Ingars Reinholds, Iveta Pugajeva and Vadims Bartkevičs
This research demonstrates the development of reliable multi-component methods for the detection of antibiotic residues in environmental biota. The efficiency of analytical performance of ultra high performance liquid chromatography (UHPLC) techniques with triple quadrupole (QqQ-MS/MS) and Orbitrap high-resolution mass spectrometry (Orbitrap-HRMS) detectors is discussed. Antibiotic residues in biota samples collected in Latvia were analysed. The contamination status was determined as rather low within acceptable levels set by the European Union Regulations.
Olga Muter, Andrejs Bērzinš, Tūrs Selga, Ruta Švinka and Visvaldis Švinka
Ceramic granules fabricated from Quaternary clay at 1200°C were tested for their flotation ability in a water model system containing silicone oil. The presence of oil in the liquid phase improved flotation of granules, probably due to sorption of oil by ceramics. Coating of granules with SiO2 resulted in decreased flotation ability, irrespectively of the presence of oil. Granules were shown to be appropriate for bacterial colonization.
Lauris Rupeks, Viktor Filipenkov, Ivars Knets, Visvaldis Vitins, Marina Sokolova, Liga Stipniece and Mara Pilmane
Hydroxyapatite is used for bone reconstruction, in order to improve its mechanical properties different substances can be added. In our study new biomaterial is created from deproteinised hydroxyaptite and endodentic cement, its mechanical properties were tested. Material was implanted subcutaneous in rats, then histological and biocompatability tests were performed. Results indicate that stuff has good mechanical properties, short setting time and gradual resorption creating porosity and ability to integrate in bone.
Raw clays from the Baltic region are characterized as smectite containing clays with significant amount of naturally occurring impurities that limiting the potential applications of crude Baltic clay resources. Purification of clay samples from Šaltiškių deposit (Venta basin) was carried out by varied concentration hydrochloric acid solutions and resulted in fine removal of carbonates and iron oxide. The main idea of this work is to widen the possible applications of local clay resources providing a new type of raw material for further organoclay production.
The aim of this study was to detect major whey proteins α-lactalbumin and β-lactoglobulin by reversed-phase high-performance liquid chromatography (RP-HPLC). RPHPLC methods were developed using the column YMC Pack-C4, which enabled the separation of whey proteins within 30 min. Mobile phase was acetonitrile/water/0.1% trifluoroacetic acid (TFA) with gradient elution, flow rate was 1.0 mL·min−1, and the detection wavelength was 210 nm. Column temperature was 40°C and injection volume was 20 μL.
Milk samples contained α-lactalbumin and total β-lactoglobulin: No. 1 - 1500 mg·L−1 and 3600 mg·L−1; No. 2 - no α-lactalbumin and 450 mg·L−1 total β-lactoglobulin; No. 3 - 800 mg·L−1 and 94 mg·L−1, respectively.
Water-soluble polymer, cationic poly(N-[3-hexyldimethyl-aminopropyl] methacrylamide bromide) (PHDAPMAA), is synthesized by radical polymerization and studied in terms of its solubility, viscosity, surface tension and conductivity. Viscometry and surface tension measurements confirmed that intramolecular hydrophobic microdomains were formed by the pendent alkyl chains. Conductivity of cationic polymer in aqueous solution was determined. Variation of conductivity versus concentration in investigated system exhibits a typical polyelectrolyte behaviour.
The paper deals with electrochemical deposition of coatings of highly entropic alloys. These relatively new materials have been recently intensively studied. The paper describes the first results of electrochemical coating with highly entropic alloys by deposition from non-aqueous solutions. An electrochemical device was designed and coatings were deposited. The coatings were characterised with electronic microscopy scanning, atomic absorption spectrometry and X-ray diffraction methods and the combination of methods of thermic analysis of differential scanning calorimetry and thermogravimetry.
To begin with, the intorduction of this paper summarises literature sources that wrongly interpret results of the bond strength between hot-dip galvanised reinforcements and concrete. The influence of the total reinforcement anchorage length on the bond strength results assessment was studied in detail. The numeric analysis of beam models with various testing anchorage lengths (the analysis input data comprised the results of previous bond strength tests carried out in a laboratory) unambiguously confirmed that when the bond strength between concrete and hot-dip galvanised reinforcement with a sufficient test anchorage length is tested in a beam test, the negative impact of the coating corrosion on bond strength with concrete may be biased. It is more objective to test bond strength with concrete in a pull-out test where a very short test reinforcement anchorage length is set out as a standard.
Corrosion tests of both annealed and not annealed bends of HR3C and S304H steels in operation conditions of black and brown coal combustion boilers in EPRU and EDE. After a long-term exposure, the samples were assessed gravimetrically and metallographically. The comparison of annealed and unannealed states showed higher corrosion rates in the annealed state; corrosion of the sample surface did not essentially differ for compression and tensile parts of the beams. Detailed assessment of both steels is described in detail in this study.
Historical lead artefacts (small figurines, appliques, bull (metal seal) can be stored in depository and archives in inconvenient storage conditions. The wooden show-case or paper packagings release volatile organic compound to the air during their degradation. These acids, mainly acetic acid are very corrosive for lead. The thin layer of corrosion products which slows atmospheric corrosion is formed on lead surface in atmospheric condition. In presence of acetic acid vapour the voluminous corrosion products are formed and fall off the surface. These corrosion products do not have any protection ability. The lead could be protected against acid environment by layer of “metal soup” which is formed on surface after immersion in solution of salt of carboxylic acid for 24 hours. The solutions of acids (with vary long of carbon chain) and their salts are examined. Longer carbon chain provides better efficiency convers layer. The disadvantages are low solubility of carboxylic acids in water and bad abrasion resistance of formed layer.