Fábio de Souza Dias

Multi-element determination of copper, iron, nickel, manganese, lead and zinc in environmental water samples by ICP OES after solid phase extraction with a C18 cartridge loaded with 1-(2-pyridylazo)-2-naphthol

A pre-concentration solid-phase procedure has been developed for the sensitive and simple determination of copper, iron, nickel, manganese, lead and zinc in environmental water samples by inductively coupled plasma optical emission spectrometry (ICP OES). After pH adjustment, the samples were percolated with the aid of a peristaltic pump on a Sep-Pak C18 cartridge loaded with 1-(2-pyridylazo)-2-naphthol (PAN). The analyte elution was carried out with the passage of HCl through the cartridge for subsequent determination by ICP OES. The experimental conditions for pre-concentration were optimized considering the following factors: the concentration and volume of the eluent, sample volume, flow-rate and pH. The optimized conditions corresponded to the use of 5 mL of 0.8 M HCl as the eluent, a sample volume of 50 mL, a flow-rate of 1.9 mL min−1 and pH 9.0. Under these conditions, the detection limits for Cu, Fe, Mn, Ni, Pb and Zn varied between 0.11 and 21 μg L−1. The relative standard deviation (RSD) for the analytes of this study did not exceed 9%, after the application of the proposed pre-concentration procedure (n = 10, 0.50 mg L−1). The effect of possible interfering species on the recovery of the analytes was also investigated. The accuracy of the method was evaluated by the analysis of a certified reference material (SLEW-3 Estuarine Water Reference Material for Trace Metals) and the proposed method was applied to samples of groundwater, drinking water and river water. The samples were analyzed by using inductively coupled plasma mass spectrometry (ICP-MS) as a comparative method and no significant differences among these results and the results obtained by the proposed method were observed.

Preconcentration and determination of copper in tobacco leaves samples by using a minicolumn of sisal fiber (Agave sisalana) loaded with Alizarin fluorine blue by FAAS

In the present study, a minicolumn of sisal fiber loaded with alizarin fluorine blue is proposed as a preconcentration system for copper determination in tobacco leaf samples by flame atomic absorption spectrometry. During the optimization procedure, a two level full factorial design (2(4)) was used at the preliminary evaluation of four factors, involving the following variables: sampling flow rate, elution flow rate, buffer concentration and pH. Regarding the studied levels, this design has shown that buffer concentration and pH were significant factors. The experimental conditions established in the optimization step were: pH=4.75, buffer concentration of 0.005 mol L(-1) for elution with HCl 1.0 mol L(-1) this system allows the determination of copper content with a detection limit (LD) of 0.018 μg L(-1) and a quantification limit (LQ) of 0.061 μg L(-1) precision expressed as relative standard deviation (R.S.D.) of 4.65 and 5.07%, utilizing concentration of 10 and 2.0 μg L(-1), respectively, and a preconcentration factor of 75, for a sample volume of 50.0 mL. Accuracy was confirmed by copper determination in the standard reference material, NIST SRM 1570 a trace element units in Spinach Leaves and by spike tests with recovery levels ranging from 93 to 100%; the procedure was applied for copper determination in tobacco leaf samples collected in Cruz das Almas City, Bahia, Brazil. The achieved concentrations of the three samples analyzed varied from 0.15 to 0.52 μg g(-1).

Determination of Manganese in Cassava Leaves by Slurry Sampling Flame Atomic Absorption Spectrometry

Abstract Cassava, Manihot esculenta crantz, constitutes one of the main foods consumed by most of the population of developing countries, mainly in the population of low income. It is largely used for its low cost and the diversity of its root and leaves products. In this paper, a slurry sampling flame atomic absorption spectrometric method for the determination of manganese in cassava leaves is proposed. The slurry sampling was used in order to shorten the analysis time and to minimize the problems associated with solid sample treatment such as wet acid digestion, dry-ashing, sample contamination, and analyte loss. The samples of cassava leaves were washed with extran 10% (v/v), soon afterwards they were dried in an oven to 60°C, triturated in a mill of spheres, and the obtained material was sifted in a mesh of 100 micrometers. Then 0.1 g of the sample was weighed in a balloons volumetric flask, the volume was completed with 25 mL of acid nitric 2,0 mol L−1, and followed by 20 minutes in an ultrasonic bath and subsequent reading in FAAS. The analyses of the certified reference material of spinach and apple leaves evidenced the accuracy of the method. The proposed method was applied for the determination of manganese in four samples of cassava leaves acquired in markets from Feira de Santana City, Brazil. The concentration of manganese found in cassava leaves varied from 202.7 to 181.3 µg g−1, with detection and quantification limits of 0.17 and 0.56 µg g−1, respectively. The precision expressed as relative standard deviation (RSD) was 1.7 and 3.2% (n = 10) for 100 and 12 µg g−1, respectively.

Determination of Phenolic Acids and Quercetin in Brazilian Red Wines from Vale do São Francisco Region Using Liquid-Liquid Ultrasound-Assisted Extraction and HPLC-DAD-MS

This work describes a method for the determination of gallic, caffeic and p-coumaric acids, as well as quercetin, in Brazilian red wines by employing reverse phase high performance liquid chromatography (RP HPLC) coupled to diode array and mass detectors. The method was performed using a sample volume of 10 µL. The limits of detections were 0.36, 0.27, 0.33 and 0.59 mg L-1 for gallic acid, caffeic acid, p-coumaric acid and quercetin, respectively. The precision, as estimated by the relative standard deviation, was between 1.0 and 2.0% for different concentrations of gallic acid, caffeic acid, p-coumaric acid and quercetin. The accuracy was evaluated by addition and recovery experiments, and the obtained values were between approximately 92 and 117% recovery. The method was then applied to the analysis of red wine samples that were collected from the Sao Francisco region, Bahia State, Brazil. The concentrations of analytes were determined in ten Brazilian wines and varied from 5.26 to 10.22 mg L-1 for quercetin, 6.65 to 43.92 mg L-1 for gallic acid, 3.58 to 7.83 mg L-1 for p-coumaric acid, and 3.59 to 10.5 mg L-1 for caffeic acid.

