Flameless Atomic Absorption Determination of Volatile Hydrides Using Cold Trap Collection

Abstract

The hydrides of arsenic, antimony, bismuth, and selenium are collected in a liquid nitrogen cold trap and then volatilized into either an argon-entrained air-hydrogen flame or into a Perkin-Elmer HGA-2000 Graphite Furnace for atomic absorption measurement. Flameless atomization results in approximately ten-fold lower detection limits. The sensitivities and detection limits in nanograms are, respectively, 1.0 and 0.2 for arsenic, 5.6 and 1 for antimony, 2.0 and 1 for bismuth, and 40 and 10 for selenium.     

Statistical Reexamination of Some Interference Patterns in the Determination of Calcium in Wheat (Triticum) by Atomic Absorption Spectrophotometry in an Air/Acetylene Flame

Abstract

The paper aims to statistically reexamine some interfereces that appear in the analysis of calcium by flame atomic absorption spectrophotometry in wheat (Triticum) sample, in the first vegetation stage.

The statistical study shows that in the air/acetylene flame for ourtype of samples the interference due to phosphorus is not significant (r²=0.19). A strong significant interference is due to the presence of Kjeldahl -, and nitrate-nitrogen in the original sample (R²=0.7869).

A multiple regression equation was calculated which allows the estimation of the masked amount of calcium, which makes un necessary the addition of a releasing agent, or the use of the N₂O-C₂H₂ flame for the elimination of interferences.     

Interferences in hydride atomization studied by atomic absorption and atomic fluorescence spectrometry

A hydride atomizer able to operate in the flame-in-tube mode and in the miniature diffusion flame mode was used to investigate interferences of arsenic in selenium atomization. A twin-channel continuous flow hydride generator was utilized to eliminate liquid phase interferences. Both atomic absorption and atomic fluorescence detectors (EDL sources) were employed. The miniature diffusion flame can tolerate interferent concentrations up to 70 μg ml⁻¹. The magnitude of interferences in the flame-in-tube atomizer is controlled by the distance between the atomization and detection zones. The best tolerance to interferents, comparable with that in the miniature diffusion flame, was obtained for the minimum distance of the zones. The figures were deteriorated by two orders of magnitude when increasing the distance between the observation and the atomization zones to 50 mm. Also a curvature and rollover of calibration graphs was observed when increasing the distance. The presence of the interferent enhanced substantially the curvature and rollover, so that the magnitude of observed interferences was dependent on the analyte concentration. All the observed interferences and the calibration graph curvature are due to the decay of free analyte atoms by reactions in the free space. The nature of the species formed is discussed. No significant depletion of hydrogen radicals was observed. As demonstrated by measurements in the miniature diffusion flame, the species formed can be reatomized by interaction with hydrogen radicals with an efficiency better than 90%.     

Determination of Selenium in Natural Waters Using the Centrifugal Photometric Analyzer

Abstract

A rapid ion exchange separation converts the methylene blue spot test for selenium into a selective and sensitive method for quantitative determination of trace quantities of selenium. Increased speed, accuracy, and reproducibility is achieved because of the parallel analysis technique of the centrifugal photometric analyzer (GeMSAEC Fast Analyzer). Natural water samples, spiked with 0.10 to 0.5 μg of selenium, were analyzed with an average accuracy of 4.2 % after removal of interferences by ion exchange.     

Improved Determination of Aluminum in Serum by Electrothermal Atomic Absorption Spectrometry and Zeeman Background Correction

Abstract

A simple but reliable method for the determination of aluminum in serum by flameless atomic absorption spectrometry is described. By use of the Zeeman background correction, the interferences are eliminated. However, considering the numerous possible sources of contamination, extreme precautions are necessary both when taking and storing the serum. The procedures preceding the dosage per se must be minimized. The within-day and clay-to-day precision data (CV %) was 3.28 and 3.82 respectively. The average recovery for aluminum was 97.5 %. We used this method on serum from 30 healthy subjects and from 300 patients on hemodialysis. The mean aluminum concentration for the healthy subjects was 5.35 μg/l (SD ± 0.53) while the values for the hemodialyzed patients ranged from 20 to 220 μg/l.     

Determination of Selenium (IV) in Biological Sample by Cathodic Stripping Voltammetry

Abstract

The determination of selenium (IV) in biological sample using cathodic stripping voltammetry is reported. It was found possible to determine selenium directly in biological samples containing such metals as zinc (II), lead (II), iron (III), arsenic (III) and magnesium (II). The results for selenium in bovine liver are reported.     

