Mirian C. Santos

Biomonitoring of metal contamination in a marine prosobranch snail (Nassarius reticulatus) by imaging laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS)

An imaging mass spectrometric method using laser ablation inductively coupled plasma spectrometry (LA-ICP-MS) was developed to determine Cu, Zn, Cd, Hg and Pb and metal distribution in longitudinal tissue sections of the marine snail Nassarius reticulatus (Gastropoda, Prosobranchia). Snails were sampled in northern Brittany (France) at three stations with different contamination levels. The quantification of metal distribution (imaging or mapping) in a thin slice of the snail tissue was carried out using different strategies: by one-point calibration and via matrix-matched laboratory standards using different biological materials (BCR 278, snail tissue, and rat brain). Together with the imaging of metals the distribution of two non-metals (carbon and sulfur) was analyzed. The imaging LA-ICP-MS analysis yielded an inhomogeneous distribution for all elements investigated. The detection limits for the distribution analysis of Cu, Zn, Cd, Hg and Pb measured by LA-ICP-MS were in the low microg g(-1) range.

Slurry Nebulization in Plasmas for Analysis of Inorganic Materials

Abstract This review summarizes and discusses the preparation of slurries for analysis of inorganic materials by inductively coupled plasma optical emission spectrometry (ICP‐OES) and inductively coupled plasma mass spectrometry (ICP‐MS). Details about the grinding step for slurry preparation, the stabilization of slurries, and the calibration strategies are critically discussed. Typical applications described in the literature and the state‐of‐the‐art including advantages and limitations of slurry analysis are presented.

Determination of toxic elements in plastics from waste electrical and electronic equipment by slurry sampling electrothermal atomic absorption spectrometry

Cadmium, chromium, lead and antimony were determined in slurries prepared using pulverized samples of personal computers and mobile phones dispersed in dimethylformamide medium. Determinations were carried out by electrothermal atomic absorption spectrometry (ETAAS) using a graphite furnace atomic absorption spectrometer. The optimization of the experimental conditions (chemical modifier, pyrolysis time, pyrolysis temperature and atomization temperatures) was accomplished by evaluating pyrolysis and atomization curves. Optimization was also used to determine the temperatures corresponding to the best sensitivities and the lowest background signals. The pyrolysis temperatures were fixed at 600 degrees C (for Cd), 700 degrees C (for Pb), 1100 degrees C (for Sb), and 1200 degrees C (for Cr); atomization temperatures were established as 1400 degrees C (for Cd), 1300 degrees C (for Pb), 1900 degrees C (for Sb), and 2300 degrees C (for Cr), and the chemical modifier (50microg NH(4)H(2)PO(4)+3microg Mg(NO(3))(2) was used for Cd and Pb while 5microg Pd+3microg Mg(NO(3))(2) was used for Sb). The use of a chemical modifier for Cr determination was not necessary. The characteristic masses were 1.9pg for Cd, 32.3pg for Pb, 54.1pg for Sb, and 9.1pg for Cr. Calibration was performed using standard additions in a range of 5-20microgL(-1) for Cd, 5-30microgL(-1) for Cr, 12.5-50microgL(-1) for Pb, and 25-100microgL(-1) for Sb with linear correlation coefficients higher than 0.99. Limits of detection were 0.9, 1.4, 6.8, and 2.9microgL(-1) for Cd, Pb, Sb, and Cr, respectively. The results indicate that recoveries for all metals agreed at a 95% confidence level when a paired t-test was applied and presented good precision. The accuracy of the proposed method was evaluated by addition-recovery experiments, showing results in the 96-112% range, and also by comparison of the results using Students t-test with another method developed using ETAAS for digested samples. Analyte concentrations in the samples investigated varied from 5 to 525, 51 to 611, and 30 to 458mgkg(-1) for Cd, Cr, and Pb, respectively, while the content of Sb was in the 0.2-1.65% range.

Determination of Cd, Cr, Hg and Pb in plastics from waste electrical and electronic equipment by inductively coupled plasma mass spectrometry with collision–reaction interface technology

