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Affinity analysis is a key biotechnique used in the fields of biology and biomedicine. Herein, we advanced the concept of moving affinity boundary (MAB) using metal ion Ni(ii) and histidine (His) as the model inorganic ion and ligand, respectively, developed the simple method of MAB affinity capillary electrophoresis (MAB-ACE), and carried out the relative experiments. The experiments manifested that (a) an MAB could be created with the model metal ion and ligand; (b) the MAB-ACE could specifically capture His rather than other amino acids, or numerous metabolites in human urine; and (c) the capture had the merits of simultaneous focusing and separation to the target metabolite of His. It was further revealed that the specificity of MAB-ACE was originated from the selective affinity interaction and the effective control of affinity conditions. The analyses of His in raw urine by the MAB-ACE are in agreement with those viathe standard amino acid analyzer, indicating the reliability of the developed method. Additionally, the MAB-ACE with UV detector had good sensitivity (LOD = 43 ng mL−1, S/N = 3), 1.0–150 μM linearity and <5% intra-/inter-day variations. The novel method has an evident potential application for capture of a target metabolite in complex biological sample. [ABSTRACT FROM AUTHOR]

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 KCu(ii)(= 18.80) > log KCo(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. [ABSTRACT FROM AUTHOR]

Since 1970, a series of systematic investigations have been performed on three modes of moving reaction boundaries (MRBs), viz.moving precipitate boundary (MPB), moving neutralization boundary (MNB) and moving chelation boundary (MCB). So far, there has not been any review on them. Herein, we firstly review the MPB with respect to its velocity, product concentration, elution displacement, stacking effect, separation effect, judgment expressions and related procedures. We then make a review on the MNB about its theory, demonstration, improvement, and uses in isoelectric focusing (IEF), sample stacking, MNB-based stacking mechanisms and relevant computer simulations. We further give a review on the MCB regarding the relevant theory, verifications, and applications in EDTA-based sweeping and computer simulation. Finally, we give an outlook on the MRB study. More than 150 references are cited. [ABSTRACT FROM AUTHOR]