Determination of vanadium by ETAAS using chromium nitrate as chemical modifier

An interference-free routine method for the determination of vanadium in alkaline sludge by ETAAS has been developed. Chromium nitrate was used as a chemical modifier. The limits of detection and quantification are 0.56 and 1.9 ng V, respectively. The relative standard deviation is±1.5% for 101.8 μg/g vanadium.     

Direct determination of lead at sub-ppb levels in secondary coolants of pressurized water reactor by electrothermal atomic absorption spectrometry with multiple injections

The method of incorporating in-situ pre-concentration technique via multiple injections followed by electrothermal atomic absorption spectrometry (ETAAS) is described for the direct determination of lead at sub-ppb levels in secondary coolants of pressurized water reactor (PWR). Prior to ETAAS measurement, water samples were concentrated by means of multiple injections (9×90 ml) and evaporation in a pyrocoated graphite tube. Optimization of the in-situ pre-concentration via multiple injections with ETAAS analysis was investigated. The feasibility of the proposed method was tested for direct determination of lead in secondary coolants of pressurized water reactor. A SRM 1643c certified reference water sample has been used for quality control. The result are in good agreement with the certified value. By the use of 0.81 ml sample volume 0.012 ppb detection limit was obtained.     

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.     

电感耦合等离子体质谱法测定石墨样品中钒含量的不确定度评价

依据测量不确定度的评价与表示方法,建立了电感耦合等离子体质谱法测定石墨样品中钒含量的不确定度评价的数学模型,并对各不确定度分量进行分析,当样品中V₂O₅含量为0.215%时,其扩展不确定度为0.035%.通过分析发现,曲线拟合、回收率以及重复性试验对测定结果有较大影响.评价方法可为石墨样品中钒的测定结果准确性和置信度提供理论依据.     

Comparative Studies on Chemical Modification by Diethyldithiocarbamate for ETV-ICP-OES and ETAAS Determination of Chromium and Nickel

The chemical modification of diethyldithiocarbamate (DDTC) in electrothermal vaporization inductively coupled plasma optical emission spectrometry (ETV-ICP-OES) and in electrothermal atomic absorption spectrometry (ETAAS) was comparatively investigated. The experimental results indicated that the formation of Cr- and Ni-DDTC chelates enhanced significantly the emission signals of Cr and Ni in ETV-ICP-OES, but decreased the absorption signal of Cr and Ni in ETAAS. The different role of DDTC in ETV-ICP-OES and ETAAS was attributed to the different functions of the graphite furnace in the two techniques. The graphite furnace was used as both a vaporizer and an atom-vessel for analytes in ETAAS, but only used as a vaporizer for the sample in ETV-ICP-OES. Thermal gravimetric analysis of Cr- and Ni-DDTC chelates and UV-Vis analysis of the sample vapor collected in CHCl₃ after vaporization of their chelates from the graphite furnace indicated that the analytes were vaporized and transported into ICP as their chelates. In addition, the vaporization mechanism of Cr and Ni was also briefly discussed.     

电热原子吸收法测定人发中硒时不同改进剂的研究

对于生物体中硒的测定,国内外已有大量报道,所用方法也相当广泛。本文利用石墨炉原子吸收对人发中硒的测定进行了研究;对使用较多的两种硒的基体改进剂:铜与镍的作用与效果进行了研究,发现铜较镍在某些方面更为优越。当选用100 μg/mL的铜作改进剂时,硒的特征浓度为0.13 ng/1％abs,测定精度为3.4％～5.4％;线性范围达400 ng。     

石墨炉原子吸收法测定钢铁及合金中微量钒

探讨了石墨炉子吸收法测定钢铁及合金中微量钒的各种实验条件及影响因素。实验表明，采用热解涂层管与光控升温相结合并在温度稳定的情况下原子化，可改善信号峰形，提高灵敏度，消除记忆效应。方法用于钢铁及合金中钒的分析，结果令人满意。     

Speciation analysis of plants in the determination of V(V) by ETAAS

Vanadium(IV) and vanadium(V) were easily separated from each other in the same plant sample and be determined independently by ETAAS (electrothermal atomic absorption spectrometry). This was achieved by treating the sample with 1 M (NH₄)₂HPO₄ which transfer only insoluble V(V) species into solution leaving V(IV) species in the solid part of the sample solution. V(IV) was then transferred into solution by ashing the precipitates and dissolving them in dilute acid. Statistical evaluations indicate that the sum of the concentrations of V(IV) and V(V) species is the same as the total concentration of vanadium determined by an independent method from the same plant sample at 95% level of confidence.

