Search

Liquefaction of biomass delivers a liquid bio-oil with relevant chemical and energetic applications. In this study we coupled it with short rotation coppice (SRC) intensively managed poplar cultivations aimed at biomass production while safeguarding environmental principles of soil quality and biodiversity. We carried out acid-catalyzed liquefaction, at 160 °C and atmospheric pressure, with eight poplar clones from SRC cultivations. The bio-oil yields were high, ranging between 70.7 and 81.5%. Average gains of bio-oil, by comparison of raw biomasses, in elementary carbon and hydrogen and high heating, were 25.6, 67, and 74%, respectively. Loss of oxygen and O/C ratios averaged 38 and 51%, respectively. Amounts of elementary carbon, oxygen, and hydrogen in bio-oil were 65, 26, and 8.7%, and HHV averaged 30.5 MJkg−1. Correlation analysis showed the interrelation between elementary carbon with HHV in bio-oil or with oxygen loss. Overall, from 55 correlations, 21 significant and high correlations among a set of 11 variables were found. Among the most relevant ones, the percentage of elementary carbon presented five significant correlations with the percentage of O (−0.980), percentage of C gain (0.902), percentage of O loss (0.973), HHV gain (0.917), and O/C loss (0.943). The amount of carbon is directly correlated with the amount of oxygen, conversely, the decrease in oxygen content increases the elementary carbon and hydrogen concentration, which leads to an improvement in HHV. HHV gain showed a strong positive dependence on the percentage of C (0.917) and percentage of C gain (0.943), while the elementary oxygen (−0.885) and its percentage of O loss (0.978) adversely affect the HHV gain. Consequently, the O/C loss (0.970) increases the HHV positively. van Krevelen’s analysis indicated that bio-oils are chemically compatible with liquid fossil fuels. FTIR-ATR evidenced the presence of derivatives of depolymerization of lignin and cellulose in raw biomasses in bio-oil. TGA/DTG confirmed the bio-oil burning aptitude by the high average 53% mass loss of volatiles associated with lowered peaking decomposition temperatures by 100 °C than raw biomasses. Overall, this research shows the potential of bio-oil from liquefaction of SRC biomasses for the contribution of renewable energy and chemical deliverables, and thereby, to a greener global economy.

Powdered milk and its derivatives are widely consumed worldwide, which require the development of reference materials for the evaluation of analytical methodologies that are developed for the analysis of these samples. In this work, the homogeneity and stability of a powdered milk laboratory reference material candidate were evaluated using chemometric tools as an alternative to analysis of variance (ANOVA). Elements Ca, Fe, K, Mg, P, Na and Zn were quantified by inductively coupled plasma optical emission spectrometry (ICP OES) after the acid digestion procedure using microwave-assisted radiation. The results obtained through not only ANOVA, but also PCA and HCA allow us to state that the material can be considered homogeneous and stable. However, the application of the chemometric tools (PCA and HCA) allowed the extraction of more information compared to ANOVA, besides confirming the homogeneity and stability of the powdered milk laboratory reference material candidate.

This work proposes the simultaneous determination of chromium and iron in powdered milk samples using high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) and sample digestion in microwave oven using nitric acid and hydrogen peroxide. The method was established using the primary line (357.869 nm) for chromium and the adjacent secondary line (358.120 nm) for iron while employing aluminum as the chemical modifier. The absorbance signals were measured by peak area using three pixels for both elements. Chromium and iron can be determined in powdered milk samples by the external calibration technique with limits of quantification of 28 ng g−1 for chromium and 19 μg g−1 for iron. The precision was evaluated by using a milk sample with chromium and iron concentrations of 0.76 μg g−1 and 151.3 μg g−1, respectively. The results expressed as relative standard deviation (n = 10) were 2.6% for iron and 3.9% for chromium. The method accuracy was confirmed by the analysis of a milk sample by a comparison of results obtained by the proposed method and those found by employing inductively coupled plasma mass spectrometry (ICP-MS). Five samples were analyzed, and the analyte concentrations found varied from 408 to 805 ng g−1 for chromium. Among the five samples, three had an iron concentration lower than 19 μg g−1 and in the other two samples, the iron concentrations varied from 151 to 199 μg g−1.

This work proposes an on-line digestion system employing 70% (w/w) hydrogen peroxide and UV radiation for producing hydroxyl radicals for the determination of chromium in beer samples by electrothermal atomization atomic absorption spectrometry (ETAAS). The digester system consists of a closed wooden box, which is painted black internally, containing a PTFE tube wrapped around a 15 W UV lamp. During the mineralization step, a peristaltic pump is employed to propel the sample solution over the UV lamp. The experimental factors UV irradiation time and hydrogen peroxide volume were optimized using a two-level full factorial design. Degradation curves at different pH conditions demonstrated that the digestion of beer is faster at alkaline pH. The results demonstrated that, in the presence of 70% H2O2 and 15 W UV radiation, 75% of the chromophore species is degraded with an irradiation time of 25 min. The degradation kinetic curves of beer samples under different conditions were also evaluated. The apparent kinetic constant (kapp) found for the process assisted by 70% H2O2 and 15 W UV light was 0.0668 min−1 (R2 = 0.9936). The on-line digestion procedure with a sample flow rate of 2 mL min−1 for 45 min allowed the determination of chromium in beer samples by ETAAS, utilizing the external calibration technique, with the analytical line 357.9 nm, in the presence of magnesium as chemical modifier with limits of detection and quantification of 0.86 and 2.90 μg L−1, respectively. The method accuracy was confirmed by the analysis of the certified reference material of ERM-CA713 wastewater provided by the European Reference Materials. Six beer samples were digested and the chromium was determined. The contents found varied from 4.26 to 33.28 μg L−1. Addition/recoveries tests were also performed to evaluate the accuracy method. The recoveries obtained varied from 93.2 to 96.4%.

This manuscript covers the application of the main techniques for simultaneous optimization of multiple responses generated by the application of multivariate designs (two-factor factorial, Central Composite, Doehlert, etc.) or by chromatographic runs in the development of analytical methods. Special attention will be given to the graphical method, desirability function, multiple response function and chromatographic response functions, since they are more frequently used in the analytical area. The advantages, disadvantages, limitations, and potentialities of these methods will also be addressed, as well as some of their applications, commenting on real examples from the literature. Some less usual methods in multiple response optimization in Analytical Chemistry will also be commented.

