Determination of vanadium and titanium in steel by inductively coupled plasma atomic emission spectrometry with modified use of a tungsten boat furnace atomizer for atomic absorption spectrometry

For electrothermal sample introduction, a commercially available tungsten boat atomizer for atomic absorption spectrometry (AAS) was transferred to a vaporizer for inductively coupled plasma atomic emission spectrometry (ICP-AES). The modification retained as much of the original design of the atomizer as possible, so that the apparatus could be switched easily between conventional tungsten boat furnace (TBF)-AAS and TBF-ICP-AES. By using this system, a procedure for the determination of vanadium and titanium in steel was investigated. The detection limits (S/N=3) of vanadium and titanium were 3.9 and 1.5 ng ml^?1, respectively. The relative standard deviations for five replicate determinations were ca. 3% for both elements. The calibration graphs were linear up to 100 μg ml^?1 vanadium(V) and 10 μg ml^?1 titanium(IV). Results of analyses of some low-alloy steel samples are given.     

An efficient flow-injection system with on-line ion-exchange preconcentration for the determination of trace amounts of heavy metals by atomic absorption spectrometry

A flow-injection system with on-line ion-exchange preconcentration on dual columns is described for the determination of trace amounts of heavy metals at μg l^?1 and sub-μg l^?1 levels by flame atomic absorption spectrometry. The degree of preconcentration ranges from 50- to 105-fold for different elements at a sampling frequency of 60 s h^?1. The detection limits for Cu, Zn, Pb and Cd are 0.07, 0.03, 0.5, and 0.05 μg l^?1, respectively. Relative standard deviations were 1.2–3.2% at μg l^?1 levels. The behaviour of the different chelating exchangers used was studied with respect to their preconcentration characteristics, with special emphasis on interferences encountered in the analysis of sea water.     

Improved cesium sensitivity in electrothermal atomic absorption spectrometry

The sensitivity for cesium determination by electrothermal atomic absorption spectrometry is improved four-fold by the addition of a large excess of potassium nitrate. Zeeman background corrections is used to compensate for the large non-specific absorption signal resulting from the potassium. The characteristic concentration and detection limit are 0.44 and 2 μg l^?1, respectively, and the coefficient of variation is 2% at the 50 μg l^?1 level. The procedure is suitable for the rapid determination of cesium in leach solutions from nuclear waste fixation experiments.     

Simultaneous determination of cadmium and lead in wine by electrothermal atomic absorption spectrometry

A method has been developed for the direct simultaneous determination of Cd and Pb in white and red wine by electrothermal atomic absorption spectrometry (ET-AAS) using a transversely heated graphite tube atomizer (THGA) with longitudinal Zeeman-effect background correction. The thermal behavior of both analytes during pyrolysis and atomization stages were investigated in 0.028 mol l⁻¹ HNO₃ and in 1+1 v/v diluted wine using mixtures of Pd(NO₃)₂+Mg(NO₃)₂ and NH₄H₂PO₄+Mg(NO₃)₂ as chemical modifiers. With 5 μg Pd+3 μg Mg as the modifiers and a two-step pyrolysis (10 s at 400°C and 10 s at 600°C), the formation of carbonaceous residues inside the atomizer was avoided. For 20 μl of sample (wine+0.056 mol l⁻¹ HNO₃, 1+1, v/v) dispensed into the graphite tube, analytical curves in the 0.10–1.0 μg l⁻¹ Cd and 5.0–50 μg l⁻¹ Pb ranges were established. The characteristic mass was approximately 0.6 pg for Cd and 33 pg for Pb, and the lifetime of the tube was approximately 400 firings. The limits of detection (LOD) based on integrated absorbance (0.03 μg l⁻¹ for Cd, 0.8 μg l⁻¹ for Pb) exceeded the requirements of Brazilian Food Regulations (decree #55871 from Health Department), which establish the maximum permissible level for Cd at 200 μg l⁻¹ and for Pb at 500 μg l⁻¹. The relative standard deviations (n=12) were typically <8% for Cd and <6% for Pb. The recoveries of Cd and Pb added to wine samples varied from 88 to 107% and 93 to 103%, respectively. The accuracy of the direct determination of Cd and Pb was checked for 10 table wines by comparing the results with those obtained for digested wine using single-element ET-AAS, which were in agreement at the 95% confidence level.     

