Premium
Compatibility of highly sulfated cyclodextrin with electrospray ionization at low nanoliter/minute flow rates and its application to capillary electrophoresis/electrospray ionization mass spectrometric analysis of cathinone derivatives and their optical isomers
Author(s) -
Moini Mehdi,
Rollman Christopher M.
Publication year - 2014
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.7106
Subject(s) - chemistry , capillary electrophoresis , chromatography , electrospray ionization , mass spectrometry , electrospray , analytical chemistry (journal) , cyclodextrin
RATIONALE Sodium salts of cyclodextrins are commonly used in capillary electrophoresis/mass spectrometry (CE/MS) analysis of illicit drugs and their optical isomers. To avoid the suppression effect of cyclodextrins under electrospray ionization (ESI), the partial filling technique (PFT) is commonly utilized, which has a limited resolution. Low‐flow nano‐ESI has been shown to reduce the suppression effect of the salts. To test the compatibility of low‐flow ESI with a background electrolyte (BGE) containing sodium salts of cyclodextrin, sheathless narrow capillary CE/MS with flow rates of low nanoliters/minute (nL/min) was applied to the separation and detection of cathinones and their positional and optical isomers for the first time. METHODS Low‐flow sheathless CE/MS using a 20‐µm‐i.d. capillary in conjunction with a porous tip interface was used for the separation of cathinone derivatives and their optical isomers. Highly sulfated γ‐cyclodextrin (HS‐γ‐CD) in conjunction with (+)‐18‐crown‐6‐tetracarboxylic acid ((+)‐18‐C‐6‐TCA) was used as the BGE and an ion trap mass spectrometer operating in full scan mode was utilized. RESULTS Utilizing low flow rate (~10 nL/min) sheathless CE/MS, the use of the sodium salt of HS‐γ‐CD as the BGE was compared with the same solution using PFT. The relative and absolute sensitivity of detection of cathinones were about the same, indicating that under low‐flow sheathless CE/MS there was no significant suppression due to the existence of HS‐γ‐CD in the electrospray process. However, enhanced resolution of cathinone derivatives and their positional and optical isomers was observed when the solution of HS‐γ‐CD was used as the BGE. The enhanced resolution was because of the presence of the HS‐γ‐CD in the entire capillary during the analysis. The addition of 15 mM (+)‐18‐C‐6‐TCA to the BGE containing HS‐γ‐CD further enhanced the resolution resulting in separation of all cathinones and their positional and optical isomers. CONCLUSIONS A novel CE/MS technique has been introduced that combines low‐flow sheathless CE/MS, with HS‐γ‐CD and 15 mM (+)‐18‐C‐6‐TCA as the BGE for separation of cathinone derivatives as well as their positional and optical isomers. Copyright © 2014 John Wiley & Sons, Ltd.