This work proposes an analytical strategy utilizing digital images (DI) for the iron inorganic speciation in white wine. The method was established by the reaction of iron(II) ions with 1,2 ortho-phenanthroline as a chromogenic reagent. Total iron was determined using the same reagent after the addition of hydroxyl ammonium chloride as a reducing agent. In both cases, digital images of the standards/chromogenic reagent and samples were acquired and stored in JPEG format. The region of interest (ROI) was determined with a constant square shape for all images. The ROI was submitted to decomposition in color values according to the RGB additive color model. However, the data obtained by the blue channel was the one used in the construction of the analytical curves because it presented the highest sensitivity. The optimization of the experimental conditions of the procedure was performed by employing multivariate techniques. The precision was evaluated using a wine sample with iron (II) and total iron contents of 0.41 and 0.69 mg L−1, respectively. The results expressed as relative standard deviations were 3.57% for iron (II) and 4.76% for total iron contents. A comparison between the results obtained for total iron by the DI method with the results found using flame atomic absorption spectrometry confirmed the method accuracy. The DI procedure was applied for speciation analysis in six white wine samples and the contents found varied from 0.41 to 1.67 mg L−1 for iron (II) and from 0.69 to 1.71 mg L−1 for total iron. These results are in agreement with those found for speciation analysis of iron in wine samples. Iron (III) contents can be found by the difference between the total iron and iron (II) contents.

This work aimed to evaluate the mineral composition of twelve samples of red jambo (Syzygium malaccensis) collected in 10 cities in the state of Bahia. The samples were digested in a digester block with a reflux system and cold finger, and the analytes were determined by optical emission spectrometry with inductively coupled plasma. The accuracy of the method was confirmed by analyzing NIST 1570a certified reference material (spinach leaves) at a 95% confidence level. The results were evaluated through Principal Component Analysis and Hierarchical Cluster Analysis, which allowed the identification of outliers in the results of the city of Jaguaquara. The analyte concentrations in the samples (mg 100 g –1) comprised a range of: Ca (3.0–28.9), Fe (0.035–0.125), K (134.8–197.5), Mg (2.7–19.8), Mn (0.012–0.131), Na (0.5–10.8), P (0.24–13.5), Sr (0.010–0.314), and Zn (0.026–0.129). This demonstrates that the fruit can be indicated as a potential nutritional supplement in human nutrition.

In this paper, we have elaborated Cu2Fe1-x CoxSnS4 (CFCTS) thin films (x = 0%, 25%, 50%, 75% and 100%) by spray pyrolysis technique on glass substrates. The effect of varying (Fe/Co) ratio on chemical composition, morphological, structural, optical and electrical properties has been investigated using energy dispersive X-ray spectrometry (EDX), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, spectrophotometer and Hall Effect measurements respectively. XRD results have shown that the change in (Fe/Co) ratio leads to the transformation of stannite CFTS (x = 0%) to stannite CCTS (x = 100%) with the same preferred orientation (112) plan. CFTS and CCTS phases have been confirmed by Raman peaks located respectively at 318 and 325 cm-1. A uniform and dense distribution of CCTS thin film were observed by scanning electron microscopy (SEM). Estimated band gap values of CFTS and CCTS thin films were equal to 1.46 eV and 1.32 eV respectively. Electrical resistivity value was decreased from 5.82 10-3 Ω.cm for CFTS thin film to 5 10-3 Ω.cm for CCTS thin film. These experimental results allow us to consider CFTS and CCTS as good candidates to be used as absorber materials in solar cell devices. Photocatalytic activities of CCTS thin film, CCTS/SnO2:F, CCTS/In2S3 and CCTS/In2S3/SnO2:F heterojunctions have been investigated under sun light irradiation using methylene blue (MB) as representative pollutant dye. It was found that the photodegradation rate was near to 86% in the presence of CCTS /In2S3 / SnO2:F heterojunction after 4 hours which leads to considering it as a good candidate to implement eco-friendly, sun-powered devices for removing organic pollution in waste water. for photocatalysis applications.

Undoped and Zn-doped FeO thin films were grown through spray pyrolysis. Zinc doping effect on the physical properties was investigated in detail. X-ray diffraction analysis confirms that all the FeO thin films showed a rhombohedral structure. The surface morphological study shows an interesting dendrite structure. The estimated band gaps energies were increased from 2.13 to 2.21 eV for indirect transition and from 1.80 to 1.85 eV for direct transition as function of doping ratio which was increased from 2 to 8 at. % Zn. The resistivity value (ρ) of un-doped FeO thin film is 6.06 × 10 Ω. cm and as adding Zn ions, ρ consequently decreased to 52 Ω. cm for 6 at. % Zn-doped FeO thin films. Vibrating sample magnetometer (VSM) measurements showed an increase of the saturation magnetization with the Zn insertion. Further, a ferromagnetic behavior was observed., We acknowledge funding from the Tunisian Ministry of Higher Education and Scientific Research

As a natural adsorbent, sisal (agave sisalana) fibers were used to extract Cu, Ni, Mn, and Zn from diesel oil samples for posterior determination (i.e., direct analytical measurements on the solid support) of the analytes by energy dispersive X-ray fluorescence spectrometry (EDXRF). In the proposed procedure, 0.2 g of sisal fiber was directly added to 5.0 mL of diesel oil contained in a glass tube. After 5 min of contact time, the mixture was filtered, and the collected fibers were oven-dried for 30 min at 70 °C. After drying, the analytes were quantified directly by EDXRF using the sisal fibers as a solid support. The calibration curves showed linear concentration ranges of 0.09–1.00, 0.12–1.00, 0.09–1.00, 0.06–1.0 μg g−1 for Cu, Ni, Mn, and Zn, respectively. The limits of detection (LOD) for Cu, Ni, Mn, and Zn were 0.03, 0.04, 0.03, and 0.02 μg g−1, respectively. The repeatability, evaluated by performing ten measurements at a concentration of 0.50 μg g−1 for each metal, with the results expressed in terms of the relative standard deviation (RSD), was 3.2, 6.5, 6.8, and 6.1% for Cu, Ni, Mn, and Zn, respectively. The results obtained by the proposed method were compared with the results obtained by a comparative method using inductively coupled plasma optical emission spectrometry, and both results showed good agreement. The proposed method was applied for Ni, Cu, Mn, and Zn determination in diesel oil samples collected from different gas stations.

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.

