0000000000321650
AUTHOR
Ingars Reinholds
showing 33 related works from this author
Thermal Analysis, Mechanical and Rheological Behaviour of Melt Manufactured Polyethylene/Liquid Crystal Polymer Blends
2011
Modification of properties of conventional thermoplastics with thermotropic liquid crystal polymers, from one hand, allows decrease their viscosities, substantially facilitating processing conditions, and, from another hand, allows increase their exploitation properties. Orientation of the labile structure of liquid crystal polymer in extrusion or injection moulding causes specific reinforcement (so-called self-reinforcement) to occur in the blends containing liquid crystal polymer. Up to now the effect of self-reinforcement is mostly investigated in the blends, containing considerable amount of liquid crystal polymer. In this research the effect of minor amounts of liquid crystalline co-po…
Mechanical properties and XRD of Nafion modified by 2-hydroxyethylammonium ionic liquids
2013
In this work, the Nafion 112 membrane impregnated with 2-hydroxyethylammonium carboxylate ionic liquids have been investigated. The used ionic liquids were 2-hydroxyethylammonium formate [HEA]F, acetate [HEA]A and lactate [HEA]L. Prepared composite membranes Nafion/ionic liquid are characterized by mechanical testing, such as tensile test and creep test. It is found that ionic liquids decrease elastic modulus and creep compliance, but do not have significant effect on the tensile strength. Also, composite membranes were studied by wide angle X-ray diffraction. All ionic liquids shift the peak maximum to the lower angle. In this work, only biodegradable ionic liquids were used for composite …
Mycotoxins in herbal teas marketed in Latvia and dietary exposure assessment
2019
The occurrence of 12 mycotoxins has been analysed by liquid chromatography - time of flight mass spectrometry in the batch of 60 herbal teas purchased from drugstores in Latvia. Among the dry tea samples, 90% were positive for one to eight mycotoxins. Enniatin B and deoxynivalenol (DON) were the most frequently detected mycotoxins in 55% and 45% of the samples, respectively. DON reached the highest level, from 129 µg kg-1 in herbal blend to 5,463 µg kg-1 in wormwood tea. Ochratoxin A (OTA) and aflatoxin B1 (AFB1) were found in 10% and 20% of the samples at the concentrations ranged between 2.99-30.3 µg kg-1 and 3.40-23.7 µg kg-1. Studies of the tea infusion process indicated that 32-100% of…
A reliable screening of mycotoxins and pesticide residues in paprika using ultra-high performance liquid chromatography coupled to high resolution Or…
2016
Abstract In this study, an ultra-high performance liquid chromatography (UHPLC) coupled to a high resolution Orbitrap mass spectrometry (Orbitrap-HRMS) was demonstrated as a promising technique in high-throughput method development for the routine analysis and contamination control of mycotoxins and pesticide residues in spices. The method was applied for the analysis of fifty ground paprika samples containing blends of sweet and hot paprika harvested in Brazil and China. The efficiency and detection sensitivity of the used UHPLC-Orbitrap-HRMS technique were compared to the results obtained using a triple quadrupole tandem mass spectrometric detector (UHPLC-QqQ-MS/MS). The values of recover…
Development and Characterization of Novel Conductive Nanofiller Based on Multi-Walled Carbon Nanotubes Grafted with Poly(3,4-Ethylenedioxythiophene)
2018
In the present study, an approach for the graft polymerization of multi-walled carbon nanotubes (MWCNTs) with 3,4-ethylenedioxythiophene (EDOT) has been evaluated. The surface of the MWCNTs was activated with thiophene groups through the amide linker followed by oxidative polymerization of EDOT monomer resulted in the development of PEDOT-g-MWCNTs. The methods of thermal gravimetric analysis (TGA), X-ray fluorescence, and Raman spectroscopy were used for characterization of functionalization efficiency. The TGA data indicated of 21% functionalization attached to MWCNTs. X-ray fluorescence confirmed the presence of Cl, and S atoms in functionalized fillers. The study of Raman spectra confirm…
