PVDF/Clay Spheres Obtained through Phase Inversion for Cu Ion Removal.

In this study, spheres of poly (vinylidene fluoride)/clay were synthesized using an easy dripping method (also known as phase inversion). The spheres were characterized by scanning electron microscopy, X-ray diffraction, and thermal analysis. Finally, application tests were carried out using commercial cachaça, a popular alcoholic beverage in Brazil. The SEM images revealed that during the solvent exchange process for sphere formation, PVDF tends to form a three-layered structure with a low-porosity intermediate layer. However, the inclusion of clay was observed to reduce this layer and also widen the pores in the surface layer. The results of the batch adsorption tests showed that the composite with 30% clay content in relation to the mass of PVDF was the most effective among those tested, with the removal of 32.4% and 46.8% of the total copper present in the aqueous and ethanolic media, respectively. The adsorption of copper from cachaça in columns containing cut spheres resulted in adsorption indexes above 50% for samples with different copper concentrations. Such removal indices fit the samples within the current Brazilian legislation. Adsorption isotherm tests indicate that the data fit better to the BET model.

Determination of Trace Elements in Cow Placenta by Tungsten Coil Atomic Emission Spectrometry.

Tungsten coil atomic emission spectrometry (WCAES) is used to determine trace levels of Mn (403.1 nm) and Cr (425.5 nm) in cow placenta. All samples were collected in Ilha Solteira, SP, Brazil. The instrumental setup is based on a tungsten filament extracted from 150 W, 15 V microscope light bulbs, a 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 2 and 8 µg L-1, and 20 and 60 µg L-1 for Mn, respectively. Recoveries for 0.30 mg L-1 spikes of each analyte were in the range 93.0-103.0%, and relative standard deviation (RSD) was between 6.50 and 7.20% for both elements. Placenta samples were microwave-assisted digested with diluted HNO3 and H2O2 and analyzed by WCAES. The results for Cr and Mn were compared with values obtained by tandem inductively coupled plasma mass spectrometry (ICP-MS/MS). No statistically significant difference was observed between the different methods by applying a paired t test at a 95% confidence level. The average concentrations of Cr and Mn in the placentas evaluated were 0.95 ± 0.22 and 2.64 ± 0.39 µg g-1, respectively. By using a short integration time, LODs for Cr and Mn were lower than values reported by recent works using a similar WCAES system.

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, SDA's 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.

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.

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 Student's 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.

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.