Triple Detection Research Articles

Validation of gas chromatography mass spectrometry (GC-MS) qualitative method for detection of paraquat in postmortem samples by sodium borohydride-platinum chloride chemical reduction

To develop a GC-MS method for the detection of paraquat by sodium borohydride-platinum chloride reduction in postmortem samples. Paraquat [1,1′-dimethyl-4,4′-bipyridilium dichloride,(PQ)] is a bipyridylium quaternary ammonium contact herbicide. At the Institute of Forensic Science and Legal Medicine (IFSLM), an average of 13 cases of PQ poisoning are submitted annually for postmortem toxicological analysis. Previously a colorimetric method for the identification of PQ was used. A more sensitive method was needed to confirm the presence of PQ. There is limited studies on liquid-liquid extraction (LLE) of postmortem fluids and tissues for determination of PQ by GC-MS. Some methods used a chemical reduction involving sodium borohydride (NaBH4) or sodium borohydride with nickel chloride (NaBH4-NiCl2), prior to LLE, to gain more volatile compounds for analysis. In the absence of NiCl2, platinum (IV) chloride (PtCl4) was used as a substitute catalyst in the validation. The aim of this validation is to identify PQ in suspected poisoning cases from postmortem samples using chemical reduction reaction, followed by LLE and then (GC-MS). The qualitative method involved an initial chemical reduction of PQ to the perhydrogenated product and monoene by-product: 500 μL blood, urine or tissue homogenate was placed in a glass tube, followed by 200 μL toluene, 400 μL PtCl4 (1% w/v) and then 500 μL NaBH4 (40% w/v) was added dropwise. The mixture was vortexed then left to stand for 1½ hours at room temperature. 1 mL 5 N sodium hydroxide solution was added to stop the reaction. For LLE, 3 mL hexane: ethyl acetate (4:1) was added to the tube and placed on shaker for 45 minutes at 300 rpm. The sample was centrifuged for 1 hour at 1400 g. The hexane:ethyl acetate layer was then transferred to a beaker and allowed to evaporate to dryness. The residue was reconstituted with 1 mL hexane, transferred to GC vial, and allowed to evaporate to dryness. The residue was then reconstituted with 100 μL hexane, and transferred to a GC vial fitted with glass insert, with 1 μL being injected into the GC-MS system (Agilent 7890A GC coupled with an Agilent 5975C VL MSD with Triple Axis Detector Mass Spectrometer). As recommended by the Scientific Working Group for Forensic Toxicology (SWGTOX), the validation parameters for qualitative confirmation/identification were specificity, recovery, carryover, repeatability and limit of detection. The method was applied to blank blood and urine samples, spiked blood and urine samples, as well as 10 suspected PQ poisoning cases (24 postmortem samples) submitted to the IFSLM. The blank blood and urine samples analysed did not yield any positive results for the analytes of interest. Blood and urine samples spiked with the PQ standard solution resulted in the detection of both the perhydrogenated product and monoene by-product. The limit of detection for both reduction products was 30 ppm. There was no detection of the analytes in the three blanks analysed after an injection of 1000 ppm PQ. The reduction products of PQ were detected in all 10 cases. Four of these cases had previously given negative results using the colorimetric test. The PtCl4 was found to be an adequate substitute catalyst in the reduction procedure. The procedure was proven to be sensitive, repeatable and robust. All sample types assessed by the method gave positive results, however stomach and content produced the best chromatograms with sharp, clearly defined and resolved peaks. In summary, the presented procedure provided excellent performance in the identification of the reduction products of PQ in postmortem samples.

Effects of malting process on molecular weight distribution and content of total and water-extractable arabinoxylan in barley

This work aims to evaluate the effects of the malting process on the malt total and water-extractable (WE) arabinoxylan (AX), also considering the barley cultivar and year of cultivation. The WEAX molecular properties were characterized by high-pressure size exclusion chromatography (HPSEC) - triple detector array (TDA). Most of the barley malt WEAX showed a molecular weight over 4.0 × 105 Da with a random coil conformation. Compared to raw barley, the malts show analogous content of AX and WEAX, similar intrinsic viscosity, less rigid conformation, and higher polydispersity. The WEAX content of malt was highly and negatively related to the common quality parameters, resulting in a useful indicator of malt modification, even more representative than the total AX content. WEAX is highly positively related to the Congress wort viscosity, and thus, lautering could be more significantly affected by WEAX rather than total AX content.

Hydrophilic Nonwoven Nanofiber Membranes as Nanostructured Supports for Enzyme Immobilization.

The high porosity, interconnected pore structure, and high surface area-to-volume ratio make the hydrophilic nonwoven nanofiber membranes (NV-NF-Ms) promising nanostructured supports for enzyme immobilization in different biotechnological applications. In this work, NV-NF-Ms with excellent mechanical and chemical properties were designed and fabricated by electrospinning in one step without using additives or complicated crosslinking processes after electrospinning. To do so, two types of ultrahigh-molecular-weight linear copolymers with very different mechanical properties were used. Methyl methacrylate-co-hydroxyethyl methacrylate (p(MMA)-co-p(HEMA)) and methyl acrylate-co-hydroxyethyl acrylate (p(MA)-co-p(HEA)) were designed and synthesized by reverse atom transfer radical polymerization (reverse-ATRP) and copper-mediated living radical polymerization (Cu0-MC-LRP), respectively. The copolymers were characterized by nuclear magnetic resonance (1H-NMR) spectroscopy and by triple detection gel permeation chromatography (GPC). The polarity, topology, and molecular weight of the copolymers were perfectly adjusted. The polymeric blend formed by (MMA)1002-co-(HEMA)1002 (Mw = 230,855 ± 7418 Da; Mn = 115,748 ± 35,567 Da; PDI = 2.00) and (MA)11709-co-(HEA)7806 (Mw = 1.972 × 106 ± 33,729 Da; Mn = 1.395 × 106 ± 35,019 Da; PDI = 1.41) was used to manufacture (without additives or chemical crosslinking processes) hydroxylated nonwoven nanofiber membranes (NV-NF-Ms-OH; 300 nm in fiber diameter) with excellent mechanical and chemical properties. The morphology of NV-NF-Ms-OH was studied by scanning electron microscopy (SEM). The suitability for enzyme binding was proven by designing a palette of different surface functionalization to enable both reversible and irreversible enzyme immobilization. NV-NF-Ms-OH were successfully functionalized with vinyl sulfone (281 ± 20 μmol/g), carboxyl (560 ± 50 μmol/g), and amine groups (281 ± 20 μmol/g) and applied for the immobilization of two enzymes of biotechnological interest. Galactose oxidase was immobilized on vinyl sulfone-activated materials and carboxyl-activated materials, while laccase was immobilized onto amine-activated materials. These preliminary results are a promising basis for the application of nonwoven membranes in enzyme technology.

Significance of Triple Detection of p16/ki-67 Dual-Staining, Liquid-Based Cytology and HR HPV Testing in Screening of Cervical Cancer: A Retrospective Study.

In addition to liquid-based cytology (LBC) and HR HPV testing, p16/ki-67 dual-staining is another method for cervical cancer screening. The combination of any two methods can improve the accuracy of screening, but some cervical lesions are still missed or misdiagnosed. In this retrospective study, the significance of LBC, HR HPV testing and especially p16/ki-67 dual-staining in cervical lesion screening was evaluated with reference to histological diagnosis. At the same time, we tried to explore the value of p16/ki-67 dual-staining combined with LBC and HR HPV testing (triple detection) in improving the diagnostic specificity of CIN2+ and reducing the missed diagnosis of CIN2+ lesions. We found that p16/ki-67 dual-staining was valuable in identifying cervical CIN2+ lesions and reducing the missed diagnosis of CIN2+ in HPV negative patients. More than 96% of CIN2+ patients were positive for two or three tests of triple detection. Whole positive triple detection can effectively predict high grade cervical lesions. In conclusion, the triple detection can distinguish almost all cervical CIN2+ lesions. Our data put forward and highlight the feasibility and significance of triple detection in cervical lesion screening.

Microscale Purification with Direct Charged Aerosol Detector Quantitation Using Selective Online One- or Two-Dimensional Liquid Chromatography.

