In Ultrapure Water Systems, which only monitor ionic purity by resistivity measurement, the organic removal capacity of the purification media may be overloaded and exhausted long before the ionexchange capacity is used up. This results in a breakthrough of organic contaminants into the product water which goes undetected by resistivity measurement. Organic build-up within the purification media also provides an environment which can support rapid bacterial growth, with resulting nuclease and pyrogen generation. For these reasons, ultrapure water expendables should be replaced regularly, not only when resistivity drops, but also based on time in service.

Purification media should not be left in an ultrapure water system for more than one year, and ideally should be replaced after six months if organic contaminants or bacterial by-products are detrimental to your application, regardless of resistivity readings.

For the new generation of systems which monitor Total Organic Carbon (TOC) and ionic purity (Resistivity), purification media should be changed when TOC and/or Resistivity values fall outside acceptable limits for your applications.

For a bacterial limit (cfu/ml) or pyrogen-free water, it is important that separate microbiological and endotoxin tests are routinely performed on the product water. Membrane Solutions’ scientists measure pyrogen contamination by determining the endotoxin level using a quantitative kinetic turbidimetric LAL (Limulus Amoebocyte Lysate) test. Associates of Cape Cod, Woods Hole, MA USA). Request TB064 for further details.