This paper proposes a closed inline system for decomposition of wine, aiming at the determination of lead using electrothermal atomization atomic absorption spectrometry (ETAAS). The system is built using a 0.8 mm diameter PTFE tube, which is wrapped around an 8 W UV lamp. The sample in the presence of 70% hydrogen peroxide is circulated on an 8 W UV lamp at the flow rate of 1 mL min−1 for 45 min. Under these conditions, the carbon content varied from 10% to 2% for a red wine sample before and after digestion, respectively. The system has allowed the determination of lead in wine samples using the analytical line 283.306 nm in the presence of aluminum as the chemical modifier and pyrolysis and atomization temperatures of 800 and 1800 °C, respectively. Then, lead can be quantified employing the external calibration technique with limits of detection 0.27 and quantification 0.89 µg L−1, and characteristics mass of 18 pg. The precision expressed by relative standard deviation (RSD%) was 2.13%, calculated using six replicates of a digested solution of a wine sample with the lead content of 16.35 µg L−1. For evaluation of the accuracy method, two wine samples were analyzed simultaneously by the method proposed and also by inductively coupled plasma mass spectrometry (ICP-MS). A statistical test demonstrated no significant difference between the means obtained by these two techniques. Also, experiments involving addition/recovery tests confirmed the method's accuracy. The system was employed for digestion and determination of lead in four Brazilian wine samples. The lead content varied from 2.19 to 43.48 µg L−1.

Liquid phase microextraction (LPME) has been widely used in extraction and preconcentration systems as an excellent alternative to conventional liquid phase extraction. In this work, a critical review is presented on LPME-based flow injection preconcentration systems. LPME techniques are classified into three main groups: single drop liquid phase microextraction (SDME), hollow fiber liquid phase microextraction (HF-LPME) and dispersive liquid-liquid microextraction (DLLME). Flow injection systems involving these techniques are described and evaluated, addressing aspects related to advantages, disadvantages, components, solvents, samples, and trends.

This work review shows a description of non-chromatographic and chromatographic procedures proposed for speciation analysis of antimony employing hydride generation (HG) coupled to atomic fluorescence spectrometry (AFS) in environmental matrices, including details of HG-AFS as the detection technique. Non-chromatographic procedures have been developed based on the determination of total antimony after a pre-reduction step. The main reductant agents used are discussed. Antimony(III) has been quantified in the presence of a masking agent. The most used are citrate and 8-hydroquinoline. Chromatographic procedures have been established utilizing High-Performance Liquid Chromatography (HPLC). Advantages and drawbacks of the main extracting agents and mobile phases employed in these procedures have been discussed. Also, alternatives to improve the method sensitivity during the determination of antimony(V) and its organic compounds by HPLC-HG-AFS are presented. Speciation procedures involving preconcentration steps have allowed methods with high sensitivity. Tables evidencing applications of non-chromatographic and chromatographic procedures in speciation studies of environmental samples are also shown. Advantages of automated and flow systems for antimony speciation studies are also highlighted.

In this paper, an on-line preconcentration system has been proposed for speciation analysis of inorganic arsenic in seawater. It is based on the selective reaction of As(III) with ammonium pyrrolidine dithiocarbamate (APDC) followed by sorption of the formed complex under a minicolumn containing polytetrafluoroethylene (PTFE). Afterward, arsenic sorbed has been eluted using a 2 mol L−1 hydrochloric acid solution. The preconcentration system was optimized employing multivariate techniques. A two-level full factorial design and a Doehlert matrix were performed to determining the critical conditions of the factors: the acidity of the sample, APDC concentration, and sample flow rate. So, the procedure using the optimized conditions allows the determination of As(III) with limits of detection and quantification of 0.02 and 0.07 μg L−1. Total arsenic has been determined after reduction of As(V) using thiourea in acid media and the limits achieved were 0.03 and 0.09 μg L−1, for detection and quantification, respectively. The precision estimated as the relative standard deviation (RSD) was 5.3%, which was calculated using seven replicates of As(III) solution with a concentration of 0.50 μg L−1. The accuracy of the method was confirmed by the analysis of the certified reference material CASS-4 seawater furnished by the National Research Council of Canada-NRCC. The system proposed was employed for speciation analysis of arsenic in five seawater samples collected from Todos os Santos Bay, Salvador, Brazil. The As(III) contents obtained varied from 0.09 to 0.51 and the total arsenic contents varied from 0.20 to 0.66 μg L−1. The results are in agreement with other data reported in the literature.

This review presents fundamentals and a critical evaluation of the multivariate optimization techniques employed by the analytical chemistry. Characteristics of the surface response methodologies (SRM) are shown and compared. Additionally, a bibliographic survey was performed in the web of science database using as keywords names of the chemometric tools utilized for experimental designs. Papers classified in the analytical chemistry area demonstrated that the two-level full factorial design had often been used for preliminary assessment of factors. For determination of critical conditions using quadratic models, the central composite design (CCD) is the technique most utilized by the analytical chemists. Remarks about standardized effects and the Pareto chart, description of the several multiple response functions employed in experimental designs, efficiencies of the SRM's and robustness tests are also discussed.

This work proposes an on-line preconcentration system using ion-imprinted polymer (IIP) for determination of bismuth in seawater employing atomic fluorescence spectrometry (AFS). The polymer was synthesized using 2- (5-bromo-2-pyridylazo) -5-diethylaminophenol (Br-PADAP) for complex formation, ethylene glycol dimethacrylate (EGDMA), cross-linking reagent and methacrylic acid (AMA) reagents, used as the functional monomer, 2,2-azobisisobutyronitrile was used as the radical initiator. The polymer was characterized employing the Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The determination of bismuth was performed employing hydride generation atomic fluorescence spectrometry (HG AFS) and the experimental conditions were optimized using a Box Behnken design involving the factors sample pH, eluent concentration and sodium tetrahydroborate concentration. So, using the optimized conditions the system allows the determination of bismuth with limits of detection and quantification of 26 and 88 ng L−1, a preconcentration factor of 19.8. All these parameters were determined using a sample volume of 25 mL. The precision expressed as relative standard deviation (RSD%) was 3.7% for a bismuth(III) solution of concentration 0.25 µg L−1. The system proposed was applied for the determination of bismuth in four seawater samples collected in Salvador City, Bahia State, Brazil. The concentrations obtained varied from 0.38 to 0.45 μg L−1. The accuracy was evaluated by addition/recovery test, and the recoveries found varied from 92% to 101%.

In this work is proposed a solid phase preconcentration system of Co2+ ions and its posterior determination by GFAAS in which fractional factorial design and response surface methodology (RSM) were used for optimization of the variables associated with preconcentration system performance. The method is based on cobalt extraction as a complex Co2+-PAN (1:2) in a mini-column of polyurethane foam (PUF) impregnated with 1-(2-pyridylazo)-naphthol (PAN) followed by elution with HCl solution and its determination by GFAAS. The chemical and flow variables studied were pH, buffer concentration, eluent concentration and preconcentration and elution flow rates. Results obtained from fractional factorial design 2(5-1) showed that only the variables pH, buffer concentration and interaction (pH X buffer concentration) based on analysis of variance (ANOVA) were statistically significant at 95% confidence level. Under optimised conditions, the method provided an enrichment factor of 11.6 fold with limit of detection and quantification of 38 and 130 ng L-1, respectively, and linear range varying from 0.13 to 10 µg L-1. The precision (n = 9) assessed by relative standard deviation (RSD) was respectively 5.18 and 2.87% for 0.3 and 3.0 µg L-1 cobalt concentrations.

In this work, analytical strategies were applied aiming at determining sources and ecological risk of PAHs in river sediments. A total of 23 PAHs (16 EPA + 7 alkylated derivatives) were determined in sediment samples. The concentration of total PAH (∑ 23 PAH) span from 0.260 to 2.10 μg g − 1 dw. The molecular ratios indicated a prevalence of pyrolytic pollution sources due to wood combustion processes and refined oil products. The ecological risk was assessed by considering the Sediment Quality Guidelines (SQGs). It was noted that all of the individual PAH concentrations are below the ERM (average variation effect). The ∑ 23 PAH was also below the total of ERL (low variation effect) from 4.02 μg g − 1 dw. The synergy between individual PAHs was assessed using the indices of quality (mSQGq). Accordingly, the risk associated with the simultaneous contamination of the total PAH varied from low to moderate for the different sediments samples of river. The river is located in the state of Bahia, in a region that concentrates the first and largest integrated industrial complex of Brazil.

This work proposes a method for the determination of free and total sulfur(IV) compounds in coconut water samples, using the high-resolution continuum source molecular absorption spectrometry. It is based on the measurement of the absorbance signal of the SO2 gas generate, which is resultant of the addition of hydrochloric acid solution on the sample containing the sulfating agent. The sulfite bound to the organic compounds is released by the addition of sodium hydroxide solution, before the generation of the SO2 gas. The optimization step was performed using multivariate methodology involving volume, concentration and flow rate of hydrochloric acid. This method was established by the sum of the absorbances obtained in the three lines of molecular absorption of the SO2 gas. This strategy allowed a procedure for the determination of sulfite with limits of detection and quantification of 0.36 and 1.21mgL-1 (for a sample volume of 10mL) and precision expressed as relative standard deviation of 5.4% and 6.4% for a coconut water sample containing 38.13 and 54.58mgL-1 of free and total sulfite, respectively. The method was applied for analyzing five coconut water samples from Salvador city, Brazil. The average contents varied from 13.0 to 55.4mgL-1 for free sulfite and from 24.7 to 66.9mgL-1 for total sulfur(IV) compounds. The samples were also analyzed employing the Ripper´s procedure, which is a reference method for the quantification of this additive. A statistical test at 95% confidence level demonstrated that there is no significant difference between the results obtained by the two methods.

The development of a collaborative study as a requirement for the preparation of a laboratory reference material candidate is reported in this paper. The evaluation was performed by 13 laboratories invited to quantify the calcium, potassium, magnesium, phosphorus, copper, iron, manganese and zinc; 8 of them presented results for all the analytes under investigation. The data were statistically analyzed by applying the z-score robust technique as recommended by ISO Guide 35. For the potassium element, laboratories 4 and 13 presented questionable results. Laboratory 5 proved to be unsatisfactory for calcium and zinc. ANOVA-PCA and DD-SIMCA were also applied to evaluate stability and interlaboratory studies results, respectively. It has been demonstrated that multivariate data analysis can be successfully applied as an alternative method to the recommendations made by ISO 13528 and ISO Guide 35 with defined confidence intervals.

In the present paper is presented a review on the application of Doehlert design in the optimization of some of the steps of analytical procedures aimed the analysis of food samples. The theoretical principles and the main characteristics of this type of design are described. In addition, the main advantages and limitations of Doehlert design over other designs (Central Composite Design and Box-Behnken) and its application in the area of food analysis are discussed. Finally, to illustrate its potential, some examples of Doehlert design application in other areas of food chemistry without the purpose of analytical determination will be briefly presented.

This work presents the advantages, drawbacks and performances of Multisyringe Flow Injection Analysis (MSFIA) systems in the determination of metals, metalloids, organic and inorganic compounds in several kind of samples employing spectroanalytical techniques. General topics, as multisyringe description, software and comparison between MSFIA and other continuous flow techniques are also discussed. Employ of MSFIA systems coupled to molecular spectrophotometry, atomic spectrometry and hyphenation with other techniques are presented.

This work proposes the use of high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry (HPLC-ICP-MS) for simultaneous speciation of arsenic and chromium in iron supplements used for the treatment of anemia. The sample preparation procedure recommended for the total determination of arsenic and chromium was established using acid digestion in a microwave assisted oven. For speciation analysis, however, the microwave-assisted extraction procedure involved the use of water as extraction solvent at 90 °C for 30 min. The chromatographic separation was performed using a mobile phase containing 1.0 mM tetrabutylammonium hydroxide (TBAH), 0.7 mM ethylenediaminetetraacetic acid (EDTA) and 5% methanol at pH 7.2. Helium was used in the collision cell for elimination of the interferences. Under optimized conditions, the separation and detection of the As(III), As(V), Cr(III) and Cr(VI) species can be performed in 5 min, permitting their quantification with the external calibration technique with standards prepared in the mobile phase. The limits of quantification obtained were 0.008, 0.010, 0.5 and 0.14 µg g−1, for As(III), As(V), Cr(III) and Cr(VI), respectively. The accuracy of the method was evaluated and confirmed by addition/recovery tests. The recoveries obtained varied from 81% to 110%. The proposed method was applied to the speciation analysis of arsenic and chromium in commercially available iron supplements acquired in several cities in Brazil and Spain. The content of the species ranged from 0.01 to 1.3 µg g−1 for arsenic, and from 0.4 to 61.2 µg g−1 for chromium.

