Multi-flow calibration (MFC) is based on monitoring the analytical signal from a single calibration standard solution at several different nebulization gas flow rates (Q), which normalizes plasma conditions and minimizes matrix effects. In the present study, MFC was evaluated, for the first time, applied to inductively coupled plasma optical emission spectrometry (ICP OES) and inductively coupled plasma mass spectrometry (ICP-MS) to analyze different and complex-matrix samples. Al, As, Cd, Cr, Cu, Mn, Pb, and Zn were determined by ICP OES, while As, Cd, Co, Cu, Hg, Mo, Mn, Ni, Se, Sb, Pb, and V were determined by ICP-MS. MFC results were compared with those obtained using external standard calibration (EC) for both techniques and in all cases, MFC showed equal or superior accuracy (recoveries between 80-120%) compared to EC, and lower relative standard deviation (RSDs ≤ 10%). Several tests were also performed using only two nebulization gas flows to build linear models for calibration (called two-flow calibration, TFC) and the accurate results (recoveries ranged from 80 to 110% for ICP OES and from 81 to 102% for ICP-MS) suggests that this strategy can be also applied, resulting in a method with high sample throughput.

Croton grewioides Baill. popularly known as “canelinha” or “canelinha-de-cheiro” has been used for the treatment of influenza, antitussive, febrifuge and headache; however, the study of its phytochemical composition is limited. The aim of this study was to investigate the effect of the extraction method and seasonality through leaf extracts of four accessions of Croton grewioides by fingerprint chromatograms aided by principal component analysis to analyze the differences and similarities among the samples. We aimed also to provide chemical characterization of isolated secondary metabolites using semi-preparative liquid chromatography. The results showed that only the chemical profile of the methanolic extracts of accessions 101 and 113 were influenced by the seasonality. For the first time, four flavonoids were isolated through semi-preparative chromatography in this species, characterized as quercetin 3-O-β-D-galactopyranosyl-(1→2)-α-L-rhamnopyranoside-(1→6)-α-L-rhamnopyranoside (1), quercetin 3-O-β-D-galactopyranosyl-(1→2)-α-apiopyranoside-(1→6)-α-L-rhamnopyranoside (2), quercetin 3-O-glucopyranoside (3) and 3-O-methyl-quercetin (4), the flavonoid (2) has been recognized as a new triglycosylated derivative.

Over the years, laser-induced breakdown spectroscopy (LIBS) has been reported in the literature as an alternative to traditional methods of analysis, becoming well established among spectroanalytical techniques. LIBS is a technique widely used for qualitative approaches; however, it is necessary considerable effort for use in quantitative analysis, mainly due to severe matrix effects. These limitations make it difficult to broaden the application of LIBS in quantitative analysis. In this sense, this review discusses recent advances in calibration strategies applied in LIBS for minimizing matrix effects and enabling determination with satisfactory accuracy and precision. Applications, advantages, and limitations of the calibration strategies, such as matrix-matching calibration (MMC), internal standardization (IS), standard addition (SA), multi-energy calibration (MEC), one-point gravimetric standard addition (OP GSA), one-point and multi-line calibration (OP MLC), slope ratio calibration (SRC), two-point calibration transfer (TP CT), single-sample calibration (SSC), multiple linear regression (MLR), principal component regression (PCR), partial least squares (PLS) and artificial neural networks (ANN) are discussed.

