Presence Of Different Substances Research Articles

An Overview of Electrochemical Sensors Based on Transition Metal Carbides and Oxides: Synthesis and Applications.

Sensors play vital roles in industry and healthcare due to the significance of controlling the presence of different substances in industrial processes, human organs, and the environment. Electrochemical sensors have gained more attention recently than conventional sensors, including optical fibers, chromatography devices, and chemiresistors, due to their better versatility, higher sensitivity and selectivity, and lower complexity. Herein, we review transition metal carbides (TMCs) and transition metal oxides (TMOs) as outstanding materials for electrochemical sensors. We navigate through the fabrication processes of TMCs and TMOs and reveal the relationships among their synthesis processes, morphological structures, and sensing performance. The state-of-the-art biological, gas, and hydrogen peroxide electrochemical sensors based on TMCs and TMOs are reviewed, and potential challenges in the field are suggested. This review can help others to understand recent advancements in electrochemical sensors based on transition metal oxides and carbides.

Comparison of several non-specific skin mucus immune defences in three piscine species of aquaculture interest

Fish skin mucus is a viscous and semipermeable barrier made mainly of water, glycoproteins and soluble proteins. It represents an important defence against the environment and previous studies have reported the presence of different substances involved in immune defence responses in it. The aim of the present work was to characterize skin mucus protease activity by zymography and esterase activity of the subfamily of carboxylesterases in three species of interest for aquaculture: gilthead sea bream, sea bass and meagre. Mucus antioxidant power was also determined by adapting ferric reducing antioxidant power (FRAP) analysis. As a result of these non-specific immune defence parameters, we compared the antibacterial capacity of skin mucus in these species via in vitro dual bacteria strains–skin mucus co-culture growths. We used Pseudomonas anguilliseptica and Vibrio anguillarum as marine pathogenic bacteria and Escherichia coli as non-pathogenic. For each fish species, in the respective zymograms, we determined a pattern of proteolytic digestion bands. A high-molecular-weight band (around 200 kDa; H-band) was evident in sea bream and sea bass, and showed chymotrypsin activity. One or two intermediate-molecular-weight bands (around 75 kDa; I-bands) with non-trypsin and non-chymotrypsin activity, and putatively with metalloprotease activity, were evident in all species. Finally, low-molecular-weight bands (between 14 and 30 kDa; L-bands) showed distinct patterns for each species and matched trypsin activity. Despite the conservative pattern of digestion bands, the levels of total proteolytic activity (TPA) were 5 and 10 times higher in meagre than in sea bass and sea bream, respectively. In parallel, three carboxylesterase activities were detected in the mucus of the three fish species, using myristate (pNPM-CE activity), butyrate (pNPB-CE activity) and acetate (pNPA-CE activity) as substrates. Both pNPB-CE and pNPA-CE were the most abundant in fish mucus, and meagre was again the species with the highest levels. In contrast, the antioxidant power of meagre skin mucus was the lowest. We established the capacity of skin mucus to block or limit bacterial growth (lytic activity) using 24 h growth curves. The log-growth phase of V. anguillarum was strongly blocked by sea bream and meagre mucus for a few hours; but not by sea bass mucus. However, if mucus was not renewed, log-growth was at the end of 24 h studied period. For its part, P. anguilliseptica growth curve was delayed by the three mucus types during the entire growth period. Only meagre achieved lytic activity against E. coli growth. All parameters studied here will be of a great interest as non-invasive bioindicators of non-specific immune defences in fish skin mucus.

VOLTAMMETRIC DETERMINATION OF ESTRADIOL IN MILK AND PHARMACEUTICALS BASED ON FUMED-SILICA MODIFIED CARBON PASTE ELECTRODE

In this study, modification of carbon paste electrode (CPE) with a nano-structured substance, fumed silica (FS), was investigated to develop a voltammetric method for the determination of an endocrine disrupting chemical, estradiol (EST). FS prominently increased the voltammetric response of CPE towards EST. The parameters that affect the volmametric performance of modified CPE were examined to find the optimal conditions. Modified electrode showed a linear response towards EST between the concentration values of 0.1 mM and 15.0 mM EST. Limit of detection value for the method developed was calculated as 0.023 mM. Production reproducibility of the modified electrode was obtained as 3.6 %. The voltammetric behavior of EST was also examined in the presence of different possible substances to evaluate their interference effects. The modified electrode successfully discriminated the oxidation potential of EST in the presence of different substances. The determination of EST was tested in milk and pharmaceutical samples to evaluate the analytical performance of the method. The recovery analysis of EST in milk samples showed that the modified electrode can be used safely in these samples. The modified electrode also achieved the determination of EST in pharmaceutical samples.