This paper proposes the use of a multisyringe flow injection analysis (MSFIA) system for inorganic antimony speciation analysis, trimethyl antimony(V) and determination of total antimony in soil samples using hydride generation atomic fluorescence spectrometry (HG-AFS). Total antimony has been determined after reduction of antimony(V) to antimony(III) using potassium iodide and ascorbic acid. For determination of total inorganic antimony the sample is percolated in a mini-column containing the Dowex 50W-X8 resin for retention of the organic species of antimony. Antimony(III) is quantified in presence of 8-hydroxyquinoline as masking agent for antimony(V) after an extraction step of the organic antimony species using the also same mini-column. The trimethyl antimony(V) content is found by difference between total antimony and total inorganic antimony. By other hand, antimony(V) is quantified by difference between total inorganic antimony and antimony(III). The analytical determinations were performed using sodium tetrahydroborate as reducing agent. The optimization step was performed using two-level full factorial design and Doehlert matrix involving the factors: hydrochloric acid and sodium tetrahydroborate concentrations and sample flow rate. The optimized experimental conditions allow the antimony determination utilizing the external calibration technique with limits of detection and quantification of 0.9 and 3.1ngg-1, respectively, and a precision expressed as relative standard deviation of 3.2% for an antimony solution of 5.0µgL-1. The method accuracy was confirmed by analysis of the soil certified reference material furnished from Sigma-Aldrich RTC. Additionally, addition/recovery tests were performed employing synthetic solutions prepared using trimethyl antimony(V), antimony(III), antimony(V) and five soil samples. The antimony extraction step was performed in a closed system using hydrochloric acid, ultrasonic radiation and controlled temperature. The method proposed was applied for analysis of thirteen soil samples collected in different sites of the Balearic Islands, Spain, and the results obtained varied from 19 to 46ngg-1 for trimethyl antimony(V) and from 113 to 215ngg-1 for total inorganic antimony. The concentrations obtained to antimony(V) were always higher than for antimony(III) in all the analyzed samples.

Robustness has been defined as being the capacity of an analytical procedure to produce unbiased results when small changes in the experimental conditions are made voluntarily. The robustness tests are important because sometimes the analyst needs to modify one or a few chemical and/or instrumental parameters of a procedure, and this can only be done if these changes do not affect the method's accuracy considering the previously optimized results. The two-level full factorial designs would be the most recommended for robustness evaluations of analytical methods. However, for operational convenience, the fractional factorial designs are more often used. The Plackett-Burman designs have been one of the most employed in robustness evaluations. Some examples of robustness test applications in some analytical methods employing different chemometric tools are given. A discussion about the terms robustness and ruggedness is made. Seventy five references are cited.

15 pags., 9 figs., Until recently, the amount of solar irradiance reaching the Earth surface was considered to be a steady value over the years. However, there is increasing observational evidence showing that this quantity undergoes substantial variations over time, which need to be addressed in different scenarios ranging from climate change to solar energy applications. With the growing interest in developing solar energy technology with enhanced efficiency and optimized management, the monitoring of solar irradiance at the ground level is now considered to be a fundamental input in the pursuit of that goal. Here, we propose the first fiber-based distributed sensor able of monitoring ground solar irradiance in real time, with meter scale spatial resolutions over distances of several tens of kilometers (up to 100 km). The technique is based on an optical fiber reflectometry technique (CP-φOTDR), which enables real time and long-range high-sensitivity bolometric measurements of solar radiance with a single optical fiber cable and a single interrogator unit. The method is explained and analyzed theoretically. A validation of the method is proposed using a solar simulator irradiating standard optical fibers, where we demonstrate the ability to detect and quantify solar irradiance with less than a 0.1 W/m resolution., This research was funded in part by: the European Commission (FINESSE, MSCA-ITN-ETN-722509; Ocean-DAS 875302); Ministerio de Ciencia, Innovación y Universidades (IJCI-2017-33856, RTI2018-097957-B-C31, RTI2018-097957-B-C33); Comunidad de Madrid and FEDER program (SINFOTON2-CM: P2018/NMT-4326

In 2016, a novel interrogation technique for phase-sensitive (Φ)OTDR was mathematically formalized and experimentally demonstrated, based on the use of a chirped-pulse as a probe, in an otherwise direct-detection-based standard setup: chirped-pulse (CP-)ΦOTDR. Despite its short lifetime, this methodology has now become a reference for distributed acoustic sensing (DAS) due to its valuable advantages with respect to conventional (i.e., coherent-detection or frequency sweeping-based) interrogation strategies. Presenting intrinsic immunity to fading points and using direct detection, CP-ΦOTDR presents reliable high sensitivity measurements while keeping the cost and complexity of the setup bounded. Numerous technique analyses and contributions to study/improve its performance have been recently published, leading to a solid, highly competitive and extraordinarily simple method for distributed fibre sensing. The interesting sensing features achieved in these last years CP-ΦOTDR have motivated the use of this technology in diverse applications, such as seismology or civil engineering (monitoring of pipelines, train rails, etc.). Besides, new areas of application of this distributed sensor have been explored, based on distributed chemical (refractive index) and temperature-based transducer sensors. In this review, the principle of operation of CP-ΦOTDR is revisited, highlighting the particular performance characteristics of the technique and offering a comparison with alternative distributed sensing methods (with focus on coherent-detection-based ΦOTDR). The sensor is also characterized for operation in up to 100 km with a low cost-setup, showing performances close to the attainable limits for a given set of signal parameters [≈tens-hundreds of pe/sqrt(Hz)]. The areas of application of this sensing technology employed so far are briefly outlined in order to frame the technology., This work was supported by project FINESSE MSCA-ITN-ETN-722509; the DOMINO Water JPI project under the WaterWorks2014 cofounded call by EC Horizon 2020 and Spanish MINECO; Comunidad de Madrid and FEDER Program under grant SINFOTON2-CM: P2018/NMT-4326; the Spanish Government under projects TEC2015-71127-C2-2-R and RTI2018-097957-B-C31. M.R.F.M and H.F.M. acknowledge financial support from the Spanish MICINN under contracts no. FJCI-2016-27881 and IJCI-2017-33856, respectively.

