STUDIA CHEMIA - Issue no.1 / 2019 - Table of contents

In this study, the sol-gel method was used to prepare Mgdoped TiO2 nanoparticles from titanium tetraisopropoxide and magnesium sulfate as the dopant precursors. Mg-doped TiO2 shows the formation of anatase phase with polyhedral and spherical particles with an average size of 25-30 nm. X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and photoluminescence were used to characterize the prepared material. The photocatalytic degradation performance of rhodamine B, nonylphenol ethoxylates, pseudoephedrine hydrochloride, and nicotine on Mg-doped TiO2 was studied under UV irradiation. The photocatalytic degradation shows that 98.92, 98.00, 98.00 and 97.95% of rhodamine B, nonylphenol ethoxylates, pseudoephedrine hydrochloride, and nicotine was decomposed by Mg-doped TiO2, respectively.

Keywords: Mg-doped TiO2; Organic pollutants; Photocatalytic degradation; Photoluminescence; Sol-gel

The removal of Cu(II) ions from aqueous solutions by adsorption onto nettle after incomplete incineration (IIN) has been studied in batch mode. The experimental isotherm results have been fitted using Langmuir, Freundlich, Temkin and Dubinin-Radushkevich equations. A comparison of kinetic models applied to the adsorption of Cu(II) ions on the adsorbent was evaluated for the pseudo-first order, the pseudo-second order and Elovich kinetic models. The pseudo-second order kinetic model was found to correlate the experimental data well. To evaluate competitive adsorption the batch experiments were carried out among the Cu(II), Pb(II) and Cd(II). The affinity order for the ternary system was Pb(II) > Cu(II) > Cd(II). FTIR and SEM analysis indicated that IIN could be used as an efficient biosorbent whose chemical structure and morphology is not altered during adsorption process.

Keywords: biosorption, heavy metals, kinetic study, thermodynamic study, Urtica dioica L.

The effect of three humic washing solution pH values (3.0, 7.0 and 9.6-its natural pH) on the removal efficiency of Pb and Cu from multimetal contaminated soil collected nearby “Larga de Sus” mine from Zlatna (Alba County, Romania) was investigated, at laboratory scale, by an ex-situ soil washing technique. In this study, a commercial soluble humic sample extracted from German Leonardite was used as washing agent to remove Pb and Cu from polluted soil. Soil washing experiments were conducted in a stirrer with orbital-rotation oscillation at a liquid/solid ratio (L/S ratio; mL:g) of 8:1, concentration of humic washing solution of 2% and various stirring times (4, 6, 12, 24 and 40 hours). The removal efficiency of Cu and Pb increased with increasing pH from 3.0 to 9.6. In investigated experimental conditions, the best removal efficiencies (60.3% in case of Cu and 48.08% in case of Pb) were obtained at alkaline pH values of humic washing solution.

Keywords: humic substances, soil washing, heavy metals, washing solution pH

The objective of this study was to determine the levels of essential (Ca, K, Na, Mg, Co, Cu, Cr, Fe, Mn) and non-essential (Al, As, Ba, Cd, Ni, Pb, Sr, Li, B) elements in the muscle, liver and skin of P. maxima and S. vulgaris. Analysis of variance was performed to determine significant differences among tissues. There were no significant differences in the metal concentrations among the tissues of both species with the exception of Fe and Li. The levels of essential metals such as Na, K, Ca and Mg were higher than 10 mg/kg; Fe and Cu were lower than 10 mg/kg. The results showed that the P. maksima and S. vulgaris are a good dietary source of essential nutrients. However, the concentrations of some nonessential metals in tissues of P. maksima and S. vulgaris exceeded the acceptable values for human consumption.

Keywords: Psetta maksima, Solea vulgaris, elements, minerals, heavy metals.

The composting is one of the most effective recycling method of green waste. The presence of some heavy metals, such as chromium, copper, manganese and zinc may influence the compost quality. The bioavailable and unavailable metal forms for plants determined by sequential analysis showed similarities in relation to the percentages of extracted forms. The lowest percentages were recorded for the bioavailable metal forms for plants uptake. Thus, the succession F6>F5>F4>F3>(F1+F2) is characteristic for chromium, the succession F5>F6>F4>F3>(F1+F2) is characteristic for copper and zinc and the succession F5>F4>F6>F3>(F1+F2) is characteristic to the zinc and manganese. Thus, by adding some organic additives, like manure, the micronutrients and heavy metals regime is influenced.

