Fábio Alan Carqueija Amorim

Separation and preconcentration procedures for the determination of lead using spectrometric techniques: A review

Lead is recognized worldwide as a poisonous metal. Thus, the determination of this element is often required in environmental, biological, food and geological samples. However, these analyses are difficult because such samples contain relatively low concentrations of lead, which fall below the detection limit of conventional analytical techniques such as flame atomic absorption spectrometry and inductively coupled plasma optical emission spectrometry. Several preconcentration procedures to determine lead have therefore been devised, involving separation techniques such as liquid-liquid extraction, solid phase extraction, coprecipitation and cloud point extraction. Citing 160 references, this paper offers a critical review of preconcentration procedures for determining lead using spectroanalytical techniques.

Determination of vanadium in petroleum and petroleum products using atomic spectrometric techniques

Vanadium is recognized worldwide as the most abundant metallic constituent in petroleum. It is causing undesired side effects in the refining process, and corrosion in oil-fired power plants. Consequently, it is the most widely determined metal in petroleum and its derivatives. This paper offers a critical review of analytical methods based on atomic spectrometric techniques, particularly flame atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (ET AAS), inductively coupled plasma optical emission spectrometry (ICP OES), inductively coupled plasma mass spectrometry (ICP-MS). In addition an overview is provided of the sample pretreatment and preparation procedures for vanadium determination in petroleum and petroleum products. Also included are the most recent studies about speciation and fractionation analysis using atomic spectrometric techniques.

Application of Multivariate Techniques in Optimization of Spectroanalytical Methods

Abstract The present article describes fundamentals and applications of multivariate techniques used for the optimization of analytical procedures and systems involving spectroanalytical methods such as flame atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (ETAAS), inductively coupled plasma optical emission spectrometry (ICP OES), and inductively coupled plasma mass spectrometry (ICP‐MS), considering the main steps of a chemical analysis. This way, applications of experimental designs in optimization of sampling systems, digestion procedures, preconcentration procedures, instrumental parameters of quantification steps of analytical methods, and robustness tests have been summarized in this work.

Determination of cadmium and lead in table salt by sequential multi-element flame atomic absorption spectrometry.

In the present paper, a simultaneous pre-concentration procedure for the sequential determination of cadmium and lead in table salt samples using flame atomic absorption spectrometry is proposed. This method is based on the liquid-liquid extraction of cadmium(II) and lead(II) ions as dithizone complexes and direct aspiration of the organic phase for the spectrometer. The sequential determination of cadmium and lead is possible using a computer program. The optimization step was performed by a two-level fractional factorial design involving the variables: pH, dithizone mass, shaking time after addition of dithizone and shaking time after addition of solvent. In the studied levels these variables are not significant. The experimental conditions established propose a sample volume of 250mL and the extraction process using 4.0mL of methyl isobutyl ketone. This way, the procedure allows determination of cadmium and lead in table salt samples with a pre-concentration factor higher than 80, and detection limits of 0.3ngg(-1) for cadmium and 4.2ngg(-1) for lead. The precision expressed as relative standard deviation (n = 10) were 5.6 and 2.6% for cadmium concentration of 2 and 20ngg(-1), respectively, and of 3.2 and 1.1% for lead concentration of 20 and 200ngg(-1), respectively. Recoveries of cadmium and lead in several samples, measured by standard addition technique, proved also that this procedure is not affected by the matrix and can be applied satisfactorily for the determination of cadmium and lead in saline samples. The method was applied for the evaluation of the concentration of cadmium and lead in table salt samples consumed in Salvador City, Bahia, Brazil.

On-line preconcentration using a resin functionalized with 3,4-dihydroxybenzoic acid for the determination of trace elements in biological samples by thermospray flame furnace atomic absorption spectrometry

In the present paper, an on-line preconcentration procedure for determination of cadmium, copper and zinc by thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) is proposed. Amberlite XAD-4 functionalized with 3,4-dihydroxybenzoic acid (XAD4-DHB) packed in a minicolumn was used as sorbent material. The metals were retained on the XAD-DHB resin, from which it could be eluted directly to the thermospray flame furnace system. The detection limits were 28 (Cd), 100 (Cu) and 77 ng L(-1) (Zn) for 60s preconcentration time, at a sample flow rate of 7.0 mL min(-1). Enrichment factors were 102, 91 and 62, for cadmium, copper and zinc, respectively. The procedure has been applied successfully to metal determination in biological standard reference materials.

