Tungsten coil atomic emission spectrometry combined with dispersive liquid–liquid microextraction: A synergistic association for chromium determination in water samples

A novel and environment friendly analytical method is reported for total chromium determination and chromium speciation in water samples, whereby tungsten coil atomic emission spectrometry (WCAES) is combined with in situ ionic liquid formation dispersive liquid–liquid microextraction (in situ IL-DLLME). A two stage multivariate optimization approach has been developed employing a Plackett–Burman design for screening and selection of the significant factor involved in the in situ IL-DLLME procedure, which was later optimized by means of a circumscribed central composite design. The optimum conditions were complexant concentration: 0.5% (or 0.1%); complexant type: DDTC; IL anion: View the MathML sourcePF6−; [Hmim][Cl] IL amount: 60 mg; ionic strength: 0% NaCl; pH: 5 (or 2); centrifugation time: 10 min; and centrifugation speed: 1000 rpm. Under the optimized experimental conditions the method was evaluated and proper linearity was obtained with a correlation coefficient of 0.991 (5 calibration standards). Limits of detection and quantification for both chromium species were 3 and 10 µg L−1, respectively. This is a 233-fold improvement when compared with chromium determination by WCAES without using preconcentration. The repeatability of the proposed method was evaluated at two different spiking levels (10 and 50 µg L−1) obtaining coefficients of variation of 11.4% and 3.6% (n=3), respectively. A certified reference material (SRM-1643e NIST) was analyzed in order to determine the accuracy of the method for total chromium determination and 112.3% and 2.5 µg L−1 were the recovery (trueness) and standard deviation values, respectively. Tap, bottled mineral and natural mineral water samples were analyzed at 60 µg L−1 spiking level of total Cr content at two Cr(VI)/Cr(III) ratios, and relative recovery values ranged between 88% and 112% showing that the matrix has a negligible effect. To our knowledge, this is the first time that combines in situ IL-DLLME and WCAES.The authors would like to thank the Spanish Ministry of Science and Innovation (Project no. CTQ2011-23968), Spanish Ministry of Education, Culture and Sport (Project no. PHB2010-0018-PC), Generalitat Valenciana (Spain) (Project no. ACOMP/2013/072), and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior in Brazil (Grant CAPES-DGU n. 243/11). L. Vidal also thanks the Spanish Ministry of Education, Culture and Sport for her travel Grant (HBP-2010-0030) and S.G. Silva is grateful to the Grant 2011/13288-7, São Paulo Research Foundation (FAPESP)

Dispersive liquid–liquid microextraction of Cd, Hg and Pb from medicines prior to ICP OES determination according to the United States Pharmacopeia

A simple, sensitive and matrix-effect free analytical method for simultaneous determination of Cd, Hg and Pb in drug samples (i.e., commercial dosage tablets) by inductively coupled plasma optical emission spectrometry (ICP OES) has been developed. According to the United States Pharmacopeia (USP) Chapter 232, those metals are considered elemental impurities from class 1 and they must be assessed in pharmaceutical production as well as in quality control evaluation. In order to increase the sensitivity of the analysis, dispersive liquid–liquid microextraction (DLLME) was performed and seven factors affecting analyte extraction were optimized by multivariate analysis. A microvolume of analyte enriched phase was directly introduced into the plasma using a multi-nebulizer, providing a high enrichment factor. When compared to conventional ICP OES analysis, DLLME improves the limit of quantitation (LOQ) values on average 40-fold for all analytes. Consequently, LOQ values were significantly lower than their permissible daily exposure limits for oral drugs. Accuracy was evaluated by addition and recovery experiments following USP recommendations in eight commercial drug samples. Recovery and RSD values were within the range of 90–108% and 1–9%, respectively.The authors are grateful to the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, process no. 141634/2017-0, 202722/2019-8, 305201/2018-2 and 428558/2018-6), the Regional Government of Valencia (Spain) (PROMETEO/2018/087) for the financial support, Agilent Technologies Inc. for the loan of the ICP OES spectrometer, and Ingeniatrics for the MultiNeb® provided. This study was financed in part by the Coordenaçao de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Finance Code 001. The authors extend their appreciation to Ministry of Science, Innovation and Universities for granting the Spanish Network of Excellence in Sample Preparation (RED2018-102522-T). This article is based upon work from the Sample Preparation Study Group and Network, supported by the Division of Analytical Chemistry of the European Chemical Society

Construction of a tungsten coil atomic emission spectrometer (WCAES)

It is here discussed the development of a low cost analytical instrument with capacity for metals determination using atomic emission measurements in an electrothermal atomization system with a tungsten coil atomizer. The main goal was to show a new frontier for using this atomizer and to demonstrate that the simple instrumental arrangement here proposed has potential for portability and for solving analytical tasks related to metals determination. Atomic emission of calcium was selected for the adjustment of instrumental parameters and to evaluate the main characteristics of the lab-built instrument. Cobalt was determined in medicines and one alloy to demonstrate its feasibility.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPES

Vortex-assisted dispersive liquid–liquid microextraction for the determination of molybdenum in plants by inductively coupled plasma optical emission spectrometry

