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A systematic study of Na+, K+, Ca2+, Mg2+, Cl-, NO3-, SO4(2-) and PO4(3-) interference on the simultaneous atomization of As, Cd, Pb and Se was carried out using an electrothermal atomic absorption spectrometer. The mixture 250 mg W + 250 mg Rh was thermally deposited on the graphite tube platform and used as permanent chemical modifier. The compromised heating program adjustments (Tp = 650&ordmC and Ta = 2200&ordmC) diminished the thermal decomposition and volatilization efficiency of the interfering species during the pyrolysis step. The Cl- and SO4(2-) anions caused the most severe interference, while NO3- only affected the analytes' atomization when high amounts (> 27 mg) were used. The anion PO4(3-) produced a strong negative interference on the Se absorbance signals. The presence of Na+, K+, Ca2+ and Mg2+ prejudiced mainly Cd, and the interference effects of Cl- salts were more pronounced than NO3- salts.

The direct analysis of high silicon content samples by Laser-Induced Breakdown Spectrometry (LIBS) is a good alternative, since the decomposition of samples with refractory characteristics is not an easy task. However, poor precision and difficulty in performing quantitative analysis due to particle size effects, heterogeneity and matrix effects are challenges which need to be overcome. An interesting approach to overcome these issues enabling quantitative measurements of Al, Ca, Fe, Mg, Si and Ti in a variety of samples by LIBS is the use of the borate fusion process for sample preparation. Results for fused glass beads were compared to those obtained for samples pressed into pellets, which is the most common sample preparation procedure for analysis by LIBS. The linearity of calibration curves (R2) using different certified reference materials (CRM) pressed into pellets was worse (R2 = 0.2105–0.9276) than that observed for those fused into glass beads (R2 = 0.5640–0.9778), but this still shows a lack of linearity. To minimize strong absorption effects caused by the matrix composition and improve the linearity, accuracy and precision of results for fused glass beads, B and Li, present in the flux, were used as internal standards. Better results were achieved for Fe, Mg and Si when the B emission line was used as an internal standard, while the Li emission line worked better for the measurement of Al, Ca and Ti. The accuracy of the method was evaluated by analyzing a CRM of soil (NIST SRM 2711) and relative errors of around 8% were found, indicating that internal standardization enables quantitative measurement by LIBS in those matrices. [ABSTRACT FROM AUTHOR]

The presence of the bicarbonate/carbon dioxide pair is known to accelerate the transition metal ion-catalysed oxidation of various biotargets. It has been shown that stable Cu(II) complexes formed with imine ligands that allow redox cycling between Cu(I) and Cu(II) display diverse apoptotic effects on cell cultures. It is also reported that Cu(II)-tetraglycine can form a stable Cu(III) complex. In the present study, radical generation from H(2)O(2) and H(2)O(2)/HCO(3)(-) in the presence of these two different classes of Cu(II) complexes was evaluated by monitoring the oxidation of dihydrorhodamine 123 and NADH and by the quantitative determination of thiobarbituric acid reactive substances (TBARs method). Cu(II)-imine complexes produced low levels of reactive species whereas Cu(II)-Gly-derived complexes, as well as the free Cu(II) ion, produced oxygen-derived radicals in significantly larger amounts. The effects of these two classes of complexes on mammalian tumour cell viability were equally distinct, in that Cu(II)-imine complexes caused apoptosis, entered in cell and remained almost unaffected in high levels whilst, at the same concentrations, Cu(II)-Gly peptide complexes and Cu(II) sulphate stimulated cell proliferation, with the cell managing copper efficiently. Taken together, these results highlight the different biological effects of Cu(II) complexes, some of which have been recently studied as anti-tumour drugs and radical system generators, and also update the effects of reactive oxygen species generation on cell cycle control., (Copyright © 2010 Elsevier Inc. All rights reserved.)