Production of Pyrogen-free Water

Distillation was used in the past to produce high purity water. Distilled water is free from inorganic salts but may contain low-boiling organics. Water purity or quality can be measured by several analytical test methods. The most common water quality measure is its electrical resistance. Pure water resistivity is about 18 M-ohms. A triple distilled water typically shows a resistivity of only about 3 M-ohms. Today the combination of UF, RO, ion exchange and activated carbon is capable of producing 18 M-ohms water. 1 1 

Ultrafiltration is used to remove pyrogens and other microorganisms from high purity water. Pyrogens are lipopolysaccharides (also known as endotoxins) with molecular sizes ranging from 20,000 dalton (-0.005 pm) up to about 200,000 dalton ( 0.1 pm) produced from bacterial cell walls. Pyrogens induce fever when injected into animals or humans and cannot be removed by autoclaving or microfiltration.l H  

Typical UF performance for pyrogen removal with a polymeric and ceramic membrane is shown in Table 13. It can be seen that both types of UF membranes can adequately remove pyrogens. The choice of UF membrane (ceramic or polymeric) will depend on operating conditions or other special process requirements. Ceramic membrane ultrafiltration can achieve a 5 log reduction in pyrogen level. These UF membranes have been validated for the production of water meeting the requirements of pyrogen-free water for injection (WFI) standards.f  

Type of Membrane Pyrogens (ng/mL) LRV Reference Feed fameate  

---

Therefore, since Loeb and Sourirajan innovated an industrially usable filtration membrane having a low permeation resistanee in 1960, the filtration separation using a membrane has been used in various industrial fields around the world, sueh as the automobile industry (closed system for recovery of eleetrodeposition paint), the eleetronies industry (produelion of ultrapure water for semiconduetor production), and the pharmaceutieal industry (eoneen-tration and purification of enzymes and antibiotics, production of pyrogen-free water, etc). 

---