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1.
Argyro G. Fragkaki Georgia Petropoulou Ioanna Athanasiadou Polyxeni Kiousi Nassia Kioukia‐Fougia Helen Archontaki Evangelos Bakeas Yiannis S. Angelis 《Journal of separation science》2020,43(11):2154-2161
Anabolic androgenic steroids are widely abused substances in sports doping. Their detection present limitations regarding the use of soft ion sources such as electrospray or atmospheric pressure chemical ionization by liquid chromatography–tandem mass spectrometry. In the current study, a novel derivatization method was developed for the ionization enhancement of selected anabolic androgenic steroids. The proposed method aims at the introduction of an easily ionizable moiety into the steroid molecule by converting the hydroxyl groups into imidazole carbamates using 1,1′‐carbonyldiimidazole as derivatization reagent. The proposed method was applied to water and urine samples spiked with exogenous anabolic androgenic steroids in various concentration levels. Steroid imidazole carbamate derivatives have shown intensive [M+H]+ signals under electrospray ionization and common fragmentation patterns in tandem mass spectrometry mode with [M‐CO2+H]+ and [M‐ΙmCO2+H]+ as major ions with low collision energy. The obtained results showed that the majority of steroids were detectable at concentrations equal or lower to their minimum required performance level according to the World Anti‐Doping Agency technical document. The proposed method is sensitive with a preparation procedure that could be easily applied to the analysis of doping control samples. 相似文献
2.
Georgakopoulos CG Vonaparti A Stamou M Kiousi P Lyris E Angelis YS Tsoupras G Wuest B Nielen MW Panderi I Koupparis M 《Rapid communications in mass spectrometry : RCM》2007,21(15):2439-2446
A new combined doping control screening method for the analysis of anabolic steroids in human urine using liquid chromatography/electrospray ionization orthogonal acceleration time-of-flight mass spectrometry (LCoaTOFMS) and gas chromatography/electron ionization orthogonal acceleration time-of-flight mass spectrometry (GCoaTOFMS) has been developed in order to acquire accurate full scan MS data to be used to detect designer steroids. The developed method allowed the detection of representative prohibited substances, in addition to steroids, at concentrations of 10 ng/mL for anabolic agents and metabolites, 30 ng/mL for corticosteroids, 500 ng/mL for stimulants and beta-blockers, 250 ng/mL for diuretics, and 200 ng/mL for narcotics. Sample preparation was based on liquid-liquid extraction of hydrolyzed human urine, and the final extract was analyzed as trimethylsilylated derivatives in GCoaTOFMS and underivatized in LCoaTOFMS in positive ion mode. The sensitivity, mass accuracy, advantages and limitations of the developed method are presented. 相似文献
3.
This work reports a sequential-injection analysis (SIA) method for the enzymatic assay of glucose with soluble glucose oxidase (GOD) and on-line sample dilution with chemiluminescence (CL) detection. A zone of sample was aspirated in the holding coil of the SIA manifold and, if necessary, was diluted on-line by means of an auxiliary dilution conduit. Then, a zone of GOD was aspirated adjacent to the sample zone and a stopped-flow period was applied to allow the enzymatic reaction to proceed with production of hydrogen peroxide. Then, zones of a catalyst (Co(II) solution) and alkaline luminol were aspirated into the holding coil. Finally, the flow was reversed and the stacked zones were sent to a flow-cell located in front of a photomultiplier tube (PMT) that monitored the CL intensity. The linear dynamic range was 1 × 10−5-1 × 10−3 mol L−1 glucose, the coefficient of variation at 8 × 10−5 mol L−1 of glucose was sr = 3.1% (n = 8), the limit of detection at the 3σ level was cL = 1 × 10−6 mol L−1 and the sampling frequency was 28 h−1. With on-line dilution by a factor of 1/200, the linear range could be extended up to 0.2 mol L−1 glucose. The advantages of the proposed method are the simple manifold and instrumentation used, the scope for automated on-line dilution, the low consumption of sample and reagents and the elimination of enzyme immobilisation procedures. The method was applied to the analysis of commercial drinks and honey with percent relative errors in glucose determination in the range 100 ± 6.1%. 相似文献
4.
Polyxeni Spilioti 《Annals of Global Analysis and Geometry》2018,53(2):151-203
In this paper we study the dynamical zeta functions of Ruelle and Selberg associated with the geodesic flow of a compact hyperbolic odd-dimensional manifold. These are functions of a complex variable s in some right half-plane of \(\mathbb {C}\). Using the Selberg trace formula for arbitrary finite dimensional representations of the fundamental group of the manifold, we establish the meromorphic continuation of the dynamical zeta functions to the whole complex plane. We explicitly describe the singularities of the Selberg zeta function in terms of the spectrum of certain twisted Laplace and Dirac operators. 相似文献
5.
