As reported in the GMP news on 4 July 2007, the USP chapters regarding TOC <643> and conductivity measurement <645> are up for revision. In the Pharmacopeial Forum issue 33(4) from July/August 2007 these two chapters are now listed under "In-Process Revisions". Their implementation is planned for the Second Supplement to USP 31.

As expected, both chapters comprise extensions indicating the advantages of an online monitoring of these two measured variables. In addition, they state the disadvantages of an offline measurement. Determining the measurement - online of offline - it is necessary to consider the way of water production: batch or continuous production. Chapter <645> is even more definite: "Except for packaged water, on-line measurements may be preferred".

As also pointed out, the extensions go back to a request by the FDA - at last they are part of the authority's 'GMP for the 21th century' initiative.

Further innovations are:
Chapter <643> now also clearly indicates that TOC measuring results can not replace the microbial monitoring of the water.
Chapter <645> has been extended by one verification step that is supposed to ensure that a device is used which is calibrated for the lower measuring ranges.

Author:
Dr. Robert Eicher
On behalf of the European Compliance Academy (ECA)