Use of 6-O-mono-substituted derivatives of β-cyclodextrin-bearing substituent with two permanent positive charges in capillary electrophoresis

Abstract

This study details the use of two permanently positively charged mono-substituted β-cyclodextrin derivatives, 6^I -deoxy-6^I-(N,N N′,N′,N^t’-pentamethyl-ethylene-1,2-diammonio)-cyclomaltoheptose dichloride (PEMEDA-β-CD) and the newly synthesised 6^I-deoxy-6^I-(N,N,N′,N′,N′-pentamethyl-propylene-1,3-diammonio)-cyclomaltoheptose (PEMPDA-β-CD) as chiral selectors in capillary electrophoresis. Cyclodextrin (CD) derivatives were tested as additives in various buffers at various pH values with the optional addition of an organic modifier. Fourteen anionogenic analytes were tested, including native amino acids, N-blocked amino acids and profens, which were detected using a UV-VIS detector at optimal wavelengths of 214 nm, 254 nm or 280 nm. A borate buffer (15 mmol L⁻¹) at pH 9.5 without the addition of an organic modifier was chosen as a suitable background electrolyte. In addition, the effect of the concentration of the chiral selector on the separation and enantioseparation of selected analytes was monitored. The additions of cyclodextrin derivatives varied within the concentration range of 0.0–5.0 mmol L⁻¹. Both chiral selectors were suitable for the enantioseparation of N-Boc-d,l-tryptophan, which was already separated on the baseline at 0.5 mmol L⁻¹ concentration of the chiral selector.