The maximum concentrations for V(V) and total vanadium in plants around the vanadium mine were found to be 24.3 and 350 μg g⁻¹, respectively.     

Determination of lead in fine particulates by slurry sampling electrothermal atomic absorption spectrometry

A simple method for determining lead in fine particulates (PM2.5) by using electrothermal atomic absorption spectrometry (ETAAS) has been developed. Particulates collected on Nuclepore filter by using a dichotomous sampler were suspended in diluted nitric acid after ultrasonic agitation. The dislodging efficiency is nearly 100% after agitation for 5 min. In order to study the suspension behavior of PM2.5 in solvents, a Brookhaven ZetaPlus Particle Size Analyzer was used to determine the particle size distribution and suspension behavior of air particulates in the solvent. The pre-digestion and modification effect of nitric acid would be discussed. Palladium was added as a chemical modifier and the temperature program of ETAAS was changed in order to improve the recovery. The slurry was introduced directly into a graphite tube for atomization. The metal content in the sample was determined by the standard addition method. In addition, a conventional acid digestion procedure was applied to verify the efficiency of the slurry sampling method. It offers a quick and efficient alternative method for heavy metal characterization in fine particulates.     

Determination of Vanadium in Tissues By Atomic Absorption Spectrophotometry

Abstract

A simple and sensitive method for the determination of vanadium in tissues was established by using atomic absorption spectrophotometry with graphite furnace atomisation. The proposed method includes formation of a chelate-complex by reacting vanadium with pyrrolidine dithiocarbamate (PDCA), extracting the chelate with xylene and measurement of the extract using atomic absorption spectrometry. The recoveries of added vanadium in various rat tissues were 96.7 and 109.3%, within 8.6% of the coefficient variation. The sensitivity of this method is 10 – 50 times higher than previous methods, the detection limit is 0.01 μg/g.     

Evaluation of electrodeposited tungsten chemical modifier for direct determination of chromium in urine by ETAAS

The direct determination of chromium in urine by electrothermal atomic absorption spectrometry (ETAAS) using graphite tubes modified with tungsten is proposed. Modification of the graphite is made by tungsten electrodeposition over the whole surface atomizer followed by carbide formation by heating the tube inside its own furnace. For tungsten electrocoating, the graphite tube and a platinum electrode were connected to a power supply as cathode and anode, respectively, and immersed in a solution containing 2 mg of W in 0.1% v/v HNO₃. Then, 5 V was applied between the electrodes during 20 min for tungsten electrodeposition over the whole atomizer. A SpectrAA 220 Varian atomic absorption spectrometer equipped with a deuterium background corrector was used throughout. Undiluted urine (20 μl) was delivered over the tungsten-treated tube and the chromium-integrated absorbance was measured after applying a suitable heating program with maximum pyrolysis at 1300 °C and atomization at 2500 °C. With electrodeposited tungsten modifier, the tube lifetime increased up to four times when compared to previous published methods for Cr determination in urine by ETAAS, reaching 800 firings. Method detection limit (3 S.D.) was 0.10 μg l⁻¹, based on 10 integrated absorbance measurements of a urine sample with low Cr concentration. Two reference materials of urines (SRM 2670) from National Institute of Standards and Technology (NIST) were analyzed for method validation. For additional validation, results obtained from eight human urine samples were also analyzed in a spectrometer with Zeeman effect background correction.     

