Ion-Exchange Chromatography and Ion-Pair Chromatography. Complementation of HPLC Analysis of Amino Acids in Body Fluids by Pre-Column Derivatization Using Ortho-Phthaldialdehyde

1995 ◽  
Vol 18 (20) ◽  
pp. 4007-4028 ◽  
Author(s):  
Burkhard H. Klein ◽  
Joachim W. Dudenhausen
Keyword(s):  
Amino Acids ◽  
Ion Exchange ◽  
Hplc Analysis ◽  
Ion Exchange Chromatography ◽  
Ion Pair ◽  
Body Fluids ◽  
Exchange Chromatography ◽  
Ion Pair Chromatography

The Synthesis, Separation and Structures of Three [Co(cyclen)((S)-AlaO)]2+ Isomers. The Alkaline Hydrolysis of [Co(cyclen)((S)-AlaO)]2+

1998 ◽  
Vol 51 (6) ◽  
pp. 461 ◽  
Author(s):  
David A. Buckingham ◽  
David A. Buckingham ◽  
Charles R. Clark ◽  
Charles R. Clark ◽  
Andrew J. Rogers ◽  
...  
Keyword(s):  
Ion Exchange ◽  
Alkaline Solution ◽  
Spectroscopic Observation ◽  
Reversed Phase ◽  
Ion Exchange Chromatography ◽  
Ion Pair ◽  
Exchange Chromatography ◽  
X Ray ◽  
Ion Pair Chromatography ◽  
Hydrolysis Of

The reaction of [Co(cyclen)(OH2)OH]2+ (cyclen = 1,4,7,10-tetraazacyclododecane) with (S)-alanine at pH 7·2 gives a mixture of three [Co(cyclen)((S)-AlaO)]2+ isomers (1)–(3). These have been isolated by using both cation ion-exchange chromatography (Dowex 50 W×2, HCl eluent) and reversed phase ion-pair chromatography (C18, p-toluenephosphate in MeOH/H2O eluent). By using a combination of 1H n.m.r. techniques (n.O.e. and COSY) for solutions in (CD3)2SO the syn(N),anti(O) (1), syn(O), anti(N) (2) and syn(N), syn(O) (3) configurations have been assigned to these isomers. These have been confirmed by single-crystal X-ray analysis: [Co(cyclen)((S)-AlaO)] I2.H2O, isomer (1), P43212, a = b = 8·55150(10), c 51·8693(11) Å, Z 8, R 0·0343; [Co(cyclen)((S)-AlaO)] (ClO4)2.H2O, isomer (2), P212121, a 8·499(3), b 14·538(5), c 16·592(4) Å, Z 4, R 0·0388; [Co(cyclen)((S/R)-AlaO)] ZnBr4, a 1 : 1 mixture containing both (S)-alanine (isomer (3)) and (R)-alanine, P21/c, a 7·618(2), b 13·806(4), c 19·094(7) Å, Z 4, R 0·0726. In alkaline solution (0·1–1·0 M NaOH, 25·0°C, I = 1·0 M (NaClO4)), equilibration between (1), (2) and (3) is faster than hydrolysis to give cis-[Co(cyclen)(OH)2]++(S)-AlaO-. Time zero spectroscopic observation (300 nm) allowed the equilibrium constant, K, for the reaction [Co(cyclen)((S)-AlaO)]2+ + OH- ↔ [Co(cyclen – H)((S)-AlaO)]+ +H2O to be determined as 1·05 M-1 at 25·0°C and I = 1·0 M. The hydrolysis reaction follows the rate law kobs = kKK1K2[OH-]2/(1+K[OH-]+KK1K2[OH-]2) with k = 1·0 s-1 corresponding to rate-determining loss of (S)-AlaO- from the ring-opened complex, [Co(cyclen – H)((S)-AlaO)OH].

Sign in / Sign up

Export Citation Format

Share Document