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排序方式: 共有243条查询结果,搜索用时 15 毫秒
191.
A new interface for capillary electrophoresis electrospray ionization (CE-ESI) is presented. High voltage is applied at the outlet of the separation capillary by a stainless steel tube, a so called liner, through which the capillary is led. A compensating current between the liquid and the liner is maintained by a natural liquid film, which is built up at the outer surface of the capillary end. Operable potential ranges for differently treated capillary ends have been examined. The liner has been evaluated for the analysis of fatty acids and prostaglandins, all run with the ESI in the negative ionization mode. This simple stainless steel liner should fill the gap, which has prevented CE-MS from being the successful tool, which it has the potential for, namely fast and unattended measurements of analytes in the nM range in complex mixtures. 相似文献
192.
Jakob Axén David Malmström Bengt‐Olof Axelsson Patrik Petersson Per J. R. Sjöberg 《Rapid communications in mass spectrometry : RCM》2010,24(9):1260-1264
Electrospray ionization performs best with volatile buffers. However, generally the best separation performance for capillary electrophoresis (CE) is achieved with non‐volatile buffers. Hyphenation of CE with mass spectrometry (MS) utilizing atmospheric pressure photoionization (APPI) enables use of a wider range of separation buffers without compromising detection sensitivity. As APPI is considered to be mass flow sensitive, the use of a larger inner diameter separation capillary (75 µm) allows larger volumes to be injected, without decreased separation performance, thus providing improved sensitivity (approx. a factor of 10), compared to the use of a 25 µm capillary. However, nebulizing gas flow and position of capillary tip in the sprayer have to be carefully optimized to prevent excessive band broadening. Further improvement in sensitivity (approx. a factor of 2) was obtained by decreasing the distance between the sprayer and ionization region, indicating that a specially designed CE/APPI‐MS interface for low flow rates will be favourable. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Fredrik Petersson Philipp Sulzer Chris A. Mayhew Peter Watts Alfons Jordan Lukas Märk Tilmann D. Märk 《Rapid communications in mass spectrometry : RCM》2009,23(23):3875-3880
This work demonstrates for the first time the potential of using recent developments in proton transfer reaction mass spectrometry for the rapid detection and identification of chemical warfare agents (CWAs) in real‐time. A high‐resolution (m/Δm up to 8000) and high‐sensitivity (~50 cps/ppbv) proton transfer reaction time‐of‐flight mass spectrometer (PTR‐TOF 8000 from Ionicon Analytik GmBH) has been successfully used to detect a number of CWA simulants at room temperature; namely dimethyl methylphosphonate, diethyl methylphosphonate, diisopropyl methylphosphonate, dipropylene glycol monomethyl ether and 2‐chloroethyl ethyl sulfide. Importantly, we demonstrate in this paper the potential to identify CWAs with a high level of confidence in complex chemical environments, where multiple threat agents and interferents could also be present in trace amounts, thereby reducing the risk of false positives. Instantaneous detection and identification of trace quantities of chemical threats using proton transfer reaction mass spectrometry could form the basis for a timely warning system capability with greater precision and accuracy than is currently provided by existing analytical technologies. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
196.
In our article [ 1 ], "A tree of linearisable second-order evolution equations by generalised hodograph transformations " we present a class of linearizable ( C -integrable) second-order evolution equations in (1+1) dimensions, using a generalized hodograph transformation. We report here the complete set of recursion operators for this class and present the resulting linearizable ( C -integrable) hierarchies in (1+1) dimensions. The autonomous class of linearizable hierarchies are extended further by considering the equations in potential form followed by the pure hodograph transformation. 相似文献
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Hans Petersson 《Mathematische Annalen》1940,117(1):453-537
Ohne Zusammenfassung 相似文献
199.
Hans Petersson 《Mathematische Annalen》1931,105(1):206-239
Ohne Zusammenfassung 相似文献
200.