Modified Kaolin And Its Application In The Chemiluminescence Ananysis

Chemiluminescence (CL) has the advantages of simple equipment, wide linear range, and fast analysis speed. In the CL analysis field, it is one of the current research focuses to develop some efficient catalysts to expand the scope of its application. Kaolin is a kind of environmentally friendly layered clay material. It is often be modified by some methods, such as high temperature calcinations, acid and alkali treatment, to prepare various kinds of catalysts, molecular sieve, and adsorbent, etc. In this work, we firstly apply the mofidied kaolin to the CL analysis as a catalyst, and newly establish the modified kaolin-ONOOH-calcein CL system. We mainly study the influence of the modified kaolin on the CL intensity of the kaolin-ONOOH-calcein system, investigate the modified kaolin CL behavior and the reaction mechanism, and successfully implement the sensitive rapid determination of the calcein in the environmental samples. It not only expands new applications of the kaolin material, but also establishes a new CL system with huge potential prospect.1. In this section, we developed a new type of high efficient CL reaction catalyst, modified kaolin, which sensitized the signals of the ONOOH-calcein system for more than 20 times. Based on powder X-ray diffraction, high resolution transmission electron microscopy, energy disperse spectroscopy, CL spectra, fluorescent spectra, free radical scavenger experiment, fluorescence lifetime, and fluorescence quantum yield, the mechanism of the modified kaolin catalyzed ONOOH-calcein CL system was proposed. On the one hand, modified kaolin has large specific surface area, which makes the regants enrichment, and it is advantageous to the chemical reaction. On the other hand, the mullite and P type molecular sieve phases in the modified kaolin have rich oxygen vacancies and a large number of reactive sites in the surface, which is conducive to the flowing of the electron cloud and improve the efficiency of the chemiluminescence resonance energy transfer (CRET). In addition, the modified kaolin changes the fluorescence of the calcein. The fluorescence lifetime and the fluorescence quantum yield of the calcein are both improved when it is mixed with the modified kaolin.2. Based on the enhancement of the modified kaolin to ONOOH-calcein CL, we have successfully applied the newly modified kaolin-ONOOH-calcein CL system to the calcein determination. Through a series of optimizing experiments, we choosed the best kaolin modification conditions and chemiluminescence analysis conditions. The CL intensity of the system is proportional to the concentration of calcein in the range of 0.1-100μM with the linear correlation coefficient 0.9995. The detection limit is 1×10-8 mol·L-1 (S/N=3). The proposed method to determine calcein by the newly CL system has good selectivity, high sensitivity, and fast response time, which can be used for calcein measurement in a real environment.