Complexation equilibrium between iron(III) and N,N'-bis(2-hydroxyphenylmethyl)-N,N'-bis(2-pyridylmethyl)-1,2-ethanediamine

Abstract

). Furthermore, most of foreign metal cations did not influence largely the determination of Fe(III).

Enhanced Retention of Chelating Reagents in Octadecylsilyl Silica Phase by Interaction with Residual Silanol Groups in Solid Phase Extraction of Divalent Metal Ions

“…13,14 In order to gain more insight into and develop the potential of this methodology, we have examined SPE of divalent metal ions with a potentially divalent hexadentate and more lipophilic chelating reagent, N,N′-di(4-chlorophenol-2-ylmethyl)-N,N′-di(pyridin-2-ylmethyl)ethane-1,2-diamine (H2L, distribution constant between H2O and CHCl3: 10 5.12 ) and have compared its performance with that in LLE already reported elsewhere. [15][16][17][18] This is the first time to demonstrate that the residual silanol group in the ODS phase plays an important role in retention of the reagent for SPE.…”

“…16 Although HSO4 -, ClCH2COO -or deprotonated silanol group is expected as the counter anion in this extraction system, further equilibrium analysis is beyond the scope of this study.…”

“…The actual difference in pH1/2 was 0.9 -1.1 (pH1/2 of 3.3 compared with 4.4 16 for Zn 2+ , 6.1 compared with 7.0 16 for Mn 2+ ). The practical concentration H2L in the ODS phase except silica body (14.3 wt%) was, however, 0.56 mol kg -1 , while the concentration in chloroform was 0.0068 mol kg -1 .…”

“…The difference in pH1/2 of Zn 2+ and Mn 2+ was similar in the respective extraction systems (2.8 in SPE, 2.6 in LLE). 16 The selectivity in LLE was also quantitatively kept in the SPE.…”

“…16 Strong coordination of nitrogen atoms of this reagent to these soft metal ions may interfere with coordination of one of two phenol groups, so as to give a protonated complex. This complex is extracted into an organic solvent or the ODS phase as an ion-pair with some anion, A-, as given by Eq.…”