Ingars Reinholds

The application of phospholipid removal columns and ultra-high performance liquid chromatography—tandem quadrupole mass spectrometry for quantification of multi-class antibiotics in aquaculture samples

In this study a robust and sensitive method based on a proposed sample purification procedure, using zirconia-coated Phree™ columns and analysis by ultra-high performance liquid chromatography with triple quadrupole tandem mass spectrometry are presented for the assessment of multi-class antibiotics in farmed fish species. The sample preparation procedure benefited from combined precipitation of proteins and selective removal of phospholipids by Phree™ columns, resulting in a high sensitivity of the method (LOQ 0.3-9mgkg(-1)). The in-house validation results (precision, repeatability, decision limit CCα, detection capability CCβ, etc.) indicate that the elaborated method is fully suitable for the analysis of the main classes of antibiotics in accordance with the European Union (EU) Commission Decision 2002/657/EC. The method was applied to the analysis of antibiotics in trout and sturgeon samples obtained from the local inland aquacultures in Latvia. The results revealed the presence of two antibiotics (enrofloxacin and trimethoprim) in 12 out of the 20 analysed fish samples at concentrations (0.33-12.2μgkg(-1)) below the MRLs, thus causing no acute risks to consumers.

Determination of pharmaceutical residues and assessment of their removal efficiency at the Daugavgriva municipal wastewater treatment plant in Riga, Latvia

Pharmaceutical products (PPs) belong to emerging contaminants that may accumulate along with other chemical pollutants in wastewaters (WWs) entering industrial and/or urban wastewater treatment plants (WWTPs). In the present study, the technique of ultra-high-performance liquid chromatography coupled to Orbitrap high-resolution mass spectrometry (Orbitrap-HRMS) was applied for the analysis of 24 multi-class PPs in WW samples collected at different technological stages of Daugavgriva WWTP located in Riga, Latvia. Caffeine and acetaminophen levels in the range of 7,570-11,403 ng/L and 810-1,883 ng/L, respectively, were the predominant compounds among 19 PPs determined in the WW. The results indicate that aerobic digestion in biological ponds was insufficiently effective to degrade most of the PPs (reduction efficiency <0-50.0%) with the exception of four PPs that showed degradation efficiency varying from 55.0 to 99.9%. Tests of short-term chemical and enzymatic hydrolysis for PP degradation in WW samples were performed, and the results reflected the complexity of different degradation mechanisms and physicochemical transformations of PPs. The toxicological studies of WW impact on Daphnia magna indicated gradual reduction of the total toxicity through the treatment stages at the WWTP.

Manufacturing, structure and properties of recycled polyethylene terephthalate /liquid crystal polymer/montmorillonite clay nanocomposites

Polyethylene terephthalate (PET)/liquid crystal polymer (LCP)/monthmorillonite clay (MMT) compositions were obtained by melt mixing. Their mechanical, structural, rheological and thermal properties were investigated.

Carbon nanotubes modified with octylthiophene derivatives for improved performance of ethylene-octene copolymer composites

The effects of poly-3-octylthiophene (P3OT) functionalized multiwalled carbon nanotubes (MWCNTs) on the structure as well as stress-strain characteristics and electrical conductivity of ethylene-octene copolymer with 17% of octene comonomer content (EOC17) are investigated. According to Raman spectroscopy and TEM analysis, thiophene groups have been successfully grafted onto the surface of MWCNTs. EOC17 nanocomposites with P3OT functionalized MWCNTs show simultaneously high values of stress at break and strain at break, even at high nanofiller content, being respectively 2.5 and 3.5 times higher than the values determined for the systems containing pristine MWCNTs. It is also demonstrated that at functionalized filler content of 10 wt%, twofold increment of the modulus of elasticity is observed. In addition to that, P3OT functionalized MWCNTs containing EOC nanocomposites possess up to 279 times greater electrical conductivity in comparison to the systems with pristine MWCNTs.

Mechanical and Heat Shrinkable Properties of Electron Beam Irradiated Polypropylene With Bisphenol A Dimethacrylate Crosslinker

Abstract Radiation crosslinking of polyolefins has gained interest for the development of advanced heat-shrinkable materials. Propylene homopolymer (PP1), polypropylene-polyethylene block copolymers (PP2, PP3) and their mixtures with 3 wt.% of bisphenol A dimethacrylate (BPDMA) crosslinking agent were irradiated with 25–150 kGy of accelerated electrons and were compared for aforementioned purpose. The studied mechanical properties indicated increased elongation in the presence of BPDMA that was contributed to the crosslinked moieties of PP and the crosslinking agent. The shrinkage stresses were comparable to that of polyethylene based heat-shrinkable material.