Keywords: green waste, compost, manure, heavy metal

The paper presents the level and spatial distribution of total chloride, arsenic and aluminum contents, and that of microbiological parameters (coliform bacteria, E. coli bacteria, intestinal enterococci) from water wells situated in the Seini area, both on the surface and in depth, using the geostatistical module of ArcGIS. The relations between the levels of microorganisms and the concentrations of chemical parameters (total chlorides, As and Al) were established using Table Curve program for generating 3D mathematical models.

Keywords: total chloride, arsenic, aluminum, microorganism, drinking water

The paper presents the rheological behavior study of the mixtures of castor oil with two types of adipic esters. The influence of adipic esters’ structure and concentration was determined, as well as that of temperature, on the rheological behavior, by setting the dependence between the shear stress τ and the shear rateγ. The analysis of the dependence between τ and γdemonstrates that the studied solutions present Newtonian behavior. The evolution of samples' viscosity with temperature was characterized by Arrhenius type equations, being established the values of viscous flow activation energy, Ea. It was also realized a characterization of annulus fluids flow under the effect of rotational motion, calculating the values of dimensionless criterion Taylor-Reynolds (TaRe)./p>

Keywords: adipic ester, flow activation energy, Newtonian behavior, Taylor-Reynolds number

In this work, excess properties (e.g. excess molar volume (VE), excess viscosity (ȠE), excess Gibbs free energy of activation of viscos flow (ΔG*E) and molar refraction changes (ΔnD) of binary solvent mixtures of tetrahydrofurfuryl alcohol (THFA) with aromatic hydrocarbons (benzene, toluene and p-xylene) have been calculated. This was achieved by determining the physical properties including density ρ, viscosity Ƞ and refraction index nD of liquid mixtures at 298.15K. Results of the excess parameters and deviation functions for the binary solvent mixtures at 298.15 K have been discussed by molecular interactions that occur in these mixtures. Generally, parameters showed negative values and have been found to fit well to Redlich-Kister equation which has been used to obtain the coefficients and evaluate the standard error.

Keywords: Binary systems, Tetrahydrofurfuryl alcohol, Deviations and excess properties, Density, Viscosity

The influent temperature has an important effect on the activated sludge process at the municipal Wastewater Treatment Plants (WWTPs). This research is associated to a case study of a Romanian municipal WWTP with Anaerobic-Anoxic-Aerobic (A2O) layout. Based on mathematical modelling it was studied the influent wastewater temperature effect on the effluent components concentration and on the concentration of pollutants and biomass concentrations at the outlet of biodegradation basins aerobic zone. Three influent temperature profiles were considered and implemented in the simulator. They reveal the representative 22 days period of the months: February (coldest water season), May (intermediate season) and July (warmest season). The simulations were performed both in steady and dynamic state. It was observed that higher influent temperatures intensify the nitrification and denitrification processes. As a result, the concentration of the nitrogen compounds in the effluent and at the end of the bioreactors decreases with the increase of the temperature. The carbon rich organic components feature a minor increase in the effluent. The study reveals that short time daily influent temperature changes do not have significant effect on the effluent components concentration, but the long-term ones affect the WWTP performance.

Keywords: wastewater treatment, mathematical modelling, Activated Sludge Model No. 1, Benchmark Simulation Model No. 1, influent temperature effects

The corrosion effect of the bleaching gel based on hydrogen peroxide on two types of dental metallic alloys, frequently used as restorative, prosthetic and implants materials was investigated by electrochemical impedance spectroscopy. The anti-corrosive behavior of Co-Cr and Cr-Ni alloys was found very different for the same experimental conditions. The best results were obtained with Co-Cr alloy, recommending the use of this material in dental treatments.

