Gottardi W
Institute for Hygiene, University of Innsbruck, Austria.
Arch Pharm (Weinheim). 1999 May;332(5):151-7. doi: 10.1002/(sici)1521-4184(19995)332:5<151::aid-ardp151>3.0.co;2-e.
Although they have been in use for nearly 170 years, the mode of action of iodine-based disinfectants is not yet clearly understood, as is manifested, for example, in diverging judgements about the relevance of the individual iodine species. Although studies based on calculated equilibrium concentrations in pure iodine solutions have already been done, there is a lack of knowledge about iodine solutions in the presence of additional iodide which would be of intrinsic importance for disinfection practice. Therefore, a re-calculation was undertaken considering variations of this parameter in the pH range 0-14. The presented calculations concern fresh iodine solutions not affected by disproportionation (iodate formation) and provide information about the equilibrium concentrations of the species I, I2, I3, I5-, I6(2-), HOI, O1-, HI2O-, IO2- and H2OI+. Additional iodide and the pH value have a very pronounced influence on the individual equilibrium concentrations (several powers of ten); hence, conditions can be indicated where the number of species of virtual importance is drastically reduced. In the most common case with iodine in the presence of additional iodide at pH < 6, only I-, I2 and I3- play a role. In the absence of additional iodide, at pH 8-9 and at high dilution (c(I2) < 10(-5) M), on the other hand, HOI accounts for over 90% of the oxidation capacity. At high iodide concentration (e.g., Lugol's solution) the species I5- and I6(2-) make up 8.2% of the oxidation capacity. The iodine cation H2OI+, frequently quoted as an active agent in disinfection, is without any relevance under the conditions occurring in practice, as are IO- and HI2O- which become important only at pH > 10. The stability problem (i.e. rate of iodate formation) arising at pH > 6 can be reduced to hypoiodous acid, as manifested in the simple rate law d[IO3]/dt = 0.25 [HOI]3/[H+] which allows an estimation of stability under weakly alkaline conditions. The results of this study allow us to deduce general qualities of aqueous iodine solutions, such as reactivity, stability, and analytical aspects, and to estimate major disinfection-orientated properties such as microbicidal activity, irritation, and incorporation effects. Though the calculations consider primarily preparations devoid of polymeric organic compounds capable of complexing iodine species, the results can be largely transferred to iodophoric preparations.
尽管碘基消毒剂已经使用了近170年，但人们对其作用方式仍未完全清楚，例如，对于各种碘形态的相关性就存在不同的判断。虽然已经有基于纯碘溶液中计算出的平衡浓度的研究，但对于存在额外碘化物的碘溶液缺乏了解，而这对于消毒实践至关重要。因此，考虑了该参数在0 - 14 pH范围内的变化进行了重新计算。所呈现的计算涉及不受歧化作用（碘酸盐形成）影响的新鲜碘溶液，并提供了关于I、I₂、I₃⁻、I₅⁻、I₆²⁻、HOI、OI⁻、HI₂O⁻、IO₂⁻和H₂OI⁺等形态平衡浓度的信息。额外的碘化物和pH值对各个平衡浓度有非常显著的影响（相差几个数量级）；因此，可以指出实际重要形态数量大幅减少的条件。在最常见的情况下，即在pH < 6且存在额外碘化物时，只有I⁻、I₂和I₃⁻起作用。另一方面，在没有额外碘化物、pH为8 - 9且高稀释（c(I₂) < 10⁻⁵ M）的情况下，HOI占氧化能力的90%以上。在高碘化物浓度（如卢戈氏溶液）下，I₅⁻和I₆²⁻形态占氧化能力的8.2%。在实际发生的条件下，消毒中经常提到的碘阳离子H₂OI⁺没有任何相关性，IO⁻和HI₂O⁻也是如此，它们仅在pH > 10时才变得重要。在pH > 6时出现的稳定性问题（即碘酸盐形成速率）可以归结为次碘酸，这在简单的速率定律d[IO₃]/dt = 0.25 [HOI]³/[H⁺]中有所体现，该定律允许估计弱碱性条件下的稳定性。本研究结果使我们能够推断碘水溶液的一般性质，如反应性、稳定性和分析方面，并估计主要的以消毒为导向的性质，如杀菌活性、刺激性和掺入效应。尽管计算主要考虑的是不含能够络合碘形态的聚合有机化合物的制剂，但结果在很大程度上可以转移到碘伏制剂上。
