Search

An adsorptive stripping voltammetric procedure for the determination of the antidepressant venlafaxine in urine using a mercury film microelectrode was developed. The method is based on controlled adsorptive accumulation of the drug at the potential of −1.00 V (vs. Ag/AgCl) in the presence of 1.25 × 10−2 mol L−1 borate buffer (pH 8.7). Urine samples were analyzed directly after performing a ten-fold dilution with the supporting electrolyte but without other pretreatment. The limit of detection obtained for a 30 s collection time was 0.693 × 10−6 mol L−1. Recovery experiments gave good results at the 10−6 mol L−1 level (bias less 5% were obtained).

Summary A catalytic cathodic stripping voltammetric procedure for the determination of total chromium in osteoblast-like cell culture medium using a mercury film microelectrode (MFM) was optimised. The method is based on the pre-concentration of the Cr(III)-diethylenetriaminepentaacetic acid (DTPA) complex by adsorption at the potential of -1.00 V ( vs. Ag/AgCl) in the presence of 10×10 -3 mol/L DTPA, 0.70 mol/L sodium nitrate, 0.04 mol/L sodium acetate and 1.0×10 -3 mol/L potassium permanganate at pH 5.9–6.0. The limit of detection obtained for a 40 s collection time was 2.80×10 -10 mol/L of chromium. The results achieved by stripping voltammetry using the MFM were compared to those obtained by atomic absorption spectrometry (AAS) to ensure the reliability of the electrochemical method. This procedure proved to be an alternative to AAS and valuable in biocompatibility studies performed in vitro using osteoblast-like cells.

Rat bone marrow cells were cultured in experimental conditions that favour the proliferation and differentiation of osteoblastic cells (i.e., 2.52×10 -4 mol l -1 ascorbic acid, 10 -2 mol l -1 β -glycerophosphate and 10 -8 mol l -1 dexamethasone) in the absence and in the presence of stainless-steel corrosion products, for a period of 18 days. An AISI 316L stainless-steel slurry (SS) was obtained by electrochemical means and the concentrations of the major metal ions, determined by atomic absorption spectrometry, were 8.78×10 -3 mol l -1 of Fe, 4.31×10 -3 mol l -1 of Cr and 2.56×10 -3 mol l -1 of Ni. Bone marrow cells were exposed to 0.01, 0.1 and 1% of the SS and at the end of the incubation period, control and treated cultures were evaluated by histochemical assays for the identification of the presence of alkaline phosphatase and also calcium and phosphate deposition. Cultures were further observed by scanning electron microscopy. Levels of total and ionised calcium and phosphorus in the culture media collected from control and metal exposed cell cultures were also quantified. Histochemical staining showed that control cultures presented a strong reaction for the presence of alkaline phosphatase and exhibited formation of calcium and phosphates deposits. The presence of 0.01% SS caused no detectable biological effects in these cultures, 0.1% SS impaired osteoblastic behaviour and, 1% SS resulted in cell death. In the absence of bone cells, levels of total and ionised calcium and phosphorus in the control and metal added culture medium were similar throughout the incubation period. A significant decrease in the levels of ionised calcium and phosphorus were observed in the culture medium of control cultures and also in cultures exposed to 0.01% SS after two weeks of incubation, an event related with the formation of mineral calcium phosphate deposits in these cultures. In cultures grown in the presence of 0.1 and 1% SS corrosion products, levels of calcium and phosphorus were similar to those observed in the absence of cells. Results showed that stainless-steel corrosion products above certain concentrations may disturb the normal behaviour of osteoblast-like rat bone marrow cell cultures.

In vitro studies to determine Fe3+ levels in mice liver samples were performed using platinum microelectrodes and atomic absorption spectrophotometry. Microelectrodes have been shown to be useful for quantitative analysis of metal ions released during the biodegradation process that occurs on implanted metallic biomaterials.

The systemization and organization of ideas and concepts is an integral part of science. In chemistry, the organization of the periodic table of the chemical elements in the 1860s was one of the greatest scientific breakthroughs ever made and in fact during the 20th century it became a universally recognized scientific icon (1). The periodic table is the fundamental classificatory scheme of the elements and summarizes the realm of chemistry (2). Simply knowing the position of an element in the periodic table tells us about its properties and is usually enough to predict how the element will behave in a wide variety of different situations or reactions (1). Based on this potential mine of information, it is possible to make reliable predictions of the properties of the compounds that each element forms. Nowadays, the concept of the periodic table is starting to interact with other sciences and reports of periodic tables of amino acids (3), genetic codes (4), protein structures (5), and biology (6) can be found in the specialized literature. Symbiosis between science and art, for example, “The Periodic Table of The Elephants” (7), can also be seen. To appeal to a better understanding of the periodic table, the Instituto Superior de Engenharia do Instituto Politécnico do Porto and the Centro de Química da Universidade do Porto promoted a contest and exhibit with the goal of stimulating a wide and heterogeneous audience, ranging from young children and their parents to graduate students from several disciplines, to explore the nature of this icon. Imaginative educational activities such as contests (8–10), games (11, 12), and puzzles (13–15) provided a way to communicate with the general public with the goal of attracting students to science. This also constituted an interesting, informative, and entertaining alternative to non-interactive lectures. Simultaneously, artistic creativity was combined with scientific knowledge.

Over the last few years, bioactive components from algae have been assuming important applications in nutraceuticals, cosmetics, flavors/fragrances, and also in the pharmaceutical industry due to increased evidence of their health benefits. Microwave- and ultrasonic-assisted extraction methods are promising environment-friendly alternatives for algal sample preparation. In this chapter, the more relevant contributions of the last decade to the current knowledge on principles, applications and comparative advantages and disadvantages over conventional processes of microwave- and ultrasonic-assisted extraction are discussed.

