摘要:

AbstractThe 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 anal

ISSN:0935-6304    

DOI:10.1002/jhrc.1240181202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe retention behavior of aromatic hydrocarbons and dansylamino acids on cation‐exchangers modified with alkylammonium ions has been examined by microcolumn liquid chromatography. Several parameters affected the retention of analytes, involving concentration of the modifier in the mobile phase, its alkyl chain length and mobile phase composition. Stationary phases modified with a reagent having longer alkyl chains achieved better column efficienc

ISSN:0935-6304    

DOI:10.1002/jhrc.1240181203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractA GC/MS study was performed in order to determine 1,4‐benzoquinone, 1,4‐cyclohexanedione, and hydroquinone derivatives on by one and in the presence of each other in different concentrations. Exhaustive investigations, related to the quantitation both of their underivatized compounds and those of their oxime/methoxime and silyl derivatives. Results proved that subsequently to the oximation/methoximation of the carbonyl groups – for the sake of a well shaped and accurately evaluable hydroquinone peak – also silylation is unavoidably necessary. Reproducibility data in the microgram/nanogram level, based on quantitation of their total ion currents and/or those of their selective fragments, were given in

ISSN:0935-6304    

DOI:10.1002/jhrc.1240181204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractAn electronic gas‐flow controller system called Advanced Flow Control (AFC), which controls not only carrier gas pressure at the column inlet but also the total gas flow including the split flow, was designed and evaluated. BASIC programming of repetitive analyses of standard mixtures under varied split ratios and pressure programs allowed automated optimization of those conditions for the desired column loading and resolution between adjacent peak

ISSN:0935-6304    

DOI:10.1002/jhrc.1240181205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of ammonia on the electron capture detector (ECD) response has been investigated. Nitrogen with different ammonia concentrations (5–20%) was used as make‐up gas. Compared to pure nitrogen, the ECD response decreased when the ammonia concentration in the make‐up gas was 5%. However, the response increased when the ammonia concentration was 20%. The response factor of 4‐chlorophenol increased 4 fold when ammonia was 20%. Also, di‐ and tri‐chlorophenols increased by 30–50%. The nitroaromatic compounds responses increased by about 2–3.7 times with 20% ammonia in the make‐up gas. The signal‐to‐noise (S/N) increased when 20% ammonia in nitrogen was used as make‐up gas compared to pure nitrogen. Also, the detector linearity increa

ISSN:0935-6304    

DOI:10.1002/jhrc.1240181206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240181207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240181208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240181209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240181210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240181211

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY