16 mM NaOCl + different concentration of H2SO4.

With the spread of coronavirus infections, the demand for disinfectants, such as a sodium chlorite solution, has increased worldwide. Sodium chlorite solution is a food additive and is used in a wide range of applications. There is evidence that chlorous acid or sodium chlorite is effective against various bacteria, but the actual mechanism is not well understood. One reason for this is that the composition of chlorine-based compounds contained in sodium chlorite solutions has not been clearly elucidated. The composition can vary greatly with pH. In addition, the conventional iodometric titration method, the N,N-diethyl-p-phenylenediamine sulfate (DPD) method and the absorption photometric method cannot clarify the composition. In this study, we attempted to elucidate the composition of a sodium chlorite solution using absorption spectrophotometry and ion chromatography (IC). IC is excellent for qualitative and quantitative analysis of trace ions. Through this, we aimed to develop an evaluation method that allows anyone to easily determine the bactericidal power of sodium chlorite. We found that commercially available sodium chlorite solution is 80% pure, with the remaining 20% potentially containing sodium hypochlorite solution. In addition, when sodium chlorite solution became acidified, its absorption spectrum exhibited a peak at 365 nm. Sodium chlorite solution is normally alkaline, and it cannot be measured by the DPD method, which is only applicable under acidic conditions. The presence of a peak at 365 nm indicates that the acidic sodium chlorite solution contains species with oxidizing power. On the other hand, the IC analysis showed a gradual decrease in chlorite ions in the acidic sodium chlorite solution. These results indicate that chlorite ions may not react with this DPD reagent, and other oxidizing species may be present in the acidic sodium chlorite solution. In summary, when a sodium chlorite solution becomes acidic, chlorine-based oxidizing species produce an absorption peak at 365 nm. Sodium hypochlorite and sodium chlorite solutions have completely different IC peak profiles. Although there are still many problems to be solved, we believe that the use of IC will facilitate the elucidation of the composition of sodium chlorite solution and its sterilization mechanism.

随着新冠病毒感染的全球蔓延，包括亚氯酸钠溶液（sodium chlorite solution）在内的各类消毒剂的需求量持续攀升。亚氯酸钠溶液属于食品添加剂，应用场景十分广泛。已有研究证实亚氯酸或亚氯酸钠对多种细菌具有抑菌效果，但其实际杀菌机制尚未被充分阐明。造成这一现状的核心原因之一，在于亚氯酸钠溶液中所含氯基化合物的组成始终未能被清晰解析。该组成会随pH值变化产生显著波动。此外，传统碘量滴定法、硫酸N,N-二乙基对苯二胺（N,N-diethyl-p-phenylenediamine sulfate, DPD）法以及吸光光度法均无法实现该组成的精准解析。本研究采用吸收分光光度法与离子色谱（ion chromatography, IC）技术，尝试解析亚氯酸钠溶液的组成。离子色谱技术可实现痕量离子的定性与定量分析，具备显著优势。借此，本研究旨在开发一套可让任意使用者轻松评估亚氯酸钠杀菌效能的分析方法。研究发现，市售亚氯酸钠溶液的纯度为80%，剩余20%的成分可能包含次氯酸钠溶液（sodium hypochlorite solution）。此外，当亚氯酸钠溶液被酸化后，其吸收光谱在365 nm处出现特征吸收峰。亚氯酸钠溶液通常呈碱性，而仅适用于酸性环境的DPD法无法对其进行检测。365 nm处吸收峰的出现，表明酸化后的亚氯酸钠溶液中存在具有氧化活性的物质。另一方面，离子色谱分析结果显示，酸化亚氯酸钠溶液中的亚氯酸根离子浓度随时间逐渐降低。上述结果表明，亚氯酸根离子或许无法与该DPD试剂发生反应，酸化亚氯酸钠溶液中可能存在其他氧化性物质。综上，当亚氯酸钠溶液被酸化后，其中的氯基氧化性物质会在365 nm处产生特征吸收峰。次氯酸钠溶液与亚氯酸钠溶液的离子色谱峰形存在显著差异。尽管仍有诸多问题有待解决，但我们认为离子色谱技术的应用将有助于推动亚氯酸钠溶液组成及其杀菌机制的解析工作。