, precision and interference. The best attainable detection limits for tellurium are 2ng (0.1 $\text{ng}\text{ml}$) and 30 ng (1.5 $\text{ng}\text{ml}$) with the zinc and the sodium borohydride methods respectively. Analytical working curves obtained from peak-height and peak-area measurements are linear over a range of approximately 4 orders of magnitude. Of the mineral acids examined in the range up to 2.0 m. nitric acid gives a depressing interference in the range greater than 0.5 m in the zinc method, whereas all of the acids greater than 1.0 m give a slight enhancement of the signal in the sodium borohydride method. The presence of several elements including other hydride-forming elements in 1000-fold ratio to tellurium causes a depressing interference, while enhancing interferences from tungsten and vanadium are observed in the zinc and the sodium borohydride methods, respectively. The present system coupled with the zinc method has been applied to the determination of tellurium in several samples of high-purity copper metal after separation of the analyte from copper by passing an ammoniacal solution of the sample through Chelex-100 resin. The results are in good agreement with those obtained by graphite furnace atomic absorption spectrometry.     

Determination of bismuth in metallurgical materials using a quartz tube atomizer with tungsten coil and flow injection-hydride-generation atomic absorption spectrometry

A method for the determination of bismuth in metallurgical materials using hydride generation coupled with a merging zones flow system and atomic absorption spectrometry using a quartz tube atomizer with tungsten coil is proposed. The parameters related to the bismuthine generation, the flow injection system and the use of a tungsten coil were studied and the optimized system shows a wide calibration range and good stability over time, without losses in sensitivity. The analytical curve is linear from 10 to 750 μg l⁻¹ of Bi with R0.999. A detection limit of 1.9 ng Bi and an analytical frequency of 60 determinations per hour were obtained. Five metallurgical reference materials were analyzed with the proposed method after their acid dissolution. The results obtained were in good agreement with certified or recommended values, and the relative standard deviations were lower than 5%.     

Studies in atomic-fluorescence spectroscopy-VII Fluorescence and analytical characteristics of arsenic, with a microwave excited electrodeless discharge tube as source

The construction of an electrodeless arsenic discharge tube and its use for atomic-fluorescence studies is described. Cool nitrogen-hydrogen and argon-hydrogen diffusion flames as well as normal premixed flames are considered as atom reservoirs and the atomic-fluorescence emission at 15 different wavelengths is evaluated. The diffusion flames give the largest emission signals at arsenic concentrations below 200 ppm, but show a premature curvature at higher concentrations because of the presence of an abnormally high density of arsenic atoms. Above 200 ppm of arsenic, the premixed air-acetylene flame is superior. The limit of detection at 1890 A is 0.2 ppm of arsenic in the nitrogen-hydrogen diffusion flame and 1.0 ppm in the airacetylene flame. A long path-length diffusion flame is also particularly useful in atomic-absorption measurements because it absorbs very little radiation in the far ultraviolet region and gives an abundance of arsenic atoms.     

Hydride Generation Graphite Furnace Atomic Absorption Determination of Bismuth in Clinical Samples with in Situ Preconcentration

A sensitive method for the determination of bismuth in clinical samples using hydride generation/trapping and atomization in a graphite furnace is described. Addition of Pd-Ir to the furnace tube surface before hydride trapping leads to great improvement in the sensitivity of the method. Calibration is achieved with simple aqueous standards carried through this same procedure. An absolute detection limit (3σ) of 100 pg and a concentration detection limit of 20 ng/liter are obtained using 5-ml sample volumes. Corresponding precisions of 8-12% are typical for analyses of these samples. Microwave-assisted sample digestion procedures using HNO₃ and H₂O₂ were used to decompose clinical materials. The method was used to determine Bi in human blood, serum, urine, and tissue before and after intake of therapeutic doses of colloidal bismuth citrate.     

Simultaneous determination of bismuth and tellurium in steels by high power nitrogen microwave induced plasma atomic emission spectrometry coupled with the hydride generation technique

An annular-shaped, high power nitrogen microwave induced plasma (N₂-MIP) produced at atmospheric pressure by an Okamoto cavity, as a new excitation source for atomic emission spectrometry (AES), has been used for the simultaneous determination of bismuth and tellurium in steels with the hydride generation method. Under the optimized experimental conditions, the best attainable detection limits at the Bi I 195.389 nm and Te I 200.200 nm lines were 110 and 86 ng/ml for bismuth and tellurium, respectively. The linear dynamic ranges for bismuth and tellurium were 300 to 30,000 ng/ml. The presence of several diverse elements was found to cause a more or less depressing interference with the proposed technique. When bismuth and tellurium in steels were determined, a large amount of Fe(III) in the solution caused a severe depressing interference, while the presence of Fe(II) showed little or no significant interference. Of the several interference-releasing agents examined, l-ascorbic acid was found to be the most preferable to reduce Fe(III) to Fe(II) prior to hydride generation. The concentrations of bismuth and tellurium in steels were determined by the proposed technique. The results obtained by this method were in good agreement with their certified values.     

Studies in atomic-fluorescence spectroscopy-VI The fluorescence characteristics and analytical determination of bismuth with an iodine electrodeless discharge tube as source

The atomic-fluorescence characteristics of bismuth atoms in cool nitrogen-hydrogen and argon-hydrogen diffusion flames burning in air are described. Excitation is obtained from the non-resonance iodine line at 2061.63 Å emitted by a microwave-excited electrodeless discharge tube operating at 2450 Mc/s. Fluorescence of the bismuth resonance line at 2061.70 Å is observed and also direct-line fluorescence at 2697 and 3025 A. In addition thirteen other much weaker lines were observed and two unidentified lines at 2880 and 2680 Å. The emissions at 2628 and 2938 Å appear to arise from “thermally assisted direct line fluorescence”. The most intense line at 3025 Å permits linear-dependence analytical atomic-fluorescence measurements to be made in the range 0.1–200 ppm with a detection limit of 0.05 ppm and with no problems of source scatter. No interference was observed from hundred-fold concentrations of fourteen ions. Matrix effects from aluminium and magnesium were overcome by raising the temperature of the cool diffusion flames. A bismuth microwave-excited electrodeless discharge tube was used as a source for atomic-absorption measurement in air-hydrogen and air-propane flames at 2231Å with a detection limit of 1 ppm and a linear-dependence analytical range of 10–100 ppm. With the iodine microwave-excited electrodeless discharge tube the detection limit for atomic absorption was 10 ppm at 2062 Å.