Enantiometric purity determination to 1 % level using a laser-based polarimetric HPLC detector

1990 ◽  
Vol 333 (1628) ◽  
pp. 166-168
Keyword(s):  
High Performance ◽  
Flicker Noise ◽  
Specific Rotation ◽  
Significant Advance ◽  
Chromatographic Peak ◽  
Chiral Molecule ◽  
Chiral Molecules ◽  
Noise Levels ◽  
Hplc Detector ◽  
Compact Design

The development of laser-based polarimetric detectors for high-performance liquid chromatography (HPLC) (Yeung et al . 1980; Bobbitt & Yeung 1986) with noise levels in the range of 0.1-10 p° has provided a significant advance in the quantitation of chiral molecules. We have designed an instrument based on an 820 nm diode laser which has the advantages of low source flicker noise and compact design (Lloyd et al . 1989). Detection limits were found to be in the range 0.1-2 pg, dependent on the specific rotation of the chiral molecule and the chromatographic peak width (Goodall et al. 1990).

History of HgTe-based photodetectors in Poland

2010 ◽  
Vol 18 (3) ◽  
Author(s):  
A. Rogalski
Keyword(s):  
High Performance ◽  
Flicker Noise ◽  
Vapour Phase ◽  
Fast Response ◽  
Thick Wall ◽  
Vapour Phase Epitaxy ◽  
Stage Of Development ◽  
In Series ◽  
Multiple Cell ◽  
And Performance

AbstractIn Poland, the HgCdTe studies began in 1960 at the Institute of Physics, Warsaw University. The material processing laboratory was created by Giriat and later by Dziuba, Gałązka, and others. Bridgman technique with sealed thick wall quartz ampoules was used to grow material suitable for research and experimental devices. Among the first papers published in 1961 and 1963 there were the Polish works devoted to preparation, doping, and electrical properties of HgCdTe.Infrared detector’s research and development efforts in Poland were concentrated mostly on uncooled market niche. At the beginning, a modified isothermal vapour phase epitaxy has been used for research and commercial fabrication of photoconductive, photoelectromagnetic and other HgCdTe devices. Bulk growth and liquid phase epitaxy were also used. Recently, the fabrication of infrared devices relies on low temperature epitaxial technique, namely metalorganic vapour phase deposition.At present stage of development, the photoconductive and photoelectromagnetic (PEM) detectors are gradually replaced with photovoltaic devices which offer inherent advantages of no electric or magnetic bias, no heat load and no flicker noise. Potentially, photodiodes offer high performance and very fast response. However, conventional photovoltaic uncooled detectors suffer from low quantum efficiency and very low junction resistance. The problems have been solved with advanced band gap engineered architecture, multiple cell heterojunction devices connected in series, and monolithic integration of the detectors with microoptics.In final part of the paper, the Polish achievements in technology and performance of HgMnTe and HgZnTe photodetectors are presented.

Design of Analog Front-end Circuit for Audio-frequency Magnetotelluric Instrument

2018 ◽  
Vol 23 (3) ◽  
pp. 305-318
Author(s):  
Yinglu Zhang ◽  
Zhenzhu Xi ◽  
Xingpeng Chen ◽  
Honglan Wei ◽  
Long Huang ◽  
...  
Keyword(s):  
Electric Field ◽  
High Performance ◽  
Notch Filter ◽  
Noise Levels ◽  
High Quality ◽  
Pass Filter ◽  
Input Noise ◽  
Front End ◽  
Analog Front End ◽  
Power Frequency

High-performance audio-frequency magnetotelluric (AMT) instrument is one means of obtaining high-quality electromagnetic (EM) data. To improve the ability of AMT system to obtain high-quality data, this paper presents a design for a high-performance analog front-end circuit for AMT instrument. It mainly consists of the input protection, preamplifier, passive high pass filter, power frequency notch filter, programmable amplifier, and active low pass filter. In addition, this paper proposes a design of low-noise, high-performance preamplifier, which improves the common-mode rejection ratio (CMRR) of analog front-end circuit and effectively enhances the signal-to-noise ratio (SNR) of the circuit. The front-end circuit utilized two-stage twin-T notch filter to effectively suppress the strong interference of fundamental component of power frequency. Also, it used signal relays to control circuit gain and selection of cutoff frequency of anti-aliasing filter, resulting in the improvement of the capability of the analog-to-digital Converter (ADC) to distinguish weak EM signal. The measured results of the electric field and magnetic field channel showed that: 1) The circuit works in frequency range of 1 Hz∼100 kHz; 2) The CMRR values of the preamplifier of electric field channel at low frequencies (1 Hz∼1 kHz) are 111 dB and 97 dB when the gains are 20 dB and 6 dB respectively; 3) The maximum attenuation fundamental power frequency can reach −39.46 dB and −39.04 dB respectively; 4) The total harmonic distortion rate at 1 kHz is 0.022% and 0.029% respectively; 5) The input noise levels of electric field channel are 12.67nV / [Formula: see text] @10Hz and 8.15V / [Formula: see text] @1kHz, while the input noise levels of magnetic field channel are 8.97nV / [Formula: see text] @10Hz and 6.16V / [Formula: see text] @1kHz; and 6) In conclusion, the analog front-end circuit is superior to meet the requirements of the AMT methods, and provides a useful reference for the development of AMT instrument.