Preconcentration and determination of trace chromium(III) by flow injection/inductively-coupled plasma/atomic emission spectrometry

A manifold incorporation an activated alumina (basic form) minicolumn is used to preconcentrate chromium(III), which is then eluted with 2 M nitric acid for detection. Calibration is linear up to 1000 μg l^? Cr, and the limit of detection for a 10-ml sample is 0.05 μg l^?1. The determination of chromium(III) in human urine is discussed.     

Determination of vanadium in urine by electrothermal atomic absorption spectrometry

After wet ashing of the urine sample with nitric acid, vanadium is chelated with cupferron, extracted into 4-methylpentan-2-one and determined by atomic absorption spectrometry with a pyrolytically-coated graphite furnace atomizer. The sensitivity allows the precise determination of 1–500 μg V l^-1 in urine. The coefficient of variation for triplicate urine measurements is <8% for 10 μg V l^-1.     

Determination of molybdenum in infant formula and human milk by electrothermal atomic absorption spectrometry with barium difluoride as matrix modifier

A method for the determination of molybdenum in infant formula and human milk by electrothermal atomic absorption spectrometry was developed and optimized. Samples were injected directly in the graphite tube with barium difluoride as the matrix modifier. The detection limit was 0.89 μg Mo l^?1. The molybdenum levels found in infant formula and human milk were 0.09–2.23 μg Mo g^?1 and 2.32–8.38 μg Mo l^?1, respectively.     

Rapid determination of copper,nickel, lead and cadmium in small samples of estuarine and coastal waters by liquid/liquid extraction and electrothermal atomic absorption spectrometry

A rapid liquid/liquid extraction of 1.25-ml samples is used with graphite-furnace atomic absorption spectrometry for the determination of dissolved trace metals in saline waters. The metals are chelated with ammonium pyrrolidine dithiocarbamate and extracted into 1,1,1-trichloroethane; 20–40 μl of extract is injected into the furnace. Sample manipulation and overall time are greatly decreased compared to other similar large-scale extraction methods; all the chemical steps are done in the sample cups of an auto-sampler for graphite-furnace a.a.s. Detection limits (Cu 0.3 μg l^?1, Cd 0.02 μg l^?1, Pb 0.7 μg l^?1, Ni 0.5 μg l^?1 are low enough for applications in routine monitoring of filterable trace metal concentrations in coastal and estuarine waters to check for compliance with Environmental Quality Standards that apply in the European Community.     

Determination of total tin in silicate rocks by graphite furnace atomic absorption spectrometry

A method is described for the determination of total tin in silicate rocks utilizing a graphite furnace atomic absorption spectrometer with a stabilized-temperature platform furnace and Zeeman-effect background correction. The sample is decomposed by lithium metaborate fusion (3 + 1) in graphite crucibles with the melt being dissolved in 7.5% hydrochloric acid. Tin extractions (4 + 1 or 8 + 1) are executed on portions of the acid solutions using a 4% solution of trioctylphosphine oxide in methyl isobutyl ketone (MIBK). Ascorbic acid is added as a reducing agent prior to extraction. A solution of diammonium hydrogenphosphate and magnesium nitrate is used as a matrix modifier in the graphite furnace determination. The limit of detection is > 10 pg, equivalent to > 1 μg l^?1 of tin in the MIBK solution or 0.2–0.3 μg g^?1 in the rock. The concentration range is linear between 2.5 and 500 μg l^?1 tin in solution. The precision, measured as relative standard deviation, is < 20% at the 2.5 μg l^?1 level and < 7% at the 10–30 μg l^?1 level of tin. Excellent agreement with recommended literature values was found when the method was applied to the international silicate rock standards BCR-1, PCC-1, GSP-1, AGV-1, STM-1, JGb-1 and Mica-Fe. Application was made to the determination of tin in geological core samples with total tin concentrations of the order of 1 μg g^?1 or less.     

Determination of selenium in human body fluids by hydride-generation atomic absorption spectrometry : Optimization of sample decomposition

The accuracy of the determination of selenium in human body fluids by hydride-generation a.a.s. depends critically upon the sample decomposition-method used. Digestion with HNO₃ alone gave low selenium recoveries, but with nitric, sulfuric and perchloric acids at a final temperature of 310°C gave results that agreed with those obtained by other techniques. The recovery of selenomethionine added to whole blood and of trimethylselenonium iodide added to urine was 97–104%. The average selenium values found for 6 healthy individuals were 88 μg l^?1 in whole blood, 75 μg l^?1 in blood plasma and 307 μg (kg Hb)^?1 in erythrocytes. A detection limit of 5 μg l^?1 Se in body fluids was found under routine conditions.     

