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1.
2.
The effect of the superposition of electroosmotic flow and pressureinduced hydrodynamic counterflow on efficiency has been investigated for different capillary electrophoretic systems. Results are shown for 50 and 75 μm internal diameter capillaries at several voltage and counterpressure levels. Hydrodynamic counterflows were successfully applied in electrokinetic chromatography in order to delay the entry of a UV-active pseudostationary phase, tetraphenyl porphyrintetrasulfonate, into the detection zone allowing the separation of neutral nitroaromatics. The separations are based on the weak charge-transfer interactions between the porphyrin and the analytes. 相似文献
3.
The impact of spilled explosives, their by-products and degradation products on human beings and the environment has been
recognised as a serious problem at areas of existing and former ammunition plants. In nature, aerobic and anaerobic degradation
processes of explosives and their accompanying compounds yield polar contaminants with relatively high water solubilities.
Most are potentially carcinogenic and mutagenic. An HPLC method applying UV-detection for nitroaromatic compounds and amperometric
detection for aminoaromatic and phenolic compounds was used for monitoring the degradation of explosives in a polluted groundwater
sample under natural conditions. Analysis was performed by direct injection of aliquots of the sample after exposition to
daylight for different periods of time.
Received: 6 January 1996/Revised: 7 March 1996/Accepted: 13 March 1996 相似文献
4.
Conditions for the determination of electrophoretic mobilities of bacteria by capillary electrophoresis (CE) were explored. Most precise values are obtained using fused silica capillaries of 1–3 m length (0.25 mm inner diameter), a background buffer with an ionic strength of 0.0015 mol/L and a pH value of 7–10 at a field strength of 120 V/cm. Capillary electrophoretic separation of three different bacteria populations on the basis of their mobility differences could be realized. Electrophoretic band widths of all bacteria populations investigated are relatively large compared to molecule bands. It finds its explanation in the different distribution of surface charge density to cross-sectional area of each single cell of a population. 相似文献
5.
As an alternative to acid pretreated UCON and FFAP capillaries for the analysis of wide-boiling free fatty acid mixtures, OV-1 : FFAP phase mixtures were used on high-temperature silylated inert glass capillary columns. The HETP-carrier gas velocity curves, peak asymmetry factors, coating efficiency, gas phase and stationary phase contributions to the mass transfer resistance were determined for various OV-1 : FFAP ratios. Mixed-phase capillaries showed optimum performance at a 2 : 1 OV-1 : FFAP ratio. The thermal and long-term stability of OV-1-stabilized FFAP columns surpassed those of the UCON and pure FFAP reference column used. 相似文献
6.
The impact of spilled explosives, their by-products and degradation products on human beings and the environment has been
recognised as a serious problem at areas of existing and former ammunition plants. In nature, aerobic and anaerobic degradation
processes of explosives and their accompanying compounds yield polar contaminants with relatively high water solubilities.
Most are potentially carcinogenic and mutagenic. An HPLC method applying UV-detection for nitroaromatic compounds and amperometric
detection for aminoaromatic and phenolic compounds was used for monitoring the degradation of explosives in a polluted groundwater
sample under natural conditions. Analysis was performed by direct injection of aliquots of the sample after exposition to
daylight for different periods of time.
Presented as a poster at the Anakon ’95 Conference in Schliersee, April 24–26, 1995 相似文献
7.
Solid phase extraction/programmed temperature vaporizer (PTV) injection in GC-analysis of toxaphene and PCBs in aqueous samples 总被引:1,自引:0,他引:1
E. Stottmeister H. Hermenau P. Hendel T. Welsch W. Engewald 《Fresenius' Journal of Analytical Chemistry》1991,340(1):31-34
Summary A high-resolution gas-chromatographic (HRGC) method with electron capture detection is described for the sensitive determination of PCBs and toxaphene in water in the lower ng/l range. The required low detection limits are guaranteed by isolation of the target compounds and concentration from the filtered water sample by solid phase extraction with specific C18 silica gel (200–250 m) alone or combined with the injection of larger extract volumes into a programmed temperature vaporizer (PTV) operating in the solvent venting mode. The bonded silica gel was prepared by reaction of the surface silanol groups with octadecyltrichlorosilane. A C18 silica of reproducible coverage was received. Practical aspects of the use of the solid phase extraction in combination with the PTV injection technique are discussed. The recoveries for toxaphene and PCBs were 85 and 78%. 相似文献
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Schmidt E Knoll L Welsch DG Zielonka M Konig F Sizmann A 《Physical review letters》2000,85(18):3801-3804
Quantum effects in N-bound solitons can be drastically enhanced compared to the fundamental soliton. In particular, the spectral photon-number correlations are much stronger. The formation of spectral domains of almost perfect positive and negative correlations is predicted. Criteria that are based on the Cauchy-Schwarz inequality are used for studying nonclassical correlations. Interferences between different soliton components of the N-bound solution being responsible for the strong changes in the coherent amplitude may also be a mechanism for the strong correlations. The results offer novel possibilities of producing light with highly nonclassical properties. 相似文献