A new procedure for determining trace concentrations of Mo in plants combining dispersive liquid–liquid microextraction and inductively coupled plasma optical emission spectrometry is proposed here. An automated discrete sample introduction system using a Flow Blurring® multiple nebulizer (FBMN) and a solenoid valve were used to insert an organic rich phase into the plasma. The experimental conditions for the microextraction procedure were: 0.5% m v−1 of 8-hydroxyquinoline, pH 3.6 and 50 μL of 1-undecanol as the extractant. A limit of detection of the instrument of 0.20 μg L−1, a limit of detection of the procedure of 17 μg kg−1 and an enhancement factor of 246 were obtained employing the developed procedure. Three certified reference materials were used to check the accuracy and no significant differences were found at the 95% confidence level between certified and determined values. The developed procedure was also successfully applied to the determination of Mo in three different varieties of sugar cane leaves samples.The authors express their gratitude to the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior CAPES (Grant CAPES-DGU 243/11) for the research fellowship provided to J.A.V.A.B. J.A.N. is thankful to Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, Brazil) for financial support. The authors are grateful to the Government of Spain (CTQ2011-23968 and PHB2010-0018-PC) and the Regional Government of Valencia (Spain) (ACOMP/2013/072) for the financial support, Agilent Technologies Inc. for the loan of the ICP-OES spectrometer and OneNeb® (Division of Ingeniatrics Tecnologías S.L.) for the FBMN prototype provided

Determination and fractionation of barium in Brazil nuts

Several sample preparation strategies were employed for determination and fractionation of barium in Brazil nuts using measurements by graphite furnace atomic absorption spectrometry (GF AAS) and inductively coupled plasma optical emission spectrometry with axial view (ICP OES). This food is widely consumed because of its nutritional value and good taste. The chemical analysis of Brazil nuts is not trivial due to their complex matrix. The fractionation of barium in Brazil nuts was studied owing to the toxicity of this element and the strong correlation between chemical form and absorption. Total concentrations of barium varied from 860 to 2084 mg kg-1. Sequential extractions were performed based on solubility in different media and also according to lipids, proteins and low molecular weight fractions (LMW). The greatest contents of barium were determined in the LMW and in the water insoluble fractions with concentrations in the range 778 to 1606 and 551 to 1520 mg kg-1, respectively. Based on these results it can be inferred that Ba is not absorbed when Brazil nuts are ingested. Considering both the contents of barium and sulfur in different fractions and stoichiometric calculations it was also possible to assume that barium occurs mainly in the BaSO4 form. The presence of this chemical form was also confirmed by thermogravimetric measurements.Diversas estratégias para preparo de amostra, determinação e fracionamento, tais como espectrometria de absorção atômica com atomização eletrotérmica em forno de grafite (GF AAS) e espectrometria de emissão óptica com plasma acoplado indutivamente com configuração axial (ICP OES), foram empregadas para o fracionamento de bário em Castanha-do-Pará. Esse alimento é amplamente apreciado tanto pelo valor nutricional, quanto pelo sabor agradável. A análise química de Castanha-do-Pará não é trivial devido à matriz complexa. O fracionamento de bário em Castanha-do-Pará foi estudado devido à toxicidade desse elemento e a correlação entre a forma química e a absorção. Os teores totais de bário nas amostras de Castanha-do-Pará variaram entre 860 e 2084 mg kg-1. Extrações sequenciais foram feitas com base na solubilidade em diferentes meios e composição química envolvendo lipídios, proteínas e compostos de baixa massa molecular (LMW). Teores mais elevados de bário foram determinados nas frações LMW e insolúvel em água que variaram entre 778-1606 e 551-1520 mg kg-1, respectivamente. Esses resultados indicaram a indisponibilidade de bário presente nesse alimento ao organismo humano. Baseando-se nos teores de bário e enxofre nas diferentes frações e em cálculos estequiométricos para as possíveis reações envolvidas pode-se inferir que bário se encontra principalmente na forma de BaSO4. Experimentos termogravimétricos também confirmaram essa suposição.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenadoria de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Analytical performance of an inductively coupled plasma optical emission spectrometry with Dual View configuration

The analytical performance of axially and radially viewed inductively coupled plasma optical emission spectrometers (AX-ICP OES and RD-ICP OES, respectively) were evaluated in terms of the Mg II/Mg I ratio, matrix effects, and detection limits (LOD). All solutions were made in either 1% v v-1 nitric acid or in a 10% v v-1 water-soluble tertiary amine solution (CFA-C) adjusted to pH 8. Using a nebulization gas flow-rate of 0.5 L min-1 and applied power of 1.3 kW, Mg II/Mg I ratio was at least 15 in any medium for both configurations. Under robust conditions, plasma processes were practically not affected by the presence of 0.1% m v-1 of Ca, K, or Na in both configurations. However, interference effects were observed with non-robust conditions, mainly with AX-ICP OES in both media. The best detection limits were obtained using AX-ICP OES under robust conditions, with solutions prepared in the amine medium.O desempenho analítico de um espectrômetro de emissão óptica com plasma indutivamente acoplado configurado axial e radialmente (AX-ICP OES e RD-ICP OES, respectivamente) foi avaliado em termos da razão Mg II/Mg I, efeitos de matriz e limites de detecção (LOD). Todas as soluções foram preparadas em ácido nítrico 1% v v-1 ou em uma mistura de aminas terciárias solúveis em água 10% v v-1 (CFA-C), ajustada para pH 8. Usando uma vazão de nebulização de 0,5 L min-1 e potência aplicada de 1,3 kW, a razão Mg II/Mg I foi pelo menos 15 em qualquer meio para ambas configurações. Em condições robustas, os processos do plasma praticamente não foram alterados pela presença de 0,1% m v-1 de Ca, K ou Na em ambas configurações. Porém, efeitos de interferência foram observados em condições não robustas, principalmente com AX-ICP OES em ambos os meios. Os melhores LOD foram obtidos usando AX-ICP OES em condições robustas e em soluções preparadas no meio contendo as aminas.310315Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq