Direct Measurement of Acid Dissociation Constants of Trace Organic Compounds at Nanomolar Levels in Aqueous Solution by Condensed Phase–Membrane Introduction Mass Spectrometry

2019 ◽  
Vol 38 (9) ◽  
pp. 1879-1889 ◽  
Author(s):  
Jackelyn F. Feehan ◽  
Joseph Monaghan ◽  
Chris G. Gill ◽  
Erik T. Krogh
Keyword(s):  
Mass Spectrometry ◽  
Aqueous Solution ◽  
Organic Compounds ◽  
Condensed Phase ◽  
Dissociation Constants ◽  
Acid Dissociation ◽  
Trace Organic Compounds ◽  
Acid Dissociation Constants ◽  
Membrane Introduction Mass Spectrometry ◽  
Trace Organic

Equilibrium studies on lithium(I) transfer into ionic liquid with a water-soluble octabromoporphyrin (H2(OBTMPyP)4+) from aqueous phase

2009 ◽  
Vol 13 (08n09) ◽  
pp. 849-853 ◽  
Author(s):  
Takuya Shimomura ◽  
Masaaki Tabata ◽  
Jun Nishimoto
Keyword(s):  
Aqueous Solution ◽  
Ionic Liquid ◽  
Ion Exchange ◽  
Dissociation Constants ◽  
Equilibrium Constants ◽  
Water Soluble ◽  
Acid Dissociation ◽  
Acid Dissociation Constants ◽  
Equilibrium Studies ◽  
Counter Ions

A water-soluble octabromoporphyrin 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin (H2(OBTMPyP)4+), H2P4+) and its lithium complex, Li(OBTMPyP)3+ , (LiP3+) , transferred quantitatively to an ionic liquid (IL), 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM+PF6-) with no addition of other counter ions. The acid-dissociation constants of H2(OBTMPyP)4+ between aqueous and BMIM+PF6- phases were determined spectrophotometrically and found to be 10-7.67 and 10-11.33 at I = 0.1 for K a1,IL = [H+]aq[HP3+]IL/[H2P4+]IL and K a2,IL = [H+]aq[P2+]IL/[HP3+]IL , respectively. Since the acid-dissociation constants involve the partition of H2(OBTMPyP)4+ between aqueous and IL phases, the determined values are ten times as low as those observed in aqueous solution. The transfer equilibrium constants of LiP3+ and NaP3+ to IL defined by K MP,IL = [MP3+]IL/[M+]aq[P2+]IL (M = Li+ or Na+) were found to be 104.83 and 101.31 for K LiP,IL and KNaP,IL , respectively. LiP3+ transferred selectively in the presence of Na+ (K LiP,IL /K NaP,IL = 103.52) to IL phase through an ion-exchange mechanism between BMIM+PF6- and Li(OBTMPyP)3+ .

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