Quest for the Missing Salicylic Acid
I am not a formulator, but I work in process validation for a contract manufacturer, and sometimes I get drawn into issues for newly formulated products. In this case, we have pilot batches for two newly-developed products (skin cleansers). Both are about 63% water and 7% glycerin, and both use Sodium Hydroxide as a PH adjuster. One contains 2% (17kg) Salicylic acid, and the initial batch assay puts it about 1kg short (batch size is 850kg). The second product is worse. It contains 0.5% (4kg) salicylic acid, and the assay is 1.4 kg short (batch size is 800kg). We have taken all the normal investigational steps (raw materials reconciliation, checked the filters, etc.), and we cannot find this missing material.
Does anyone have any experience with a loss such as this? So far, this remains a mystery.
Thanks in advance for any help.