Determination of Cr(III) and Cr(VI) in environmental waters by derivative flame atomic absorption spectrometry using flow injection on-line preconcentration with double-microcolumn adsorption

The species of Cr(III) and Cr(VI) in water samples were determined by flow injection on-line preconcentration and separation on two-microcolumn system-derivative flame atomic absorption spectrometry during a collaborative analysis for certification. The Cr(III) and Cr(VI) in water samples were retained on two microcolumns with ion exchange resin and were eluted directly to nebulizer by 15% HNO³ and 8% NH⁴NO³, respectively. The characteristic concentration (at the sensitivity grade of 2 mV min^?1 for 1 min of preconcentration time) for Cr(III) and Cr(VI) were 0.130 and 0.0985 μg l^?1, in the order which were 332- and 431-fold better than those of FAAS, and 45- and 47-fold better than those of FI-FAAS, respectively. The relative standard deviations were 3.27% and 3.66% with corresponding detection limits (3σ) of 0.244 and 0.235 μg l^?1, respectively. The linear ranges of determinations for Cr(III) and Cr(VI) were 0～100 μgm l^?1 with correlation coefficients of 0.9984 to 0.9996. The satisfactory recovery of 94.4%～106% for Cr(III) and Cr(VI) could be obtained from water samples.     

Novel ultrasonic‐assisted deep eutectic solvent‐based dispersive liquid–liquid microextraction for determination of vanadium in food samples by electrothermal atomic absorption spectrometry: A multivariate study

A green, efficient, simple and sensitive pre‐concentration method has been developed for the determination of vanadium(V) in foodstuffs using deep eutectic solvent–ultrasonic‐assisted dispersive liquid–liquid microextraction. In the developed procedure, the extraction of vanadium(V) was achieved using 2‐hydroxy‐3‐methoxybenzaldehyde thiosemicarbazone as a chelating agent, choline chloride–phenol as extracting solvent and tetrahydrofuran as dispersive solvent. Vanadium(V) concentration was measured using electrothermal atomic absorption spectrometry. Various analytical parameters including pH, type and molar ratio of deep eutectic solvent, ultrasonication time and amount of ligand were studied. A multivariate study was carried out for optimization of the variables. The pre‐concentration factor was calculated as 50. Under optimal conditions, limit of detection, limit of quantification and relative standard deviation were calculated as 0.025 μg l^?1, 0.175 μg l^?1 and 3.4%, respectively. The accuracy of the procedure was confirmed using certified reference materials and standard addition method. The obtained results confirm adequate recoveries for vanadium(V) (>96%). This technique was fruitfully applied for determination of vanadium in foodstuffs.     

Determination of vanadium in water by atomic absorption spectrometry with electrothermal atomization and using hot injection and preconcentration on the graphite tube

A sensitive method for the determination of vanadium in water by atomic absorption spectrometry with electrothermal atomization and using hot injection and preconcentration on the graphite tube is described. The water sample (200 μl) is added to the heated graphite tube in four portions over 200 s. Magnesium nitrate is used as matrix modifier. The precision, accuracy and interferences of the method were investigated. The method allows vanadium down to 0.27 μg l^?1 to be detected.     

Direct determination of lead in blood by electrothermal atomic absorption spectrometry with L'vov platform and matrix modification

An electrothermal atomic-absorption procedure with the L'vov platform and a simple five- or ten-fold sample dilution with a matrix-modifier solution containing diammonium hydrogenphosphate, Triton X-100 and nitric acid, is described for the direct determination of relatively low levels of lead in heparinized blood. The graphite-furnace parameters and matrix-modifier composition are optimized. Sensitivity, imprecision, accuracy and detection limit are reported. Results obtained by standard addition for ten human blood samples (30–400 μg l^?1 lead) were confirmed by an extraction/flame atomic-absorption reference method. Differences in mean lead values ranged from 2 to 31 μg l^?1 with 5.1% mean relative difference. The mean relative standard deviations for consecutive and between-day determinations were 4.6 and 9%, respectively. Accuracy was verified by analyzing six bovine-blood standards certified for lead in the range 70–1100 μg l^?1; deviations of found concentrations from expected values ranged from 0 to 44 μg l^?1 with 4.3% mean relative error. Recovery experiments done with human blood gave 104% (90–121%) of the added lead. The method offers several advantages for routine application in comparison with the extraction/flame atomic-absorption procedure.     