Development of a modified electrode by using a nanocomposite containing acid-activated multi-walled carbon nanotube and fumed silica for the voltammetric determination of clopyralid

This is the first study in the literature, which presents the voltammetric determination of herbicide clopyralid (CLD). A novel modified glassy carbon electrode was developed by using the nanocomposite containing acid-activated multi-walled carbon nanotube (A-MWCNT) and fumed silica (FS). The effective surface area of the electrode (8 times) and the reduction peak current values of CLP (369 times) increased in the presence of A-MWCNT-FS nanocomposite. This revealed that the electrode had an electro-catalytic effect on the electrochemical reduction of CLP. Cyclic voltammetry and electrochemical impedance measurements indicated that electron transfer rate of Fe(CN)64−/3− redox couple on the modified electrode was much higher over the bare electrode. Scanning electron microscopy images showed that A-MWCNT and FS formed a homogeneous nanocomposite by dispersing each other. It was observed that electrochemical reduction of CLP was more favourable in pH values between 2 and 4. Electrochemical reduction of CLP on the modified electrode was an adsorption-controlled process. Electrochemical reduction peak currents linearly increased with CLP concentrations in the range of 0.005μM and 10.0μM. The detection limit was calculated as 0.8nM. Measurement and fabrication reproducibilities of the modified electrode were obtained as 2.94% (N: 10) and 3.34% (N: 5), respectively. Electrochemical reduction behaviour of CLP was not affected by the presence of different substances in the measurement solution. The GC/A-MWCNT-FS electrode allowed to determine the CLP in real samples such as urine, river water, sugar beet, wheat and herbicide formulations (Phaeton and Lontrel). The results indicated that the electrochemical sensor prepared in this study could be a very promising alternative to current analytical methods used to determine CLP.

Visualizing the Effects of Sputum on Biofilm Development Using a Chambered Coverglass Model.

Biofilms consist of groups of bacteria encased in a self-secreted matrix. They play an important role in industrial contamination as well as in the development and persistence of many health related infections. One of the most well described and studied biofilms in human disease occurs in chronic pulmonary infection of cystic fibrosis patients. When studying biofilms in the context of the host, many factors can impact biofilm formation and development. In order to identify how host factors may affect biofilm formation and development, we used a static chambered coverglass method to grow biofilms in the presence of host-derived factors in the form of sputum supernatants. Bacteria are seeded into chambers and exposed to sputum filtrates. Following 48 hr of growth, biofilms are stained with a commercial biofilm viability kit prior to confocal microscopy and analysis. Following image acquisition, biofilm properties can be assessed using different software platforms. This method allows us to visualize key properties of biofilm growth in presence of different substances including antibiotics.

Modeling of the chemical stage in water radiolysis using Petri nets

The biological effect of ionizing radiation is mediated practically always by the clusters of radicals formed by densely ionizing track ends of primary or secondary particles. In the case of low-LET radiation the direct effect may be practically neglected and the radical clusters meet a DNA molecule always some time after their formation. The corresponding damage effect (formation of DSB) depends then on the evolution running in individual clusters, being influenced by present chemical agents. Two main parallel processes influence then final effect: diffusion of corresponding radical clusters (lowering radical concentrations) and chemical reactions of all chemical substances present in the clusters. The processes running in the corresponding radical clusters will be modeled with the help of continuous Petri net, which enables us to study the concurrent influence of both the processes: lowering concentration of radicals due diffusion and due chemical reactions. The given model may be helpful especially when the effect of radicals on DSB formation (DNA damage) at the presence of different substances influencing radiobiological effect is to be studied.

Potentiometric determination of mefenamic acid in pharmaceutical formulation by membrane sensor based on ion-pair with basic dye

Abstract The characteristics, performance and application of membrane sensors based on ion-pair Brilliant Green mefenamate are described. The sensor's response to the mefenamate ion has the sensitivity of (86.0 ± 2.0) mV/pC over the range of 9 × 10 −5 –1 × 10 −2 mol/L and the detection limit of 4.5 × 10 −5 mol/L at pH 8.5–12. The sensor is easily assembled at a relatively low cost and has fast response time (5–10 s). The proposed sensor displayed good selectivity for mefenamate ion in the presence of different substances. It was used to determine mefenamic acid in pharmaceuticals.

