Bacteriological purity

Water quality is usually defined in terms of chemical and bacteriological purity, particulate matter content, and endotoxin levels. Potable water is normally from the municipal water system, which may have been treated with chlorine to control microbiological growth. Soft water and deionized water have undergone ion exchange or similar treatment to eliminate unwanted ionic species, such as Mg2+ and/or Ca2+. Purified water, water for injection, and other types of water meeting compendial specifications are produced by ion exchange, reverse osmosis, distillation, or a combination of such treatments. 

An action guideline of not more than 10 CFUs/100 ml for bacteriological purity is suggested. As with the purified water system, the sampling and testing frequency for the water for injection (WFI) system is defined in the protocol and can be reduced after the system is qualified and validated. 

Purified water is typically prepared by ion exchange, reverse osmosis or a combination ofthe two treatment processes. Purified water is intended for use as an ingredient in the preparation of compedial dosage forms. It contains no added substances, and is not intended for use in parenteral products. It contains no chloride, calcium, or sulfate, and is essentially free of ammonia, carbon dioxide, heavy metals, and oxidizable substances. Total solids content will be no more than 10 ppm, pH will be 5-7, and the water will contain no coliforms. The United States Pharmacopoeia National Formulaiy (USP) requires that purified water comply with EPA regulations for bacteriological purity of drinking water (40 CFR 141.14, 141.21). Table 4 is a quantitative interpretation of United States Pharmacopoeia XXI standards for purified water. ... 

Note that WFI is essentially the same as purified water with the exception of endotoxins and bacteriological purity. USP requires WFI to contain less than 0.25 USP Endotoxin Unit per ml. The USP has no bacteriological purity requirements for WFI at all. However, the proposed large volume parental GMP s (CFR 212.49) requires counts less than 10 CFU/100 ml. 

Cellulose acetate as a medium for electrophoresis was introduced by Kohn in 1958. It was developed from bacteriological cellulose acetate membrane filters and is commercially available as high purity cellulose acetate strips, which are thin and have a uniform micropore structure. 

The final criterion of satisfactory sterilization of domestic water is the reduction in bacterial concentration to very low values. Bacteriological examination of drinking water uses the coliform bacteria Escherichia coli—often referred to as E, coli) as an indication of the purity of the water since these bacteria are the normal inhabitant of the intestinal tract and constitute about 30% of the dry weight of adult human feces. Water suitable for human consumption should contain less than one viable coliform per 100 mL. 

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