This paper proposes a method using high resolution continuum source graphite furnace atomic absorption spectrometry (HR CS GFAAS) for the sequential determination of cadmium and lead in organic pharmaceutical formulations. The temperature program for cadmium was established employing the pyrolysis and atomization temperatures of 800 °C and 1400 °C, respectively, and the atomization temperature of 2000 °C for lead, being that the pyrolysis temperature for lead is the same used for the cadmium atomization. The analytical measures were performed using the primary lines for cadmium (228.802 nm) and (217.001 nm) for lead. The absorbance signals obtained were quantified by peak area using 3 pixels for both analytes, utilizing as chemical modifier an acid mixture palladium-magnesium. Employing the optimized conditions, the method allows the sequential determination of cadmium and lead, with limits of detection and quantification of 4 and 13 ng g− 1 for cadmium and 49 and 165 ng g− 1 for lead, respectively. The characteristics masses were also calculated, being 1.6 pg for cadmium and 12.4 pg for lead. The precision expressed as relative standard deviation (%RSD) were 5.0% for cadmium and 6.2% for lead, determined by ten replicates of a sample solution with cadmium and lead contents of 38 and 303 ng g− 1, respectively. The method accuracy was evaluated and confirmed by analysis of two certified reference materials of leaves furnished by National Institute of Standards and Technology (NIST). Furthermore, addition/recovery tests were also performed using three different real samples. The recoveries obtained varied from 94 to 114%, it confirming the method accuracy. The method was applied for the determination of cadmium and lead in ten different pharmaceutical formulations and the analyte concentrations found in the samples varied from 16 to 51 ng g− 1 for cadmium and of 179 to 318 ng g− 1 for lead, being that for six samples the lead contents were lower than the limit of quantification (165 ng g− 1) and for three samples the cadmium concentrations were lower than 13 ng g− 1. All samples were also analyzed employing inductively coupled plasma mass spectrometry (ICP-MS) and the results obtained are agreement with those achieved by HR CS GFAAS.

Submitted by Gisele Mara Hadlich (gisele@ufba.br) on 2019-01-14T01:47:21Z No. of bitstreams: 1 Determination and evaluation of the mineral composition of breadfruit (Artocarpus altilis) using multivariate analysis technique.pdf: 533500 bytes, checksum: 2126fa71b9fb9c9133a217f866568538 (MD5) Approved for entry into archive by Jessica Alves (alves.jessica@ufba.br) on 2019-03-20T13:47:47Z (GMT) No. of bitstreams: 1 Determination and evaluation of the mineral composition of breadfruit (Artocarpus altilis) using multivariate analysis technique.pdf: 533500 bytes, checksum: 2126fa71b9fb9c9133a217f866568538 (MD5) Made available in DSpace on 2019-03-20T13:47:47Z (GMT). No. of bitstreams: 1 Determination and evaluation of the mineral composition of breadfruit (Artocarpus altilis) using multivariate analysis technique.pdf: 533500 bytes, checksum: 2126fa71b9fb9c9133a217f866568538 (MD5) Breadfruit is a fruit originated from South Pacific and afterward it was widespread in rest of Oceania. In Brazil it is known as “fruta pão” and has been consumed mainly by humble people. In home use, breadfruit has been consumed cooked, fried or roasted. Industrially, it has been employed to prepare breads and flours. In the present paper, the mineral composition of breadfruit (Artocarpus altilis) was determined and evaluated. Raw breadfruit samples and cooked using domestic methods as boiling and microwave heating were digested in acid media and the elements potassium, calcium, phosphor, magnesium, iron, sodium and manganese were determined employing inductively coupled plasma optical emission spectrometry (ICP OES). Cadmium and lead were also determined using graphite furnace atomic absorption spectrometry (GFAAS), but the concentrations found were lower than the limits of quantification for these elements. Eleven samples were acquired in several cities from Bahia state, Brazil. All these samples were analyzed in triplicate. The data obtained were evaluated employing the multivariate analysis techniques: Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA). Both techniques showed that the cooking methods using microwave heating and boiling cause loss of the nutrients. PCA also evidenced that the element concentrations in the samples cooked using microwave heating are higher than in the samples cooked by boiling using stove. The average concentrations of the determined elements (expressed as mg 100 g−1 of sample) in raw samples were as follows: 269.4 for potassium, 40.97 for phosphorus, 26.32 for calcium, 24.35 for magnesium, 1.41 for sodium, 0.1891 for iron and 0.0381 for manganese. Microchemical Journal

In this work, a simple, fast, and robust method was developed for the direct and simultaneous determination of copper and iron in flours using solid sample analysis and high-resolution continuum source graphite furnace atomic absorption spectrometry. The secondary lines at 217.894 and 217.812 nm were used for all simultaneous measurements of copper and iron, respectively. The pyrolysis and atomization temperatures were of 1400 and 2400 °C, respectively, and no chemical modifier was necessary. The slope of calibration curve obtained, using the rice flour certified reference material (NIST 1568a) as solid standard, presented no significant difference when compared with the slope of external calibration curve using aqueous standard, at 95 % confidence level. Under these conditions, the limits of quantification obtained were 0.38 (Cu) and 0.11 (Fe) mg kg−1, respectively. The relative standard deviations (RSD) varied from 0.5 to 14 % for copper and from 4.9 to 17 % for iron. The method accuracy was confirmed by analysis of two certified reference materials, rice flour NIST 1568a and wheat flour NIST 1567a, and the results were in agreement with the certified values, at 95 % confidence level. The proposed method was applied for the analysis of flour samples (corn, wheat, and white bean), both of conventional and organic cultivation. The concentration values varied in the range of 0.6–5.9 mg kg−1 for copper and of 2.6–50.4 mg kg−1 for iron. The iron concentrations in all samples analyzed were not in agreement with the value established by the Brazilian legislation, which is of 42 mg of iron per kilogram of flour.

The present paper proposes the employ of a mixture containing sucrose–tartaric acid–citric acid as chemical modifier for the determination of lead using electrothermal atomization with atomic absorption spectrometry (ET AAS). The reagent concentrations in the modifier solution were established using a mixture design. Using the optimized conditions the pyrolysis and atomization temperatures established were 900 and 2000 °C, respectively. So, the method allows the determination of lead with limits of detection and quantification of 0.14 and 0.46 μg L − 1 , characteristic mass of 18 pg and a precision expressed as relative standard deviation of 1.3%, 2.6% and 4.0% for lead solutions with concentrations of 10.0, 5.0 and 2.0 μg L − 1 , respectively. The accuracy was confirmed by analysis of the following certified reference materials: NIST SRM 1515 (apple leaves), NIST SRM 1570a (trace elements in spinach leaves), NIST SRM 1643e (trace elements in water), CASS-4 (nearshore seawater) and BCR-713 effluent wastewater IRMM. The method proposed was applied for the determination of lead in surface water samples collected in the Paraguacu River, Cachoeira City, Brazil in August 2015. Nine samples were analyzed and the lead content found varied from 0.64 to 8.25 μg L − 1 , being always lower than the permissible maximum level stipulated by the Brazilian Ministry of Health, which is 10.0 μg L − 1 .