Enhancement of Sensitivity for Selenium Determination in Atomic Absorption Spectrophotometry by Introducting Hydrogen Selenide into an Argon-Hydrogen Flame

Abstract

The sensitivity for selenium determination with atomic absorption spectrophotometry is enhanced to a large extent by introducing hydrogen selenide gas into an argon-hydrogen flame. As a reducing agent, zinc granular and stannous chloride is successfully used for quantitative and rapid productions of hydrogen selenide from selenium(IV) solution. The sensitivity for 1 % absorption of the signal is estimated to be about 0.02 ppm of selenium.     

Ion-Exchange Method for Analysis of Four Arsenic Species and its Application to Tap Water Analysis

Abstract

Arsenic (III), arsenic (V), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) were separated by ion-exchange chromatography. The elution sequence was as follows: 1.5 M ammonia followed by 0.12 M hydrochloric acid yielding As(III); 1 M hydrochloric acid followed by water yielding first As(V) and then MMA. Detection was performed by hydride generation-atomic absorption spectrometry.

The possible interferences of 13 metallic ions have been studied and none of them was found to interfere.

The method provides good linearity, precision, accuracy, and sensitivity. It has been applied to the speciation of arsenic in tap water samples from North West of Spain (a region about 29500 Km²).     

Determination of Arsenic in Organic Compounds and Other Matrices by Flame Emission Spectrometry

Abstract

A direct and simple method for arsenic in organic compounds involves merely dissolution of the sample in an organic solvent, such as benzene, cyclohexane, or methyl isobutyl ketone, and direct aspiration into a fuel-rich acetylene-oxygen flame. The arsenic line at 2350 Å is used; the detection limit is 2.2 ü/ml. From iron and copper matrices arsenic is isolated by extraction from a solution 9 M in HCI and 0.25 M in KI with benzene.     

Atomic Absorption Spectrophotometry of Chromium Using an Enhancing Effect of Sodium Dodecyl Sulfate

Abstract

In the atomic absorption spectrophotometry of chromium with the air-acetylene flame, the absorption of chromium was increased by about 120% in the presence of sodium dodecyl sulfate (SDS) above the critical micelle concentration (CMC). This phenomenon was applied to overcoming interferences from many coexisting cations and some acids.     

Utilization of Dual Phase Gas Diffusion FIA with a Mass Spectrometer as a Detector

Abstract

The coupling of dual phase gas diffusion flow injection analysis with mass spectrometry has been shown to be feasible. This combined technique offers a high degree of selectivity and sensitivity. This technique was developed to determine whether volatile mixed arsenic selenium hydrides are formed in dual phase gas diffusion flow injection analysis hydride generation.     

Reduction of effects of structured non-specific absorption in the determination of arsenic and selenium by electrothermal atomic absorption spectrometry

The presence of iron and phosphates in biological matrices causes deuterium arc background-correction systems to overcompensate at several arsenic and selenium resonance lines. The addition of platinum as matrix modifier has a significant effect on both the absorbance/time profile of iron and the formation of gaseous phosphate decomposition products. A nickel/platinum matrix modifier is shown effectively to control the problems in the determination of selenium arising both from thermal instability and spectral interferences. The same combination eliminates the spectral interferences found at the arsenic resonance lines. Remaining problems are the thermal stabilization of organometallic arsenic compounds present in biological samples. When radioactived-labelled ⁷⁴As compounds prepared in vivo were applied, none of the tested matrix modifiers (Ni, Cu, Ag, Pd, Zr, Ce, Ce + magnesium nitrate) showed a significant influence on the volatility of arsenic in whole blood and urine from rats.     

Determination of microgram amounts of arsenic in geological materials and waters by wavelength-dispersive x-ray fluorescence spectrometry

Microgram quantities of arsenic are determined in geological materials or water samples by coprecipitating the analyte with elemental selenium and using x-ray fluorescence directly on the precipitate. The coprecipitation step removes elemental interferences and converts the sample to a thin film. The selenium matrix enhances the fluorescent emission of arsenic which enables 0.2 μg g^?1 to be determined. The method is applied to a series of geological reference materials and a seawater sample.     

Automated Determination of Arsenic,Selenium, Antimony,Bismuth and Tin by Atomic Absorption Utilizing Sodium Borohydride Reduction

Abstract

An automated system for the determination of arsenic, selenium, antimony, bismuth and tin is described. These elements and their compounds are reduced with sodium borohydride to the corresponding hydride. Sensitivity of the automated system is comparable and in most cases better than the manual technique. The automated method was found superior to the manual with respect to reproducibility and ease of operation.     

