Our Preservative Effectiveness Testing (PET) service evaluates the ability of a formulation to inhibit microbial growth throughout its intended shelf life. We perform testing in accordance with USP <51> Antimicrobial Effectiveness Testing, including method suitability, to confirm that the test system accurately measures preservative performance.
Preservative effectiveness testing is a critical requirement for cosmetic, pharmaceutical, and personal care products that rely on antimicrobial systems for product safety. Therefore, USP 51 testing supports both regulatory compliance and product quality assurance.
USP <51> defines standardized challenge testing procedures used to assess whether a product’s preservative system effectively controls microbial growth over time. Method suitability is performed to demonstrate that the product matrix does not interfere with microbial recovery or enumeration. As a result, suitability testing ensures that PET results are reliable and scientifically valid.
The test method is published by the United States Pharmacopeia and is widely accepted by regulators and quality organizations.
Preservative effectiveness testing typically includes microbial enumeration at defined intervals. Standard evaluation timepoints include:
Day 14 (D14)
Day 28 (D28)
Additional interim or extended timepoints may be included based on product type or regulatory requirements.
Our PET service includes:
Method suitability assessment
Inoculation with standard challenge microorganisms
Controlled incubation and sampling
Microbial enumeration at defined timepoints
Evaluation against USP <51> acceptance criteria
Clear and defensible reporting
In addition, we review results for consistency and regulatory alignment prior to report issuance.
Preservative effectiveness testing is commonly performed on:
Cosmetic and personal care products
Topical pharmaceutical products
Creams, lotions, gels, and liquids
Products with water-based or high-risk formulations
Because preservative performance directly affects product safety, routine PET supports both development and ongoing quality programs.
Pentyl Labs delivers clear and defensible USP 51 with suitability testing with practical turnaround times. Moreover, we support broader microbiological services, including microbial limits testing and time-kill studies. As a result, PET data integrates smoothly into regulatory submissions and product safety programs.
📩 Contact [email protected] to request Preservative Effectiveness Testing (PET).