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Mobile Phase Additives (mobile + phase_additive)
Selected AbstractsMobile phase additives for enhancing the chromatographic performance of astaxanthin on nonendcapped polymeric C30 -bonded stationary phasesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 1 2009Philipp Kaiser Abstract Astaxanthin shows peak deformation and reduced peak area response when eluted with methanol and methyl tert -butyl ether on nonendcapped polymeric C30 -bonded HPLC phases. The present study tested different column manufacturers, column batches, and ten mobile phase additives including acids, bases, buffers, complexing and antioxidant agents for improvement of peak shape and peak area response. Concerning chromatographic benefits and feasibility, ammonium acetate was found to be the best additive followed by triethylamine for all columns tested. Variation of the mobile phase pH equivalent and the column temperature showed no synergistic effects on peak shape and peak area response. Results indicate that peak tailing and variation of peak area response are due to different on-column effects. Possible mechanisms of the observed phenomenon will be discussed. [source] Enatiomeric analysis of simendan by CE with , -CD as chiral selector compared with CMPA-HPLCBIOMEDICAL CHROMATOGRAPHY, Issue 10 2004Famei Li Abstract The chiral separation of simendan enantiomers using capillary electrophoresis was studied with , -cyclodextrin (, -CD) as chiral selector. The in,uences of the concentration and pH of borate buffer solution, , -CD concentration and methanol content in the background electrolyte were investigated. These factors were compared with those in an HPLC with , -CD as chiral mobile phase additive (CMPA-HPLC). The quanti,cation properties of the developed CE method were examined. A baseline separation of simendan enantiomers was achieved in the background electrolyte of 20 mmol/L borate buffer (pH 11.0) containing 12 mmol/L , -CD-methanol (50:50 in volume ratio). The CE method is comparable with CMPA-HPLC in chiral resolution, although the optimal pH in CE (11.0) is much higher than that (6.0) in CMPA-HPLC. This chiral CE method is applicable to the quantitative ananlysis and enantiomeric excess value determination of l -simendan. Copyright © 2004 John Wiley & Sons, Ltd. [source] Enantioselective chromatography of alkyl derivatives of 5-ethyl-5-phenyl-2-thiobarbituric acid studied by semiempirical AM1 methodCHIRALITY, Issue 8 2002Krzysztof Zborowski Abstract Complexation of alkyl derivatives of 5-ethyl-5-phenyl-2-thiobarbituric acid (2-thiophenobarbital) enantiomers by ,-cyclodextrin was investigated by the AM1 method. The inclusion complexes of ,-cyclodextrin with neutral and anionic forms of these enantiomers have been modeled and energetically optimized. The chiral discrimination of enantiomers was analyzed in terms of differences in the interaction energies. The calculated interaction energies between each enantiomer of the investigated 2-thiobarbiturates and ,-cyclodextrin confirm the ability of ,-cyclodextrin to act as a mobile phase additive in reversed-phase HPLC to separate enantiomers by liquid chromatography and rationalize their order of elution. Chirality 14:632,637, 2002. © 2002 Wiley-Liss, Inc. [source] Ionic liquids as mobile phase additives for high-performance liquid chromatography separation of phenoxy acid herbicides and phenolsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 23-24 2009Xialin Hu Abstract In this present study, 1-butyl-3-methylimidazolium chloride ([C4MIM]Cl), 1-octyl-3-methylimidazolium chloride ([C8MIM]Cl), and 1-decyl-3-methylimidazolium chloride ([C10MIM]Cl) were adopted as mobile phase additives in the high performance liquid chromatography (HPLC) to simultaneously separate phenoxy acid herbicides and phenols at neutral pH. It was found that by using 20,mM of [C4MIM]Cl, baseline separation and good chromatograms for all the acid compounds were obtained on a normal reversed-phase C18 column. The retention time of the target acid compounds shortened with the increase of the alkyl chain length and the concentrations of ionic liquids, probably due to the delocalization of the positive charge on the imidazolium cation, the repulsion between chlorine ions of ionic liquids and the acid compounds, as well as the stereo-hindrance effect. The mechanism with ionic liquids