The Study On The Stacking Of Trace Heavy Metal Ions Via Moving Neutralization Boundary Electrophoresis And Its Application

The environmental pollution hazards have caused great attention of human. In all kindsof environmental hazards, the disease caused by heavy metal ions (HMIs) is too numerous tomention individually, therefore, it is of great importance to develop an efficient and sensitivedetection technique for the trace analysis of HMIs. The application of traditional analysismethods of HMIs is limited due to the common problems of complex operation, lowsensitivity, large sample volume and high cost. In recent years, the theoretical andexperimental study of moving reaction boundary (MRB) is developing rapidly. Movingneutralization boundary (MNB) has been widely used in the field of biological chemicalanalysis including the basic research of isoelectric focusing and titration as well as thestacking of amphoteric analyte, protein and small molecular drugs. However, it was rarelyreported that the concept of MNB was used for the sample condensation of HMIs. In thispaper, MNB was used to the condensation of HMIs for the first time. A novel method of traceanalysis of HMIs with visual offline sample stacking via MNB is established and it has beensuccessfully used for the stacking and the detection of heavy metal ions in electroplate wastewater. The main points of this paper are summarized as follows:1. Preliminary establishment of the novel model of offline sample stacking for the traceanalysis of HMIs via capillary electrophoresis (CE). In the Chapter2, based on the theory ofMNB and moving precipitation boundary (MPB), we established the model of offline samplestacking for the trace analysis of HMIs via CE, elaborated on the stacking mechanism of thismodel, and derived the expression of the velocity of the cathodic-direction boundary.2. Experimental verification of the novel model of offline sample stacking for the traceanalysis of HMIs via CE. In the Chapter3, specific experiments were done to verify theexpression of the velocity of the cathodic-direction boundary. The experiment results agreedwell with the prediction and we can draw conclusions as follows:(1) the moving velocity anddirection of MNB system could be controlled by the relative fluxes of hydrogen ion in phaseα and hydroxyl ion in phase β;(2) the MNB-based sample stacking could result incontrollable pre-concentration of mode metal ion of copper, and higher than120foldpre-concentration of copper ion was achieved;(3) strong stacking efficiency is present in the cathodic-direction rather than anodic-direction MNB system;(4) five model HMIs weresuccessfully stacked together with the MRB-based stacking technique.3. Practical application of the novel model of offline sample stacking for the traceanalysis of HMIs via CE. In the Chapter4, further method validation was done to this noveltechnology of offline sample stacking for the trace analysis of HMIs via CE and thedeveloped method has been successfully used for the stacking and the detection of heavymetal ions in electroplate waste water. Six metal ions in the waste water was stacked anddetected and the pre-concentration factors are up to77.41-150. The LODs are obviouslylower than the national standards. The intra-day and inter-day assay precisions and accuraciesare well and the relative standard deviations (RSDs) were less than7.42%.