This study presents a microwave-assisted procedure for sample preparation of cocoa beans using diluted HNO3 with H2O2 for the determination of Ba, Ca, Cu, K, Mg, Mn, P, S, Sr and Zn by inductively coupled plasma optical emission spectrometry (ICP OES). Doehlert modified design was used for optimization of experimental condition, and the volume of H2O2 (0, 0.5, 1.75 and 3 mL) and concentration of HNO3 (0.5, 3.75 and 7 mol L-1) were evaluated. The best experimental conditions were chosen considering lower residual acidity (RA), lower dissolved organic carbon (DOC) and the acceptable trueness range (80-120%), were 5 mL of 3.75 mol L-1 HNO3 and 1.75 mL of 30% v v-1 H2O2. The procedure was validate using certified reference materials (CRMs), digested using the optimized conditions. The proposed procedure was applied in twelve samples of cocoa beans, and the concentrations (mg kg-1) ranged from: 7.6-27 (Ba), 520-1955 (Ca), 11-26 (Cu), 6212-10855 (K), 1677-2516 (Mg), 13-29 (Mn), 4679-6104 (P), 1499-1898 (S), 7-32 (Sr) and 34-46 (Zn). A Pearson correlation plot was proposed to evaluate the correlation between elements, revealing high correlations between Mg and K; K and P; Cu and Mn; Cu and Zn; Cu and S.

The methodology developed in this study through the acquisition of fingerprint chromatograms by liquid chromatography-diode array detector (LC-DAD), aided by principal component analysis, made it possible to assess, in a rational way, the chemical differences between six accessions of Lippia alba and to verify the influence of the method of extraction, the seasonality and the individuality of each accession on chemical composition of its extracts. Among all extracts analyzed against cancer cell lines, eight of them showed to be more promising against a human leukemia cell line (HL-60), displaying cell growth inhibition percentage ranging between 40.0 and 52.0%. In the inhibitory activity assays against acetylcholinesterase enzyme, all extracts showed weak inhibitory effect, with highlight only for six of them, which displayed inhibition ranging between 27.0 and 32.0%.

This review attempts to present a broad view of the technique laser-induced breakdown spectroscopy (LIBS), since its origin, fundamentals, sample preparation strategies, use of chemometric tools for data processing, the advantages and limitations with regard to qualitative and quantitative analysis, aplications and future trends as an analytical technique that is in consolidation in analytical chemistry. LIBS is a rapid and versatile, which is able of providing qualitative and quantitative analytical information for practically any sample, in a virtually non-destructive way, without any substantial sample preparation. The instrumentation is simple, robust, compact, and enables remote analysis. The advancement of the LIBS applications in the areas of agriculture, environmental, food, biological/pharmaceutical, forensic, metallurgy and electronic waste were discussed in detail in this review. We consider that this review will be an important tool concerning dissemination of the LIBS, mainly for audience of undergraduate courses, and disciplines related to instrumental analysis.

This study describes the application of laser-induced breakdown spectroscopy (LIBS) for the direct determination of Ca, K and Mg in powdered dietary supplements. Multi-energy calibration (MEC) method was applied to obtain a calibration curve. With MEC, it was possible to observe spectral interferences and select adequate emission lines from LIBS. For Ca and Mg, five lines were selected and for K just two lines among four could be selected (compromising the results). The trueness for dietary supplements ranged from 81 to 103% for Ca and 74 to 106% for Mg. For K, just the samples S3 (95%) and S5 (109%) showed acceptable trueness values. In the case of Ca and K, besides the MEC, the normalization using C as internal standard also improved the figure of merit results. The MEC and normalization processes showed that possible matrix effect and spectral interferences could be avoided, and the results of trueness and precision were satisfactory.

In this study, two laser-based techniques, laser-induced breakdown spectroscopy (LIBS) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) were used for analytical signal evaluation of Ti, Al, and V and investigation of possible harmful elements eventually present as minor elements in Ti alloys. Due to the lack of certified reference materials, samples were also analyzed by wavelength dispersive X-ray fluorescence (WDXRF) and inductively coupled plasma optical emission spectrometry (ICP OES) after microwave-assisted digestion. To maximize the efficiency of LIBS and LA-ICP-MS, operational conditions were adjusted aiming to find optimal analytical performance. LIBS showed several Ti emission lines and few signals for Al and V. LA-ICP-MS was able to detect all three major constituents. For quantitative analysis, the correlation of intensity signals from LIBS analysis with reference values obtained by ICP OES was not successful, showing that there are still difficulties for quantification using solid samples. Measurements using ICP OES showed that additionally to major constituents, only Fe was present in concentrations around 0.2%. Analysis by WDXRF confirmed the presence of Fe. Results using both methods, i.e., ICP OES and WDXRF, were in good agreement.

