Determining Acceptable Residue Limits

Q. How do you determine acceptable residue limits when performing a cleaning validation?

A. All Alconox Inc. cleaners have an oral LD50 of greater than 500 mg/Kg acceptable residue limit. Alconox®, Liquinox® and Citranox® all have an oral LD50 of greater than 5 g/Kg. If you calculate 1/1000 of the LD50 as a potential residue in a dose of the pharmaceutical, knowing the number of doses, you can get the total residue in a batch.

Knowing the surface area of your equipment you can calculate a residue per sq cm that will give you a maximum of 1/1000 of the LD50 in a dose. This is usually a fairly high number and since it is easy to clean and measure to higher standards, it is practical to set a detection limit lower than the calculated acceptable limit – typically at 1-10 ppm of 25 ml of some extracted solution per 100 sq cm wipe of a surface.

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