Characterization and evaluation of the uncertainty of new powdered milk laboratory reference material were proposed following the recommendations of the ISO Guide 35. A characterization was established through the interlaboratory comparison with the participation of 15 laboratories, being one international. To obtain the property value, initially, the data from the collaborative trial were statistically evaluated using the Grubbs, Cochran, and z-scores tests to identify possible outliers. One-way ANOVA and linear regression analysis were employed to obtain the standard uncertainties associated with characterization (uchar), between-bottle homogeneity (ubb), and long-term stability (ults). The properties values and combined uncertainty (URM) for at the 95% confidence level (k = 2) were as follows (mg g−1): Ca (8.795 ± 1.137), Fe (0.107 ± 0.017), K (11.727 ± 1.983), Mg (0.841 ± 0.125), Na (3.654 ± 0.672), P (7.572 ± 1.174), and Zn (0.032 ± 0.005). Based on the confidence ellipses obtained in the results of the laboratories, it was possible to infer the causes that led to the dispersion of the values. The new material can be a good alternative to evaluate routine procedures, quality control, and validation of analytical methods related to samples of milk and dairy products.

This work presents a multisyringe flow injection analysis (MSFIA) system for the automatic spectrophotometric determination of total iron in wine. The reaction is based on the complexation of Fe(II) with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (Br-PADAP). Ascorbic acid was used as reducing reagent for Fe(III) to Fe(II) and, in this way, to determine the total iron content in wine. The absorbance of the Fe(II)-(Br-PADAP)2 complex was measured at 748 nm. The proposed method provided a working rage from 0.36 to 5 mg L−1 of Fe(II), with a detection limit of 0.11 mg L−1 of Fe(II), a relative standard deviation of 0.42% (3 mg L−1 of Fe(II), n = 10), and a 46 h−1 injection throughput. The system is very simple, rapid and selective, and has been successfully applied to determine total iron in red, rose and white wine without any need for sample pre-treatment steps. The results agree well with ICP-AES, which used as a reference method.

This paper proposes a simple, rapid and green ultrasound assisted and ionic liquid dispersive microextraction procedure using pyrocatechol violet (PV) as complexing reagent and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)- imide [C6MIM][Tf2N] as ionic liquid for the detection of tin employing electrothermal atomic absorption spectrometry (ETAAS). The optimization step was performed using a two-level full factorial design involving the following factors: pH of the working media, amount reagents, ionic liquid volume and extraction time and the chemometric response was tin recovery. The procedure allowed the determination of tin with limits of detection and quantification of 3.4 and 11.3 ng L-1, respectively. The relative standard deviation was 4.5% for a tin solution of 0.50 mu g L-1. The validation method was confirmed by analysis of rice flour certified reference material. The method was applied for the quantification of tin in several food samples. The concentration range found varied from 0.10 to 1.50 mu g g(-1).

An extraction procedure involving ultrasound assisted radiation was proposed for the determination of mercury in river sediment samples using cold vapour atomic absorption spectrometry (CV AAS). The optimization step was performed using a two-level full factorial design, being that the studied factors were thiourea and hydrochloric acid concentrations, time and temperature of sonication and absorbance as the chemometric response. The experimental conditions of the extraction procedure found by optimization were as follows: hydrochloric acid concentration, 4 mol L−1; thiourea concentration, 0.75% (m v−1); sonication time, 20 min and sonication temperature, 60 °C. The validation studies demonstrated that by employing the optimized conditions, the method allows the determination of mercury using an external calibration technique with limits of detection and quantification of 10 and 35 ng L−1, respectively, and precision expressed as a relative standard deviation of 4.31% for a mercury solution with a concentration of 5.00 μg L−1. The limits of detection and quantification calculated for a sample mass of 0.20 g are respectively 1.04 and 3.46 ng g−1. The method accuracy was confirmed by analysis of the certified reference materials: NIST SRM 2709a San Joaquim Soil and BCR 320 Channel sediment. This method was applied for the determination of mercury in five sediment samples collected from the Sao Paulo River (Bahia State, Brazil). The mercury concentrations obtained varied from 13.8 to 38.5 ng g−1. These values are compatible with other data reported in the literature for mercury contents in uncontaminated sediment samples.

Simplex is an optimization technique that, in a general sense, does not require the use of complex mathematical and statistical tools and can be very useful in the development of analytical methods. In this work, a tutorial reviewing the basic concepts, fundamental approach and a work guide are presented for those who contemplate simplex optimization as a tool to develop analytical methods. The characteristics and rules for applying the basic and modified simplex algorithms commonly used for optimization are also described. Some studies demonstrating the application of simplex optimization in analytical chemistry are discussed to illustrate the applicability of this technique.

This paper describes a rapid and sensitive method for determination of the hair dye Basic Blue 41 in wastewater samples using screen-printed carbon electrodes modified with graphene (SPCE/Gr). The method is based on the reversible reduction of azo groups of the dye at potential of −0.23 V/−0.26 V, where both the anodic and cathodic currents increased 1,300 % when compared to screen-printed carbon (SPCE) and glassy carbon electrodes (GCE). The optimization of a square wave voltammetric method was performed by means of 23 factorial design, Doehlert matrix and multi-response assays, and the best parameters were: frequency (54.8 Hz), step potential (6 mV), pulse amplitude (43.7 mV) and pH 4.5. The analytical curve was constructed from 3.00×10−8 to 2.01×10−6 mol L−1, with detection and quantification limits of 5.00×10−9 and 1.70×10−8 mol L−1, respectively. The repeatability of the method evaluated for 10 consecutive measurements at concentrations of 1.70×10−7 mol L−1 and 1.70×10−6 mol L−1, showed relative standard deviation of 3.56 and 0.57 %, respectively. The sensor based in SPCE/Gr was successfully applied in wastewater samples collected from a drinking water treatment plant and validated by comparison with HPLC-DAD method with good accuracy.