We propose here the quantification of the phosphorus content in cola drinks by molybdenum blue method. Molybdenum blue method was carried out in the wells of a microplate, where method miniaturization represents reduction in reagents required, improved safety, reduced waste stream, and increased sample throughput. The phosphate concentration was determinate using scanned images of the microplate. Extraction of RGB values was carried out using ImageJ, the pugling Readplate was used allowing extraction of RGB values of all wells simultaneously. A Microsoft Excel spreadsheet is afforded in Google Drive, it organize data taken from ImageJ to afford calibrations curves and phosphate concentration in cola drinks. Calibration curves were prepared at 500-2500 µg L-1 of P with good linearity (R > 0.95). Phosphate concentrations in cola drinks determinate using digital images method are statistically equivalent to concentrations determined using a spectroscopic method at a 95% confidence interval.

A method for determination of arsenic in mineral fertilizers by continuous flow hydride generation atomic absorption spectrometry (CF-HG-AAS) was developed by using diluted acid and digester block with perfluoroalkoxy (PFA) tubes to sample preparation. An additional sample preparation procedure using microwave-assisted digestion was evaluated and compared with the proposed procedure. A full factorial design was applied to investigate the effect of the variables and the best conditions found were 7 mol L−1 HNO3 + 30% (m/m) H2O2 as reagents, 4 h of digestion and concentration of reagents diluted 1:1. The effect of concomitants on the analytical signal of arsenic was investigated and no one significant interference was observed, with recoveries ranged from 97 to 103%. The accuracy of proposed method was evaluated by certified reference material (NIST SRM 695) and recovery of 95% was obtained. The arsenic concentration (8.9 ± 0.2 mg kg−1) found in the fertilizer is below of maximum concentration established by Brazilian legislation.

<p>In this work, the transesterification of jupati (<italic>Raphia taedigera Mart.</italic>) oil using ethanol and acid catalyst was examined. The production of biodiesel was performed using a central composite design (CCD). A range of values for catalyst concentration (1 to 4.21%), temperature (70-80 °C), and the molar ratio of alcohol to oil (6:1-13.83:1) were tested, and ester content, viscosity, and yield were the response variables. The synthesis process was optimised using response surface methodology (RSM), resulting in the following optimal conditions for the production of jupati ethyl esters: a catalyst concentration of 3.85% at 80 °C and an alcohol-to-oil molar ratio of 10:1.</p>

<p>The aim of this study was to evaluate the extraction of elements Ba, Cd, Cr, Hg and Pb in solid samples, using a microwave oven with closed flasks and to understand the physicochemical parameters involved in this process. The conducting of this study was based on directive 2009/48/CE, which specifies the levels of elements in the materials used by children. A total of eight samples were used to evaluate the extraction process. A full factorial design 2³ was performed and principal component analysis (PCA) was used to select only critical samples (simultaneously high residual solid content and metal concentrations) for the proposed process, reducing the number of samples tested. A second full factorial design 2³ was performed with selected samples (masterbatch, polymer and kaolin) and the following variables investigated: addition of H₂O₂, addition of analytes, and HNO₃ volume. The responses observed for this factorial design were recoveries of the analytes (Ba, Cd, Cr, Hg, and Pb) and a desirability function was used in order to combine all responses. The conclusions were that it is not possible to digest some samples with different physicochemical characteristics (masterbatch and polymer, for example) in the same batch and that the proposed system can be used to perform sample screening.</p>

Simple and sensitive procedures for the extraction/preconcentration of molybdenum based on vortex-assisted solidified floating organic drop microextraction (VA-SFODME) and cloud point combined with flame absorption atomic spectrometry (FAAS) and discrete nebulization were developed. The influence of the discrete nebulization on the sensitivity of the molybdenum preconcentration processes was studied. An injection volume of 200 µL resulted in a lower relative standard deviation with both preconcentration procedures. Enrichment factors of 31 and 67 and limits of detection of 25 and 5 µg L-1 were obtained for cloud point and VA-SFODME, respectively. The developed procedures were applied to the determination of Mo in mineral water and multivitamin samples.

