Reviewed and Approved by Matt Traynor, PhD, Innovation and Validation Director, Certified Laboratories
Several cosmetic and over-the-counter (OTC) drug products are formulated with petrolatum due to its emollient, protective, and water-resistant properties. Examples include moisturizer, lip balm, healing ointment, sunscreen, and many more.
However, it presents challenges for cosmetic and OTC laboratory testing. Matthew Traynor, PhD, Certified Laboratories Innovation and Validation Director, explains the method our labs use and the steps customers need to take prior to testing their products.
Q: Why is Petrolatum Difficult to Quantify in Finished Products?
A: Certified Laboratories is one of only a few testing laboratories that offer finished goods testing of products containing petrolatum. Petrolatum is difficult to accurately quantify as it is composed of a mix of different chain-length hydrocarbons, and there is significant batch-to-batch variability between different petrolatums. Many of the other ingredients used in your finished good are likely to also be hydrocarbons (e.g. waxes, lanolin, etc.).
Q: Why Does Certified Laboratories Require Both the Raw Material Petrolatum and a Placebo Sample for Testing?
A: Due to the unique nature of each batch of petrolatum, there is no universal standard. For this reason, when testing your product, Certified Laboratories will always require the raw material petrolatum used in that specific batch of products and a placebo sample (containing all ingredients except petrolatum).
Our labs use the raw material petrolatum as a standard against which to quantify the percentage of petrolatum in your finished good. For this reason, we require that you submit a Certificate of Analysis for the raw material when submitting samples.
Certified Laboratories uses the placebo as a background sample to subtract out of the final calculations all the hydrocarbons present in the samples that are not petrolatum. This is why a placebo specific to the exact batch is required every time you submit samples for testing.
Q: What Steps Must be Taken Before Submitting Petrolatum-Containing Products for Testing?
A: We require that all petrolatum products be submitted for feasibility testing prior to submitting samples for routine testing as this method does not work for all formulations or sample types. In addition, if it’s an over-the-counter (OTC) product, we require that product verification be completed before routine testing commences.
Q: Does this Method Meet FDA and ICH Validation Requirements?
A: Since this is a “subtraction” method, it does not meet FDA or ICH method validation requirements for “Specificity.”
The ICH requirement states that the method, “Must be specific to the analyte being measured, and specificity can be demonstrated through the absence of interference.” This method does not meet that requirement.
If you choose to use this method for your OTC finished goods testing, when the product is inspected by the FDA, you may be asked to justify your choice of test method. The FDA may be open to deviations from the standard ICH method validation requirements if it can be shown there is no alternative method. Our technical experts are happy to discuss this before you proceed with this testing. Please contact us with any questions.
Certified Laboratories continues to research alternative methods to replace the current one. Currently, however, to the best of our knowledge, there is no alternative method for the assay of petrolatum that meets all ICH/FDA method validation requirements.