Methods for vanadium determination in fuel oil by GF AAS with microemulsification and acid digestion sampling

Two methods for vanadium determination in fuel oil are proposed using GF AAS. The first is based on the preparation of a microemulsion followed by direct injection into the graphite tube. The pyrolysis and atomization temperatures, 1500 and 2700 oC, respectively, were chosen from the temperature curves. This procedure allows determination of vanadium with a detection limit of 0.10 µg g-1 and characteristic mass of 87 pg. The other method uses total acid digestion of the sample with sulfuric acid, nitric acid and hydrogen peroxide. In this procedure, the pyrolysis and atomization temperatures recommended were 1000 and 2700 oC, respectively. Among the analytical characteristics for this method are a detection limit of 0.25 µg g-1 and a characteristic mass of 63 pg. The accuracy of both procedures was confirmed by the determination of vanadium in the certified reference material NIST SRM 1634c-trace metals in fuel oil.

EspEctromEtria dE absorção atômica: o caminho para dEtErminaçõEs multi- ElEmEntarEs

This paper present an overview of way covered for the spectrometry of atomic absorption (AAS), tracing a line of the historical events in its development and its establishment as a multielement technique. Additionally, the efforts carried by through several researchers in the search for the instrumental evolution, the advances, advantages, limitations, and trends of this approach are related. Several works focusing its analytical applications are cited employing simultaneous multielement determination by flame (FAAS) and/or graphite furnace (GF AAS), and fast sequential multielement determination using FAAS are reported in the present review.

Multivariate optimization of simple procedure for determination of Fe and Mg in cassava starch employing slurry sampling and FAAS

A slurry sampling procedure has been developed for Fe and Mg determination in cassava starch using flame atomic absorption spectrometry. The optimization step was performed using a univariate methodology for 200mg samples and a multivariate methodology, using the Box-Behnken design, for other variables, such as solvent (HNO3:HCl), final concentration (1.7molL-1) and time (26min). This procedure allowed determination of iron and magnesium with detection limits of 1.01 and 3.36mgkg-1, respectively. Precision, expressed as relative standard deviation (%RSD), was of 5.8 and 4.1% (n=10) for Fe (17.8mgkg-1) and Mg (64.5mgkg-1), respectively. Accuracy was confirmed by analysis of a standard reference material for wheat flour (NIST 1567a), which had certified concentrations of 14.1±0.5mgkg-1 for Fe and 40±2.0mgkg-1 for Mg, and the concentrations found using proposed method were 13.7±0.3mgkg-1 for Fe and 40.8±1.5mgkg-1 for Mg. Comparison with concentrations obtained using closed vessel microwave digestion was also realized. The concentrations obtained varied between 7.85 and 17.8mgkg-1 for Fe and 23.7-64.5mgkg-1, for Mg. The simplicity, easily, speed and satisfactory analytical characteristics indicate that the proposed analytical procedure is a good alternative for the determination of Fe and Mg in cassava starch samples.

Application of Factorial Design and Desirability Function to Develop a Single Analytical Procedure for the Determination of Metals in Different Tissues of Blue Crab (Callinectes danae)

In this scientific work, it was developed a single analytical procedure for the sample preparation of different tissues of blue crabs using microwave-assisted digestion for the determination of Cu, Mn, Fe and Zn by fast sequential flame atomic absorption spectrometry (FS FAAS). The limits of quatification were 10.5, 1.6, 8.9 and 19.3 μg g for Cu, Mn, Fe and Zn, respectively. The precision was estimated in terms of repeatability using the relative standard deviation (RSD, n = 7) 3.4% for Cu; 4.8% (Mn); 4.7% (Fe) and 4.7% (Zn) and accuracy of the procedure was confirmed by analysis of certified reference material (CRM) of oyster tissue (NIST 1566B) with concentration values of 71.3 for Cu, 18.3 for Mn, 202.5 for Fe and 1415 μg g for Zn. The procedure has been applied for the determination of Cu, Mn, Fe and Zn in several blue crab samples from Cachoeira River estuary, Ilhéus, Bahia, Brazil.

Development of procedure for sample preparation of cashew nuts using mixture design and evaluation of nutrient profiles by Kohonen neural network

A procedure using ICP OES for sample preparation for the determination of copper, iron and manganese in cashew nuts was developed. Constrained simplex-centroid design was applied in the optimization of the digestion in microwave oven procedure, and the results evaluated from topological maps of the Kohonen network. The best proportion evaluated for the digestion of the sample with HNO3, H2O2 and H2O was 10:45:45 (%). With optimized conditions, the detection limits were 0.63, 4.3 and 0.37 mg kg-1, and quantification 2.1, 14 and 1.2 mg kg-1 for Cu, Fe and Mg, respectively. The precision (% RSD) was 1.84, 2.31 and 2.73, for Cu, Fe and Mg, respectively. The procedure proposed had the accuracy confirmed using NIST 1568b (at 95% reliability) and was applied in the samples obtaining concentrations in the range of 10.7-19.4, 44.3-67.2 and 11.0-21.4 mg kg-1 for Cu, Fe and Mg, respectively.