Mixture Design Optimization of an Analytical Procedure for Iron Extraction and Determination From Cassava Leaves by Slurry Sampling Flame Atomic Absorption Spectrometry

ABSTRACT This paper applies statistical simplex-centroid design to mixture modeling for optimization of the liquid phase composition of cassava slurry leaves in the development of an analytical procedure for iron determination using flame atomic absorption spectrometry (FAAS). This procedure is based on a slurry formation from powdered cassava leaves and a liquid mixture composed of HNO3, HCl, and H2O2 after an ultrasonication process. A quadratic model fitted to the analytical response shows the existence of an experimental region, characterized by low proportions of H2O2, for which higher responses are obtained. The proposed procedure allows the determination of iron in the cassava leaves with a detection limit of 1.1 µg g−1. The precision expressed as relative standard deviation (%RSD, n = 10) was 1.5% for iron concentrations of 25 µg g−1. The developed procedure was validated by the comparison of results obtained from the application of the digestion procedure and the analysis of certified reference materials: Apple leaves (NIST 1515). Results found were in agreement with the certified values. The proposed method was applied for the determination of iron in four samples of cassava leaves acquired in markets of Feira de Santana City, Brazil. The concentration of iron found in the cassava leaves varied from 250.8 ± 0.7 to 283.4 ± 0.7 µg g−1.

Direct determination of phenolic acids and hydroxymethylfurfural in wines elaborated in Vale do São Francisco region-Brazil by HPLC DAD

The present paper describes a direct method for the determination of gallic acid, hydroxymethylfurfural, vanillic, caffeic, p-coumaric, ferulic, caftaric, cis-coutaric, fertaric and trans-coutaric acids in Brazilian red wines by direct injection employing reverse phase high performance liquid chromatography (RP HPLC DAD). The method was performed using a sample volume of 10 μL and the separation process was established employing a monolithic column. The method was applied for analysis of red wine samples collected from the Sao Francisco region, Bahia State, Brazil. Ten wine samples were analysed and the contents of caftaric acid varied from 13.28 to 46.83 mg L−1, cis-coutaric acid from 1.01 to 2.13 mg L−1, trans-coutaric acid from 2.13 to 17.56 mg L−1, fertaric acid from 1.11 to 2.43 mg L−1, ferulic acid from 0.31 to 3.97 mg L−1, hydroxymethylfurfural from 0.59 to 8.83 mg L−1, vanillic acid from 2.90 to 11.57 mg L−1, caffeic acid from 4.20 to 14.20 mg L−1, p-coumaric acid from 0.26 to 12.46 mg L−1 and ferulic acid from 0.31 to 3.97 mg L−1.

Metals in geopropolis from beehive of Melipona scutellaris in urban environments

Geopropolis, a different type of propolis, presents a mixture of resin and exudates, containing wax, silt, and sand particles. This product has been the subject of research interest for its physicochemical properties, economic importance, and likely for environmental monitoring. The determination of toxic metals in hive products has been reported as an efficient tool for environmental monitoring. As the honey production is now common in urban environments, this study aimed to determine the concentration of toxic metals in the Melipona scutellaris geopropolis of the Metropolitan Region of Salvador, Bahia. Geopropolis and soil samples were collected from seven important beehives between June 2015 and July 2016. After EPA 3050B acid digestion procedure, metals were determined by ICP OES. As the geopropolis is partially made from soil, the values of Cr and Fe were extremely more important than the values reported in propolis, wax, and honey found in other worldwide studies. It gives different characteristics to this product depending on the location of the hive and characterizes it as an efficient integrating indicator of soil pollution. Using the enrichment factor, we determined that the soils around the meliponary are not or only slightly polluted by Cu, Cr, Ni, Pb and Zn. However, there was a shift in the particle size of geopropolis, being loamier and less sandy than the surrounding soil. In such case, a higher metal content could be expected, though no metal enrichment in the geopropolis was found, even a decrease in zinc, possibly due to the exclusion of metals by bees, was noted. Nevertheless, the results on the proportions of lithogenic metal and anthropogenic metal indicate that some metals have an external origin (about 20% for Ni and Cu). Geopropolis can be considered as a good environmental indicator even in low contaminated areas.

Ultrasound-assisted emulsification of solidified floating organic drop microextracted for pre-concentration of cadmium in food and water samples

In this study, a procedure for the pre-concentration and determination of cadmium in food samples by flame atomic absorption spectrometry (FAAS) was developed based on ultrasound-assisted emulsification microextraction with solidification of floating organic droplet (USAEME-SFO) using 1-(2-thiazolylazo)-p-cresol (TAC) as complexing reagent. The limits of detection and quantification were 0.60 μg L−1 and 2.0 μg L−1, respectively. The methods precision was expressed as relative standard deviation of 3.0% (10 μg L−1). Accuracy was evaluated through certified reference sample analysis of tomato leaves (SRM 1573a), rice flour (NIES 10b), and Drinking Water Standard 1071, and the recovery test results ranged from 90 to 100%. The procedure was applied for the determination of cadmium in corn flour, bean, cabbage, and mineral water samples in which the analyte concentration ranged from 0.30 to 2.1 μg g−1 for food samples and from 0.30 to 0.46 μg L−1 for water samples.