The pharmaceutical industry is increasingly faced with challenging separations of complex crude reaction mixtures at the microscale that require the adoption of new platforms for rapid target isolation, impurity determination, and quantitation. In this study, we describe an online microscale one- or two-dimensional liquid chromatography (1D/2D-LC) system with heart-cutting and multi (triple) detector triggering in either dimension to address this need. The advantages of charged aerosol detection (CAD) are discussed for the direct quantitation of limited quantity samples, without utilizing a second analytical instrument or gradient compensation pump. In addition to the significant time and cost savings, there is no minimum recovery requirement that exists when compared to gravimetric methods for accurate microscale quantitation. This platform has been successfully used to purify 0.5-5.0 mg scale reactions in 96- or 384-well reaction plates with a gradient time of 4 min per sample. Separations performed in both dimensions are complete in less than 12 min, including trapping and column equilibration time. The isolated arrays of small-quantity investigational compounds at a high purity enable rapid exploration of chemical reaction parameters and synthetic route scouting for biological target validation.

Multi-analyte High-Throughput Microplate-SERS Reader with Controllable Liquid Interfacial Arrays.

High-throughput surface-enhanced Raman scattering (SERS) reader, especially for liquid sample testing, is of great significance and huge demand in biology, environment, and other analytical fields. Inspired by the principle of microplate reader, herein, we developed a microplate-SERS reader for semiautomatic and high-throughput assays by virtue of three-dimensional liquid interfacial arrays (LIAs). For the first time, the formation of LIA in oil-in-water state, water-in-oil state, and two-dimensional plane state is realized by operating the hydrophilicity (contact angle) of the container. Through the force analysis of LIA, the effect of organic (O) phase density on the relative position of LIA was quantified. In addition, the optimized reader offers fast and continuous semiautomatic detection of 12 samples below 10 min with great signal reproducibility (calibration with the characteristic peak of O phase as the internal standard). The isolated wells in the microplate prevent analyte cross talk, allowing accurate quantification of each sample. Multiplex analysis capability highlights that this reader has the ability of rapid identification and quantification of samples containing various analytes and concentrations. The results demonstrate high-resolution dual and triple analyte detection with fully preserved signal and Raman features of individual analytes in a mixture, which implies that it also has excellent anticounterfeiting applications. This microplate-SERS reader combines the superior advantages of the LIA, microplate, and SERS techniques to retrieve the molecular vibrational fingerprints of various chemicals in complex media.

Polymerization Initiated by Graphite Intercalation Compounds Revisited: One-Pot Synthesis of Amphiphilic Pentablock Copolymers

This study reports the first attempt to employ a potassium–graphite intercalation compound (KC24) as an initiator for the one-pot synthesis of a multi-block copolymer. The results obtained show that KC24 successfully initiated the copolymerization, leading to a copolymer consisting of poly(styrene), poly(methyl methacrylate) and poly(ethylene oxide) blocks. When all three comonomers were introduced simultaneously or in a specific sequence, the resulting copolymers had molecular masses in the range between 170,000 Da and 280,000 Da. Their composition was investigated by size-exclusion chromatography with triple detection (dRI/UV/IR) and 1H-NMR. The analyses indicated that all copolymers were enriched in methyl methacrylate (50–66 mol%) despite the fact that the comonomers were added in equimolar amounts. Due to the layered structure of the initiator, the polymerization took place in the graphite interlayer spaces and lead to extensive delamination, indicating at the potential to produce in situ graphite/copolymer composite materials.

The Effect of Chemical Modification on the Rheological Properties and Structure of Food Grade Modified Starches

Starch in its pure form can be used as a functional component of numerous food products; however, much better results both in terms of technological and economical aspects are obtained with the use of modified starches. The aim of the work was to establish how chemical modification affects the molecular structure of potato starch and, as a consequence, its rheological properties as well as texture forming ability. Commercial food-grade potato starch preparations oxidized starch, acetylated starch, distarch phosphate, acetylated distarch phosphate and acetylated distarch adipate were the investigated material. The experimental methods included: viscographic analysis of pasting properties, flow rheometry, texture profile analysis, size exclusion chromatography with triple detection. The obtained data were further analyzed employing principal component and hierarchical cluster analysis. It was found that chemical modification leads to substantial changes in the molecular and functional properties of starch products. Oxidation process leads to depolymerization, which causes a substantial decrease in viscosity. Acetylation results mostly in stabilization of rheological properties during thermal processing. Crosslinking of starch leads to an improvement in thickening capabilities, while the type of crosslinking agent used for modification has a secondary effect. Sterilization of all types of modified potato starch pastes leads only to minor changes in their texture and rheological properties.

