Ion chromatography chelation

The selectivity characteristics of high performance chelation ion chromatography when separating a range of metal ions with a number of complexing eluents has been investigated (71). 

The exploitation of competitive metal complexation between ligands in the eluent and surface bonded chelating groups allows a wide range of control over the retention order and the selectivity coefficients of several groups of metal ions. 

Oxalic acid Picolinic acid Dipicolinic acid 

According to Eq. (4.21), the bidentate ligand ethylenediamine forms a chelate complex in form of a five-membered ring. In Eq. (4.22), the bidentate ligand is replaced by two monodentate methylamine ligands of approximately the same donor power, meaning that the enthalpy of the Cu—bond formation is approximately the same in the two reactions. 

Copper complexes with ethylenediamine (left) and methylamine (right) 

The simplest procedure for the preparation of chelating stationary phases is the coating of poly(styrene-co-divinylbenzene)-based resins. This type of surface modification works well with aromatic dyes such as aurintricarboxylic acid [63] or quinaldic acid [64], because they strongly adsorb on styrene-based resins due to hydrophobic and n-tt interactions. 

However, separation efficiency of this type of stationary phase is not very high because of the low conformational mobility of the adsorbed dyes. The most widely applied chelating stationary phases for HPCIC are those with covalently bonded ligands at the substrate surface, which provide enhanced accessibility for 

Historically, organic polymers with various covalently functionalized chelating groups were the dominating chelating stationary phases. A very well-known product of this type is Chelex 100 (Bio-Rad Laboratories, Hercules, 

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Pauli B, Foulkes M, Jones P. 1994. Determination of alkaline earth metals in offshore oil-well brines using high-performance chelation ion chromatography. Anal Proc 31 209-211. 

Truscott, J. B., Jones, P., Fairman, B. E., and Evans, E. H., Determination of actinides in environmental and biological samples using high-performance chelation ion chromatography coupled to sector-field inductively coupled plasma mass spectrometry, J. 

See ION EXCHANGE Ion Chromatography Instrumentation Ion Chromatography Applications Chelation Ion Chromatography Isotope Separation... 

Figure 2 Isocratic separation of standard mixture of 14 lanthanides and yttrium on a 250 mm x 4 mm column, packed with 5 pm silica IDA. Eluent 1.6x 10" moll" HNO3 with 0.5moll KNO3 flow rate 1.0 ml min " k column temperature 65°C, sample volume 20 pi, sample concentration of each metal was 4 ppm in 0.2% HNO3. Detection, Arsenazo III postcolumn reaction at 658 nm. (Reprinted with permission from Nesterenko PN and Jones P (1998) Isocratic separation of lanthanides and yttrium by high performance chelation ion chromatography. Journal of Chromatography A 804 223-231 Elsevier.)...

Figure 1 Separations on silica IDA columns with different elution protocols. (A) Isocratic separation of four metal ions on a 100mmX4mm column packed with 5pm IDA silica. Eluent, lOmmoll nitric acid. Detection, PAR postcolumn reaction at 510nm. (Unpublished work, Nesterenko PN and Jones P.) (B) Isocratic separation of five metal ions on a 250 mm x 4 mm column packed with 5 pm IDA silica. Eluent, 0.5 mol I KCI, 20mmoll picolinic acid, and 12.5mmoll" nitric acid. Detection, PAR postcolumn reaction at 510 nm. (Unpublished work, Nesterenko PN and Jones P.) (C) Step gradient separation of Mn(ll), Cd(ll), Co(ll), Zn(ll), and Pb(ll). Eluent conditions 0.1 mol r NaCI (pH 2.6) switched to 0.1 mol 1 NaCI (pH 1.6) at time = 3 min prior to standard injection. Column, 250mm X 4 mm, packed with 8 pm silica IDA. Detection, PAR postcolumn reaction at 495 nm. (Reprinted with permission from Bashir W and Pauli B (2002) Ionic strength, pH and temperature effects upon selectivity for transition and heavy metal ions when using chelation ion chromatography with an iminodiacetic acid bonded silica get column and simple eluents. Journal of Chromatography 942 73-82 Elsevier.)...

Figure 3 The separation of Ba(ll) 1.5 ppm, Ni(ll) 1 ppm, Co(ll) 2 ppm, Zn(ll) 1 ppm, Pb(ll) 5 ppm, Cd ll) 2.5 ppm, Mn(ll) 1.5 ppm, and Cu(ll) 5 ppm on the aminophosphonic acid functionalized silica column, 250 mm x 4.6 mm. Eluent ImolT KNO3, 5 mmol 1 HNO3. Detection, PAR/ZnEDTA postcolumn reaction at 495 nm. (Reprinted with permission from Nesterenko PN, Shaw MJ, Hill S, and Jones P (1999) Aminophosphonate-functionalised silica A versatile chromatographic stationary phase for high performance chelation ion chromatography. Microchemical Journal 62-. 58-69 Elsevier.)...

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