What are the steps for synthesizing luminol luminescent reagents?

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Luminol had already appeared in the 1980s and was first discovered to have a strange property of emitting light after oxidation. Later, continuous research proved that it can react with blood because it contains iron, which can be fully oxidized and decomposed to produce blue light. Therefore, it has been widely used in the field of criminal investigation or other luminescent experiments. Due to its extremely sensitive and efficient speed, this method has also become a popular choice for luminescent reagents in the market. What are the reaction steps in the experiment? Let's take a look together.

1、 Luminescence experimental method

Firstly, pour a certain amount of potassium hydroxide powder, dimethyl sulfoxide, and filtered luminol powder into a dry triangular flask, and then shake the triangular flask. Place it in the dark to observe if there is any blue light appearing. It emits light quickly and generally lasts for 0.5 hours. Its brightness can increase with the intensity and time of shaking.

2、 Experimental synthesis steps

1. Add a certain amount of 3-nitrophthalic acid and hydrazine aqueous solution to a three necked bottle containing a thermometer and reflux condenser tube, heat it over low heat to slowly dissolve the solid, and let it cool.

2. Add diethylene glycol and a few small particles of zeolite to the experimental bottle, and then modify it into a vacuum distillation device connected to a circulating water vacuum pump. Gradually raise the temperature and slowly open the water pump to remove the water vapor from the bottle. Gradually raise the temperature and keep the reaction warm for about 10 minutes.

3. After heating, cool it to around 80 degrees Celsius, transfer the material from the bottle to a beaker while it is hot, add hot water and stir evenly, then let it stand. After cooling and crystallization, filter it to obtain the yellow intermediate product 3-nitrophthaloyl monohydrazine.

4. Add sodium hydroxide into the beaker containing intermediate reactants, fully stir and dissolve, then add sodium sulfite, heat it to boiling reaction for about 10 minutes, and use glass rod to intermittently stir during the reaction.

5. After the reaction is completed, when the temperature drops to 50 degrees, glacial acetic acid is added for acidification. After cooling, it crystallizes and is filtered and dried to obtain yellow crystal Luminol.

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