Physical Load Among Construction Workers and Analysis with Objective Ergonomics Research Method

There is growing number of work related musculoskeletal disorders among workers in construction industry. Employees in construction professions admit physical load and discomfort in various body parts after the work. Accordingly to Eurostat statistical data 60 % of total work related diseases are attributed to musculoskeletal disorders in Latvia. The aim of this study was to determine physical load of construction auxiliary workers and bricklayers using objective ergonomics research method HR monitoring and subjective ergonomic risk assessment methods. The research involved full time 8 auxiliary construction workers and 7 bricklayers. Analysis of the heart rate monitoring data proved that objective physical load analysis method is more precise than subjective workload evaluation methods. Results showed that construction workers workload falls into hard and moderate work heaviness category. More experienced workers with longer length of service were subjected to lower work heaviness category.

Comparison of Tandem Quadrupole Mass Spectrometry and Orbitrap High Resolution Mass Spectrometry for Analysis of Pharmaceutical Residues in Biota Samples

Abstract 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.

Evaluation of Mechanical and Structure Properties of Electron Beam Cross-Linked Ethylene-Octene Copolymer Nanocomposites with Multi-Walled Carbon Nanotubes

Recently, ionizing radiation has found an application in nanotechnology especially attributed to the improvement of nanocomposites. In the present paper, we have developed and evaluated radiation cross-linked nanocomposites made of ethylene-octene copolymer (EOC) with 0-15 wt.% of multi-walled carbon nanotubes (MWCNTs) and irradiated by 5 MeV accelerated electrons. The influence of combined factors of MWCNT filler content and the irradiation up to 150 kGy on the tensile stress-strain properties at 25–50°C was analysed. The cross-linking efficiency was also evaluated. The results indicated improvement in tensile properties with an increase of MWCNT content and the irradiation up to 150 kGy dose. The combined influence of both factors was determined. The gel content of irradiated EOC/MWCNTs was equal to 45-86% that indicated sufficient cross-linking efficacy of EOC with MWCNTs acting as reinforcing fillers in the matrix.

New Thermoshrinkable Materials of Radiation Modified Polypropylene-Elastomer Composites with Cross-Linking Agents

In this work, electron beam modified heterogeneous composites of isotactic polypropylene (PP) with chlorinated polyethylene (CPE) have been investigated. The PP/CPE blend composites with an excess of elastomer (30/70 wt%) have been modified with trimethylolpropane triacrylate (TMPTA) and bisphenol-A-dimethacrylate (BPDMA) cross-linking agents and have been irradiated with accelerated electrons up to ionizing radiation doses from 25 to 150 kGy. The internal stresses characterizing the thermoshrinkage properties (TMP) thermorelaxation stresses formed in thermal heating and the residual stresses resulting in the process of full setting and cooling of materials have been investigated for radiation cross-linked oriented (extended up to 100%) composite samples. The dependence of cross-linking efficiency and the TMP characteristics of PP/CPE heterogeneous blends have been compared to properties of a low density polyethylene (LDPE), which has been commonly used as thermoshrinkable material (TSM) in polymer industry. It has been proved that the radiation-chemically modified PP multiphase composites with elastomers and the crosslinking promoters are comparable perspective materials for creation thermoshrinkable materials with higher or similar thermoshrinkage properties compared to currently exploited TSM.

Radiation-chemically modified PP/CNT composites

Abstract In this work, the authors studied the effects of electron beam (EB)-induced changes in stress-strain characteristics, heat shrinkage stresses, and structure characteristics on polypropylene (PP) composites containing bisphenol-A-dimethacrylate (BPDMA) as the radiation sensitizer and different contents of multi-walled carbon nanotube (CNT) filler (0–2 wt.%). The effect of stearic acid (SA) as the surface modifier on the improvement of CNT dispersion in the PP matrix was also studied. Initially, PP blends with different contents (up to 10 wt.%) of BPDMA were prepared to determine the effective concentration of the sensitizer for the modification of the PP matrix. PP/BPDMA composites and blends filled with CNTs were irradiated up to 25–50 kGy of radiation doses. The properties of unirradiated compositions and those modified by EB, were compared. Radiation-induced changes were confirmed by gel fraction and by the changes in Fourier transform infrared spectroscopy spectra. The results showed an increase in Young’s modulus, yield strength, and thermal-relaxation stresses for the irradiated PP/CNT compositions grafted with 3 wt.% of BPDMA and compatibilized with SA.