Research On Construction And Application Of Detection Methods On Trace Substances In Sorghum

The trace materials of tannin and heavy metal ions in sorghum grains are twoimportant factors in the evaluation on the quality of sorghum. The content of tannin hasa great influence on the output rate and taste of wine. The type and concentration ofheavy metals also are influential on wine’s quality and aging in the brewing process.Although the traditional detection of the two substances both have high sensitivity andgood detection effect, but they often need analysis and detection equipments,which arelarge and expensive, and also need professional personnels to operate. All these reasonsmake it difficult to realize real-time monitoring. Therefore, according to the existingtechnology problems, based on ferric（Ⅲ） can complex with thiocyanate ion and tannin,a fast and efficient detection method has been carried on. In addition, according oninhibition of heavy metal ions on urease and photosensitive effect of means ofporphyrin, urease-porphyrin materials have been screened which are sensitive to Cd²⁺,and the interaction of porphyrin and urease were preliminary studied. Researches werecarried out as follows:①Based on the property of ferric（Ⅲ） with thiocyanate and tannin occuringspecific reaction to form a stable three element metal ionic compounds, a new methodfor ferric thiocyanate spectrophotometric determination of the tannin in sorghum grainsorghum was established. The results showed that the color of liquid changedsignificantly after the reaction of ferric thiocyanate and tannin, and there was anobvious absorption peak at575nm. Specially, the detection can be finished within15mins. Under the optimized conditions, the concentration of tannins between0.0001-0.06mg/mL was obeyed the Lambert-Beer’s law. Correspondingly, theregression equation was Y=13.664X+0.0389, and the correlation coefficient R²was0.9993. The average recovery of this new method was in the range of95.50%¹04.00%,and the RSD<0.5%. Used this new method to determined tannins content in sorghumsamples, and the results were consisted with national standard test method（GBT15686-2008）.②After exploring the best conditions of test paper and tannin, a new rapid methodof ferric thiocyanate–chitosan to detect sorghum tannic was established. Ferricthiocyanate test paper method could complete the detection within5mins. under thecondition of pH=7.0⁹.0, that tannins reacted with ferric thiocyanate test paper proforming magenta stable complex, and the color of the paper was proportional to thecontent of tannins of sorghum samples. Then the content of tannins could bedetermined through the comparation with standard colorimetric card. Detection limitwas up to10^-3mg·mL-1. Using this new method to determine tannins content of sorghumsamples, it was found that the results could realize semi quantitative detection whichwas consisted with national standard test method（GBT15686-2008）.③In order to make the test paper realize quantitative detection, based on theprinciple of optical sensor, further Optimization of ferric thiocyanate test paper methodwas studied. The signal of the optical sensor showed that, when the concentration oftannins was in the range of10^-35g/L, there was a good linear relation. This method hashigh sensitivity, wide linear range, high average recovery rate as95.86%, and lowdetection limit reaching0.0002g/L.The results were consisted with national standardtest method（GBT15686-2008）, and the maximum relative difference were less than0.7%. In brief, the detection results was satisfactory.④A new complexes composed of urease and porphyrin was established usingUV-Vis spectroscopy, and the urease-porphyrin complexes which is sensitive tocadmium ion (Cd²⁺). The results showed when urease and non-soluble porphyrininteracting in tris-hydrochloric acid buffer solution, the spectral behavior ofnon-water-soluble porphyrin was affected, the maximum absorption peak of absorbanceand position were changed. The existing balance or structure was influenced by Cd²⁺.Research on the spectral behavior of urease-porphyrin complexes andurease-porphyrin-Cd²⁺complexes, it could found that the complexe of the highersensitivity were urease-ZnTPP and urease-TPPS1than that of other complexes. Theconstruction and screen of porphyrin materials were a solid foundation for a highlysensitive biosensor applying for metal ions detection.