scholarly journals Study on chemical constituents of different species of Dendrobium

2020 ◽  
Vol 165 ◽  
pp. 05026
Author(s):  
Zhenghui Wan ◽  
Qingjun Huang
Keyword(s):  
Mobile Phase ◽  
Research Method ◽  
High Performance ◽  
Chemical Constituents ◽  
Chromatographic Peak ◽  
Column Temperature ◽  
Injection Volume ◽  
Chinese Pharmacopoeia ◽  
Processing Techniques ◽  
Theoretical Plates

The objective of this study is to determine the erianin of 10 species of Dendrobium by high performance liquid chromatography (HPLC). Processing techniques were washed, dried and ground. The research method for determining the content of erianin was adopted from Chinese Pharmacopoeia 2015 Edition. Acetonitrile-0.05% phosphoric acid (37:63) was used as mobile phase. The samples were separated on Sharpsil-TC18 column(4.6*150mm;5μm) at a flow rate of 1.2mL/min and detected at 230nm, and the column temperature was kept at 30℃. The injection volume was 20μL. The number of theoretical plates was not less than 6000 according to the chromatographic peak of erianin. The result of the study showed erianin was detected only in Dendrobium chrysotoxum among the 10 species of Dendrobium. and the content was 0.098%. Conclusion: The content of erianin in Dendrobium chrysotoxum met the specification of no less than 0.03% in the 2015 edition of Chinese Pharmacopoeia.

scholarly journals Thermodynamic and Extrathermodynamic Studies of Enantioseparation of Imidazolinone Herbicides on Chiralcel OJ Column

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Wenjian Lao
Keyword(s):  
High Performance Liquid Chromatography ◽  
Chiral Separation ◽  
Mobile Phase ◽  
High Performance ◽  
Chromatographic Peak ◽  
Chiral Column ◽  
Higher Temperature ◽  
Lower Temperature ◽  
The Moment ◽  
Imidazolinone Herbicides

A homologous series of chiral imidazolinone herbicide was previously resolved on Chiralcel OJ column in high performance liquid chromatography. However, the mechanism of the chiral separation remains unclear. In this study, chromatographic behaviors of five chiral imidazolinone herbicides were characterized by thermodynamic and extrathermodynamic methods in order to enhance the understanding of the chiral separation. Thermodynamic parameters of this study were derived from equilibrium constant () that was estimated from the moment analysis of the chromatographic peak. Van't Hoff plots of ( versus ) were linear at a range of 15–50°C, only nonlinear at a range of 5–15 °C with n-hexane (0.1%, trifluoroacetic acid)-2-propanol 60/40 (v/v) mobile phase. The enantiomer retention on the chiral column was entropy-driven at a lower temperature (5°C) and enthalpy-driven at a higher temperature (10 to 50°C). Enantioseparations of four of the five imidazolinone herbicides were enthalpy-driven, only entropy-driven for imazaquin. Enantioseparation mechanisms were different in between 5–10°C and 15–50°C probably due to the conformational change of the OJ phase. Enthalpy-entropy compensation showed similar mechanisms in retention and chiral separation for the five or enantiomers. Several extrathermodynamic relationships were able to be extracted to address additivity of group contribution.

scholarly journals Design, Optimization and Analysis of Supersonic Radial Turbines

2019 ◽  
Author(s):  
Lukas Benjamin Inhestern ◽  
James Braun ◽  
Guillermo Paniagua ◽  
José Ramón Serrano Cruz
Keyword(s):  
High Performance ◽  
Ad Hoc ◽  
Three Dimensional ◽  
Critical Factor ◽  
Design Tool ◽  
Navier Stokes ◽  
Design Parameters ◽  
Design Variables ◽  
Compact Design ◽  
Radial Outflow