as mobile additives for the separation of acid compounds was discussed. [source] Mobile phase additives for enhancing the chromatographic performance of astaxanthin on nonendcapped polymeric C30 -bonded stationary phasesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 1 2009Philipp Kaiser Abstract Astaxanthin shows peak deformation and reduced peak area response when eluted with methanol and methyl tert -butyl ether on nonendcapped polymeric C30 -bonded HPLC phases. The present study tested different column manufacturers, column batches, and ten mobile phase additives including acids, bases, buffers, complexing and antioxidant agents for improvement of peak shape and peak area response. Concerning chromatographic benefits and feasibility, ammonium acetate was found to be the best additive followed by triethylamine for all columns tested. Variation of the mobile phase pH equivalent and the column temperature showed no synergistic effects on peak shape and peak area response. Results indicate that peak tailing and variation of peak area response are due to different on-column effects. Possible mechanisms of the observed phenomenon will be discussed. [source] Utility of ionic liquids in analytical separationsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 11 2007Shahab A. Shamsi Abstract Ionic liquids (ILs), as separation media, have made significant contributions in the past decades in advancing research in gas chromatography (GC), liquid chromatography (LC), and capillary electrophoresis (CE). This review, covering reports published from the mid 1980s to early 2007, shows how ILs have been used so far in separation science, originally primarily as GC stationary phases and later as mobile phase additives (both millimolar and major percent levels) for LC and CE. Representative GC and LC chromatograms as well as CE electropherograms are shown. In addition, the very recent findings on the development of ionic liquids with surfactant properties and its applications for chiral and achiral analysis are discussed. [source] Evaluation of the silanol-suppressing potency of ionic liquidsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 8 2006Micha, Piotr Marsza Abstract Recently, increasing attention has been paid to the use of ionic liquids for high-performance liquid chromatography (HPLC) and capillary electrophoresis. In the present study, the silanol-suppressing potency of ionic liquids was evaluated by HPLC using the two-retention site model proposed previously by Nahum and Horváth (J. Chromatogr. 1981, 203, 53,63). The binding constant, KA, in that approach has been demonstrated to reliably reflect the ability of the ionic liquids to block the silanols of the silica support material of the stationary phase. The determinations were carried out for ionic liquids of the 1-alkyl-3-methylimidazolium group with the use of a series of basic drugs as the test analytes. Comparison of ionic liquids with standard mobile phase additives such as triethylamine showed the former to possess advantages as silanol suppressors in HPLC. The main advantage of the method is that it provides a simple and fast determination of the silanol complex stability, which allowed comparison of the suppressing efficiency of several ionic liquids. [source] Enantiomeric separation of dansyl amino acids using macrocyclic antibiotics as chiral mobile phase additives by narrow-bore high-performance liquid chromatographyCHIRALITY, Issue 3 2004V. Scott Sharp Abstract Seven macrocyclic antibiotics were evaluated as chiral selectors for the enantiomeric separation of 11 dansyl amino acids using narrow-bore high-performance liquid chromatography (HPLC). The macrocyclic antibiotics were incorporated as mobile phase additives to determine the enantioselective effects on the chiral analytes. The resolution and capacity factor (k,) of each analyte were assessed while varying the structure of macrocyclic antibiotic and the mobile phase buffer pH. The selectivity of the chiral selectors was measured as a function of changes in these parameters. All 11 dansyl amino acids were separated by at least one of the chiral selectors. Three-dimensional computer modeling of the more effective chiral selectors illustrated the importance of macrocyclic antibiotic structure concerning stereospecific analyte interaction. Chirality 16:153,161, 2004. © 2004 Wiley-Liss, Inc. [source] | ||||||||||