Speciation of chromium in mineral waters and salinas by solid-phase extraction and graphite furnace atomic absorption spectrometry

A simple GF-AAS method for speciation analysis of chromium in mineral waters and salinas was developed. Cr(VI) species were separated from Cr(III) by solid-phase extraction with APDC (ammonium pyrrolidinedithiocarbamate). The APDC complexes were formed in the sample solution under proper conditions, adsorbed on Diaion HP-2MG resin and the resin was separated from the sample. After elution with concentrated nitric acid Cr(VI) was determined by GF-AAS. Total chromium was determined by GF-AAS directly in the sample and Cr(III) concentration was calculated as the difference between those results.

The detection limit of the method defined as 3 s of background variation was 0.03 μg l⁻¹ for Cr(VI) and 0.3 μg l⁻¹ for total chromium. RSD for Cr(VI) determination at the concentration of 0.14 μg l⁻¹ was 9%, and for total chromium at the concentration of 5.6 μg l⁻¹ was 5%. The recovery of Cr(VI) was in the range of 94–100%, dependently on type of the sample.

The investigation of recovery of the spiked Cr(VI) showed that at concentration levels near 1 μg l⁻¹ and lower recovery may be reduced significantly even by pure reagents that seem to be free from any reductants.     

Analysis of mineral water from Brazil using total reflection X-ray fluorescence by synchrotron radiation

The total reflection X-ray fluorescence using synchrotron radiation (SRTXRF) has become a competitive technique for the determination of trace elements in samples that the concentrations are lower than 100 ng ml⁻¹. In this work, thirty-seven mineral waters commonly available in supermarkets of Rio de Janeiro, Brazil, were analyzed by SRTXRF. The measurements were performed at the X-Ray Fluorescence Beamline at Brazilian National Synchrotron Light Laboratory (LNLS), in Campinas, São Paulo, using a polychromatic beam with maximum energy of 20 keV for the excitation. Standard solutions with gallium as internal standard were prepared for calibration of the system. Mineral water samples of 10 μl were added to Perspex sample carrier, dried under infrared lamp and analyzed for 200 s measuring time. It was possible to determine the concentrations of the following elements: Si, S, K, Ca, Ti, Cr, Mn, Ni, Cu, Zn, Ge, Rb, Sr, Ba and Pb. The elemental concentration values were compared with the limits established by the Brazilian legislation.     

Effect of ultrastructural changes on the toughness of bone

The ultrastructure of bone can be considered as a conjunction between the biology and the biomechanics of the tissue. It is the result of cellular and molecular activities of bone formation, and its organization dominates the mechanical behavior of bone. Following this perspective, the objective of this review is to provide a current understanding of bone ultrastructure and its relationships with the toughness of the tissue. Therefore, we first provide a discussion on the organization of bone constituents, namely collagen, mineral, and water. Then, we present evidence on how the toughness of bone relates to its ultrastructure through the formation of microdamage. In addition, attention is given to how damage accumulation serves as a toughening mechanism. Finally, we describe how changes in the ultrastructure-caused by osteogenesis imperfecta, gamma irradiation, fluoride treatment, and aging affect the toughness and competence of bone.     

The effects of chronic hypoperfusion on rat cranial bone mineral and organic matrix

Arteriovenous malformations (AVM) of the brain, errors in the development of the vasculature, produce high flow arteriovenous shunts. They steal blood from surrounding brain tissue, which is chronically hypoperfused. Hypoperfusion is a condition of inadequate tissue perfusion and oxygenation resulting in abnormal tissue metabolism. In the present study Fourier transform infrared (FTIR) spectroscopy was used to investigate the effects of hypoperfusion on rat cranial bone mineral and organic matrix at the molecular level. FTIR spectroscopic analysis revealed that in cranial bones of an experimental group the relative amount of carbonate and phosphate groups increased whereas that of protein (amide I) decreased. Curve-fitting analysis of the v₂ carbonate band showed that amounts of type A and type B carbonates increased slightly (p=0.423 for both) whereas, type L carbonate decreased slightly (p=0.522) in hypoperfused cranial bones. Analysis of the C–H region revealed a significant increase (p=0.037) in the lipid to protein ratio. Because the lipid content is high, hypoperfused cranial bone tissue is more prone to lipid peroxidation. Dialdehydes derived from lipid peroxidation can make cross-links with collagen and might lead to disturbances in the collagen cross-link profile. The 1660 cm^–1/1690 cm^–1 partial area ratio derived from curve-fitting analysis of the Amide I band is sensitive to the relative amount of collagen non-reducible cross-link hydroxylysyl/lysylpyridinolines (Pyr) and reducible cross-link dihydroxylysinonorleucine (DHLNL) and this ratio reflects collagen maturity. In chronic hypoperfusion a significant decrease (p=0.004) was observed in this ratio. This means there were less mature collagen cross-links. Disturbances in the collagen maturation can affect mineralization process and lead to formation of pathologic structures in cranial bones. These findings clearly demonstrate that FTIR spectroscopy can be used to extract valuable information at molecular level, leading to better understanding of the effect of hypoperfusion on rat cranial bones.     

用于水中矿物油测定的新型萃取剂

探讨了用于水中矿物油测定的新型萃取剂的筛选和超纯新型萃取剂的制备方法,对选定的新型萃取剂与目前我国常用萃取剂的萃取能力进行了较详细的对比研究.     

