TOC vs HPLC. Is it necessary to run both?

We currently apply a HPLC swab for active and a TOC rinse sample for detergent. Is it possible just to perform a swab on TOC for the active and detergent?

I understand that the active needs to be slightly soluble in water to work but what happens if the API is insoluble?

Time, money and resources would be greatly reduced if HPLC could be knocked out of the equation.

How about if the API is insoluble, run the HPLC test for it?

If anyone can put up links to support TOC only I would appreciate it


Dear Matt
HPLC is a specific method and TOC is a general method
Generally, as we dont know the formulation of detergent, we test it by TOC and we prove its absence.
You can apply the same method for API also, but you should know the % of carbon in your API



HPLC is used for insoluble or only slightly soluble API/excipients.
TOC is used for soluble or some slightly soluble API/excipients. It will pick up the carbon from both the API/excipients as well as the detergent used. To use it to rule out API contamination, your company must find the ppm (%, however your units are) for the API based on the LD50 (lethal dose for 50% population). Take the LD50 and multiply by the ratio of carbon in the API.

Ex: API X is soluble, contains 35.2g carbon per 97.83g of API, and has a LD of 50mg/kg; %carbon in API is 35.2g/97.83g = .3598%; ,max ppm will be 50 * .3598 = 17.99ppm. Our company would assign a TOC ppm spec of 10ppm for that API. TOC may be used.

Ex: API x is soluble, does not contain carbon, and had a LD50 of 50mg/kg. Since there is no carbon, TOC will not tell you if any API residue is present. HPLC must be used.