P-process chaser detector in [formula omitted] - [formula omitted] coincidences

We propose two types of neutron-γ1−γ2 triple coincidence detectors (not constructed) to chase gamma transitions to produce p-nuclei following the neutron emission in the (γ,n) reaction. Neutrons are detected with 24 3He counters embedded in a polyethylene moderator in Type I detector and with 6 liquid scintillation detectors in Type II detector, respectively. γ rays are detected with two high-purity germanium detectors and four LaBr3(Ce) detectors. The detector which is referred to as p-process chaser detector is used to search for mediating states in 180Ta through which the isomeric and ground states in 180Ta are thermalized in the p-process. A search is made for both resonant states and unresolved states in high nuclear-level-density domain.

Co-enrichment and triple PCR detection of three foodborne pathogens

A triple PCR method was established for the detection of Salmonella enteritidis, Staphylococcus aureus and Vibrio parahaemolyticus. The three strains were mixed cultured in SSV enrichment medium for 16 h, specific primers were designed for Salmonellaenteritidis invA gene, Staphylococcus aureus nuc gene and Vibrio parahaemolyticus collagenase gene, respectively, and the triple PCR system was established. By optimizing the primer concentration, annealing temperature and cycle times of the triple PCR system, thus optimal triple PCR system was established. The system was evaluated from three aspects: specificity, repeatability and sensitivity. The optimized result showed that, in the triple PCR system, the primers concentration of invA, nuc and collagenase were 10 nmol/L, 12.5 nmol/L and 12.5 nmol/L, respectively. The optimum annealing temperature was 55.6 ℃. The primers of the target bacteria had good specificity, and the detection sensitivity of the system was high. The sensitivity of the three strains in the triple PCR system was above 10~2 CFU/mL. The established triple PCR method has high specificity, high sensitivity and good repeatability, which provided a new technical support for the rapid detection of Salmonella enteritidis, Staphylococcus aureus and Vibrio parahaemolyticus.

HPLC-Triple detector (Coulometric array, diode array and mass spectrometer) for the analysis of antioxidants in officinal plants

This work demonstrates the use of a triple detector for the screening of antioxidants in officinal plants. The triple detector consisted of a coulometric array (CAD), a diode array (DAD) and a mass spectrometer (MS) detector, which were connected to a HPLC system. DAD gave an overall profile of bioactive compounds. CAD allowed to select the most promising redox species and quantify their concentration based on the Faraday's law. Finally, MS was used for identification. The approach was applied to screen the main antioxidants in 19 officinal plants. Furthermore, the electron transfer properties obtained by CAD were highly correlated with the results of classical DPPH (r = 0.80), FRAP (r = 0.87) and ORAC (r = 0.90) assays and, thus, could be used to predict the antioxidant capacity of plant extracts by stepwise linear regression models (R2 = 0.99). Overall, the triple detector system allows a comprehensive approach to screen and characterize the antioxidant compounds in natural plant extracts.

A highly sensitive bioanalytical method for the quantification of vinblastine, vincristine, vinorelbine and 4-O-deacetylvinorelbine in human plasma using LC-MS/MS

A highly sensitive method was developed for the quantification of vinblastine, vincristine, vinorelbine, and its active metabolite 4-O-deacetylvinorelbine in human plasma using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Deuterated isotopes were used as internal standard and liquid-liquid extraction with tert-butyl methyl ether (TBME) was used for sample pre-treatment. The final extract was injected on a C18 column (50 × 2.1 mm ID, 5 µm). Gradient elution was used in combination with Reversed Phase chromatography to elute the analytes and internal standards from the column in 5 min and the API4000 triple quadrupole MS detector was operating in the positive ion mode. The calibration model, accuracy and precision, selectivity and specificity, dilution integrity, carryover, matrix factor and recovery, and stability were evaluated over a concentration range from 0.025 to 10 ng/mL for vinblastine, vinorelbine, and 4-O-deacetylvinorelbine and from 0.1 to 40 ng/mL for vincristine. The intra- and inter-assay bias and precisions were within ± 12.4% and ≤ 10.6%, respectively. This method was successfully applied to study the pharmacokinetics of vincristine in paediatrics and vinorelbine and 4-O-deacetylvinorelbine using in vivo mouse models.