A procedure based on the use of a quadrupole inductively coupled plasma-mass spectrometer equipped with a collision-reaction interface (CRI) for control of spectral overlap interferences was developed for simultaneous determination of Cd, Cr, Hg, and Pb in plastics from waste electrical and electronic equipment (WEEE). The injection of H(2) and He (80 and 60 mL min(-1), respectively) into the sampled plasma, colliding and reacting with potentially interfering polyatomic ions, allows interference-free determination of chromium via its isotopes (52)Cr and (53)Cr that are freed from overlap due to the occurrence of (40)Ar(12)C(+), (40)Ar(12)C(1)H(+), (36)S(16)O(+) or (1)H(36)S(16)O(+). Cadmium, Hg and Pb were directly determined via their isotopes (110)Cd, (111)Cd, (112)Cd, (199)Hg, (200)Hg, (201)Hg, (202)Hg, (206)Pb, (207)Pb, and (208)Pb, without using CRI. The CRI can be quickly activated or deactivated before each analyte measurement. Limits of detection for (52)Cr were 0.04 or 0.14 μg L(-1) with He or H(2) injected in CRI. Cadmium and Pb have LODs between 0.02 and 0.08 μg L(-1) and Hg had 0.93-0.98 μg L(-1), without using CRI. Analyte concentrations for samples varied from 16 to 43, 1 to 11, 4 to 12, and 5 to 13 mg kg(-1) for Cr, Cd, Hg and Pb, respectively.

A espectrometria atômica e a determinação de elementos metálicos em material polimérico

Polymeric materials are widely used in the chemical industry and are part of our daily lives. Inorganic species may be added to them as additives, anti-oxidizing agents, stabilizers, plasticizers, colorants and catalysts and may be present in a wide range of concentrations. Their determination demands the development of analytical methods considering different kinds of polymeric materials, their composition and the final use of the material. Although many different analytical techniques may be used, this review emphasizes those based on atomic absorption and emission spectrometry. Solid sampling techniques and digestion methods are described and discussed and compared considering published results.

Standard dilution analysis of beverages by microwave-induced plasma optical emission spectrometry.

In this work, standard dilution analysis (SDA) is combined with microwave-induced plasma optical emission spectrometry (MIP OES) to determine seven elements in coffee, green tea, energy drink, beer, whiskey and cachaça (Brazilian hard liquor). No sample preparation other than simple dilution in HNO3 1% v v(-1) is required. Due to relatively low plasma temperatures, matrix effects may compromise accuracies in MIP OES analyzes of complex samples. The method of standard additions (SA) offers enhanced accuracies, but is time-consuming and labor intensive. SDA offers a simpler, faster approach, with improved accuracies for complex matrices. In this work, SDAs efficiency is evaluated by spike experiments, and the results are compared to the traditional methods of external calibration (EC), internal standard (IS), and standard additions (SA). SDA is comparable to the traditional calibration methods, and it provides superior accuracies for applications involving ethanol-containing beverage samples. The SDA-MIP OES procedure is effective. Using only two calibration solutions, it may be easily automated for accurate and high sample throughput routine applications.

Direct determination of chromium in empty medicine capsules by tungsten coil atomic emission spectrometry

Tungsten coil atomic emission spectrometry (WCAES) is used to determine trace levels of Cr in medicine capsules. No sample preparation other than 10 min vortex mixing with HNO3 and H2O2 is required. Matrix decomposition is carried out directly on the atomizer to minimize matrix effects and improve precision and accuracy. The entire analysis takes less than 12 min per sample including sample preparation. The instrumental setup is based on a tungsten filament extracted from 150 W, 15 V microscope light bulbs, solid state power supply, fused silica lens, crossed Czerny–Turner spectrograph and a thermoelectrically-cooled charge-coupled device detector. The limits of detection (LOD) and quantification (LOQ) for Cr are 3 and 9 µg L−1, which correspond to procedure LOD and LOQ of 0.4 and 1 µg g−1, respectively. These values allow for quantification at a level 28-fold lower than the maximum daily Cr intake from medicine and medicine formulations recommended by the United States Pharmacopeial Convention (USP). The procedures linear dynamic range is between 3–100 µg L−1, with a R2 = 0.9992. It was applied to different empty medicine capsule samples and WCAES results were not significantly different from values found by inductively coupled plasma optical emission spectrometry (ICP OES) by applying a single-factor ANOVA test at the 95% confidence level (p > 0.05). The precision, calculated as %RSD, is between 5.2–7.4%. This is a simple, fast, efficient and potentially portable analytical procedure that may be used in quality control and regulation enforcement applications.

Direct analysis of clay and refractory materials slurries by inductively coupled plasma optical emission spectrometry with axial viewing using the simplified generalized standard additions method