Mercury film microelectrodes were used to determine iron in osteoblast-like cell culture medium by performing adsorptive cathodic stripping voltammetry in the presence of catechol. The optimized analytical conditions are a catechol concentration of 5.00 × 10−4 mol L−1, pH 8.0 and a collection potential of −1.80 V which eliminates the copper interference. The reoxidation period was limited to the time between switching to −0.10 V and scanning up to the metal peak (ca. −0.40 V). The limit of detection obtained for a 30 s collection time was 1.93 × 10−8 mol L−1 iron. The results achieved by this procedure and using the square-wave voltammetry technique are accurate and precise. Biological assays were performed to evaluate the mineralization process.

Summary Adsorptive stripping voltammetric procedures, using mercury film microelectrodes, were optimised and applied to quantify total iron, chromium and nickel in samples of osteoblast-like cells culture medium and mice organs (liver, kidney and spleen) obtained from, respectively, in vitro and in vivo 316L stainless steel corrosion products biocompatibility and toxicity studies. The methods were based on the pre-concentration of the iron-catechol complex by adsorption at the potential of −1.80 V ( vs. Ag/AgCl), of the chromium-diethylenetriaminepentaacetic acid complex at −1.00 V or −1.15 V ( vs. Ag/AgCl) and of the nickel-dimethylglyoxime complex at −0.70 V ( vs. Ag/AgCl). The detection limits achieved for each metal ion (i) in the culture medium were 1.93×10 −8 mol/L Fe, 2.80×10 −10 mol/L Cr and 7.70×10 −9 mol/L Ni for a collection time of 30 s, 40 s and 10 s, respectively, and (ii) in the mice organ solutions were 1.37×10 −8 mol/L Fe, 1.54×10 −8 mol/L Cr and 1.58×10 −9 mol/L Ni for an adsorption time of 25 s, 25 s and 15 s, respectively. The accuracy of the proposed procedures was verified by comparison of the results obtained by adsorptive stripping voltammetry with those attained by atomic absorption spectrometry for the same set of samples and good agreement was found. The in vitro study showed that stainless steel corrosion products affect the expression of the osteogenic phenotype. The in vivo mice model, used to investigate the systemic effects provoked by the corrosion products per se , indicated that Fe, Cr and Ni are partially accumulated in the organs studied and that Ni induced the more significant morphological alterations.

The effect of the ionic strength and composition of solutions in the direct potentiometric determination of total and ionized calcium content using a calcium selective electrode was investigated. In the presence of a constant complexation buffer (CCB), the addition of sodium chloride and sodium bicarbonate causes a decrease in the limit of detection of the potentiometric response. When the procedure was tested in osteoblast-like cell culture medium no electrode interferences or method interferences were observed by the presence of proteins, i.e., the total and ionized calcium in this medium can be measured by potentiometric means.

This work characterizes levels of main air pollutants in a preschool environment (3-5-years old children). The main gaseous pollutants, namely Total Volatile Organic Compounds (TVOCs), formaldehyde, carbon monoxide (CO), carbon dioxide (CO2), and ozone (O-3) were concurrently measured indoors and outdoors for 22 consecutive days at a preschool situated in urban zone of Chaves in north of Portugal. The results showed that with exception to TVOCs, levels of all indoor pollutants were below legislative guidelines.

The quality of indoor and outdoor air is one of the most discussed topics nowadays, as it is an important parameter influencing human health. Exposure to various health-hazardous atmospheric pollutants may result in various adverse health effects. To understand the relationship between air quality and health, it is important to study pollutants that have the most hazardous effects on human health. In that regard, polycyclic aromatic hydrocarbons are one of the most important pollutants. Polycyclic aromatic hydrocarbons (PAHs) are the largest known group of carcinogens that are ubiquitously found in the environment (air, water, soils and sediments). The scientific evidence available up to this date indicates that exposure to PAHs in various occupational environments can lead to health burdens among exposed workers being considerably higher than those for general population. In particular, industrial processes that involve the pyrolysis or combustion of coal production and use of coal-derived products are the major sources of PAHs. Thus, this chapter is dedicated to occupational exposure to PAHs. A discussion on PAHs is given covering their major aspects. The work also focuses on exposures to PAHs in various PAH-related occupations and associated health effects.

The objective of this work was to investigate the levels of some relevant indoor pollutants (total volatile organic compoundsTVOCs, ozoneO3, carbon dioxideCO2, carbon monoxideCO, formaldehydeHCHO, total suspended particulate matterTSP) with emphasis on Polycyclic Aromatic Hydrocarbons (PAHs) in a pre-school environment and to assess the risks associated with the exposure to carcinogenic PAHs for 35 years old children. The levels of indoor pollutants were sampled during 15 days at one preschool located in urban zone of Porto, Portugal. Obtained CO and TSP levels were in compliance with the existent Portuguese legislation on indoor air of public building whereas mean concentrations of TVOCs, CO2, and formaldehyde exceeded (up to 4.5 times) the limit values. Total concentration of 18 TSPbound PAHs ranged from 0.40 to 16.0 ng m-3 (mean of 4.75 ng m-3). Estimated values of lifetime lung cancer risks exceeded 40 times the healthbased guideline levels thus demonstrating that longterm exposure to PAHs at the respective levels might cause some adverse health outcomes. (c) 2015 Taylor & Francis Group, London.