Preparation Process for Water for Injection (WFI) in Pharmaceuticals

There are basically two types of water preparation in pharmaceuticals. Water for Injection (WFI) preparation process and purified water preparation process. The analytical standards for the two water are almost very similar, the only difference is that Water for Injection (WFI) system in pharmaceuticals has stricter bacterial control standards than USP standards for purified water process and has to pass the bacterial endotoxin test. 

Preparation methods are very similar to a particular point, however, Water for Injection (WFI) preparation process in pharmaceuticals must include distillation or double pass reverse osmosis techniques.

Dechlorination: This refers to the removal of chlorine from the water. There are several ways of dechlorination.This include injection of a reducing agent like sodium metabisulfite and exposure to a high dosage of UV rays can dechlorinate. However, the most common one is filtration through activated carbon media. 

Water for Injection (WFI) preparation process in pharmaceuticals is dechlorinated by carbon. Carbon dechlorinates by chemically reacting with the free chlorine in water to form hydrochloric acid and carbon monoxide or dioxide. High doses of UV light rays are widely used in water purification systems for both disinfection and TOC reduction. Another use of UV is dechlorination though it is a relatively new process.

Ion removal: There are basically three types of ion reduction processes these include membrane processes, ion exchange processes, and distillation processes. Membranes are used in water purification systems to remove ions, remove particulate, remove organic compounds, and remove living organisms. Membranes are different from one another in terms of pore size, molecular weight, and even on ion rejection. 

Ion removal membranes include membranes such as reverse osmosis membranes and nanofiltration membranes. These are used in ion reduction processes. The ion exchange systems provide additional ion reduction process, making the water much lower in conductivity than required and it also provides a back up for membrane process. Distillation can also be used to remove ion, however, it is very expensive.

Bacterial control: In bacteria control, one has to be careful to ensure that bacteria does not pass to pharmaceutical water for injection. Bacteria control includes both procedures and equipment. Equipment utilized are ultraviolet (UV) lights, ozone generation systems for production of ozone, heating systems for thermal treatment, and chemical injection and recirculation systems. Procedures in this process include periodic sanitizations and also general operational techniques to avoid intrusion of bacteria. 

Bacterial control is usually applied during processing, storage and even distribution. UV light is an excellent non-chemical method of disinfecting Water for Injection (WFI). Thermal sanitization involves the use of heat to kill the bacteria. Ozone can also be used since it is a very strong oxidizing agent it can, therefore, oxidize bacteria. Chemicals can also be used to kill bacteria as a means of bacteria control.

Removal of specific impurities: There are various different sources of water for Injection (WFI) used during preparation process in pharmaceuticals. Every source is different and therefore the possibilities of specific contaminant problem are possible. These contaminants include Iron, manganese, hydrogen sulfide, hardness ions, particulate matter, high conductivity. Filtration can be used to remove any heavy loads. Cartridge filters are also used to remove essentially any sized particles. However, they are expensive. 

The last stage is storage. Care and hygiene must be maintained during storage of WFI. Bacteria control must also be incorporated at this stage.