Keywords: dental alloys, hydrogen peroxide, electrochemical impedance spectroscopy

The current study analysed the effect of high-dose statin loading prior to primary percutaneous coronary intervention on oxidative stress markers, in patients with acute ST-elevation myocardial infarction (STEMI). Besides the lipid lowering effect, statins have antioxidant properties that might reduce myocardial ischemia-reperfusion injury. From a total of 37 patients, 18 patients received high-dose statin before coronarography and were included in the statin group, while 19 statin naive patients were included in the control group. Peripheral venous blood samples were obtained before coronary reperfusion, at 1 hour and 24 hours after that. The following markers of oxidative stress were determined from the serum: malondialdehyde (MDA), reduced glutathione to oxidized glutathione ratio (GSH/GSSG) and total antioxidant capacity (TAC). Values are shown as medians and interquartile ranges. MDA concentration and TAC had non-significant differences between the two groups, at all time frames. Before angioplasty, GSH/GSSG ratio was comparable between the two groups: 3.59 (2.13-5.37) in the statin group vs 2.69 (2.15-5.02) in the control group, p=0.49. At 1 hour after reperfusion, values were still similar: 2.26 (1.32-4.28) in the statin group vs 2.33 (1.88-2.50) in the control group, p=0.55. After 24 hours, there was a significant increase of GSH/GSSG ratio in the statin group 2.41 (1.58-3.28) vs 1.56 (1.12-2.03) in the control group, p=0.01. This finding suggest that, in STEMI patients, high-dose statin loading before primary percutaneous coronary intervention significantly reduces oxidative stress burden, early after administration.

Keywords: oxidative stress, acute myocardial infarction, statin, glutathione, percutaneous coronary intervention

As a consequence of the epidemic of obesity, prediction of metabolic syndrome (MetS) is relevant because of its subsequent association with type 2 diabetes and cardiovascular disease. Also, MetS is considered a state of insulin resistance (IR). This study aimed to evaluate the capacity of different indirect IR scores to identify patients with MetS, compared to standard criteria of MetS diagnosis. To the best of our knowledge, the cut-off values of these indexes, as indicators of MetS, in the Romanian population, have not been established. We used a non-parametric extension of the induced ROC regression methodology to determine the cut-off values of HOMA-IR, QUICKI, McAuley indexes, taking into account the MetS components instead of using 90th percentile criteria. Although HOMA is more commonly used in practice (probably due to its easy use), McAuley Score seems to have a better specificity in identifying patients with MetS. This is different between men and women; if in women, McAuley index has the highest sensitivity, in men, HOMA and QUICKI indexes have the highest sensitivity and specificity.

Keywords: insulin, glycemia, HOMA, QUICKI, McAuley, metabolic syndrome

In this study, the radiopacity of chairside Computer-Aided Design-Computer-Aided Manufacturing (CAD-CAM) milling materials was evaluated in comparison with dental structures. 105 specimens of 7 different thicknesses from 5 different types of chairside CAD-CAM milling materials: feldspar ceramic, hybrid ceramic, lithium disilicate glass-ceramic, zirconia-reinforced lithium silicate ceramic and a resin nano-ceramic were used for this in vitro study. Digital radiographs were obtained using an aluminum step wedge, a specimen of a tooth slice and 3 specimens from each material. Radiodensity was determined for each material using dedicated software. Lava Ultimate and Vita Suprinity were found as having higher radiopacity, whilst Vita Mark II and Vita Enamic were lower in radiopacity in comparison with dental structures. The radiodensity of Emax CAD was between enamel and dentine. Radiopacity of each CAD-CAM milling material was different and both material’s type and thickness significantly affected the radiopacity.

Keywords: CAD-CAM, chairside, milling materials, radiopacity

The research was conducted in order to evaluate the effect of natural (β-carotene and ascorbic acid) antioxidants on the oxidative stability of alimentary chicken fat in order to improve its safety and extend the shelf life. Peroxide value was significantly influenced by the storage time (p < 0.001) in chicken fat and 0.01% additivated fat. In control was found the highest level of peroxide value followed by 0.01% and 0.05% additivated fat. Regardless of the type of fat, the highest peroxide index level was found at 180 days of storage. Saturated fatty acids content increased, but monounsaturated and polyunsaturated fatty acids content decreased during refrigerated storage. Storage time showed to be most correlated with monounsaturated fatty acids for control (r = 0.93), followed by 0.01% additivated fat (r = 0.87) and 0.05% additivated fat (r = 0.76). The development of rancidity in chicken fat was significantly (p < 0.01) reduced by the addition of β-carotene and ascorbic acid in concentration of 0.05%.

