The difference between purified water and water for injection also lies in the water preparation process. The preparation process of purified water can have various choices, but the pharmacopoeia of various countries has limited conditions for the injection process of water for injection. For example, the United States Pharmacopoeia clearly stipulates that the preparation process of water for injection can only be distillation and reverse osmosis, while the Chinese pharmacopoeia stipulates that the production process of water for injection must be distillation. These are necessary conditions for each country to ensure the quality of water for injection according to its actual situation. At present, many people equate water for injection with purified water, which is actually misleading. Purified water can be obtained by ion exchange, reverse osmosis, EDI, ultrafiltration and other treatments. Purity is also very high, but compared with water for injection is still very far. Purified water in the medical aspects of the main achievements are medical equipment cleaning, pharmaceutical production, test water and so on. In China, purified water is used as the source water for injection, which shows the difference between the two.
The electrolyte in the water is almost completely removed, and the insoluble colloidal substances and microbial particles, dissolved gases and organic matter in the water have also been removed to a very low degree. Purified water is water obtained for medicinal use by distillation of raw water, ion exchange, reverse osmosis or other suitable methods in line with drinking water standards, and does not contain any additives. It can be used as a solvent or test water for the preparation of ordinary pharmaceutical preparations, but shall not be used for the preparation of injections. In general, the residual salt content in pure water should be controlled below 0.1mg/L, and the conductivity should be 0.1us/cm when the water temperature is 25℃.
The purity of water is similar to that of purified water. The main difference between water and purified water is that the water does not contain microorganisms and pyrogens. It is obtained by distillation of purified water. It is required to monitor each preparation link at any time, and regularly clean and disinfect the preparation and delivery equipment of water for injection. Generally stored above 80℃, insulated circulation above 65℃ or sterile storage below 4℃, and used within 12 hours of preparation. According to the Chinese Pharmacopoeia, water for injection is water made by distillation of purified water; Should meet the requirements of bacterial pyrogen test; Water for injection must be produced, stored and distributed under conditions that prevent pyrogen generation. There are two methods for preparing water for injection in the United States Pharmacopeia, namely distillation and reverse osmosis. Water for injection can be used as solvent or diluent for sterilization preparations such as injection and eye drops. Cleaning of injection containers. Sterilization water for injection refers to water for injection prepared according to the production process of injection. It is sterile and pyrogen free water for injection and can be considered as a preparation.
In addition to controlling chemical indexes and particulate pollution, the pharmaceutical water systems must effectively deal with and control the contamination of microorganisms and bacterial endotoxins. The purified water system can use reverse osmosis, while the water for injection system uses more distillation, and the distilled water machine is often the main water point in the distribution loop (water loop) of the purified water system. In terms of the selection of pharmaceutical water sources, the United States Pharmacopeia has greater flexibility. According to its provisions, water for injection can be made from drinking water through distillation or reverse osmosis, and enterprises are not required to use purified water as the source water to prepare water for injection.
Using the water that meets the drinking water standards as the source water, or using the purified water that meets the standards to prepare water for injection, can not always ensure that the effluent reaches the prescribed standards, which is related to the performance of the selected equipment. It should also be noted that the quality of the source water must be monitored and that the point of intake should be as far away from the source as possible.
A comparison of the United States Pharmacopeia water quality standards for purified water and water for injection shows the major differences. Their physical and chemical indexes are the same, but the requirements of water for injection on pyrogen and microorganisms are higher than that of purified water, and there is a difference in the purity of water.