| Aflatoxins are a kind of the most toxic mycotoxins. Aflatoxin B1 is served as carcinogen I by IARC. AFB1 is not only of strong toxicity, but also widely pollute the environment. AFB1 pollution in grain is often reported, and the detection rate is as high as 80%～100%. Many developed countries and regions have set up strict limits for AFB1. Although the related limit in our country had been revised for times, it was obviously higher compared to international limits. Consequently, it is much necessary to increase detection sensitivity of AFB1. The aim of rapidness, accuracy quantification and simple operation can be achieved through detecting the derived fluorescence response after changing the nature weak fluorescence under the exposure of UV-light. It can be applied to different detection processes to improve sensitivity of each method. Meanwhile, it will resolve the problems such as high detection limits and not being acted on international convention.Nowadays, deriving methods mainly include electrochemistry derivitation, photochemistry derivitation and reagent derivitation. However, reagent deriving method was one of the lower cost, more efficient and convenient methods. Meanwhile, there were a lot of questions, such as heated needed by TFA and I2, produced on line by Br2, reagent prepared everyday, being largely corrosive and toxicy and so on, which made operation inconvenient, and the enhancing factor were not largly broken through. In recent years, as the second generation of supermolecule,β-CDs were gradually paid close attention to by scholars domestic and overseas in flied of food detection, because of the special construction of "lyophobic inside and hydrophile outside"and application of fluorescence enhancing to guest molecules such as medicine molecules and pigment. There have been researches to indicate thatβ-CDs can be applied as the novel fluorescence enhancing materials, because it is able to increase the fluorescence response of AFB1 in some degree, as same as economic and non-toxic. Nevertheless, these researches were concentrated on the binary system formed directly by AFB1 andβ-CDs. Therefore, being widly used has been limited as the drawbacks of long reaction time and easily effection of temperatue.With more and more attention paid on quality safty of agriculture products and food, stricter and stricter international limit set on AFB1, finding new sensitive deriving reagent to enhance AFB1 nature fluorescence was one of the AFB1 detecting technical development tendencies. In this paper, effection on AFB1 fluorescence byβ-CDs and metal iron was studied, a new fluorescence enhance reagent which was highly efficient and low cost was exploited and applied in AFB1 detecting method, fluorescence enhancing mechanisation was explored. As following were the main conclusions:(1) Fluorescence enhancement of AFB1 by system of M-β-CD was studied by fluorescence spectrophotometry. In system of Hg2+-β-CD, fluorescence intensity of AFB1 was markedly enhanced. When ratio of methanol in solvent was 50%, reaction molar ratio ofβ-CD and HgCl2 with AFB1 were both more than 300:1, the fluorescence enhancement could achieve the maximum-16 times, significantly higher than various derivation reported and in National standard.(2) Hg2+-β-CD was used as fluorescence enhancing agent to replace traditional derivation, in order to improve the detection sensitivity. And a high sensitive and rapid determination of AFB1 was established. The fluorescence intensity was linearly related to the AFB1 concentration in the range of 0.1～40μg/L with a correlation coefficient of 0.9998. The detection limit was 0.08μg/kg. The recovery was between 90～100% by spiking 10μg/kg of AFB1 in samples. There are no significant differences between the new method and national standard method, as well as fast method.(3) According to Benesi-Hidebrand Method, Thermodynamics Method, Ultraviolet Absorption Spectroscopy, Fluorescence Spectroscopy and KI Quenches Experiment, the fluorescence was protected as AFB1 inserted into the cavity ofβ-CDs to form binary complex systems. theβ-cyclodextrin and aflatoxin B1 formed 1:1 stoichiometries at low concentrations ofβ-cyclodextrin; 1:2 stoichiometries at high concentrations. The parameters ofΔG,ΔH andΔS are negative value. It indicates that the complexation reactions release heat and happen spontaneously. The enthalpy was the dominating force in the formation of inclusion complexes. At the same time, it was supposed that AFB1 was formed metallo-chelate with Hg, which was inserted into the cavity ofβ-CDs to form ternary complex as guest molecule. Then the rigid structure of AFB1 was enhanced to make the fluorescence largely increased. |
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