Analytical Evaluation of the Silver Sulfide Membrane Electrode

Abstract

A membrane electrode selective for sulfide and silver ion has been described. No interferences were found for sulfide ion measurements, and only mercuric ion had a measurable interference with silver ion. Other characteristics of this electrode which are evaluated include speed of response and temperature coefficients. The use of the silver sulfide membrane electrode as an end-point detector in potentiometric titrations under oxidizing conditions is illustrated.     

Flame Emission Spectroscopy of Aqueous and Nonaqueous Solutions in the Nitrous Oxide-Acetylene Flame

Abstract

The relative emission intensities and detection limits for 183 lines and bands of 52 elements in the nitrous oxide-acetylene flame have been determined. Linearity of the emission intensity with concentration was investigated and detection limits of the elements in 80 percent acetone were also obtained and compared with those of aqueous solutions. Emission was observed for all the elements in acetone solution, and only selenium did not give a measureable emission in aqueous solution.     

Method for Determination of Selenium and Arsenic in Human Urine by Atomic Fluorescence Spectrometry

Abstract

The study presents the method for simultaneous determination of selenium and arsenic in human urine by atomic fluorescence spectrometry (AFS). According to the procedure developed, a sample is first digested in the microwave system, then chemically treated in the flow through a hydride generation system, and finally exposed to measurements in a double‐channel atomic fluorescence spectrometer. It has been revealed that selenium and arsenic can be accurately determined with detection limit of 0.13 and 0.16 µg/L and repeatability (RSD) of 1.0 and 1.2%, respectively. The urine samples taken from a control group and from persons subjected to a special diet were analyzed. The obtained results proved that the method developed was capable of controlling reliably even slight changes of both elements in a wide range of their concentrations, and, as such, that it can be recommended to be used for clinical and toxicological purposes.     

Development of sensitive GC-AAS instrumentation for analysis of organometallic species in the environment

Abstract

Atomic absorption spectrometry provides a highly sensitive element-specific detection system for organometallic species preseparated by gas chromatography. Both flame and flameless atomisation systems have been used and high sensitivity attained with elements such as Sn, Pb and As. Non-ionic alkyl or hydride species which are G.C.-volatile may be analysed directly, whilst ionic species generally require conversion to a hydride or a butylated form prior to analysis.

The development of a G.C.-A.A.S. interface will be described, together with the optimisation of an A.A.S. detector based upon a hydrogen diffusion flame, which is sensitive to picogram levels of organometallic compounds. The G.C.-A.A.S. equipment has been further interfaced with a two-stage thermal desorption system for analysis of vapours collected on polymeric absorbents. The application of the system to the analysis of organometallic species of Pb in a variety of environmental media will also be described.     

Flame Atomic Absorption Spectrometry Assay for Copper Determination in Pharmaceutical Products for Veterinary Use

Abstract

The scope of the present study is to quantify copper in pharmaceutical products of veterinary use, using flame atomic absorption spectometry (f_AAS). The determination is carried out after samples' mineralization in a HCl:HNO₃ (20∶1, v:v) mixture followed by the instrument quantification and the validation of the result. The validation indicates that the interferences from the whole analytical system and their measurement do not influence the results and ensure that there are no other effects which have not been considered.     

Organic solvents as interferents in arsenic determination by hydride generation atomic absorption spectrometry with flame atomization

Interference effects of various organic solvents miscible with water on arsenic determination by hydride generation atomic absorption spectrometry have been studied. Arsine was chemically generated in continuous flow hydride generation system and atomized by using a flame atomizer able to operate in two modes: miniature diffusion flame and flame-in-flame. The effects of experimental variables and atomization mode were investigated: tetrahydroborate and hydrochloric acid concentrations, argon, hydrogen and oxygen supply rates for the microflame, and the distance from the atomization region to the observation zone. The nature of the species formed in the flame due to the pyrolysis of organic solvent vapors entering the flame volume together with arsine is discussed. The observed signal depression in the presence of organic solvents has been mainly attributed to the atomization interference due to heterogeneous gas–solid reaction between the free arsenic atoms and finely dispersed carbon particles formed by carbon radicals recombination. The best tolerance to interferences was obtained by using flame-in-flame atomization (5–10 ml min^− 1 of oxygen flow rate), together with higher argon and hydrogen supply rates and elevated observation heights.