Investigation of the microrheological properties of the branched polystyrene using 2-(2-bromoisobutyryloxy) ethyl methacrylate as the inimer

ABSTRACT A novel functional inimer 2-(2-bromoisobutyryloxy)ethyl methacrylate(BiBEM) both with the double bond and bromide was designed and synthesised. The branched polystyrene (PS) was prepared by the atom transfer radical polymerisation (ATRP), using BiBEM as inimer (initator) and CuBr complexed with bipyridine as catalysts in toluene at 80°C. The molecular weight and the branching degree of the polystyrene were analysed by using triple detection size-exclusion chromatography (TD-SEC) and the storage modulus in a wide and high-frequency range of polystyrene microrheological properties were studied by the diffusive wave spectroscopy (DWS). By adjusting the ratio of inimer to catalysts, a series of branched polystyrene polymers with different molecular weight and branching degree were obtained. The increase of the BiBEM concentration led to a higher degree of branching, while higher molecular weight and broader molecular weight distribution are accompanied. The branched polystyrene showed low storage modulus and lower chain entanglement compared to linear analogues.

Extraction of anabolic steroids with aqueous-organic mixtures from hexanic solutions

The extraction of anabolic steroids (1,4-androstadiene-3,17-dione; 17α-methyltestosterone; 19-norethiocholanolone; 4-hydroxytestosterone; 4-androstene-3,17-dione; 5α-androstane-3β,17β-diol; dehydroepiandrosterone; calusterone; clostebol; methandienone; methyldienolone; nandrolone; testosterone; epitestosterone; tibolone; 19-norandrostenedione; 1-methylene-5α-androstan-3α-ol-17-one) by aqueous-organic mixtures from hexane solutions was studied at the temperature (20 ± 1) °C. Based on the experimental data obtained, the partition ratios of anabolic steroids were calculated, which were used to optimise the standard sample preparation procedure in the process of determining the compounds under study in biologically active dietary supplements and specialised sports nutrition. It was found that the most effective and selective extractants from hydrocarbon solutions are water-acetonitrile mixtures containing from 10 to 20 % by volume of water. An extraction technique has been developed for sample preparation of biologically active dietary supplements for subsequent gas chromatographic determination of anabolic steroids in them using a triple quadrupole mass spectrometric detector. The proposed method is characterised by a standard deviation of 10–15 % and a detection limit about 10 μg/kg of biologically active dietary supplements, which makes it possible to reliably determine impurities of prohibited anabolic steroids in them.

Exploiting Potential Biotechnological Applications of Poly-γ-glutamic Acid Low Molecular Weight Fractions Obtained by Membrane-Based Ultra-Filtration

Since the potentialities of applications of low molecular weight poly-γ-glutamic acid (γ-PGA) chains have been so far only partially explored, the separation of diverse molecular families of them, as well as their characterization for potential bioactivity and ability to form films, were investigated. Two different approaches based on organic solvent precipitation or on ultra- and nano-filtration membrane-based purification of inexpensive commercial material were employed to obtain size-specific γ-PGA fractions, further characterized by size exclusion chromatography equipped with a triple detector array and by ultra-high-performance liquid chromatography to assess their average molecular weight and their concentration. The γ-PGA low molecular weight fractions, purified by ultra-filtration, have been shown both to counteract the desiccation and the oxidative stress of keratinocyte monolayers. In addition, they were exploited to prepare novel hydrocolloid films by both solvent casting and thermal compression, in the presence of different concentrations of glycerol used as plasticizer. These biomaterials were characterized for their hydrophilicity, thermal and mechanical properties. The hot compression led to the attainment of less resistant but more extensible films. However, in all cases, an increase in elongation at break as a function of the glycerol content was observed. Besides, the thermal analyses of hot compressed materials demonstrated that thermal stability was increased with higher γ-PGA distribution po-lymer fractions. The obtained biomaterials might be potentially useful for applications in cosmetics and as vehicle of active molecules in the pharmaceutical field.

