Chiral electrokinetic chromatography‐electrospray ionization‐mass spectrometry using a double junction interface

Abstract

A double junction interface was utilized to preserve separation efficiency and alleviate ion suppression from sulfated β-cyclodextrin (S-β-CD) in electrokinetic chromatography-electrospray ionization-mass spectrometry. The utility of the approach was demonstrated by chiral EKC-MS analysis of dihydroxyphenylalanine and methyldihydroxyphenylalanine enantiomers using either low concentration (counter-migration mode; 0.1% S-β-CD) or high concentration (carrier mode; 2% S-β-CD). In the counter-migration mode, S-β-CD anions were supplied continuously from the junction reservoir to the separation column so that the effective separation length was preserved. This interface is especially useful under carrier mode in which high concentration of S-β-CD will migrate toward the ESI source. With the use of the double junction interface, the S-β-CD exited the separation column will remain in the junction reservoir, whereas the analyte will flow toward the ESI source through a connecting column. As a result, no ion suppression was observed and the sensitivity was improved significantly.

Chiral Separations using Miniaturized Techniques: State of the Art and Perspectives

“…With this approach, the authors obtained good results, avoiding contamination of the MS due to the absence of the charged CD in the interface also increasing the sensitivity. The CD was migrating in the counter‐flow mode . On the other hand, a similar approach was advanced by Fanali's and Chankvetadze's groups in 1998 for the separation of ibuprofen and some of its metabolites using CE‐MS with a commercial ESI interface and adding to the BGE vancomycin.…”

Recent advances in amino acid analysis by capillary electromigration methods, 2011–2013

“…dl ‐2‐amino‐2‐methyl‐3‐(3,4‐dihydroxyphenyl) propanoic acid (MDOPA) and dl ‐2‐amino‐3‐(3,4‐dihydroxyphenyl) propanoic acid (DOPA) enantiomers were separated and identified using electrokinetic chromatography ESI + MS . A double junction interface preserved separation efficiency and alleviated ion suppression from sulfated β‐CD (S‐β‐CD).…”

New approaches in sensitive chiral CE

“…Regarding MS detection, noteworthy that it has been the most employed alternative detection technique in the last two years, which demonstrates the high potential of the coupling CE‐MS for chiral separations. As it can be seen in Table , the methodologies developed have been realized by different CE modes, such as EKC , MEKC , CEC , and ligand exchange CE (LECE) , which have been coupled for the analytes detection to different mass analyzers as quadrupole, IT, triple quadrupole, and QTOF. Using EKC mode with CDs, additional strategies, such as PFT or CMT , have been employed in order to overcome the possibility of contamination of the ionization source induced by the chiral selector and to increase method sensitivity.…”

“…As it can be seen in Table , the methodologies developed have been realized by different CE modes, such as EKC , MEKC , CEC , and ligand exchange CE (LECE) , which have been coupled for the analytes detection to different mass analyzers as quadrupole, IT, triple quadrupole, and QTOF. Using EKC mode with CDs, additional strategies, such as PFT or CMT , have been employed in order to overcome the possibility of contamination of the ionization source induced by the chiral selector and to increase method sensitivity. PFT strategy has been carried out with a neutral CD (α‐CD) in combination with an ionic capillary coating (polybrene–dextran sulfate–polybrene) that reversed the EOF , and in combination with CMT when a negative CD (S‐β‐CD) was used in normal polarity (anionic CD migrated in counter current from the MS detector during the separation) .…”

“…PFT strategy has been carried out with a neutral CD (α‐CD) in combination with an ionic capillary coating (polybrene–dextran sulfate–polybrene) that reversed the EOF , and in combination with CMT when a negative CD (S‐β‐CD) was used in normal polarity (anionic CD migrated in counter current from the MS detector during the separation) . In the case of the CMT described by Hung et al , a double junction interface was employed to permit the use of phosphate buffer (because it provided better separation in comparison with the use of formate buffer) and an anionic CD (S‐β‐CD) under conditions of low pH (2.3) and normal polarity. Thus, phosphate and CD anions had a net mobility toward the junction reservoir and, therefore, the entrance in the ESI source was avoided to cause ion suppression, whereas the analytes flowed toward the ESI source through a connecting column.…”