In research and experimental scenarios such as biochemical testing and clinical diagnosis, Trinder's reagents have become core consumables due to their excellent reaction performance. Among them, EHSPT (commonly known as TOOS) is a commonly used reagent for peroxidase coupling reactions due to its strong water solubility and chemical stability. However, many researchers have encountered such difficulties: the newly prepared TOOS solution, which is clearly transparent and clear, turns yellow or even red after just two days of storage. This article will analyze the core reasons for the discoloration of TOOS solution from the root, provide scientifically feasible response strategies, and assist in the smooth development of scientific research work.

TOOS reagent powder

1、 In depth analysis: Two core causes of TOOS solution discoloration

（1） Core inducement one: Oxidation reaction dominates color change in solution state

TOOS reagent powder has good stability in a dry and sealed state, and is not easily oxidized or deteriorated, which is also one of its favored key characteristics. But once formulated into an aqueous solution, the situation will undergo significant changes. As a highly water-soluble derivative of aniline sodium salt, TOOS molecules exhibit enhanced activity in solution and significantly increase sensitivity to oxygen. When the solution is exposed to air, TOOS undergoes a slow oxidation reaction, producing colored oxidation products. This process directly causes the solution to gradually change from initially colorless and transparent to light yellow. If the degree of oxidation increases, the color will further change to orange yellow or even red. Moreover, the higher the ambient temperature, the faster the oxidation process, and the time for the solution to change color will be significantly shortened.

（2） Key drivers: the combined impact of multiple environmental factors

In addition to the oxidation reaction induced by oxygen, the combined effect of various environmental factors can also accelerate the discoloration of TOOS solution. Firstly, there is the factor of light exposure. TOOS molecules have a certain photosensitivity to strong light, especially ultraviolet light. Strong light exposure can activate the photosensitive groups inside the molecule, triggering unexpected photochemical reactions, disrupting the stability of the reagent, and leading to color changes. Next is the humidity environment. If the storage environment has high humidity, it can cause moisture to enter the poorly sealed reagent bottle, which not only dilutes the concentration of TOOS solution, but may also introduce impurities in the air, indirectly accelerating the color change process.

2、 Scientific Response: Correct Storage and Use Strategies for TOOS Solutions

（1） Core measures: Sealed refrigeration to delay oxidation

Sealed refrigeration is a direct and effective storage method for the core cause of oxidation reaction. After preparing the TOOS solution, researchers should immediately pour it into a clean container, tighten the bottle cap to ensure a tight seal, and prevent air from entering. Subsequently, store the sealed solution in a refrigerated environment at around 4 ℃. A low-temperature environment can significantly reduce the rate of oxidation reaction and significantly delay the discoloration of the solution.

（2） Auxiliary support: Avoid light and high temperature environments

To further improve the preservation effect, it is necessary to strictly avoid the influence of light and high temperature on TOOS solution. It is recommended to choose brown glass bottles as storage containers. Brown glass can effectively block the penetration of ultraviolet and strong light, reducing the damage of light to reagents; If using a transparent container, it should be stored in an opaque reagent cabinet. At the same time, the storage location should be away from heat sources, such as laboratory ovens, alcohol lamps, heating equipment, etc., to maintain a stable storage environment temperature in the low temperature range. During the experimental operation, the exposure time of TOOS solution should also be shortened as much as possible to avoid prolonged operation under strong light.

（3） Fundamental principle: Reasonable planning of usage, ready to use

No matter what storage method is used, it cannot completely prevent the slow deterioration of TOOS solution. Therefore, ready to use is the fundamental principle to ensure the quality of reagents. Researchers should accurately estimate the required amount of TOOS solution based on experimental needs, prepare it as needed, and avoid preparing too many solutions at once for long-term storage. This not only ensures that fresh and stable reagents are used in each experiment, guaranteeing the accuracy of experimental data, but also effectively reduces reagent waste caused by solution discoloration and failure, and lowers experimental costs.

3、 Key question: Can the discolored TOOS solution still be used?

When discoloration is observed in TOOS solution, researchers do not need to panic excessively. They can first investigate whether there are improper storage conditions, such as inadequate sealing, exposure to high temperatures or strong light environments. If it is confirmed that the oxidation discoloration is caused by long-term exposure to air or high temperature, and the solution color is dark (such as orange red), it indicates that the reagent has undergone significant deterioration, and it is not recommended to continue using it in the experiment to avoid affecting the accuracy of the detection results. If the solution only appears slightly pale yellow and the storage conditions are generally compliant, the activity of the reagent can be verified through low-dose pre experiments.

Product packaging

If you encounter other problems during the storage process of TOOS reagents or need high-quality Trinder's reagent products, you may contact Hubei Xindesheng Material Technology Co., Ltd. As a strong enterprise specializing in the research and development, production, and sales of biochemical reagents, Hubei Xindesheng has built TOOS reagents with years of technical accumulation. These reagents not only have high purity and strong stability, but also provide professional technical support for customers. If you need to learn more about product details or technical issues, you can visit the official website of Hubei Xindesheng or contact our online customer service at any time. We will be dedicated to serving you!