| Cysteamine hydrochloride has important animal nutrition value as the feed additive. However, it is easy to deliquescence with less resistance against temperature, and susceptible to oxidation under neutral and alkaline condition. In addition, it has a poor palatability to most livestock, these problems affect the promotion and application of cysteamine hydrochloride. In this paper, the author synthesis the complexes with cysteamine hydrochloride and Zinc sulfate heptahydrate as raw materialby adopting the technology of coordination chemistry, for stabilized of the cysteamine hydrochloride, and protecting the unstable thiol and amino stability of ligand. Study the the synthesis process and biological activity of the complexes of cysteamine with Zinc(II), and also extend the use of its modified glassy carbon electrode.The research content mainly includes the following parts:1. The complexes were synthesized with cysteamine hydrochloride and Zinc sulfate heptahydrate as main raw materials in aqueous solution. The composition and structure of the complexes were characterized by elemental analysis, infrared spectra, thermogravimetry, to determine the molecular formula of the complexes were(C2H7NS)2·Zn2Cl2, C4H12O2N2S2 Zn, C6H21O4N3S4Cl2Zn2, respectively. Thesolvent evaporation method is adopted to develop the single crystal of the complex 1, the crystal structure of the Zinc(II) complex belongs to monoclinic system, space group P 21/n, with cell parameters of a=0.84294(4), b=0.83920(4), c=1.65787(8) nm, Z=2, and D=2.041 g/cm3. Compound 1,(C2H6NS)2Zn.Zn Cl2, was synthesized by the complex ratio of the ligand to Zn(II) is approximately 1:1 in double distilled water according to the following reaction, a reaction p H of 6.5 was maintained by a 0.1 mol/L Na OH solution; the reaction was stirred and maintained at 80℃ for 1.5 hour; Compound 2,(C2H6NS)2Zn, was synthesized by the complex ratio of the ligand to Zn(II) is approximately 2:1 in double distilled water according to the following reaction, a 0.1 mol/L Na OH solution controlled the p H at 10, the reaction was stirred and maintained at 80℃ for 1.5 hours; Compound 3,(C2H7NS)3·Zn SO4·Zn Cl2, was synthesized by the complex ratio of the ligand to Zn(II) is approximately 3:2 in double distilled water. Na OH maintained the reaction p H at 5.5; the reaction was stirred and maintained at 70℃ for 1 hour.2. Under the temperature of 25℃, using p H potentiometric method to obtain proton constant(lg K1H10.92,lg K2H8.25), the dissociation constant(Ka15.62E-09,Ka21.20E-11) of cysteamine hydrochloriden, and the stability constants(lgk536.74) and thermodynamic functions(△rH$m=-157.14 k J/mol,△rS$m=176.74 J/mol/K,△rG$m=-209.60 k J/mol) of the complex of cysteamine hydrochloride with Zinc(II) ions, and calculated the conditional stability constants with different p H conditions. Zinc(II) ions and cysteamine hydrochloride coordination reaction is spontaneous exothermic reaction process, according to the result of △rG$m< 0, △rH$m< 0, △rS$m> 0. The stability constants and conditional stability constants of complex were large, it is observed that the complex of cysteamine hydrochloride with Zinc(II) ions was very stable.3. Investigates the nutritional value of complexes in high temperature, acid and alkali environment and mixed ions on its nutritional values.(1). Changing external environment and temperature, the content of cysteamine in complexes did not significantly change, suggests that along with the rise of temperature in the process of high temperature and feed processing, cysteamine will not oxidized by high temperature(120℃).(2). When m(complex) : m(calcium iodate) < 25:10, the cysteamine was completely oxidation of the complexes. When the feed was added one of the complexes, the content is no more than this range, avoid to cause cysteamine was no nutritional value by oxidation. When m(cysteamine zinc) : m(calcium iodate) > 100:1, the content of cysteamine was no change, very little oxidation of cysteamine, it can consider to add the ratio of complexesand oxidantzinc around 100:1.(3). Reductant has certain protective effect for the complexes, as the ratio of reducing agent, complexes and quality of copper sulfate was 5:5:1, cysteamine is not affected by copper ions.(4). In addition, in strong acidic conditions, three kinds of complexes could be released in full, with the acid decreased, the complexes only release the part. It shows that the PH increase against the release of cysteamine, probably because of alkaline environment, the complexes disaggregation reaction from the direction to the reverse reaction direction, thus reduce cysteamine to release a quantity.4. Research found that we studied the biological activity of the complexes, observed the cysteamine release rate above 75% within half an hour in the simulated intestinal gastric juice.5. And, the complex 3 modified glassy carbon electrode for the determination ofcopper in the solution of lysine copper chelating. |
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