Reliability of Non-Contact Infrared Thermometers for Fever Screening Under COVID-19.

PurposeFever is one of the most typical clinical symptoms of coronavirus disease 2019 (COVID-19), and non-contact infrared thermometers (NCITs) are commonly used to screen for fever. However, there is a lack of authoritative data to define a “fever” when an NCIT is used and previous studies have shown that NCIT readings fluctuate widely depending on ambient temperatures and the body surface site screened. The aim of this study was to establish cut-off points for normal temperatures of different body sites (neck, forehead, temples, and wrist) and investigate the accuracy of NCITs at various ambient temperatures to improve the standardization and accuracy of fever screening.Patients and MethodsA prospective investigation was conducted among 904 participants in the outpatient and emergency departments of Chengdu Women’s and Children’s Central Hospital. Body temperature was measured using NCITs and mercury axillary thermometers. A receiver operating characteristic curve was used to determine the accuracy of body temperature detection at the four body surface sites. Data on participant characteristics were also collected.ResultsAmong the four surface sites, the neck temperature detection group had the highest accuracy. When the neck temperature was 37.35°C as the optimum fever diagnostic threshold, the sensitivity was 0.866. The optimum fever diagnostic thresholds for forehead, temporal, and wrist temperature were 36.65°C, 36.65°C, and 36.75°C, respectively. Moreover, triple neck temperature detection had the highest sensitivity, up to 0.998, whereas the sensitivity of triple wrist temperature detections was 0.949. Notably, the accuracy of NCITs significantly reduced when the temperature was lower than 18°C.ConclusionNeck temperature had the highest accuracy among the four NCIT temperature measurement sites, with an optimum fever diagnostic threshold of 37.35°C. Considering the findings reported in our study, we recommend triple neck temperature detection with NCITs as the fever screening standard for COVID-19.

Pre- and Post-Resection Urine Metabolic Profiles of Bladder Cancer Patients: Results of Preliminary Studies on Time Series Metabolomics Analysis.

Simple SummaryBladder cancer is one of the most frequently diagnosed cancers worldwide and due to non-specific symptoms, it is often detected at a late stage. For this reason, possible diagnostic alternatives that could be used for non-invasive screening are still being sought. In recent years, metabolomics approach has been frequently used for this type of research, using urine or blood collected from two groups: patients with a given disease and healthy volunteers. Usually, to minimize the impact of between-subject differences, participants of the study are matched in terms of age, gender, or BMI. Another way to rule out the impact of this variability is to analyze samples taken at intervals from the same patient. Therefore, the aim of our study was to validate results obtained using the traditional approach on a small group of patients, from whom samples were taken before and after resection of the bladder tumor, in a given time frame.The incidence of bladder cancer (BCa) has remained high for many years. Nevertheless, its pathomechanism has not yet been fully understood and is still being studied. Therefore, multiplatform untargeted urinary metabolomics analysis has been performed in order to study differences in the metabolic profiles of urine samples collected at three time points: before transurethral resection of bladder tumor (TURBT), the day after the procedure and two weeks after TURBT. Collected samples were analyzed with the use of high-performance liquid chromatography hyphenated with time-of-flight mass spectrometry detection (HPLC-TOF/MS) and gas chromatography coupled with triple quadrupole mass spectrometry detection (GC-QqQ/MS, in a scan mode). Levels of metabolites selected in our previous study were assessed in order to confirm their potential to differentiate the healthy and diseased samples, regardless of the risk factors and individual characteristics. Hippuric acid, pentanedioic acid and uridine confirmed their potential for sample differentiation. Based on the results of statistical analysis for the paired samples (comparison of metabolic profiles of samples collected before TURBT and two weeks after), a set of metabolites belonging to nucleotide metabolism and methylation processes was also selected. Longitudinal studies proved to be useful for the evaluation of metabolic changes in bladder cancer.