Tsiafoulis CG Exarchou V Tziova PP Bairaktari E Gerothanassis IP Troganis AN 《Analytical and bioanalytical chemistry》2011,399(6):2285-2294
The rapid and accurate determination of specific metabolites present in biofluids is a very demanding task which is essential
in both medicine and chemistry. l-carnitine (3-hydroxy-4-N-trimethylammonium butyrate) is an important metabolite which participates in a series of biological paths and therefore its
determination is of diagnostic importance. A single quantum coherence filtering 1H NMR methodology was used for the accurate and rapid determination of l-carnitine in human serum samples. The methodology is based on spectral simplification, and specifically on the distinction
of the N-methyl proton signal of l-carnitine that is greatly overlapped in the 1H-NMR spectrum of serum. The quantitative results provided by the proposed method are in excellent agreement with those obtained
by the enzymatic method, which is widely used. The proposed method is rapid (~20 min of experimental time), selective, sensitive,
and has good analytical characteristics (accuracy, reproducibility). Selected protein precipitation methods were also investigated
and sample pretreatment with EtOH is suggested. 相似文献
6.
This work reports a hybrid flow-injection analysis (FIA)/sequential-injection analysis (SIA) method for the rapid enzymatic assay of glucose with soluble glucose oxidase (GOD). The method relies on the sequential injection of segments of the sample and of a solution of enzyme by means of a multi-port selection valve in a flowing water stream. As the two zones are swept downstream, they overlap and merge so that the glucose in the sample is enzymatically oxidised. The generated hydrogen peroxide is merged with an alkaline luminol solution and the chemiluminescence (CL) intensity is monitored and related to the glucose concentration in the sample. The linear range of the method for glucose determination is 0.01-1 mmol L−1, the relative standard deviation is 3.9% at the 0.08 mmol L−1 level (n = 8), the limit of detection at the 2σ level is 4 μmol L−1 glucose and the injection rate is 80 h−1. The method was applied to the analysis of energy drinks and honey with relative errors in glucose determination in the range 100 ± 4.3%. The advantages of the proposed method are the wide linear range, the simple instrumentation used, the low consumption of sample and reagents, the elimination of catalysts and immobilised enzymes and the high sample throughput. 相似文献
7.
Paschalidou Polyxeni Pashalidis Ioannis 《Journal of Radioanalytical and Nuclear Chemistry》2019,320(3):807-812
Journal of Radioanalytical and Nuclear Chemistry - The present paper describes a relatively simple, effective, very selective and economic method for the determination of uranium in calcite and... 相似文献
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9.
Polyxeni Moschogianni Stergios Pispas Nikos Hadjichristidis 《Journal of polymer science. Part A, Polymer chemistry》2001,39(5):650-655
Tetrakis bromomethyl benzene was used as a tetrafunctional initiator in the synthesis of four‐armed star polymers of methyl methacrylate via atom transfer radical polymerization (ATRP) with a CuBr/2,2 bipyridine catalytic system and benzene as a solvent. Relatively low polydispersities were achieved, and the experimental molecular weights were in agreement with the theoretical ones. A combination of 2,2,6,6‐tetramethyl piperidine‐N‐oxyl‐mediated free‐radical polymerization and ATRP was used to synthesize various graft copolymers with polystyrene backbones and poly(t‐butyl methacrylate) grafts. In this case, the backbone was produced with a 2,2,6,6‐tetramethyl piperidine‐N‐oxyl‐mediated stable free‐radical polymerization process from the copolymerization of styrene and p‐(chloromethyl) styrene. This polychloromethylated polymer was used as an ATRP multifunctional initiator for t‐butyl methacrylate polymerization, giving the desired graft copolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 650–655, 2001 相似文献
10.
Paschalidou Polyxeni Pashalidis Ioannis 《Journal of Radioanalytical and Nuclear Chemistry》2019,321(3):973-975
The effect of EDTA-masking on the alpha-spectral characteristics corresponding to uranium analysis in ground- and seawater samples after cation-exchange and electrodeposition is systematically investigated. Addition of EDTA (1 mmol l?1) to the investigated samples results in dramatic increase of the spectra quality, including improvement of the separation efficiency up to 75% and 85% for ground and seawaters, respectively. For EDTA concentrations lower than 1 mmol l?1 the spectral resolution and counting efficiencies decline, whereas for higher concentrations the resolution increases but the separation efficiency decreases due to the U(VI) stabilization in solution.
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