FLUID SYSTEMS TFC SPIRAPRO pharmaceutical spiral nanofiltration elements lower operating costs for a variety of pharmaceutical selective rejection applications, including desalting and organics concentration. The elements utilize a proprietary polyamide thin-film composite membrane. The molecular weight cut-off is such that the membrane will pass monovalent salts like sodium chloride, yet retain divalent salts, proteins and sugars. Retention of sugars, such as lactose, typically exceeds 99 percent. The typical operating pressure ranges from 200 to 500 psi, with a pressure drop per element of up to 10 psi, or a total of up to 50 psi for a vessel with five elements arranged in series.