The feasibility of clays and refractory materials analysis by direct introduction of slurries in an inductively coupled plasma optical emission spectrometry (ICP-OES) with axial viewing using the simplified generalized standard additions method (GSAM) was evaluated. The adopted approach is a multivariate extension of the conventional standard additions method, and uses two independent variables for determination of the analytes’ concentrations (the sample masses and the volumes of reference solutions added) and one dependent variable, the response. The relationship between the sample mass, volume of the reference solution added and the signal intensity is assumed to be linear. Concentrations of the analytes can be found either geometrically, from the slope of the two-dimensional response plane in a three-dimensional space, or mathematically from the ratio of the parameters estimated by multiple linear regression. Aluminium, Ca, Fe, K, Mg, Na, P, Si, and Ti were determined in clays and refractory materials slurries (10% v/v HNO3) of certified reference materials. The software “Teach/Me” was used to fit the data. Aluminium oxide was detected in the 0.36–73.0%, CaO in the 0.03–2.13%, Fe2O3 in the 0.56–3.39%, K2O in the 0.03–3.58%, MgO in the 0.06–0.47%, Na2O in the 0.01–0.45%, P2O5 in the 0.05–0.13%, SiO2 in the 22.2–98.42% and TiO2 in the 0.06–1.95% range. Applying a paired t-test it was shown that all results were in agreement at a 95% confidence level with certified values. The application of GSAM was demonstrated as an effective method for the analysis of clays and refractory materials slurries.

Clay and refractory materials slurries in inductively coupled plasma optical emission spectrometry: effects of mechanochemical synthesis on emission intensities of analytes

Neste trabalho foi investigada a aplicacao da sintese mecanoquimica para promover reacoes na amostra e sintetizar novos compostos visando aumentar as intensidades de emissao de elementos presentes em suspensoes de argilas e materiais refratarios quando introduzidas em espectrometro de emissao optica com plasma acoplado indutivamente com configuracao axial. A hipotese formulada e que e possivel gerar compostos mais volateis durante a moagem e esses novos compostos causam aumento da intensidade dos sinais de emissao para os analitos em suspensoes introduzidas no plasma. A acao de dois modificadores, LiBO 2 e Na 2 CO 3 , adicionados durante a etapa de moagem foi investigada. As argilas e materiais refratarios foram moidos juntamente com os modificadores quimicos durante 2 h usando um moinho de bolas de alto impacto com recipiente e bolas de carbeto de tungstenio. As suspensoes foram preparadas dispersando as argilas e os materiais refratarios modificados em solucao 10% v v -1 HNO 3 e, posteriormente, sonicadas em banho de ultra-som para melhorar a homogeneizacao. Os compostos produzidos durante a etapa de moagem foram caracterizados por difracao de raios X e analise termogravimetrica. Ambas as tecnicas indicaram a formacao de novos compostos nas argilas e materiais refratarios por sintese mecanoquimica. Os efeitos da modificacao quimica foram avaliados pelas mudancas nas intensidades de emissao dos analitos Al, Ca, Fe, K, Mg, P, Si e Ti. Ambos modificadores causaram aumento na sensibilidade para todos os analitos de ate 665% (Na 2 CO 3 ) e 583% (LiBO 2 ) quando comparados as intensidades dos sinais de emissao obtidos para os analitos nas suspensoes preparadas com as amostras sem modificacao quimica. The developed work investigated the application of mechanochemical synthesis for promoting reactions in the samples and for synthesizing new compounds for increment of emission intensities of analytes in clays and refractory materials slurries in inductively coupled plasma optical emission spectrometry with axial viewing. The hypothesis is that it is possible to generate more volatile compounds during the grinding step and these new compounds will increase the intensities of emission signals for slurries introduced in the plasma. The action of two chemical modifiers, LiBO 2 and Na 2 CO 3 , added during the grinding step was evaluated. The clays and refractory materials mixed with the chemical modifier were ground for 2 h using a high impact ball mill with a tungsten carbide grinding container and balls. Slurries were prepared by dispersing the modified clays and refractory materials in 10% v v -1 HNO 3 solution and by shaking them in an ultrasonic bath to ensure good dispersion. The compounds produced during the grinding step were characterised by X-ray diffraction and thermogravimetric analysis. Both techniques indicated the formation of new compounds in clays and refractory materials by mechanochemical synthesis. Chemical modification effects were evaluated by changes of the emission intensities of Al, Ca, Fe, K, Mg, P, Si, and Ti. Both modifiers caused increments of sensitivities for all analytes in up to 665% (Na 2 CO 3 ) and 583% (LiBO 2 ) compared to the emission signals for analytes present in slurries prepared using samples ground without adding modifiers.

Sampling and Sample Homogeneity as Introductory Topics in Analytical Chemistry Undergraduate Courses

ABSTRACT This work deals with the development of an experiment to evaluate the effect of sample characteristics on precision and accuracy of the sampling step. Parameters such as sample homogeneity, particle sizes, and sample mass were evaluated by analyzing the standard deviations (n = 3) obtained for Ca, Fe, Mg, Na, P, S, and Zn determinations in a breakfast cereal sample by inductively coupled plasma optical emission spectrometry. The proposed experiment can improve the assimilation of important concepts such as sampling, sample representativity, precision and accuracy by undergraduate students in analytical chemistry laboratory courses.