Determination of Vanadium in Foods by Atomic Absorption Spectrophotometry

ABSTRACT

A simple and sensitive method for the determination of vanadium in foods was established by using atomic absorption spectrophotometry with graphite furnace atomization. The proposed method includes formation of a chelate-complex by reacting vanadium with pyrrolidine dithiocarbamate (PDCA), extracting the chelate with xylene and measurement of the extract by atomic absorption. The recoveries of added vanadium to various foods were 91.3 and 109.1%, within 7.9% of the coefficient variation. The sensitivity of this method is 10 - 50 times higher than previous methods with a detection limit of 0.01 μg/g.     

ETAAS method for the determination of Cd, Cr, Cu, Mn and Se in blood fractions and whole blood

An electrothermal atomic absorption method (ETAAS) for the direct determination of trace elements (Cd, Cr, Cu, Mn, Se) both in blood fractions (erythrocytes, plasma and lymphocytes) and whole blood was developed. Zeeman background correction and graphite tubes with L'vov platforms were used. Samples were diluted with HNO3/Triton X-100 and pipetted directly into the graphite tube. Ashing, pretreatment and atomization steps were optimized carefully for the different fractions and elements applying different matrix modifiers for each element. For the lymphocyte fraction a multi-fold injection technique was applied. Low detection limits of the ETAAS method (Cd 0.13 microgram/L, Cr 0.11 microgram/L, Cu 0.52 microgram/L, Mn 0.13 microgram/L, Se 0.7 microgram/L of whole blood) combined with small quantities of sample necessary for analysis allow determination of trace elements in this matrix. Verification of possible differences in the trace element status of humans was performed with statistical significance (P < 0.05). In addition, a contribution to the determination of normal values of essential elements was achieved. The method was applied for determination of trace elements in human blood and blood fractions of two groups (n = 50) different in health status.     

Detection of bias errors in ETAAS Determination of copper in beer and wine samples

A method that evidences changes in the shape of the absorbance profiles obtained by graphite furnace atomic absorption spectrometry (ETAAS) is proposed. The method is based upon the apparent content curves model previously described for molecular spectroscopy and it permits the detection of possible sources of bias errors. Moreover, a procedure that allows to detect the existence of constant and/or proportional errors is also described. Both models has been applied to the determination of copper in wine and beer samples with and without pre-treatment of the samples. Results obtained evidence the usefulness of the proposed models.     

Determination of lead in fine particulates by slurry sampling electrothermal atomic absorption spectrometry

A simple method for determining lead in fine particulates (PM_2.5) by using electrothermal atomic absorption spectrometry (ETAAS) has been developed. Particulates collected on Nuclepore filter by using a dichotomous sampler were suspended in diluted nitric acid after ultrasonic agitation. The dislodging efficiency is nearly 100% after agitation for 5 min. In order to study the suspension behavior of PM_2.5 in solvents, a Brookhaven ZetaPlus Particle Size Analyzer was used to determine the particle size distribution and suspension behavior of air particulates in the solvent. The pre-digestion and modification effect of nitric acid would be discussed. Palladium was added as a chemical modifier and the temperature program of ETAAS was changed in order to improve the recovery. The slurry was introduced directly into a graphite tube for atomization. The metal content in the sample was determined by the standard addition method. In addition, a conventional acid digestion procedure was applied to verify the efficiency of the slurry sampling method. It offers a quick and efficient alternative method for heavy metal characterization in fine particulates. Received: 2 August 2000 / Revised: 25 October 2000 / Accepted: 28 October 2000     

Determination of boron in silicon-doped gallium arsenide by electrothermal atomic absorption spectrometry and ultraviolet-visible spectrophotometry