ICP-AES法测定南酸枣及其提取物中矿质元素含量

南酸枣作为一种分布广泛的药食同源植物,其营养活性成分的研究日益受到关注,然而关于其矿质元素的分布与体外释放情况的研究未见报道。采用电感耦合等离子体原子发射光谱法(ICP-AES)测定了南酸枣皮、枣肉及其水提物、胃消化物中九种矿质元素含量。结果发现:枣肉中Fe,Ca,Zn,Mn,Al,Mg,Cu,K和P的含量分别为27.37,269.88,1.51,2.45,1.95,195.30,2.45,2970.11,133.94μg·g-1,低于枣皮中的含量,分别为枣皮含量的40.31%,11.70%,21.68%,4.27%,10.58%,15.76%,68.72%,42.04%,22.59%。南酸枣肉微波辅助水提物中Mn的释放率最高(81.68%),Fe最低(4.42%);而枣皮中Zn的释放率最高(79.00%),Al最低(4.94%),除Fe,Zn和Cu外,南酸枣肉中其他各元素的释放率均显著高于枣皮。在模拟胃部消化后,南酸枣肉中矿质元素的释放率在3.25%~87.51%之间;枣皮中释放率在7.11%~50.69%之间,除Fe和Cu外,南酸枣肉各元素的释放率均显著高于枣皮。微波辅助提取更有助于南酸枣肉中Fe,Ca,Mn,Mg,K的释放,其释放率高于胃液消化。而胃液消化过程对枣皮的影响更显著,除Zn外,其他元素释放率均高于微波辅助水提。该实验结果明确了南酸枣肉及枣皮中矿质元素分布与释放的差异,为进一步研究南酸枣中矿质元素的人体吸收利用提供积极的指导作用。     

Sorption of Cypermethrin Diastereoisomers to Quartz,Corundum, Goethite,Kaolinite and Montmorillonite

Differential sorption and degradation of different pesticide stereoisomers in soil may result in accumulation of the most strongly sorbed and the slowest degradable isomers. In this work the pyrethroid cypermethrin (8 isomers) has been used for test of stereochemical interactions with surfaces of the minerals quartz, corundum, goethite, kaolinite and montmorillonite. The sorption of three diastereoisomeric fractions denoted Cis A, Trans C and Cis B + Trans D were quantified by use of GC-ECD in batch experiments with initial cypermethrin concentrations in the range 1-9 µg/L. Correction for cypermethrin sorbed to surfaces of the shaking flasks were accomplished to obtain net sorption isotherms for the minerals, all of which were well fitted by the Freundlich equation. Bonding affinities per unit surface area decreased in the order: corundum > quartz > kaolinite > montmorillonite > goethite. The isotherms for sorption of all diastereoisomeric fractions to quartz, corundum and goethite were all linear, whereas non-linear isotherms were found for sorption of Cis A and Trans C fractions to kaolinite and montmorillonite. Corundum, quartz and goethite showed a significantly stronger sorption of Cis A than the other fractions, while kaolinite sorbed Cis B + Trans D most strongly. The observed differences predict less leaching and slower degradation of the Cis A fraction in subsoils low in organic carbon.     

矿产资源开发与泥石流灾害及其防治对策

由于掠夺式开采以及环境保护滞后于经济发展,我国矿产资源开发利用产生了比较严重的环境问题。本文在分析我国矿山人为泥石流灾害状况的基础上,提出了改善生态环境保护与重建的法治建设环境,加大矿山生态环境保护的监督管理力度,并具体提出了矿山人为泥石流灾害预防和工程治理的措施。     

Quantitative property-property relationship (QPPR) approach in predicting flotation efficiency of chelating agents as mineral collectors

The QPPR approach has been used to model cupferrons as mineral collectors. Separation efficiencies (Es) of these chelating agents have been correlated with property parameters namely, log P , log K oc , substituent-constant σ , Mullikan and ESP derived charges using multiple regression analysis. Es of substituted-cupferrons in the flotation of a uranium ore could be predicted within experimental error either by log P or log K oc and an electronic parameter. However, when a halo , methoxy or phenyl substituent was in para to the chelating group, experimental Es was greater than the predicted values. Inclusion of a Boolean type indicative parameter improved significantly the predictability power. This approach has been extended to 2-aminothiophenols that were used to float a zinc ore and the correlations were found to be reasonably good.     

Liquid chromatography with diode array detection and multivariate curve resolution for the selective and sensitive quantification of estrogens in natural waters

Following the green analytical chemistry principles, an efficient strategy involving second-order data provided by liquid chromatography (LC) with diode array detection (DAD) was applied for the simultaneous determination of estriol, 17β-estradiol, 17α-ethinylestradiol and estrone in natural water samples. After a simple pre-concentration step, LC–DAD matrix data were rapidly obtained (in less than 5 min) with a chromatographic system operating isocratically. Applying a second-order calibration algorithm based on multivariate curve resolution with alternating least-squares (MCR-ALS), successful resolution was achieved in the presence of sample constituents that strongly coelute with the analytes. The flexibility of this multivariate model allowed the quantification of the four estrogens in tap, mineral, underground and river water samples. Limits of detection in the range between 3 and 13 ng L⁻¹, and relative prediction errors from 2 to 11% were achieved.