Laboratory of Analytical Biochemistry and Bioseparation, Key Laboratory of Microbiology of Educational Ministry, School of Life Science and Biotechnology, Shanghai Jiao Tong University, Shanghai, China.
Kohlrausch regulating function (KRF) has been well defined from a moving boundary system for over 50 years. Recently, a series of theoretical and experimental studies were carried out on the concept of moving reaction boundary (MRB), including moving precipitate boundary, moving neutralization boundary and moving chelation boundaries (MCB). However, there has not been any direct evidence to show whether the KRF has validity for a MRB or not. In this paper, the KRF is derived from the equation of MRB under condition of nonzero boundary velocity. The result directly shows the relation between the KRF and a MRB. The relation is verified by some experimental and simulation results on MCB and moving neutralization boundary as well as Svensson's classic IEF. Furthermore, a Kohlrausch inequality was defined from the equation of MRB and was further proved by numerous data. The results show that we can use the KRF for the investigation on a MRB under the condition of nonzero boundary velocity, whereas we ought to notice with great attention that the KRF does possibly have invalidity under some special cases, such as stationary electrolysis and IEF. The findings hold an evident significance to the study of a MRB with the KRF.
[Show abstract][Hide abstract] 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.
The Analyst 01/2010; 135(1):140-8. DOI:10.1039/b912799b · 4.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The condensation of low abundance zwitterion substance, such as protein and peptide, has great significance to the study on proteomics. This paper develops the theory on design of online stacking conditions of zwitterion by a moving reaction boundary (MRB) in capillary electrophoresis (CE). This concerns the choice of running and sample buffers, velocity design of MRB, and salt effect on the stacking. The theoretical results unveil that: (1) the velocity of MRB formed with weak acidic buffer and strong alkali should be set between zero and the velocity of zwitterion in the alkali phase, or no stacking occurs; (2) if a strong alkali is used to prepare the sample, a much long front plug of strong base must be injected before the alkaline sample plug for complete stacking, whereas no such front plug is needed if a weak alkali with enough high concentration and pH value is used to prepare the sample buffer; (3) the existence of salt in sample matrix has a weak effect on the stacking of zwitterion if sample is prepared with weak alkaline buffer, while has a dramatic effect on the same stacking if with a strong base buffer. In addition, the concentration of weak alkali used for preparation of sample should be set at the point, at which the velocity of MRB is as much as possible close to that of negative zwitterion. The developed theory and its computation are quantitatively proved by the experiments of zwitterion stacking by the MRB as shown in the previous and the accompanying papers. The proposed theoretic results hold obvious significances on-column stacking of low abundance zwitterions, such as amino acid, or peptides or proteins, in CE.
[Show abstract][Hide abstract] ABSTRACT: This article is the seventh in a series examining biannually the methodological developments in the field of CE analysis of inorganic species and covers relevant documents published between January 2009 and December 2010. Following an analysis of the significant accomplishments that have impacted the field in two recent years, a survey of advances in general CE methodology is presented. Subsequently, several notable trends that can be perceived in this well-established field are discussed: the continuing rise of ME and consequent development of suitable detection techniques, most notably contactless conductivity detection, the constant pace of advances in speciation analysis, and an increase in non-analytical CE applications to study complexation and (bio)transformation reactions of metal analytes. A range of recently emerged multi-detection designs, ICP-MS interface devices, and separation systems, for which outpacing work has been conducted, are also brought into focus.
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