Adsorption of Nitrogen Oxides, Water Vapour and Ozone onto Activated Carbon

Noxious gases and odours in cabin air are reduced by activated carbon filters. However, the adsorption process involved in cabin air filtration is very complex because of the large number of influencing parameters. Some important parameters are changes in the input concentrations and surrounding conditions. Furthermore, the presence of different substances leads to their mutual influence on the respective adsorption processes. The separation of nitrogen oxides is an especial focus of discussion in Germany at present because of decreasing ambient exposure limits. One part of the study presented herein deals with the binary adsorption of nitrogen dioxide in humid air at varying NO2 input concentrations, relative humidity and temperature. In order to obtain more information about this process, after initial validation of the test procedure employed, breakthrough curves of NO2 have been undertaken in the present study. In the second part of the study, the influence of a third adsorptive (ozone) on the adsorpt...

Potentiometric determination of diclofenac in pharmaceutical formulation by membrane electrode based on ion associate with base dye

The characteristics, performance and application of membrane electrode based on ion associate of diclofenac with base dye Safranine T are described. The electrode response to diclofenac has the sensitivity of 47 ± 1.0 mV decade −1 over the range of 5 × 10 −5 to 5 × 10 −2 mol/L at pH 6–12, and the detection limit of 3.2 × 10 −5 mol/L. The electrode is easy assembled at a relatively low cost has fast response time (2–4 s) and can be used for a period up to 3.5 months without any considerable divergence in potential. The proposed sensor displayed good selectivity for diclofenac in the presence of different substances. It was used to determine diclofenac in pharmaceuticals by means of the standard addition method.

Mechanical Properties of Alginate Beads Hosting Hepatocytes in a Fluidized Bed Bioreactor

Fluidized bed bioartificial liver has been proposed as a temporary support to bridge patients suffering from acute liver failure to transplantation. In such a bioreactor, alginate beads hosting hepatocytes are in continuous motion during at least six hours. After having shown in vitro the functionality of such a device, the present study aims at analyzing the potential mechanical alterations of the beads in the bioreactor, perfused by different surrounding media. Compression experiments are performed and coupled for analysis with Hertz theory. They provide qualitative and quantitative data. The average value of the shear modulus, calculated for the different cases studied varied from 2.4 to 10.4 kPa, and could therefore be considered as a quantitative measure of the beads mechanical properties. From the compression experiments and the estimated values of the shear modulus, we could now evaluate the effect of different operating conditions (fluidization, presence of cells, surrounding medium) on the mechanical behavior of alginate beads. On the one hand, the motion during six hours in the bioreactor does not alter the beads significantly. On the other hand, the presence of different substances in the fluid phase might change their mechanical strength. These results can be considered as new encouragements to use such a device as a bioartificial organ.

Development of a reliable alkaline wastewater treatment process: optimization of the pre-treatment step

Alkaline waters produced by caprolactam plants polymerizing the fibres of nylon-6 are characterized by a very high alkalinity, salinity and COD values, in addition to the presence of recalcitrant organic molecules. These characteristics make alkaline wastewaters very difficult to treat; so the development of the suitable sequence to carry out in a depuration process appears of great interest. The proposed general process consists of three main steps: first, pre-treatment for the acidification of the polluted stream, second, a successive extraction of the bio-recalcitrant compound (noted as cycloexanecarboxysulphonic acid (CECS)) and a final biological treatment. In particular, this paper deals with the pre-treatment step: it consists of an acidification process by means of sulphuric acid with the concomitant precipitation of black slurries in the presence of different substances, such as solvents, CaCl 2, bentonite, several flocculants and coagulants. The aim of this study is to set an experimental procedure, which could minimize fouling problems during sludge filtration. The use of additives like bentonite seems to give the best results, because it allows good COD reductions and a filterable precipitate, which avoids excessive fouling problems of the experimental apparatus.

Identification of Compounds in Wine by HPLC—Tandem Mass Spectrometry

In this work several compounds were detected in wines by HPLC-tandem mass spectrometry. In particular cinnamic and benzoic acids, tyrosol, apigenin-7-glucoside and luteolin-7-glucoside were identified and quantified in Italian wines. Red wines show bigger amount of cinnamic and benzoic acids than white wines. tyrosol is in bigger amount with respect to two flavones: luteolin-7-glucoside and apigenin-7-glucoside. These last two flavones are only in some wine, but it can be important to detect the presence of different substances in small amount to be able to characterize a wine.