Keywords: chemical stabilization, β-caroten, ascorbic acid, peroxide index, fatty acid profile

A new alternative super glue post-treatment method for the enhancement of fingermarks over two different non-porous surfaces including glass slides and high density polyethylene (HDPE) sheets have been investigated. This is the first documented application of 2,3,6,7-tetrahydro-9- methyl-1H,5H-quinolizino(9,1-gh)coumarin or coumarin-480 for the enhancement of cyanoacrylate fumed fingermarks. Coumarin-480 in ethanol was used as cyanoacrylate post-treatment dye. Fingermarks of seven different donors were aged for three different time periods (1 day, 1 week and 4 weeks) over non-fluorescent glass slides and HDPE sheets and developed with cyanoacrylate fumes. Upon staining with coumarin-480, fingermarks of varying qualities were observed under long UV radiations. Rhodamine 6G was used to assess the relative sensitivity of the coumarin-480 for the enhancement cyanoacrylate developed fingermarks. Pseudo-operational trials were conducted on glass bottles and high density polyethylene shopping bags. Coumarin-480 produced superior enhancement on HDPE shopping bags and glass bottles than the rhodamine 6G.

Keywords: Fingermarks enhancement, Cyanoacrylate post treatment dye, Coumarin-480, Fluorescent dye

The presence of nitrite and nitrate in milk and dairy products may cause serious health problem for consumers. Thus, a simple and accurate ion-pair reversed-phase high performance liquid chromatographic (IP-RP-HPLC) method has been developed and validated for determination of nitrite and nitrate in some dairy drinks based on Zonar Milk Serum. The separation was achieved on a Synergy Hydro-RP polar endcapped C18, 80Å, 4m (250  4.6 mm) column using isocratic elution with 0.01M n-octylamine and methanol, 90:10 (v/v) at pH=7; with flow rate of 1 mL·min-1 and detection at 214 nm and 25°C. A linear response (R2 ≥ 0.9994) was observed in the range between 3.125 and 75 μg mL-1 for the nitrite and nitrate standard solutions. The limits of detection (LOD) and quantification (LOQ) were found as 0.25 μg mL-1 and 0.8 μg mL-1 for nitrite and 0.4 μg mL-1 and 1.2 μg mL-1 for nitrate, respectively. The method was validated according to ICH guidelines with respect to selectivity, linearity, detection and quantitation limits, accuracy, precision. The good analytical performance verified for this method indicates that it is suitable the monitoring of nitrite and nitrate in dairy drinks based on Zonar Milk Serum.

Keywords: Nitrite, Nitrate, IP-RP-HPLC, validation, Zonar Milk Serum dairy drinks

This paper aims to investigate the “in vivo” behavior (over an extended period of time - six months) of hydroxyapatite and SiO2-TiO2 coating of Ti6Al7Nb alloy implants manufactured by selective laser melting. Innovative chemical implant coating by immersion technique was studied and the results were analyzed by optical and scanning electron microscopy (SEM). The results showed better osseointegration process for the coated implants and a much stabler biological behavior on the surface of the chemical treated implants.

Keywords: chemical coating, Ti6Al7Nb, surface treatment, bioactivity, SLM, laser processing

Capillary zone electrophoresis (CZE) could be a useful technique for the quantification of active substances from transdermal therapeutic systems (TTSs). TTSs are pharmaceutical forms in development that may release one or more active substances with some significant advantages as increased compliance to treatment, avoidance of first hepatic passage and low manufacturing costs. A simple, reliable, efficient, and lowcost CZE method was developed and validated for the simultaneous determination of levofloxacin (fluoroquinolone) and meloxicam (non-steroidal anti-inflammatory) from TTSs. The selected experimental parameters were 50 mM borax (pH 9.3) as background electrolyte, +25 kV applied voltage, 50 mbar/5 seconds hydrodynamic injection and 40°C temperature, using an uncoated fused-silica capillary with (51 cm total length/43 cm effective length, 50 μm i.d.). CZE experiments were performed in less than four minutes with a resolution of 7.79 at a wavelength of 335 nm. Validation of the method presented good linearity data, precision (RDS% < 1 for migration times and RDS% < 2 for peaks area) and sensitivity (LOD 3.43 and 16.05 μg·mL-1, LOQ 10.38 and 54.55 μg·mL-1 for levofloxacin and meloxicam, respectively). Recovery of the active substances ranged between 85.14% and 96.38%. Our developed CZE method proved its applicability for analysis of the two substances from TTSs.

Keywords: levofloxacin, meloxicam, capillary zone electrophoresis, transdermal therapeutic systems