Study On The Speciation Of Calcium And Magnesium In The Complex System By Hyphenated Techniques

It is a well-known fact that the toxicity, bioavailability, and transport properties of an element are highly dependent upon its chemical species. In the past, total quantification of an element was used to determine potential health hazards or benefits, but in recent years, more and more research groups have acknowledged that elemental quantification alone is not sufficient. To completely understand the ways in which particular elements will affect living organisms, it is necessary to determine the species within which the elements are found, and to quantify those species. Analysis performed to identify and/or quantify one or more distinct chemical species in a sample is known as speciation analysis.The capillary electrophoresis (CE) is developed rapidly in the eighties of the 20th century as a novel separation and analysis technology. It is considered to be one of the strongest influence branches of analysis field at the end of last century, as well as the frontier of this field. It has many advantages: high efficiency, quick analysis speed, many analysis modes, little reagent consumption, wide application, easy automation, etc. Thus it shows extremely important application to life sciences, biotechnology, clinical medicine, medicine analysis and environmental science and so on.Microdialysis(MD) is a membrane-based sampling technique, in which the driving force behind the separation is the concentration gradient alone-an electrical field or an ionic strength gradient across the membrane. It allows monitoring within a physiological environment with a minimum of disturbance to the animal. Microdialysis sampling is a technique that has been used for in vivo and in vitro monitoring of compounds of pharmaceutical, biomedical, and environmental interest.Inductively coupled plasma atomic emission spectrometry (ICP-AES) offers extending good advantages in terms of low detection limit, high precision, wide linear range and simultaneous multi-elements determination, widely used in trace-element analysis fields in recent years. CE coupled with ICP-AES has the individual advantages of capillary electrophoresis and inductively coupling plasma spectrometry, it realized the combination of efficient separation and element alternative measurement. It was considered as a powerful analytical method. Microdialysis sampling technique places a constraint on the analysis method because of providing the very small sample volume. On the other hand, microdialysis provides the advantage of clean samples that do not require cleanup prior to analysis. An on-line coupling of microdialysis sampling to CE analysis is described that uses the advantages of microcolumn separations to overcome the small volume limitation. The MD-CE and MD-CE coupled with ICP-AES have the advantages of microsampling and separate detection analysis.The hyphenation of microdialysis capillary electrophoresis and inductively coupling plasma spectrometry has become a kind of rising separation and detection method. It can be applied to environmental protection, food, biology, clinic and Chinese Traditional Medicine (CTM), etc. It is well known that the physiology, toxicity, biogeochemical behavior, environmental behavior and transformation of trace toxic elements are highly depended on their chemical speciation to some great extent. Speciation analysis has already become an active front subject in environmental sciences, biochemistry and life sciences at present.In this paper, the research has been carried on foundation of microdialysis capillary electrophoresis and inductively coupling plasma atomic emission spectrometry and their application to the speciation analysis of complex systems, such as biological samples (blood, plasma) and Chinese herbs. The main contents were described as fellow:1. A new method for making an interface of the microdialysis(MD)-capillary electrophoresis(CE) and inductively coupled plasma atomic emission spectrometry(ICP-AES) is introduced. The feasibility of this method and its application are tested. The analysis performance of the interface has been studied, such as nebulizer flow rate, efficiency of nebulization, precision, detection limit. The experimental result shows this interface has these advantages: on line analysis, good stability, high nebulisation efficiency and high precision, and to avoide diluting samples. The application of the developed MD-CE-ICP-AES for the speciation analysis of Ca²⁺, CaEDTA^2-, Mg²⁺ and MgEDTA^2- is highlighted. The detection limit of these elements is lower than 18μg·L^-1, RSD for those lower than 5%.2. A new method for speciation analysis of magnesium species and quantification of free magnesium concentrations in rat plasma was developed by on-line coupling capillary electrophoresis (CE) with inductively coupled plasma atomic emission spectrometry (ICP-AES). Baseline separation of magnesium speciation was achieved by CE-ICP-AES in a 120 cm length×100μm inside diameter (I.D.) fused-silica capillary at 20 kV using a solution of 50 mmol·L^-1NaAc-HAc (pH=5.5) as electrolyte buffer. The forms of magnesium in rat plasma have seven different species. The free Mg²⁺ in the plasma was identified by the spiked standard magnesium and free magnesium concentration by peak area is 14.0mg·L^-1. The precisions (relative standard deviation, RSD, n=10) of migration time and peak area for the magnesium species were less than 5%. The recoveries of the free magnesium species in four samples were in the range of 95.8 to 103.8%.3. The analytical method for speciation analysis of the species of calcium and magnesium in rat blood was studied using ultrasonic-assisted dialysis coupled with inductively coupled plasma atomic emission spectrometry. Ultrasonic dialysis comparing with regular hemodialysis significantly improve the permeance of small molecular substances. The hyphenated technique is simple and convenient, which is fit for the separation and analysis of biological samples. The optimal separation of calcium and magnesium speciation was achieved by CE-ICP-AES in a 120 cm length×100μm inside diameter (I.D.) fused-silica capillary at 18 kV using a solution of 50 mmol·L^-1Tris-HCl (pH=7.4) as electrolyte buffer. The forms of calcium and magnesium in the dialysate of rat blood have four different species. Then the peak of free Ca²⁺ and Mg²⁺ in the dialysate was identified by the spiked standard species as them has the same retention time.4. Speciation analysis of Ca, Mg and determination of thirteen element in Blumea balsanifera and Dendrobium by Microwave Extraction and CE-ICP-AES. Using water as medium, the different species of calcium and magnesium was extracted from Chinese herb by microwave-asistant extraction. The speciation analysis of calcium and magnesium was studied by CE-ICP-AES. The results showed there were four and six species for Ca, four and three species for Mg in Blumea balsanifera and Dendrobium, respectively. And the free species of Ca, Mg were identified in the herbs. The contents of thirteen elements in the herbs have been determined by ICP-AES with microwave digestion. The recoveries of the Ca, Mg,etc. in the samples ranged from 97 to 106%. The results were in good agreement with the reference values.