The present work proposed an analytical method for the direct determination of chromium in infant formulas employing the high-resolution continuum source electrothermal atomic absorption spectrometry combined with the solid sample analysis (SS-HR-CS ET AAS). Sample masses up to 2.0mg were directly weighted on a solid sampling platform and introduced into the graphite tube. In order to minimize the formation of carbonaceous residues and to improve the contact of the modifier solution with the solid sample, a volume of 10 µL of a solution containing 6% (v/v) H2O2, 20% (v/v) ethanol and 1% (v/v) HNO3 was added. The pyrolysis and atomization temperatures established were 1600 and 2400 °C, respectively, using magnesium as chemical modifier. The calibration technique was evaluated by comparing the slopes of calibration curves established using aqueous and solid standards. This test revealed that chromium can be determined employing the external calibration technique using aqueous standards. Under these conditions, the method developed allows the direct determination of chromium with limit of quantification of 11.5 ng g(-1), precision expressed as relative standard deviation (RSD) in the range of 4.0-17.9% (n=3) and a characteristic mass of 1.2 pg of chromium. The accuracy was confirmed by analysis of a certified reference material of tomato leaves furnished by National Institute of Standards and Technology. The method proposed was applied for the determination of chromium in five different infant formula samples. The chromium content found varied in the range of 33.9-58.1 ng g(-1) (n=3). These samples were also analyzed employing ICP-MS. A statistical test demonstrated that there is no significant difference between the results found by two methods. The chromium concentrations achieved are lower than the maximum limit permissible for chromium in foods by Brazilian Legislation.

An assisted liquid-liquid extraction of copper, iron, nickel and zinc from vegetable oil samples with subsequent determination by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS) was optimized by applying a full factorial design in two levels and the response surface methodology, Box-Behnken. The effects of the acid concentration and the amplitude, cycle and time of sonication on the extraction of the analytes, as well as their interactions, were assessed. In the selected condition (sonication amplitude = 66%, sonication time = 79 s, sonication cycle = 74%), using 0.5 mol L(-1) HCl as the extractant, the limits of quantification were 0.14, 0.20, 0.21 and 0.04 μg g(-1) for Cu, Fe, Ni and Zn, respectively, with R.S.D. ranging from 1.4% to 3.6%. The proposed method was applied for the determination of the analytes in soybean, canola and sunflower oils.

The present paper reports the advantages, drawbacks and applications of the main techniques of sample preparation employed during the determinations of total mercury and methylmercury in food matrices employing analytical methods such as: cold vapor atomic absorption spectrometry (CV AAS), cold vapor atomic fluorescence spectrometry (CV AFS), inductively coupled plasma mass spectrometry (ICP-MS), voltammetry, and neutron activation analysis. The use of slurry sampling, solid sampling, microwave assisted extraction, reflux system by cold finger and Vigreux column was discussed. Also a brief text on the use of chromatographic techniques for the speciation analysis of mercury is presented. A list of 134 references is cited and the analytical characteristics of some these procedures proposed are shown as tables.

Submitted by Gisele Mara Hadlich (gisele@ufba.br) on 2018-10-02T18:09:12Z No. of bitstreams: 1 1-s2.0-S0039914017310494-main.pdf: 301332 bytes, checksum: c47f41a8de22952ea1b705b044d9b6db (MD5) Approved for entry into archive by Jessica Alves (alves.jessica@ufba.br) on 2018-10-04T15:09:57Z (GMT) No. of bitstreams: 1 1-s2.0-S0039914017310494-main.pdf: 301332 bytes, checksum: c47f41a8de22952ea1b705b044d9b6db (MD5) Made available in DSpace on 2018-10-04T15:09:57Z (GMT). No. of bitstreams: 1 1-s2.0-S0039914017310494-main.pdf: 301332 bytes, checksum: c47f41a8de22952ea1b705b044d9b6db (MD5) Previous issue date: 2018 This work presents the optimization of a sample preparation procedure using microwave-assisted digestion for the determination of nickel and vanadium in crude oil employing inductively coupled plasma optical emission spectrometry (ICP OES). The optimization step was performed utilizing a two-level full factorial design involving the following factors: concentrated nitric acid and hydrogen peroxide volumes, and microwave-assisted digestion temperature. Nickel and vanadium concentrations were used as responses. Additionally, a multiple response based on the normalization of the concentrations by the highest values was built to establish a compromise condition between the two analytes. A Doehlert matrix optimized the instrumental conditions of the ICP OE spectrometer. In this design, the plasma robustness was used as chemometric response. The experiments were performed using a digested oil sample solution doped with magnesium(II) ions, as well as a standard magnesium solution. The optimized method allows for the determination of nickel and vanadium with quantification limits of 0.79 and 0.20 μg g−1 , respectively, for a digested sample mass of 0.1 g. The precision (expressed as relative standard deviations) was determined using five replicates of two oil samples and the results obtained were 1.63% and 3.67% for nickel and 0.42% and 4.64% for vanadium. Bismuth and yttrium were also tested as internal standards, and the results demonstrate that yttrium allows for a better precision for the method. The accuracy was confirmed by the analysis of the certified reference material trace element in fuel oil (CRM NIST 1634c). The proposed method was applied for the determination of nickel and vanadium in five crude oil samples from Brazilian Basins. The metal concentrations found varied from 7.30 to 33.21 μg g−1 for nickel and from 0.63 to 19.42 μg g−1 for vanadium. Talanta

A non-chromatographic automated system for the speciation and determination of inorganic and trimethylantimony (TMSb) exploiting multisyringe flow injection analysis (MSFIA) with hydride generation (HG) and atomic fluorescence spectrometry (AFS) is described. A cationic minicolumn was used for retaining the methylated forms of Sb which can generate hydrides, minimizing errors in the inorganic antimony speciation step. The optimization was performed in a multivariate way by employing a three-variable Box–Behnken design and a multiple response strategy. So, this method allows the quantification of Sb using the external calibration with aqueous standards. The method is suitable for monitoring drinking, surface and ground waters according to regulations established by the EU directives for antimony (5.0 μg L−1), and it was applied to the speciation of inorganic antimony and TMSb in several spiked water samples with recoveries close to 100%. The detection limits were 0.03 μg L−1 for Sb(III) and Sb(V) and 0.13 μg L−1 for TMSb. The method was satisfactorily applied to the determination of Sb(III), Sb(V) and TMSb in different water samples collected in Balearic Islands, Spain.

This work evaluated the influence of the cooking methods (cooked in a water bath, in a stove, and in a microwave oven) on the mineral composition of mustard leaves (Sinapis alba). So, raw and cooked samples were digested and afterward the elements calcium, magnesium, potassium, sodium, iron, zinc, phosphor, barium and sulfur were determined using inductively coupled plasma optical emission spectrometry (ICP OES). The experimental work involved a set of five samples from different locations, processed in triplicates. The results were evaluated employing Principal Component Analysis (PCA), Hierarchical Cluster Analysis (HCA) and Linear Discriminate Analysis (LDA). All techniques showed that the mineral content of the raw and cooked samples in a water bath is different from the samples cooked in stove and microwave oven. Especially for potassium, whose content is strictly controlled for chronic renal patients, this study showed that cooking using microwave oven has the greatest efficiency for reduction.