New packaging solutions for high pressure treatments of food

High pressure is a promising technology for developing new processes in food treatment. In most cases, pre-packaged foods are used in high pressure treatments (HP). Consequently, the behavior of the package under treatment conditions is an important factor. The following work was devoted to the evaluation of different packages under high pressure conditions in the presence of different substances used as simulants. Three main characterizations were carried out after HP treatment: mechanical resistance, barrier properties and integrity. The experimental results using multilayer plastic films (PA/PE) have led to the selection of several solutions which may be used as packages for high pressure treatments.

Study of β-1,3-glucanase activity during autolysis of Aspergillus nidulans by FPLC ion-exchange chromatography

The behaviour of β-1,3-glucanase activity during Aspergillus nidulans autolysis was studied in a basal medium and in the same medium supplemented with 0.5 g l-1 of microcrystalline cellulose, laminarin, pectin, seedling of Lycopersicum esculentum extract, chitin and xylan respectively. In any case β-1,3-glucanase activity was detected in the culture fluid before the onset of the autolysis, but afterwards a progressive increase of β-1,3-glucanase activity took place with incubation time. In the media supplemented with pectin and seedling of Lycopersicum esculentum extract higher activity in the first days of autolysis was found. The activity at the end of the studied process by sample was 2.5, 2.1, 2.5, 1.9, 2.2, 2.3 and 2.3 U, and the specific activity 83, 53, 85, 55, 64, 90 and 53 mU mg-1 of protein for each medium respectively. The β-1,3-glucanase activity in Aspergillus nidulans seems to be related to autolysis and not to the presence of different substances in the culture medium. The behaviour of β-1,3-glucanase activity during the degradative process was followed by FPLC ion-exchange chromatography. Three proteins (I, II, III) with β-1,3-glucanase activity were separated and quantified. These proteins have similar behaviour in all the media. Proteins I and II increase progressively with incubation time but protein III is only present at the first and last days of autolysis.

Presence of cells and fibers immunoreactive toward antibodies to different peptides or amine in the digestive tract of the snailHelix aspersa.

An immunocytological study of four different parts of the gut of Helix aspersa clearly demonstrates the presence of many cells and fibers immunoreactive toward antibodies directed to vertebrate (α, β-endorphin, α, β-MSH, ACTH 1-24 and ACTH 17-39, met-enkephalin, somatostatin, insulin, glucagon, P.P., serotonin) or invertebrate (FMRF-amide) peptides. These results are evidence of the presence of different substances related to known peptides or amines in the epithelial and connective tissue cells and nerve fibers of the snail gut. Immunocytochemistry may help to elucidate the morpho-functional characteristics of the enteroendocrine cells of H. aspersa.

Protection of the pancreatic β-cell glucoreceptor mechanism for insulin secretion during culture in chemically defined medium

High concentrations of glucose have a protective effect on the glucoreceptor mechanism for insulin secretion during culture of pancreatic islets in chemically defined media. To study at what level glucose exerts this effect, insulin secretion from beta-cell-rich mouse pancreatic islets was measured before and after culture for 1 week in the presence of different substances. Before culture, glucose and inosine were potent stimulators, mannose and fructose were less potent and xylitol had no effect on secretion. Culture in 3mm-glucose resulted in a 10-fold decrease in the insulin response to glucose stimulation. A less marked decrease was noted after culture in 20mm- or 30mm-glucose. Inosine-stimulated secretion was much decreased after culture in high concentrations of glucose, whereas the responses to mannose or fructose were unchanged. After culture in 30mm-mannose, glucose-stimulated secretion was similar to that observed after culture in high concentrations of glucose, whereas the response to mannose had much decreased. There were no secretory responses to glucose or fructose after culture in 30mm-fructose, or to glucose or xylitol after culture in 30mm-xylitol. Culture in 10mm-inosine did not preserve any significant response to glucose or inosine. The insulin contents of islets and culture media were higher after culture in high concentrations of glucose, mannose or inosine than after culture in fructose, xylitol or low concentrations of glucose. It is suggested that glucose, and to some extent mannose, preserves the glucoreceptor mechanism for insulin secretion by influencing an early stage in glucose metabolism, presumably glucokinase activity.

Sobre a estabilidade da vitamina B, em soluções para uso hipodérmico

It has been verified that substances such as glycocol, xantin, chlorobutanol and riboflavin, do not exercise protective action upon the stability of tiamin in isotonic solutions dosing 10 mg of Vitamin B1 for ml. On the other hand, even in presence of different substances used with the view of the isotonisation, the sodium sulfite, decompose the tiamin, that conserves rationally well, when dissolved in isotonized solutions for glycose, sucrose, levulose or inositol.