Evaluation of Mechanical and Structure Properties of Electron Beam Cross-Linked Ethylene-Octene Copolymer Nanocomposites with Multi-Walled Carbon Nan…
2016
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 d…
Recent applications of carbonaceous nanosorbents for the analysis of mycotoxins in food by liquid chromatography: a short review
2019
Carbonaceous nanomaterials (multi-walled carbon nanotubes (MWCNTs), graphene, and graphene oxide (GO)) have attracted attention over the last decade as adsorbents suitable for the analysis of organic and inorganic pollutants. In the present paper we review methods of mycotoxin analysis that involve sample extraction with carbonaceous nanosorbents, reported from 2011 onwards. Recent studies have highlighted the advantages of magnetically modified MWCNTs and GO in mycotoxin analysis, which may enable sample isolation through magnetic separation, reduce the interaction of nanoparticles, and enhance the recovery of analytes. The papers covered in this review point to promising applications of …
The application of phospholipid removal columns and ultra-high performance liquid chromatography-tandem quadrupole mass spectrometry for quantificati…
2016
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 f…
Manufacturing, structure and properties of recycled polyethylene terephthalate /liquid crystal polymer/montmorillonite clay nanocomposites
2013
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.
Effective Degradation of Cigarette Butts via Treatment with Old Landfill Leachates
2021
In this paper, results of feasibility study on microplastics (MPs) assessment in leachates from the Latvian solid municipal landfill Getliņi are discussed. The application of leachates for the treatment of cigarette butts (CGB) was evaluated. Methods of fluorescent microscopy, Fourier transform infrared (FTIR) spectroscopy and FTIR-microscopy were used for the identification and characterization of MPs in the leachates and analysis of CGB. Presence of the secondary MPs (e.g., degraded polyolefin mixtures) was determined in the tested landfill leachates, while cellulose acetate (CA) was not determined in these products. The leachates were tested as potential media for the thermophilic (55°C)…
Kombinētie darba vides riski speciālajās pirmsskolas izglītības iestādēs, aizsardzības un preventīvie pasākumi
2016
Novērtēta kombinēta fizikālo, ergonomisko, psihosociālo u.c. faktoru ietekme speciālās pirmskolas izglītības iestādes darba vidē. Veikti objektīvie mērījumi, nosakot asinsspiediena un pulsa rādītājus. Statistiski analizēti speciālās un vispārējo pirmsskolas izglītības iestāžu darbinieku (95 respondenti) rezultāti par darbinieku veselību, spriedzes līmeni un darba vidi. Autors pielietojis FMEA metodi kombinēto risku analīzei. Noteikts, ka ergonomisko faktoru uzlabošana un darbinieku izglītošana pareizu darba metožu efektīvu atpūtas metožu (muskuļu grupu relaksācijas, redzes atslodzes vingrinājumi u.c.) pielietošanā var sekmīgi nodrošināt darbinieku veselības veicināšanu darba vidē, uzlabot p…
Elastic properties of UV irradiated polyethylene-octene copolymer composites with functionalized multi-walled carbon nanotubes
2016
ABSTRACTPolyethylene-octene copolymer (E38) is melt compounded with carboxylated carbon nanotubes (CNT-COOH) in the presence of maleic anhydride grafted polyethylene (PEgMA). The effects of CNT-COOH in the amount of 1–10 wt. % on the mechanical properties of E38 based composite are investigated. It is revealed that addition of CNT-COOH considerably increases the stiffness and mechanical strength of the E38 based composites. The effect of UV irradiation on the structure as well as on the mechanical properties of E38/PEgMA/CNT-COOH composites is also investigated. Results of the investigation testify that UV resistance of the E38 based composites increases by increasing the content of CNT-COO…
Mycotoxins in cereals and pulses harvested in Latvia by nanoLC-Orbitrap MS
