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Influence of capacity on the retention characteristics in Zwitter Ion Chromatography (ZIC) and ZICHydrophilic Interaction Chromatography (HILIC) onfour different sulfobetaine stationary phases
A number of covalently bonded zwitterionic stationary phases with inner quaternary amines and outer sulfonic acids in varying capacities was synthesized based on poly (styrene-DVB) particles by graft polymerization. The different spacer lengths and capacities are used as an investigative tool, fo...
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| Format: | Doctoral Thesis |
| Language: | English |
| Published: |
Philipps-Universität Marburg
2014
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| Online Access: | PDF Full Text |
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| Summary: | A number of covalently bonded zwitterionic stationary phases with inner quaternary amines
and outer sulfonic acids in varying capacities was synthesized based on poly (styrene-DVB)
particles by graft polymerization. The different spacer lengths and capacities are used as an
investigative tool, for the retention behavior of the inorganic anions in ZIC and ZIC-HILIC
modes. The separation mechanism is explored by varying eluent ionic strength, eluent pH
and the volume fraction of organic modifier. Remarkably, the increasing capacity exhibits
different characteristics of anions retention for all exchangers in two modes. Hence, this
leads to increased, decreased or no significant change in the retention times of inorganic
anions. Moreover, no change in the separation mechanism and selectivity of anions occurred
when investigating the influence of eluent concentration, pH of eluent and acetonitrile
content for various capacities of zwitterionic columns. It should be noted that high values
of the capacity of the SB2-exchanger exhibit a different separation mechanism for inorganic
anions in comparison to a previous study made for the ZIC-mode. Furthermore, a new
correlation between spacer length and the capacity and their impact on the retention time
of anions in ZIC and ZIC-HILIC modes were found. The results of variations of acetonitrile
content, buffer concentration and mobile phase pH show that pharmaceuticals can be separated based on hydrophilic, hydrophobic and anion/cation-exchange interactions between
the stationary phase and analyte. For a differentiation between the separation mechanism
for the first time a set of cation and anion exchangers based on the same core material has
been used as investigative tool. In addition, we have proven the suitability of ZIC-HILIC stationary
phases for the determination of the chromatographic hydrophobicity parameter.
The pharmaceutical deferoxamine mesylate (DFOM) is a chelating agent which forms complexes
with multiple charged metal ions of biological importance (Fe3+, Al3+) and other metals.
We could demonstrate that the sulfobetaine exchangers are able to separate the Fe(III)-
DFOM and Al(III)-DFOM complexes by IC-ICP-AES. The results of the eluent ionic strength
and pH variations show that metal-DFOM complexes were separated based on a cation exchange
mechanism.
Excess adsorption isotherms of water from acetonitrile were measured for ten zwitterionic
stationary phases (eight sulfobetaine exchangers have been prepared and two commercially
available stationary phases) using the minor disturbance method. The retention factors of
the eight pharmaceutical compounds (Deferoxamine mesylate, Thiamine.HCl, Diclofenac
sodium, Cyclopentolate.HCl, Dexamethasone sodium phosphate, Tetracaine.HCl, Pilocarpine
.HCl and Chloramphenicol) can be correlated with the maximum excess of water adsorption. |
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| DOI: | 10.17192/z2014.0498 |