The Q7A refers to this as being controlled and monitored. I don’t think that necessarily says that
each batch has to be tested. I think part of that is the reliability of the process and how much risk
the manufacturer is willing to take. The monitoring in that case could be the monitoring of the
temperature of the azeotrope for distillation.
The exact quote here is, “solvents can be recovered and re-used in the same process or in
different processes, provided that the recovery procedures are controlled and monitored”, “to
ensure that solvents meet appropriate standards before re-use or co-mingling with other
approved materials”. You’ve got a decision to make. The answer generally is you need to make
sure the material meets your requirements. If your requirements are simply satisfied by
temperature controls, fine. But, you need to establish those requirements and, quite frankly, it
would be a very unusual process that you would not already know it was good at the time you
went to use it. But it is possible you just have to make that decision whether you’re satisfying this
requirement.
A lot depends on the design of that solvent recovery system. For example, if you design a solvent
recovery system where the recovered solvent is then sent to a vessel and stored there, then it
might be feasible that you would implement some type of batch testing of each vessel of
recovered solvent. But, if it’s a continuous process, obviously, that would not be feasible, so you
have to have other controls in place to provide you that assurance regarding the quality of that
recovered solvent.
It’s more important to recognize that you could have different requirements for the recovered
solvent than you did for the virgin solvent. That especially becomes true when we start talking
about azeotropes.