2021
Twenty-seven mycotoxins in unprocessed cereals (n = 110) and pulses (n = 23) harvested in Latvia were analysed by nanoflow liquid chromatography combined with Orbitrap high-resolution mass spectrometry. One or more mycotoxins were found in 99% of the cereals and 78% of the pulses. Deoxynivalenol, zearalenone and T-2 and HT-2 toxins were prevalent in 9 to 86% of the cereals, mostly below their maximum levels as set by the European regulations. Non-regulated type A and B trichothecenes were prevalent in 5 to 87% of the cereals, at concentrations of 0.27–83 µg kg−1 and 1.7–4,781 µg kg−1, respectively. Quantification of emerging mycotoxins was also provided. Enniatins were detected in 94% of th…
New Thermoshrinkable Materials of Radiation Modified Polypropylene-Elastomer Composites with Cross-Linking Agents
2014
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 radiat…
Tritīda jona noteikšana cietos blanketa zonas materiālos
2007
Darbā izstrādāta un pētīta metode tritija formas tritīda jonu noteikšanai cietos blanketa zonas materiālos. Analizētas EXOTIC 8/8 eksperimentos apstarotas litija ortosilikāta lodītes. Kā tritīda jonu modeļviela lietots litija hidrīds. Metodes izstrādē gāzveida produkti detektēti ar gāzes hromatogrāfu. Šķīdināšanas eksperimentos analizēta tritija aktivitāte gāzes fāzē ar gāzes-plūsmas proporcionālo skaitītāju DDH-32 un šķīdumā ar šķidrās scintilācijas metodi. Kā akceptoru sistēmas lietoti vienmolāri dihromāta un nitrāta šķīdumi (akceptori skābē) un trīsmolāra nitrāta šķīdums ūdenī. Divmolāras sērskābes šķīdumā un ūdenī noteikts tritija formu saturs (T- 20±4%, T+ 79±4%, T2 2±2%). Noteiktais t…
Determination of pharmaceutical residues and assessment of their removal efficiency at the Daugavgriva municipal wastewater treatment plant in Riga, …
2017
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 i…
Thermal and Mechanical Properties of Unvulcanized Polypropylene Blends with Different Elastomers: Ethylene-Propylene-Diene Terpolymer, Nitrile-Butadi…
2013
In this work, composites of isotactic polypropylene (PP) with three unvulcanized elastomers – terpolymer of ethylene-propylene-dicyclopentadiene (EPDM), chlorinated polyethylene (CPE) and copolymer of acrylonitrile-butadiene (NBR) – have been investigated. The purpose of the investigation was to create PP/elastomer blend composites of significantly different compositions (with an excess of PP, intermediate ones, and with an excess of elastomer) and to study the dependence of tensile behaviour and elastic properties on the blends with different component ratio. Tensile properties have been recognized from the stress-strain curves. The changes of elastic modulus have been characterized with r…
Properties of PP/MWCNT-COOH /PP composites made by melt mixing versus solution cast /melt mixing methods
2015
An approach on improvement of the properties of polypropylene / carbon nanotube (PP/CNT) composites is reported. PP blend compositions with carboxylic acid functionalized multi-walled carbon nanotubes (MWCNT-COOH) at filler content 1.0 wt.% were researched. One part of the composites was manufactured by direct thermoplastic mixing PP with the filler, but the other one was made from solution casted masterbatch with the following thermoplastic mixing. An increase of mechanical properties (Young's modulus, storage modulus and tensile strength), compared to an increase of glass transition temperature indicated a reinforcement effect of CNTs on PP matrix, determined from the tensile tests and di…
Impact of non-functionalized and ionic liquid modified carbon nanotubes on mechanical and thermal properties of ethylene- octene copolymer nanocompos…
2016
In this article the development and characterization of composites made from metallocene based ethylene-octene copolymer (EOC) with 38% octene content, non-modified or modified multi walled carbon nanotubes (MWCNTs), covalently functionalised with long chain hexadecyl moiety imidazolium ionic liquid (IL-f-MWCNTs), is presented. The procedure of MWCNTs functionalization is discussed. In order to obtain a good dispersion of the filler, composites with MWCNTs and IL-f-MWCNTs in the concentration range of 0.5-12 wt.% were made by ultrasonication / thermoplastic mixing method. The results indicated improvement in mechanical properties with increase of the filler content. The methodology of the d…