Neste trabalho foi feita a determinação de nove metais em amostras superficiais e testemunhos de sedimentos de cinco locais de amostragens nos rios Preto, Turvo e Grande em períodos chuvoso e seco. Os metais foram determinados por espectrometria de absorção atômica com atomização por chama. Análise de componentes principais dos dados foi feita para avaliar os fatores que controlam as variações nas concentrações de metais. A granulometria e teor de matéria orgânica foram determinantes das concentrações de metais. No rio Preto (área urbana) concentrações elevadas de Zn são provenientes de aporte antrópico, enquanto que no rio Turvo (represamento, área rural) níveis elevados de nitrogênio total, Al, Cr, Cu, Fe, K, Mn e Ni foram decorrentes do escoamento superficial agrícola. Os demais locais mostraram menores concentrações de metais, porém violações dos valores guia de qualidade de sedimento, principalmente para Cr e Mn, indicam a necessidade de estratégias de gerenciamento da Bacia Hidrográfica do Turvo/Grande.

In this work, nine metals were determined in superficial samples and sediment cores obtained from five sampling sites in the Preto, Turvo, and Grande Rivers during the wet and dry seasons. The metals were determined by flame atomization atomic absorption spectrometry. Principal component analysis of the data was performed to evaluate the factors responsible for the variations in metal concentrations. Granulometry and organic matter were the determining factors of metals concentrations. In the Preto River (urban area), high Zn concentrations are due to anthropic sources, whereas the high levels of total nitrogen, Al, Cr, Cu, Fe, K, Mn, and Ni in the Turvo river (damming, rural area) are due to agricultural runoff. Although lower concentrations of metals were observed at the remaining sites, violations of the guide values for sediment quality, particularly for Cr and Mn, indicate the need for management strategies for the Turvo/Grande Hydrographic Basin.

Este estudo foi centrado na avaliação química de amostras de solos provenientes de diversas estações de pesquisa na Antártica. Amostras de solos de referência foram coletadas em locais com mínimo impacto antrópico, distantes das estações de pesquisa. Locais selecionados nas vizinhanças das estações Frei Montalva e Escudero (Chile), Grande Muralha (China), Bellingshausen (Rússia) e Artigas (Uruguai) foram os pontos a priori supostamente antropizados deste estudo. O procedimento de extração sequencial (SEP) baseado no protocolo proposto pelo BCR (Community Bureau of Reference) foi aplicado para a determinação de Cu, Mn e Zn. Com o auxílio dos métodos PCA (análise de componentes principais) e PARAFAC (análise de fatores paralelos) foram extraídas informações significativas a partir dos dados brutos obtidos com SEP. As amostras de solos afetadas pelas estações de pesquisa estão associadas com elevadas concentrações de metais pesados (especialmente Cu e Zn, dentre os elementos investigados, nas frações mais lábeis de SEP aplicado). Este indício de contaminação está relacionado com o uso de óleo diesel para geração de energia pelas estações antárticas.

The aim of this study was to carry out a broad chemical investigation of selected soil samples from Antarctica, near different Antarctic scientific stations. Soil samples collected in background reference sites, with minimal human impact, far away from the stations were used as control samples. Anthropogenic places at the vicinity of the following stations Frei Montalva and Escudero (Chile), Great Wall (China), Bellingshausen (Russia) and Artigas (Uruguay) were studied as a priori human impacted sites. The sequential extraction procedure (SEP) based on the BCR (Community Bureau of Reference) protocol was applied for Cu, Mn and Zn determination. With the help of PCA (principal component analysis) and PARAFAC (parallel factor analysis) methods, meaningful information was extracted from the raw data obtained from SEP procedure. Soil samples affected by the scientific stations are associated with higher heavy metal contents (especially Cu and Zn, between the investigated metals, in the most labile fractions of the SEP applied). This pollution signal is associated with diesel use for the energy generation by the Antarctic stations.