Trace determination of some aromatic molecules by laser two-photon ionization

A simplified yet sensitiive system is described for the detection of the two-photon ionization signal in solution. The photo-ionization cell consists of a quartz cuvette and a pair of stainless steel electrodes. Several aromatic compounds, including quinones, can be detected in the ng l^?1–mg l^?1 range both in hexane and in methanol; detection limits of pyrene in hexane and in methanol are 0.02 μg l^?1 and 4 μg l^?1, respectively. The detectability in hexane is much better than that in methanol. The detection limits and the molar absorptivities at the excitation wavelength are shown to be correlated.     

Automated method for the determination of boron in water by flow-injection analysis with in-line preconcentration and spectrophotometric detection

A sensitive, automated method for the determination of boron in water samples is described, involving flow injection with on-line ion-exchange preconcentration and spectrophotometric detection of the azomethine-H—boron complex. The method is applicable to various water samples and is free from interferences, even in coloured samples. Detection limits of 5 μg l^?1 at 20 samples h^?1 and 1 μg l^?1 at 10 samples h^?1 with relative standard deviations of < 10% at 1–10 μg l^?1 and < 5%at 10–200 μg l^?1 levels of boron were achieved. The recoveries for spiked natural water samples ranged from 96 to 101%. The method compares favourably with inductively coupled plasma atomic emission spectrometry.     

Determination of antimony in steel by hydride generation and by electrothermal zeeman atomic absorption spectrometry

Procedures are described for the determination of antimony in steel. Samples by decomposed with a nitric/perchloric acid mixture and antimony is determined either by a.a.s. after hydride generation with sodium tetrahydroborate or by graphite-furnace a.a.s. with Zeeman background correction. Some reference steel samples were analyzed by both methods and by instrumental neutron activation. The results obtained (45–680 μg g^?1 antimony) were in very good agreement; detection limits were about 3 μg g^?1. The relative standard deviation for samples with > 50 μg g^?1 antimony was 〈 5%.     

Preconcentration and Spectrophotometric Determination of Chromium (VI) and Total Chromium in Drinking Water by the Sorption of Chromium Diphenylcarbazone with Surfactant Coated Alumina

Abstract

A simple and inexpensive method for determining chromium (VI) in drinking water by spectrophotometry after preconcentration with sodium dodecyl sulphate (SDS) coated alumina column is described. Chromium(VI) is reacted with diphenylcarbazide (DPC) and the Cr-DPC complex is quantitatively adsorbed onto a SDS coated alumina column from 800 ml of sample solution. The complex is then eluted with a 8 ml mixture of methanol, acetone and hydrochloric acid and determined by spectrophotometry. Total chromium can be determined after oxidation of chromium (III) to chromium (VI) by KMnO₄. The relative standard deviation (10 replicate analyses) at the 10 μg l^?1 of chromium (VI) and 10 μg l^?1 of total chromium were 3.5% and 3.4% and corresponding limits of detection (based on 3 σ) were 0.040 μg l^?1 and 0.033 μg l^?1, respectively.     

Determination of bismuth,cadmium and lead in soil extracts by atomic absorption spectrometry with loop sample introduction

Bismuth, cadmium and lead in soil extracts with aqua regia, 2 M nitric acid, 2.5% acetic acid or ammonium acetate solution from top-soils at different locations in Turkey, were determined by atomic absorption spectrometry with loop sample introduction. Detection limits were 0.8, 0.025 and 0.5 μl^?1 for bismuth, cadmium and lead, respectively, after concentration with ammonium pyrrolidinedithiocarbamate. Use of a silica tube for atom trapping improved the detection limits.     

Electrothermal atomic absorption spectrometry of elements after electrochemical deposition on graphite electrodes

The application of electrochemical deposition on graphite rods for separation and preconcentration prior to electrothermal atomic absorption spectrometry (a.a.s.) is examined. The metals to be determined are electrolyzed onto a graphite rod which is tehn transferred to a cup atomizer for a.a.s. Although only some of the element present in the solution is deposited on the surface of the graphite rod, favorable preconcentration rates are obtained. The method was tested on the determination of cadmium in aqueous solution. The precision is satisfactory for concentrations down to 5 × 10^?8 g l^?1 cadmium, and the detection limit is 4 × 10^?9 g l^?1.