Our CIP only uses water, is there any reason to include TOC in our cleaning validation, or could we get by with micro testing and screening for our known active (fluoride)?
at first sight, there should be no need for TOC (TOC is only one method among others, and as a personal opinion, no the best one), but some additional thoughts:
If you have no organic components in the formulation, TOC makes no sense.
If fluoride is the only active, then the equipment is regarded as dedicated, and thus the active (and specially if it does not degrade) is not an issue for cleaning validation. But if the active is not an issue, you may have to evaluate the absence of excipients from different formulations (although all with the same active), and there may be a need for TOC analysis. If the equipment is dedicated to a product, there is no need for cleaning validation apart from a visual cleanliness check.
Sometimes the excipients are critical. As an example, we manufacture three different kinds of toothpaste (with a fluoride as an active!), with the same formulation but with different flavors, and the cleaning issue is neither the active nor the main excipients, but the flavor, because even when there is no health risk associated to a cross contamination, a contamination with other flavor is unacceptable from the patients point of view, so the “worst case” cleaning issue is the flavor.
If fluoride is your worst case, but not the only active processed in the equipment, check if the cleaning method you are validating takes the other actives into account, or if it has been tailored to eliminate the fluoride and leaves the other actives untouched. If this is the case, your worst case may be other active and not the fluoride, and TOC may be an option for the analytical method.