Simple Solution for Single Final Vial Filling of Ga-68 Radiopharmaceuticals in One Hot Cell Isolator at Small-Scale Radiopharmacy Laboratories under …
2020
A simple solution for fulfilling biosafety and national drug agency demands of radiation and biosafety during Ga-68 radionuclide containing radiopharmaceutical production (RP) by small scale laboratories has been demonstrated based on a novel sterile seal concept of multi-layer bag system prototype. These mid-and inner enclosures of the prototype with vial inside were sterilized by 50 kGy of gamma radiation. The microbial safety validation based on two-week testing confirmed successful sterilization of the sealing bags with vails. The analysis of physicochemical properties, namely mechanical properties, gel fraction studies revealed that sterilization did not cause any undesired changes in …
Two-dimensional liquid chromatography - high resolution mass spectrometry method for simultaneous monitoring of 70 regulated and emerging mycotoxins …
2020
Heat shrinkable behavior, physico-mechanical and structure properties of electron beam cross-linked blends of high-density polyethylene with acryloni…
2016
Abstract In this study, heat-shrinkable composites of electron beam irradiated high-density polyethylene (HDPE) composites with acrylonitrile-butadiene rubber (NBR) were investigated. HDPE/NBR blends at a ratio of components 100/0, 90/10, 80/20, 50/50 and 20/80 wt% were prepared using a two-roll mill. The compression molded films were irradiated high-energy (5 MeV) accelerated electrons up to irradiation absorbed doses of 100–300 kGy. The effect of electron beam induced cross-linking was evaluated by the changes of mechanical properties, gel content and by the differences of thermal properties, detected by differential scanning calorimetry. The thermo-shrinkage forces were determined as the…
Liquid Crystalline Copolyester Made from Recycled Polyethylene Terephthalate and p-Acetoxybenzoic Acid: Synthesis, Characterization and Blending with…
2013
Physical Load Among Construction Workers and Analysis with Objective Ergonomics Research Method
2016
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 o…
Determination of Fungi and Multi-Class Mycotoxins in Camelia sinensis and Herbal Teas and Dietary Exposure Assessment
2020
In this paper, a study of fungal and multi-mycotoxin contamination in 140 Camellia sinensis and 26 herbal teas marketed in Latvia is discussed. The analysis was performed using two-dimensional liquid chromatography with time-of-flight mass spectrometry (2D-LC-TOF-MS) and MALDI-TOF-MS. In total, 87% of the tea samples tested positive for 32 fungal species belonging to 17 genera, with the total enumeration of moulds ranging between 1.00 ×
Mechanical, structural and magnetic properties of polypropylene/iron ferrite magnetic nanocomposites
2012
In this research, composites of polypropylene (PP) and a relatively small concentrations of iron ferrite (Fe3O4) nanopowder equal to 2, 5 and 10 wt.% have been made. An methacrylate monomer 2,2'-bis-(4-(2-methylprop-2-enoyloxy)phenyl)- propane (BAD) was added at a small amount (3 wt.%) to part of the composites during the thermoplastic mixing. The BAD has been used as a compatibilizing agent on the phase interaction between the filler and the matrix of polypropylene. It has been found that composites have adjustable mechanical, structural and magnetic properties dependent on the content of magnetic filler. Increase of concentration of ferrite particles affects a notable increase of elastic …
Development of a Rapid Method for the Determination of Phenolic Antioxidants in Dark Chocolate Using Ultra Performance Liquid Chromatography Coupled …
2017
