A novel isotachophoresis of cobalt and copper complexes by metal ion substitution reaction in a continuous moving chelation boundary

Abstract

A novel separation mode of isotachophoresis (ITP) was advanced for the study on the continuous moving chelation boundary (MCB) formed with EDTA and two metal ions of Co(II) and Cu(II). The experiments were performed systemically. The relevant results indicated that: (1) there were three boundaries in the whole system, viz., a sharp MCB, a wide moving substitution boundary (MSB) and a sharp complex boundary (CB); (2) within the MSB, an ion substitution reaction occurred between [Co-EDTA](2-) and Cu(II), and the reaction resulted in the release of Co(II) and EDTA from [Co-EDTA](2-) and the binding of Cu(II) with the released EDTA due to log K(Cu(II)) (= 18.80) > log K(Co(II)) (= 16.31); (3) because of the novel ITP mode induced by the MSB as well as the merging of the MCB and CB, the original low concentration Co(II) and Cu(II) were chemically separated as two characteristic coloured zones of pink [Co-EDTA](2-) and blue [Cu-EDTA](2-), and the sensitivities for detection of the two metal ions were greatly enhanced. The quantitative analyses of the zone composition by ICP-AES and UV-vis spectrophotometry supported the mechanism of the novel separation mode induced by the MSB. The further theoretical and experimental results indicated that the separation mode was a novel ITP relied on moving reaction boundary (MRB), rather than a classic ITP based on the moving boundary system developed about 60 years ago. These findings provide guidance for the development of the MRB and the MCB-based ITP separation of metal ions in environmental and biological matrices.

Colorimetric assay for parallel detection of Cd2+, Ni2+and Co2+using peptide-modified gold nanoparticles

“…Glutathione (GSH) was chosen as a masking agent for Cd 2+ due to the interaction between Cd 2+ and thiols, 14 imidazole as a masking agent for Ni 2+ due to its chelation ability toward Ni 2+ , 4 and EDTA forms especially strong complexes with Co 2+ . 15 At first, we tested the feasibility and specificity of these masking agents toward metal ions (Cd 2+ , Ni 2+ , and Co 2+ ) in our proposed method (Fig. 6A, 6B, and 6C).…”

Equivalence‐point electromigration acid–base titration via moving neutralization boundary electrophoresis

“…proteins, or peptides, or amino acids) and drugs in capillary electrophoresis (CE) [24-26, 31, 32] and condensation of target compound in free-flow electrophoresis (FFE) [33]. Third, the concept of moving chelation boundary has been applied for the illumination on mechanism of EDTA-based sample sweeping of heavy metal ions in CE [24,27]. Fourth, the newly developed ideal of MAB has been used for the selective capture of a target metabolite in complex biomatrix of human urine [28].…”

“…In 1990s, the idea of equivalent electromigration reaction between H 1 and OH À was developed for protein concentration [23]. During the last decade, Cao et al [24][25][26][27] advanced systemic theories and methods of MRB, such as moving precipitate boundary [24], neutralization boundary (MNB) [24][25][26], chelation boundary (MCB) [24,27] and affinity boundary [28]. Supporting Information Fig.…”

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2010–2012)

“…Methods that exploit metal complex formation benefit from the localised concentration effects to enhance complex formation. Zhang et al reported the concentration and separation of Co 2+ and Cu 2+ complexes with EDTA . The separation is based on differences in metal‐EDTA complex formation constants and the formation of metal ion substitution reaction in a continuous moving chelation boundary (MCB).…”