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91.
The performance of fluorescence detectors in capillary electrophoresis is maximized when the excitation light intensity is modulated in time with optimal frequencies. This is especially true when photomultiplier tubes are used to detect the fluorescent light. The photomultiplier tube amplified raw output signal can in principle be captured directly by a personal computer sound card (PCSC) and processed by a lock-in emulated by software. This possibility is demonstrated in the present work and the performance of this new setup is compared with a traditional data acquisition system. The results obtained with this “PCSC and lock-in emulated by software” were of the same quality or even better compared to that obtained by conventional time integrators (Boxcars) and data acquisition boards. With PCSC the limits of detection (LOD) found for both naphthalene-2,3-dicarboxaldehyde-derivatized tyrosine and alanine were 3.3 and 3.5 fmol (injection of 5 nL of samples at 0.66 and 0.70 μmol/L), respectively. This is at least three times better compared to conventional systems when light emitting diodes (LEDs) are used as the excitation source in fluorescence detectors. The PCSC linear response range was also larger compared to conventional data acquisition boards. This scheme showed to be a practical and convenient alternative of data acquisition and signal processing for detection systems used in capillary electrophoresis.  相似文献   
92.
甾醇边链的化学修饰   总被引:1,自引:0,他引:1  
韩广甸  温宏艳 《有机化学》1992,12(3):233-240
本文对近年来甾醇边链结构改造的新方法和新动向--Barton 的Gif系统氧化反应及Breslow的远程功能化反应进行了综述。  相似文献   
93.
聚合物与有机染料多层复合膜电致发光颜色的直流电压调制马於光,薛善华,黄劲松,田文晶,刘式墉,沈家骢,刘晓冬(吉林大学分子光谱与分子结构开放实验室,集成光电子学国家重点实验室,长春,130023)(白求恩医科大学,长春,130023)关键词聚合物,发光...  相似文献   
94.
High resolution atomic absorption measurements of lead at 283 nm in a vapor cell were performed by frequency doubling an 850 nm laser diode to obtain 425 nm light, followed by sum frequency generation of the harmonic radiation with a second 850 nm laser diode.  相似文献   
95.
Deprotonation of an oxiranyl β-proton takes place in a stereoselective manner providing the corresponding oxiranyl ‘remote’ anion. The anion is stabilized by chelation between the lithium and the carbonyl moiety of an ester, lactone, imide, or keto-group in the form of a five-membered cyclic intermediate. Certain ester-stabilized oxiranyl anions are stable and can be left in THF solution at −78°C for several hours. The generated anions undergo a stereoselective alkylation reaction to provide products, which could be useful intermediates in the synthesis of bioactive naturally occurring α-methylene bis-γ-butyrolactones.  相似文献   
96.
Zhang T  Fang Q  Wang SL  Qin LF  Wang P  Wu ZY  Fang ZL 《Talanta》2005,68(1):19-24
The signal-to-noise level of light emitting diode (LED) fluorimetry using a liquid-core-waveguide (LCW)-based microfluidic capillary electrophoresis system was significantly enhanced using a synchronized dual wavelength modulation (SDWM) approach. A blue LED was used as excitation source and a red LED as reference source for background-noise compensation in a microfluidic capillary electrophoresis (CE) system. A Teflon AF-coated silica capillary served as both the separation channel and LCW for light transfer, and blue and red LEDs were used as excitation and reference sources, respectively, both radially illuminating the detection point of the separation channel. The two LEDs were synchronously modulated at the same frequency, but with 180°-phase shift, alternatingly driven by a same constant current source. The LCW transferred the fluorescence emission, as well as the excitation and reference lights that strayed through the optical system to a photomultiplier tube; a lock-in amplifier demodulated the combined signal, significantly reducing its noise level. To test the system, fluorescein isothiocyanate (FITC)-labeled amino acids were separated by capillary electrophoresis and detected by SDWM and single wavelength modulation, respectively. Five-fold improvement in S/N ratio was achieved by dual wavelength modulation, compared with single wavelength modulation; and over 100-fold improvement in S/N ratio was achieved compared with a similar LCW-CE system reported previously using non-modulated LED excitation. A detection limit (S/N = 3) of 10 nM FITC-labeled arginine was obtained in this work. The effects of modulation frequency on S/N level and on the rejection of noise caused by LED-driver current and detector were also studied.  相似文献   
97.
We report a new, solid-state, integrated optical array sensor platform. By using pin printing technology in concert with sol-gel-processing methods, we form discrete xerogel-based microsensor elements that are on the order of 100 μm in diameter and 1 μm thick directly on the face of a light emitting diode (LED). The LED serves as the light source to excite chemically responsive luminophores sequestered within the doped xerogel microsensors and the analyte-dependent emission from within the doped xerogel is detected with a charge coupled device (CCD). We overcome the problem of background illumination from the LED reaching the CCD and the associated biasing that results by coating the LED first with a thin layer of blue paint. The thin paint layer serves as an optical filter, knocking out the LEDs red-edge spectral tail. The problem of the spatially-dependent fluence across the LED face is solved entirely by performing ratiometric measurements. We illustrate the performance of the new sensor scheme by forming an array of 100 discrete O2-responsive sensing elements on the face of a single LED. The combination of pin printing with an integrated sensor and light source platform results in a rapid method of forming (∼1 s per sensor element) reusable sensor arrays. The entire sensor array can be calibrated using just one sensor element. Array-to-array reproducibly is <8%. Arrays can be formed using single or multiple pins with indistinguishable analytical performance.  相似文献   
98.
As facile,green,low-cost as possible:One more electron-deficient azaacene (TCAF) with deep LUMO (-4.52 eV), strong electronic affinity,excellent yield,and simple purification procedure was successfully created and explored as good electron injection material.It is believed TCAF would be a promising and pervasive acceptor material and bring in more significant achievements to green and sustainable organic electronics including OLEDs,OFETs,OPVs, and perovskite solar cells,etc.  相似文献   
99.
Summary The effects of concentration, separation and spectral similarity as factors influencing the accuracy of iterative target testing factor analysis (ITT-FA) are investigated for three component systems by the application of analysis of variance (ANOVAR). ANOVAR is applied over a range of peak separations to map the changing effects of the three factors with increasing overlap. Two error responses were measured and analysed, (a) Relative cluster error (RCE) a measure of the error over all peaks in a cluster and (b) Relative peak error (RPE) the error of an individual peak. Multicomponent analysis (MCA) a method requiringa priori spectral information, is used as a referee method for ITT-FA.  相似文献   
100.
Perfluoro-1,3,5-tris(p-quaterphenyl)benzene (PF-13Y) and perfluoro-1,3,5-tris(p-quinquephenyl)benzene (PF-16Y) have been synthesized and characterized. They showed higher glass transition temperatures compared with perfluoro-1,3,5-tris(p-terphenyl)benzene (PF-10Y). Organic light-emitting diodes were fabricated using these materials as the electron-transport layers. PF-13Y and -16Y are better electron transporters than PF-10Y. The electron mobilities of PF-10Y and Alq3 were measured by the time-of-flight technique. PF-10Y showed higher electron mobilities (10−4 cm2/V s) and weaker electric field dependence compared with Alq3.  相似文献   
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