Two methods have been developed for the determination of boron impurities in silicon-doped gallium arsenide (GaAs) for electronics. The first method employs the electrothermal atomic absorption spectrometry (ETAAS), the second, the UV-Vis molecular absorption spectrophotomety. In both cases the GaAs sample is decomposed with aqua regia (1+1). To prevent Ga(III) interference on the ETAAS determination of boron, a double extraction of the chlorogallic acid (HGaCl4) in diethyl ether is performed. To improve the overall ETAAS performance, the graphite tubes were pre-treated with iridium(III) and tungsten(IV). A mixed chemical modifier containing Ni(II), Sr(II) and citric acid was also used. The characteristic mass (m0) is 301 +/- 47 pg and the detection limit (3sB) is 2.4 microg g(-1). The classic UV-Vis spectrophotometric procedure using curcumin was also extended to the determination of boron in GaAs. By masking Ga(III) with EDTA and a preliminary extraction of boron with 2-ethyl-hexane 1,3-diol, performed on a semi-micro scale, a detection limit of 0.6 microg g(-1) was achieved. Both methods were applied to the analysis of two Si-doped GaAs samples which were suspected of being boron-contaminated. Results are compared with those obtained by direct analysis of the decomposed sample solution using the inductively coupled plasma atomic emission spectrometry (ICP-AES).     

Preliminary studies on flow-injection in situ trapping of volatile species of gold in graphite furnace and atomic absorption spectrometric determination

Volatile species of gold in acidified medium were generated at room temperature by the reduction of NaBH₄ using a flow injection vapor generation (FI-VG) system, and trapped in situ on the graphite furnace inner wall to get ETAAS detection. Reaction coil inner-wall and inside of the gas–liquid separator were conditioned by passing through a liquid containing micro amounts of Pd(II) and sodium diethyldithiocarbamate (DDTC) and NaBH₄. The FI manifold design, the precondition of the FI-VG system and the effect of temperature parameters for ETAAS are discussed. Optimization of the FI and chemical parameters, such as effect of sample acidity, effect of sodium tetrahydroborate concentration, effects of the flow rates for sample, reagent and carrier gas, effects of HCl and DDTC concentration in rinsing solution were investigated. A detection limit of 0.8 ng/ml (3σ) was obtained with a 40 s trapping time and a sampling frequency of 50/h. The precision of 2.2% R.S.D. (n=11) was obtained at 50 ng/ml level. The method was used for the determination of gold in ore sample digest solution. The recoveries of gold in ore sample digest dilute solution by spiking of 25 ng/ml gold were 90–106%. The results obtained were in good agreement with those obtained from direct ETAAS.     

Comparative study on the use of Ir, W and Zr-coated graphite tubes for the determination of chromium in slurries of human scalp hair by electrothermal atomic absorption spectrometry

The use of Ir, W and Zr-coated graphite tubes, as permanent chemical modifiers, was studied for the determination of chromium in human scalp hair by ETAAS using the slurry sampling technique. The use of Mg(NO₃)₂ and Pd, as aqueous chemical modifiers, was also investigated and compared to the use of the permanent chemical modifiers. Scalp hair samples were pulverized using a Zr vibrational ball mill, (mean particle diameter of 0.8 μm) and suspended in ultrapure water. The lowest limit of detection, 44.5 μg kg^–1,was achieved for the use of W-coated graphite tubes. The repeatability of the overall procedures (slurry preparation and ETAAS determination) were 15.7, 14.5 and 16.7% for W- and Zr-coated graphite tubes and Mg(NO₃)₂, respectively. The methods were applied to several reference materials, CRM 397 (human hair), DOLT-1 (dogfish liver) and DORM-1 (dogfish muscle), and the results obtained were in agreement to the certified values. Finally, the methods were applied to several human scalp hair samples from healthy adults.     

Determination of elements in lithium potassium niobate and lithium niobate containing vanadium by ICP-AES

The elements in lithium potassium niobate and lithium niobate containing vanadium (such as aluminum, lithium, niobium, potassium and vanadium) were determined by inductively coupled plasma atomic emission spectrometry after fusion of the sample with ammonium hydrogensulfate. The samples were completely decomposed and high precision results were obtained for the metallic elements. Oxygen has been determined by a helium carrier fusion thermal conductivity method using both a nickel capsule and tin as a melting flux in a graphite crucible.     

Radioisotope X-ray fluorescence analysis of vanadium in petroleum coke samples

Radioisotope X-ray fluorescence spectrometry, RIXRF, was used for the determination of vanadium in Venezuelan petroleum coke samples using a simple standardless method and fundamental parameter approach. The values obtained by this method were in agreement with values measured by graphite furnace atomic absorption spectrometry, GFAAS.