Ultra-sensitive speciation analysis of tellurium by manganese and iron assisted photochemical vapor generation coupled to ICP-MS/MS

Photochemical vapor generation (PVG) of Te4+ was undertaken with a simple reactor consisting of a polytetrafluoroethylene reaction coil wrapped around a low-pressure mercury tube lamp and using a flow-injection for sample delivery. The composition of a reaction medium, the influence of irradiation time and the effect of added sensitizers and interferents were investigated using high-resolution continuum source atomic absorption spectrometry and a miniature diffusion flame atomizer. A mixture of 5 M acetic acid and 3.5 M formic acid and sample flow rate of 4 mL min−1 permitting a 36 s irradiation time were found optimal for PVG of Te4+. The addition of 250 mg L−1 Mn2+ and 15 mg L−1 Fe2+ ions as sensitizers enhanced the overall PVG efficiency 2.75-fold to 50 ± 2%. In order to achieve higher sensitivity necessary for determination of Te in real environmental samples, PVG was coupled to inductively coupled plasma triple quadrupole mass spectrometer and detection was performed with O2 in the reaction cell utilizing a mass shift mode of measurement (m/z 128 → m/z 144) to ensure interference free ion detection. A limit of detection 1.3 ng L−1 and repeatability (RSD) 0.9% at 250 ng L−1 were achieved. This ultrasensitive methodology was validated for speciation analysis of Te in water samples of various matrix complexities (fresh water, well water, seawater and contaminated water). Since no response was observed from Te6+ under optimal PVG conditions, Te4+ was selectively determined by direct PVG. The sum of Te4+ and Te6+ was determined after pre-reduction of Te6+ in 6 M HCl (95 °C), evaporation to dryness and reconstitution in the reaction medium containing sensitizers. Very good accuracy was demonstrated by spiked recoveries for both Te4+ and total Te in water samples and also by total Te determination in fresh water Standard Reference Material NIST 1643f.

Synthesis and Study of Thermoresponsive Amphiphilic Copolymers via RAFT Polymerization.

Synthesis and study of well-defined thermoresponsive amphiphilic copolymers with various compositions were reported. Kinetics of the reversible addition-fragmentation chain transfer (RAFT) (co)polymerization of styrene (St) and oligo(ethylene glycol) methyl ether methacrylate (PEO5MEMA) was studied by size exclusion chromatography (SEC) and 1H NMR spectroscopy, which allows calculating not only (co)polymerization parameters but also gives valuable information on RAFT (co)polymerization kinetics, process control, and chain propagation. Molecular weight Mn and dispersity Đ of the copolymers were determined by SEC with triple detection. The detailed investigation of styrene and PEO5MEMA (co)polymerization showed that both monomers prefer cross-polymerization due to their low reactivity ratios (r1 < 1, r2 < 1); therefore, the distribution of monomeric units across the copolymer chain of p(St-co-PEO5MEMA) with various compositions is almost ideally statistical or azeotropic. The thermoresponsive properties of p(St-co-PEO5MEMA) copolymers in aqueous solutions as a function of different hydrophilic/hydrophobic substituent ratios were evaluated by measuring the changes in hydrodynamic parameters under applied temperature using the dynamic light scattering method (DLS).

Phytohormones and Elicitors Enhanced the Ecdysteroid and Glycosylflavone Content and Antioxidant Activity of Silene repens

In the course of the ongoing chemical study of species of Silene genus, S. repens Patrin as a common species of the genus, was selected as the object of this study. Using high-performance liquid chromatography with photodiode array detection and electrospray ionization triple quadrupole mass spectrometric detection (HPLC-PDA-ESI-tQ-MS), the presence of 12 ecdysteroids and 6 glycosylflavones was established in S. repens introduced seedlings. 20-Hydroxyecdysone and polypodine B, as well as sileneside E and schaftoside, were the dominant compounds in introduced seedlings of S. repens. The effect of exogenous phytohormones and elicitors on the productivity and accumulation of ecdysteroids and glycosylflavones in introduced seedlings of S. repens was investigated for the first time. It was found that the use of ethyl arachidonate (100 mg/L) to increase the productivity of S. repens is justified. To obtain S. repens with a high content of ecdysteroids and glycosylflavones, it is recommended to apply epibrassinolide (100 mg/L) and 4-chlorophenoxyacetic acid (100 mg/L), respectively. Antioxidant activity of S. repens against 2,2-diphenyl-1-picrylhydrazyl radical (DPPH·) was determined, and it was revealed that sileneside E and schaftoside, as well as meloside A and isovitexin had the highest antioxidant activity among the studied compounds of S. repens.