Development of a new comprehensive method based on one-step liquid-liquid extraction (LLE) combined with ultra-high-performance liquid chromatography-Orbitrap high resolution mass spectrometry (UHPLC-Orbitrap-HRMS) for the determination of eight phenolic compounds in dark chocolate is demonstrated. The study focuses on the optimization of sample preparation, chromatographic separation and Orbitrap-HRMS detection parameters to adjust selectivity and sensitivity of the method. The LLE mixture of formic acid-water-acetonitrile (2:58:40, v/v) and hexane at the component ratio of 1:1 (v/v) was applied for sample preparation. The inter-day and intra-day precision expressed from the relative stand…
Mechanical and thermomechanical properties of radiation modified poly(ethylene-octene)/Ni-Zn ferrite nanocomposites
2013
Poly(ethylene-1-octene) copolymer (POE) composites filled with nickel-zinc ferrite nanoparticles have been modified by exposure to an electron beam at doses up to 500 kGy. The influence of radiation dose and ferrite content on mechanical properties has been investigated. Thermomechanical properties – thermorelaxation stresses formed in thermal heating and thermo 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. Increase of concentration of ferrite particles and increase of radiation dose affects a notable increase of elastic modulus and reduces the deformabil…
The Occurrence and Dietary Exposure Assessment of Mycotoxins, Biogenic Amines, and Heavy Metals in Mould-Ripened Blue Cheeses
2020
The occurrence and dietary exposure assessment of 16 mycotoxins, 6 biogenic amines (BAs), and 13 metallic elements in blue-veined cheeses (n = 46) is reported. Co-occurrence of mycophenolic acid (&le
Recent Applications of Carbonaceous Nanosorbents in Solid Phase Extraction for the Determination of Pesticides in Food Samples
2018
This article covers recent trends of carbonaceous nanomaterial supported solid phase extraction for the liquid and gas chromatography analysis of pesticides in food samples. Several advanced carbonaceous nanosorbents have been reported over the previous decade for pesticide extraction, such as graphene derivatives modified by combination with silica, amines, polymers, and/or magnetic nanoparticles. The advances in this field have opened possibilities for using neat or modified carbon nanotubes or graphene-type sorbents for the pre-concentration of polar or nonpolar pesticides by solid phase extraction (SPE) or micro-SPE methods or to apply such nanomaterials for the removal of matrix compon…
Jauni viedie materiāli no multifāzu polimēru kompozīcijām, to fizikāli-mehānisko, deformatīvo un struktūras īpašību izmaiņas jonizējošā starojuma un …
2014
Promocijas darbā pētītas poliolefīnu – multifāzu kompozīcijas ar elastomēriem un šķērssaistīšanās promotoriem. Izvērtēta radiācijķīmiskās modificēšanas un lielas indukcijas magnētiskā lauka (B = 1,0-1,7 T) ietekme uz pētīto kompozītsistēmu stiprības-deformācijas, struktūras īpašībām, kā arī novērtēta magnētiskā lauka un jonizējošā starojuma mijiedarbības ietekme uz poliolefīnu makromolekulu šķērssaistīšanās efektivitāti. Iegūtas jaunas teorētiskas un praktiskas atziņas par radiācijķīmiski modificētu poliolefīnu multifāzu kompozīciju ekspluatācijas īpašībām, kas ļāva radīt jaunus uz polipropilēna bāzētus termonosēdmateriālus.
Mechanical Properties of Composite SPEEK Polymer Membranes Modified with Ionic Liquids
2015
In this work, the mechanical properties of sulphonated polyetheretherketone (SPEEK) membranes impregnated with 3 different ionic liquids (1-butyl-2,3-dimethyl- imidazolium dimethylphosphate ([BMMIM][Me2PO4])), 1,2,3-trimethylimidazolium dimethylphosphate ([MMMIM][Me2PO4])), 1,3-dimethylimidazolium dimethylphosphate ([MMIM][Me2PO4])) have been investigated. Prepared SPEEK/ionic liquid composite membranes are characterized by mechanical testing both in room and elevated temperatures. It was found that the stiffness and tensile strength of composites decreased by increasing the content of ionic liquid and the length of alkyl radical in ionic liquid as well as by increasing the temperature.