Abstract New compact engine architectures such as pressure gain combustion require ad-hoc turbomachinery to ensure an adequate range of operation with high performance. A critical factor for supersonic turbines is to ensure the starting of the flow passages, which limits the flow turning and airfoil thickness. Radial outflow turbines inherently increase the cross section along the flow path, which holds great potential for high turning of supersonic flow with a low stage number and guarantees a compact design. First the preliminary design space is described. Afterwards a differential evolution multi-objective optimization with 12 geometrical design parameters is deducted. With the design tool AutoBlade 10.1, 768 geometries were generated and hub, shroud, and blade camber line were designed by means of Bezier curves. Outlet radius, passage height, and axial location of the outlet were design variables as well. Structured meshes with around 3.7 million cells per passage were generated. Steady three dimensional Reynolds averaged Navier Stokes (RANS) simulations, enclosed by the k-omega SST turbulence model were solved by the commercial solver CFD++. The geometry was optimized towards low entropy and high power output. To prove the functionality of the new turbine concept and optimization, a full wheel unsteady RANS simulation of the optimized geometry exposed to a nozzled rotating detonation combustor (RDC) has been performed and the advantageous flow patterns of the optimization were also observed during transient operation.

scholarly journals Enhanced Near-Field Chirality in Periodic Arrays of Si Nanowires for Chiral Sensing

Molecules ◽  
2019 ◽  
Vol 24 (5) ◽  
pp. 853 ◽  
Author(s):  
Emilija Petronijevic ◽  
Concita Sibilia
Keyword(s):  
Near Field ◽  
Chiral Molecule ◽  
Chiral Molecules ◽  
Si Nanowires ◽  
Simple Experiment ◽  
Excitation Scheme ◽  
Periodic Arrays ◽  
Optical Chirality ◽  
Resonant Modes ◽  
Chiral Sensing

Nanomaterials can be specially designed to enhance optical chirality and their interaction with chiral molecules can lead to enhanced enantioselectivity. Here we propose periodic arrays of Si nanowires for the generation of enhanced near-field chirality. Such structures confine the incident electromagnetic field into specific resonant modes, which leads to an increase in local optical chirality. We investigate and optimize near-field chirality with respect to the geometric parameters and excitation scheme. Specially, we propose a simple experiment for the enhanced enantioselectivity, and optimize the average chirality depending on the possible position of the chiral molecule. We believe that such a simple achiral nanowire approach can be functionalized to give enhanced chirality in the spectral range of interest and thus lead to better discrimination of enantiomers.

Space and the Chiral Molecule

2000 ◽  
Author(s):  
Robin Le Poidevin
Keyword(s):  
Mirror Image ◽  
Chiral Molecule ◽  
Chiral Molecules ◽  
Philosophical Debate ◽  
Geometrical Properties ◽  
Logical Construction ◽  
Living Things ◽  
Famous Argument ◽  
Pedagogical Relation ◽  
Optical Isomerism

According to classical stereochemistry, the molecules of some substances have doubles, in the sense of incongruent mirror-image counterparts. This is the phenomenon of optical isomerism, first identified 150 years ago by Pasteur. In some cases, the double occurs naturally; in others, it has to be artificially synthesized. These molecules thus share a geometrical feature with such familiar objects as our hands, and, indeed, it is this connection that gives the feature its technical name: chirality (from the Greek for hand, kheir). Instances of chirality in chemistry are numerous, especially in living things: examples of chiral molecules include adrenaline, glucose, and DNA. Optical isomerism is interesting, both historically—it played a crucial role in the emergence of structural chemistry and in the attempt to link chemistry with physics— and, I believe, philosophically. I should like to take this opportunity to revisit the scene of an earlier article of mine (Le Poidevin, 1994) in which I examined the implications optical isomerism has for a philosophical debate concerning the nature of space. In that article I argued that chirality in chemistry reinforces a conclusion that Graham Nerlich (1994), in a brilliant reconstruction of a famous argument of Kant’s, had derived from more visible instances of chirality: that we should be realists about the geometrical properties of space. I did not, however, want to follow Nerlich (and Kant) in drawing a more radical conclusion: that we should be realists about the existence of space. That may sound paradoxical, but it is possible (or so I thought) to regard space as a logical construction from its contents and still think of it, qua construction, as possessing certain intrinsic properties that we do not merely impose on it by convention. Since then, I have become more sympathetic to Nerlich’s position. Chirality is best understood by thinking of space as an entity in its own right. So chemistry has some lessons for the philosophy of space. But the pedagogical relation goes the other way, too: the philosophy of space has interesting implications for chemistry.

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