Anderson Santos Souza

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.

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.

Method development for the determination of lead in wine using electrothermal atomic absorption spectrometry comparing platform and filter furnace atomizers and different chemical modifiers

A method has been developed for the determination of lead in wine by electrothermal atomic absorption spectrometry without any sample preparation and calibration against aqueous standards, using 7.5 microg Pd as a chemical modifier. The results obtained for seven wines using the proposed method and an acid digestion procedure did not show any significant difference using a Students t-test. Atomization in a transversally heated filter atomizer (THFA) was compared with atomization in a conventional transversally heated platform furnace. The former provided a 2.6-fold higher sensitivity, improving the characteristic mass from 34 to 12 pg and a 1.6-fold better limit of detection (0.3 microg L(-1) compared to 0.5 microg L(-1)) for aqueous solutions using the same injection volume of 20 microL. However, the average precision, expressed as the relative standard deviation for the determination of lead in wine under routine conditions was improved from 4.6% with platform atomization to 0.6% in the THFA. The lead content found in seven arbitrarily chosen white and red wines, five from Brazil, one from Chile and one from Spain, ranged from 6 to 60 microg L(-1) Pb with an average content of 11.4 microg L(-1) Pb for the wines from South America.

Direct determination of iron and manganese in wine using the reference element technique and fast sequential multi-element flame atomic absorption spectrometry

A procedure is proposed for the direct determination of manganese and iron in wine employing fast sequential flame atomic absorption spectrometry and the reference element technique to correct for matrix effects. Cobalt, silver, nickel and indium have been tested as reference elements. The results demonstrated that cobalt and indium at a concentration of 2 and 10mgL(-1) were efficient for quantification of manganese and iron, respectively. Under these conditions, manganese and iron could be determined with quantification limits of 27 and 40microg L(-1), respectively. The proposed method was applied to the determination of manganese and iron in 16 wine samples. The content of manganese varied from 0.78 to 2.89mgL(-1) and that of iron from 0.88 to 9.22mgL(-1). The analytical results were compared with those obtained by inductively coupled plasma optical emission spectrometry after complete mineralization using acid digestion. The statistical comparison by a t-test (95% confidence level) showed no significant difference between the results.

Role of 5-HT3 and 5-HT2C receptors located within the medial amygdala in the control of salt intake in sodium-depleted rats

In the present study, we investigated the role of 5-HT(3) and 5-HT(2C) receptors located within the medial amygdala (MeA) in the control of water and salt intake in sodium-depleted rats. Pharmacological activation of 5-HT(3) receptors located in the medial amygdala by the selective 5-HT(3) receptor agonist m-CPBG significantly reduced salt intake in sodium-depleted rats, an effect that is reverted by pretreatment with the selective 5-HT(3) receptor antagonist ondansetron. In addition, the injection of ondansetron alone into the medial amygdala had no effect on salt intake in sodium-depleted and in sodium-repleted rats. Pharmacological stimulation of 5-HT(2C) receptors located in the medial amygdala by the selective 5-HT(2C) receptor agonist m-CPP failed to modify salt intake in sodium-depleted rats, whereas the blockade of these receptors by the selective 5-HT(2C) receptor antagonist SDZ SER 082 significantly reduced salt intake in this same group of animals. These results lead to the conclusion that the pharmacological activation of 5-HT(3) receptors located within the MeA inhibits salt intake in sodium-depleted rats and that, in this same brain region, the functional integrity of 5-HT(2C) receptors is required to achieve the full expression of sodium appetite in sodium-depleted rats.

Determination of the mineral composition of Brazilian rice and evaluation using chemometric techniques

The mineral composition of Brazilian rice samples was determined and the data obtained were evaluated using principal component analysis (PCA) and hierarchical cluster analysis (HCA). Nineteen commercial rice samples were analyzed, six being brown, seven parboiled and six white. The elements were determined employing inductively coupled plasma optical emission spectrometry (ICP OES), and the accuracy was confirmed using a certified reference material of rice flour. The PCA showed the formation of three clusters: a group with the brown rice samples, other with the parboiled rice samples and another of the white rice samples. PCA also showed that the brown rice samples are richer in minerals than the white and parboiled rice samples. Calcium, sodium, zinc and manganese in white rice samples are higher than in parboiled rice samples, while the parboiled rice has higher contents of iron, magnesium, strontium, potassium and phosphor. HCA also demonstrated formation of three major groups, confirming the results obtained by PCA. Application of HCA in the subgroups of rice samples clearly showed separation of rice brands and also separation between the raw and cooked samples. The mineral composition in the rice samples analyzed agrees with data reported by other authors. This paper revealed that the mineral compositions for white, brown and parboiled rice are significantly different.

Multivariate optimization techniques in food analysis – A review

This work presents a critical review of multivariate techniques employed for optimization of methods developed in food analysis. A comparison between the response surface methodologies has been performed, it evidencing advantages and drawbacks of these. Applications of the main chemometric tools (central composite and Box Behnken designs and Doehlert matrix) often utilized for optimization of sample preparation procedures and also instrumental conditions of analytical techniques for determination of organic and inorganic species in food samples are shown. Also, a brief discussion on the use of multiple responses and robustness test in food analysis has been presented.

Multivariate optimization of an ultrasound-assisted extraction procedure for Cu, Mn, Ni and Zn determination in ration to chickens

In this work, multivariate optimization techniques were used to develop a method based on the ultrasound-assisted extraction for copper, manganese, nickel and zinc determination from rations for chicken nutrition using flame atomic absorption spectrometry. The proportions of extracting components (2.0 mol.L-1 nitric, hydrochloric and acetic acid solutions) were optimized using centroid-simplex mixture design. The optimum proportions of this mixture taken as percentage of each component were respectively 20%, 37% and 43%. Variables of method (sample mass, sonication time and final acid concentration) were optimized using Doehlert design. The optimum values found for these variables were respectively 0.24 g, 18s and 3.6 mol.L-1. The developed method allows copper, manganese, nickel and zinc determination with quantification limits of 2.82; 4.52; 10.7; e 9.69 µg.g-1, and precision expressed as relative standard deviation (%RSD, 25 µg.g-1, N = 5) of 5.30; 2.13; 0.88; and 0.83%, respectively. This method was applied in the analytes determination from chicken rations collected from specialized commerce in Jequié city (Bahia State/Brazil). Application of paired t-test at the obtained results, in a confidence level of 95%, does not show significant difference between the proposed method and the microwave-assisted digestion.

Assessment of Trace Elements in Tissues of Fish Species: Multivariate Study and Safety Evaluation

Levels of As, Cd, Cr, Cu, Li, Mn, Mo, Ni, Pb, Sb and Se in muscle, gill, stomach, liver, kidney and gonad tissues of six different fish species ( Caranx latus, Bagre marinus, Archosargus rhomboidalis, Lutjanus synagris, Scomberomorus cavalla and Sphyraena guachancho) from the Todos os Santos Bay (Bahia State, Brazil) were evaluated. The elements were determined by inductively coupled plasma mass spectrometry (ICP-MS) after wet digestion using reflux system with a cold finger. The detected concentration ranges were as follows (mg kg -1 dry weight): < 0.49-27.31 for As, < 0.013-1.12 for Cd, 0.38-6.05 for Cr, 0.17-28.12 for Cu, < 0.092-1.19 for Li, 0.16-55.9 for Mn, < 0.034-1.24 for Mo, < 0.067-15.57 for Ni, < 0.013-0.60 for Pb, < 0.144 for Sb and 0.57-14.6 for Se. Highest concentrations of trace elements were observed in kidney, liver and gill tissues.