Mobile Phase Conditions (mobile + phase_condition)

Distribution by Scientific Domains

Selected Abstracts

Preparation of a heterogeneous hollow-fiber affinity membrane having a mercapto chelating resin and its recovery of Hg2+ cations

Bing Wang
Abstract A kind of heterogeneous hollow-fiber affinity filter membrane with a high chelating capacity for Hg2+ was prepared by phase separation with blends of a mercapto chelating resin and polysulfone as the membrane materials, N,N -dimethylacetamide as the solvent, and water as the extraction solvent. The adsorption isotherms of the hollow-fiber affinity filter membrane for Hg2+ were determined. The heterogeneous hollow-fiber affinity filter membrane was used for the adsorption of Hg2+ cations through the coordination of the mercapto group and Hg2+ cations, and the effects of the morphology and structure of the affinity membrane on the chelating properties were investigated. The chelating conditions, including the chelating resin grain size, pH value, concentration of the metallic ion solution, mobile phase conditions, and operating parameters, had significant effects on the chelating capacity of the hollow-fiber affinity filter membrane. The results revealed that the greatest chelating capacity of the hollow-fiber affinity filter membrane for Hg2+ was 1090 ,g/cm2 of membrane under appropriate conditions, and the adsorption isotherms of Hg2+ could be described by the Langmuir isotherm. The dynamic chelating experiments indicated that the hollow-fiber affinity membrane could be operated at a high feed flow rate and that large-scale removal of Hg2+ could be realized. 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Separation of ternary systems of hydrophilic ionic liquid with miscible organic compounds by RPLC with refractive index detection

Dongli Zhang
Abstract A rapid and simple analytical method was developed for the simultaneous and quantitative determination and separation of hydrophilic imidazolium ionic liquids (ILs) (1-butyl-3-methylimidazolium chloride, [C4mim]Cl; 1-hexyl-3-methylimidazolium chloride, [C6mim]Cl; 1-octyl-3-methylimidazolium chloride, [C8mim]Cl; 1-allyl-3-methylimidazolium chloride, [Amim]Cl; or 1-allyl-3-methylimidazolium bromide, [Amim]Br) with miscible ethyl acetate and EtOH and their mixtures using reverse phase liquid chromatography coupled with refractive index detection (RPLC,RI). The influence of 60 to 100% (volume percentage) methanol in the mobile phase on the IL systems ([C4mim]Cl, [C6mim]Cl, [C8mim]Cl, [Amim]Br, or [Amim]Cl)-ethyl acetate-EtOH was investigated. The optimum mobile phase for the system [C8mim]Cl-ethyl acetate-EtOH, [C4mim]Cl-ethyl acetate-EtOH, [Amim]Br-ethyl acetate-EtOH and [Amim]Cl-ethyl acetate-EtOH was methanol/water (60:40, v/v), and methanol/water (70:30, v/v) for [C6mim]Cl-ethyl acetate-EtOH. Under optimum mobile phase conditions for each system, the RSD of the retention time ranged from 0.02 to 0.04%, and the RSDs of the peak area percent ranged from 0.23 to 1.85%, which showed good reproducibility of the RPLC-RI method. The RPLC-RI method can determine IL, ethyl acetate, and EtOH simultaneously in 5 min, and the analytes, especially IL, can be eluted completely. The results show that the RPLC-RI method can be used to separate and determine ILs in mixtures with organic compounds simultaneously and quantitatively. [source]

Comparison of ethylammonium formate to methanol as a mobile-phase modifier for reversed-phase liquid chromatography

Martin M. Waichigo
Abstract Ethylammonium formate (EAF), (C2H5NH3+HCO2,), is a room-temperature ionic liquid that has a polarity similar to that of methanol (MeOH) or acetonitrile. The separation at 1 mL/min of a test mixture of vitamins or phenols on a polystyrene-divinylbenzene column using either an EAF- or MeOH-water mobile phase is similar in terms of both resolution and analysis time. Because the viscosity of EAF is higher than that of MeOH, the plate count for phenol at room temperature is lower by about a factor of 1.1,1.4 depending on the flow rate. However, van Deemter plots show that this loss in plate count at 1 mL/min can be recovered and improved from 1500 to 2400 plates by working at a slightly elevated temperature of 55C. A slower flow rate such as 0.8 mL/min can also substantially improve the plate count as compared to 1,1.5 mL/min. Log P (octanol partition coefficient) versus log k, data for a variety of neutral test solutes are again similar whether EAF or MeOH is used as the organic modifier. Resolution of certain peak pairs such as 2,4-dinitrophenol/2,4,6-trinitrophenol and p -aminobenzoate/benzoate is enhanced using EAF as compared to MeOH. One advantage of EAF is that control of retention of solutes such as water-soluble vitamins under totally aqueous mobile phase conditions is environmentally preferable for quality control applications. In addition, EAF seems to be a milder mobile-phase modifier than MeOH for certain proteins such as lysozyme. [source]

Phospholipids in liquid chromatography/mass spectrometry bioanalysis: comparison of three tandem mass spectrometric techniques for monitoring plasma phospholipids, the effect of mobile phase composition on phospholipids elution and the association of phospholipids with matrix effects

Yuan-Qing Xia
Because plasma phospholipids may cause matrix effects in bioanalytical liquid chromatography/tandem mass spectrometry (LC/MS/MS) methods, it is important to establish optimal mass spectrometric techniques to monitor the fate of phospholipids during method development and application. We evaluated three MS/MS techniques to monitor phospholipids using positive and negative electrospray ionization (ESI). The first technique is based on using positive precursor ion scan of m/z 184, positive neutral loss scan of 141 Da and negative precursor ion scan of m/z 153. The second technique is based on using class-specific positive and negative selected reaction monitoring (SRM) transitions to monitor class-representative phospholipids. The third technique, previously reported, utilizes in-source collision-induced dissociation (CID)-based positive SRM of m/z 184,,,184. We recommend the all-inclusive technique 1 for use in qualitative assessment of all classes of phospholipids and technique 2 for use in quantitative assessment of class-representative phospholipids. Secondly, we evaluated the elution behaviors of the plasma phospholipids under different reversed-phase mobile phase conditions. The phospholipid-eluting strength of a mobile phase was mainly dependent on the type and amount (%) of the organic eluent and the strength increased in the order of methanol, acetonitrile and isopropyl alcohol. Under the commonly used gradient and isocratic elution schemes in LC/MS/MS bioanalysis, not all the phospholipids are eluted off the column. Thirdly, we investigated the association between phospholipids and matrix effects in positive and negative ESI using basic, acidic and neutral analytes. While the phospholipids caused matrix effects in both positive and negative ESI, the extent of ionization suppression was analyte-dependent and was inversely related to the retention factor and broadness of the phospholipids peaks. The lysophospholipids which normally elute earlier in reversed-phase chromatography are more likely to cause matrix effects compared to the later-eluting phospholipids in spite of the larger concentrations of the latter in plasma. Copyright 2009 John Wiley & Sons, Ltd. [source]