Accessible silanol sites - beneficial for the RP-HPLC separation of constitutional and diastereomeric azaspirovesamicol isomers.
Different RP-HPLC columns (phenyl, conventional ODS, cross-linked C(18) and special end-capped C(8) and C(18) phases) were used to investigate the separation of four basic ionizable isomers. Using ACN/20mM NH(4)OAc aq., a separation was observed exclusively on RP columns with higher silanol activity at unusual high ACN concentration, indicating cation-exchange as main retention mechanism. Using MeOH/20mM NH(4)OAc aq., another separation at low MeOH concentrations was observed on both, RP columns with higher as well as RP columns with lower silanol activity, which is mainly based on hydrophobic interactions. The isomers were also separated on a bare silica column at higher MeOH content using NH(4)OAc. Since cation-exchange governs this retention, the elution order was different compared to the RP phases. A strong retention on the silica column was observed in ACN, which could be attributed to partition processes as additional retention mechanism.
Forschungszentrum Dresden-Rossendorf, Research Site Leipzig, Institute of Radiopharmacy, Permoserstr. 15, 04318 Leipzig, Germany. b.wenzel@fzd.de
Barbara
B
Wenzel
Steffen
S
Fischer
Peter
P
Brust
Jörg
J
Steinbach
D000097:Acetonitriles; D001372:Aza Compounds / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D056148:Chromatography, Reverse-Phase / Q000379:methods*; D007536:Isomerism; D010880:Piperidines / Q000737:chemistry* / Q000378:metabolism; D012821:Silanes / Q000737:chemistry* / Q000378:metabolism
D000097:Acetonitriles; D001372:Aza Compounds; D010880:Piperidines; D012821:Silanes; C082343:silanol; C006189:vesamicol; C032159:acetonitrile