Behavior of Cation-Exchange Materials in Capillary Electrochromatography

Cikalo, Maria G.; Bartle, Keith D.; Myers, Peter

doi:10.1021/ac980960s

Cited by 40 publications

(23 citation statements)

References 24 publications

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“…At low mobile phase pH, high EOF velocities can be realized through the introduction of strong cation-exchange (SCX) functionalities to the stationary phase. This also improves the separation of basic analytes by the dominating ion-exchange mechanism [23][24][25][26][27][28][29][30][31]. Retention in CEC is often assumed to result from independent contributions of the analytes' LC and CZE behavior.…”

Section: Introductionmentioning

confidence: 99%

Electrochromatographic retention of peptides on strong cation‐exchange stationary phases

Nischang¹,

Höltzel²,

Tallarek³

2010

Electrophoresis

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We analyze the systematic and substantial electrical field-dependence of electrochromatographic retention for four counterionic peptides ([Met5]enkephalin, oxytocin, [Arg8]vasopressin, and luteinizing hormone releasing hormone (LHRH) ) on a strong cation-exchange (SCX) stationary phase. Our experiments show that retention behavior in the studied system depends on the charge-selectivity of the stationary phase particles, the applied voltage, and the peptides' net charge. Retention factors of twice positively charged peptides ([Arg8]vasopressin and LHRH at pH 2.7) decrease with increasing applied voltage, whereas lower charged peptides (oxytocin and [Met5]enkephalin at pH 2.7, [Arg8]vasopressin and LHRH at pH 7.0) show a concomitant increase in their retention factors. The observed behavior is explained on the basis of electrical fieldinduced concentration polarization (CP) that develops around the SCX particles of the packing. The intraparticle concentration of charged species (buffer ions, peptides) increases with increasing applied voltage due to diffusive backflux from the enriched CP zone associated with each SCX particle. For twice charged and on the SCX phase strongly retained peptides the local increase in mobile phase ionic strength reduces the electrostatic interactions with the stationary phase, which explains the decrease of retention factors with increasing applied voltage and CP intensity. Lower charged and weaker retained peptides experience a much stronger relative intraparticle enrichment than the twice-charged peptides, which results in a net increase of retention factors with increasing applied voltage. The CP-related contribution to electrochromatographic retention of peptides on the SCX stationary phase is modulated by the applied voltage, the mobile phase ionic strength, and the peptides' net charge and could be used for selectivity tuning in difficult separations.

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Section: Introductionmentioning

confidence: 99%

Electrochromatographic retention of peptides on strong cation‐exchange stationary phases

Nischang¹,

Höltzel²,

Tallarek³

2010

Electrophoresis

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“…In order to achieve a higher EOF at pH values below 5 and hence a shorter analysis time, stationary phases with strong cation exchange (SCX) groups have been introduced for CEC [4 -11]. The assumption that these materials would generate an EOF independent of mobile phase pH value was not entirely fulfilled [6,7,12]. On using SCX phases for the separation of strongly basic pharmaceutical compounds (tricyclic antidepressants), abnormally high plate numbers in the range of several millions have been reported [4,5].…”

Section: Introductionmentioning

confidence: 99%

Capillary electrochromatography with bare silicas of different pore sizes as stationary phases

Steiner

Lobert²

2003

J of Separation Science

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Capillary electrochromatography with bare silicas of different pore sizes as stationary phases Bare silica can be used with reversed phase eluents for the chromatographic separation of basic analytes. It provides high surface charge density within a certain pH range, thus generating a high electroosmotic flow (EOF) when applied in electrochromatography. The influence of pore size on EOF velocity and mass transport is demonstrated. High EOF and fast mass transfer were encountered with 100 nm and 200 nm material and related to a pore perfusion mechanism. On a silica with 200 nm average pore size at pH 7, an EOF velocity of 2 mm/s was obtained at 600 V/cm. Silicas with pore diameters between 6 nm and 200 nm, corresponding to surface areas between 500 m/g and 10 m/g (data calculated from inverse size exclusion chromatography experiments), were used for CEC and HPLC separation of strongly basic solutes. On separation of tricyclic antidepressants by CEC, "normal" and "abnormal" efficiencies were achieved and were found to vary with the charge density within the separation column.

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“…Column preparation lytical tool for probing the Hanford nuclear site environment. Recently, Cikalo et al [24] have CEC columns with Spherisorb-SCX were packed studied the behavior of cation-exchange materials in by slurry packing technique as reported in the capillary electrochromatography. In this paper, the literature [21,25].…”

Section: Introductionmentioning

confidence: 99%

Separation of peptides by strong cation-exchange capillary electrochromatography

Zou

Liu

et al. 2000

Journal of Chromatography A

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Behavior of Cation-Exchange Materials in Capillary Electrochromatography

Cited by 40 publications

References 24 publications

Electrochromatographic retention of peptides on strong cation‐exchange stationary phases

Electrochromatographic retention of peptides on strong cation‐exchange stationary phases

Capillary electrochromatography with bare silicas of different pore sizes as stationary phases

Separation of peptides by strong cation-exchange capillary electrochromatography

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