doi:10.1016/j.chroma.2006.09.095
Copyright © 2006 Elsevier B.V. All rights reserved.
Chromatographic behaviour of peptides on a mixed-mode stationary phase with an embedded charged group by capillary electrochromatography and high-performance liquid chromatography
F. Progenta, M. Tavernaa, A. Bancob, A. Tchaplab and C. Smadjaa,
, 
aUniv Paris-Sud, JE 2495, Protéines et Nanotechnologies en Sciences Séparatives, F-92296 Châtenay-Malabry Cedex, France
bUniv Paris-Sud, EA 4041, Groupe de Chimie Analytique de Paris-Sud, F-91400 Orsay, France
Received 22 July 2005;
revised 11 September 2006;
accepted 22 September 2006.
Available online 1 November 2006.
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Abstract
Retention behaviour of biological peptides was investigated on a stationary phase bearing an embedded quaternary ammonium group in a C21 alkyl chain by both high-performance liquid chromatography (HPLC) and capillary electrochromatography (CEC). In HPLC experiments, variation of acetonitrile (ACN) content in the mobile phase showed that peptides are mainly separated by RP mechanism. The weak or negative retention factors observed as compared to C18 silica stationary phase suggested the involvement of an electrostatic repulsion phenomenon in acidic conditions. Comparison of HPLC and CEC studies indicated that (i) ion-exclusion phenomenon is more pronounced in HPLC and (ii) higher ACN percentage in mobile phase induce for some peptides an increase of retention in CEC, pointing out the existence of mechanisms of retention other than partitioning mainly involved in chromatographic process. This comparative study demonstrated the critical role of electric field on peptide retention in CEC and supports the solvatation model of hydrolytic pillow proposed by Szumski and Buszewski for CEC using mixed mode stationary phase in CEC.
Keywords: Chromatographic retention; Capillary electrochromatography; Mixed mode stationary phase; Peptides
Fig. 1. Plot of the log(k) vs. ACN percentages in the mobile phase. Column: Stability BS-C23, 300 Å, dp = 5 μm, 250 mm × 2 mm, mobile phase: phosphate buffer, pH 2.5/ACN, from 40/60 to 100/0 (v/v). Buffer concentration in mobile phase: 50 mM. Analytes: eledoisin (□), renin substrate (
), FGGF (×), eledoisin RP (●), Arg-Arg-gastrin (*), EGF (Δ).
Fig. 2. Chromatograms of eledoisin RP (0.1 mg/ml) obtained on the Stability BS-C23, (A) with 5% ACN (v/v); (B) without ACN in the mobile phase. Column: Stability BS-C23, mobile phase: phosphate buffer, pH 2.5/ACN. Total buffer concentration in mobile phase: 50 mM.
Fig. 3. Relationship between the Si and physico-chemical characteristics of the investigated peptides (A) peptide mass and (B) hydrophobicity. Column: Stability BS-C23, mobile phase: phosphate buffer, pH 2.5/ACN, from 40/60 to 100/0 (v/v). Total buffer concentration in mobile phase: 50 mM.
Table 1.
Physico-chemical characteristics of investigated peptides
a The embl-heidelberg.de: EMBL WWW Gateway to Isoelectric Point Service was employed for calculating the p
I values as well as the net-charge values of peptides at different pHs.
b Hydrophobicity was estimated on www.expasy.org with Protscale, using parameter of Kyte and Doolittle
[20].
Table 2.
Chromatographic retention factor in HPLC and in CEC at 60 and 20% of ACN in the mobile phase
