Q&A with Mason Schwartz: Technical Learnings about Vaporized Peracetic Acid (VPA)
Inventor of VPA technology and current Director of Research & Development and Operations with REVOX Sterilization Solutions, Mason Schwartz, discusses the science behind VPA.
1. The VPA sterilization process has a distinct advantage over many other sterilization solutions because it is executed at room temperature. From a chemistry standpoint, why is this important?
Mason Schwartz: It’s important because every ten degree Celsius increase in temperature doubles the reaction potential of the chemistry itself, which drives corrosion.
We avoid that corrosion by operating at true room temperature (18–30°C).
2. Why is an inherently acidic molecule like peracetic acid distinctly less harsh when used to sterilize in vapor form?
MS: In the liquid phase, peracetic acid is corrosive because it has a low pH. A vapor does not act in this same manner and pH is not considered in the vapor phase.
In formal compatibility studies, we see an excellent compatibility profile with over 100 materials tested. Even copper, after being exposed in 10 repeated four-hour cycles, only showed a slight dulling of the original gloss. One theory that accounts for this is that the concentration of acetic acid in contact with the materials is quite low as compared to that of the liquid state.
3. Vapor and gas appear to be very similar; what are their distinctions?
MS: A vapor is a substance in the particle/gas phase at temperatures lower than its critical boiling point, which means that the vapor can be condensed to a liquid by increasing the pressure on it without reducing the temperature. The critical point of PAA is 25°C, so it would be considered a vapor at temperatures below 25°C and a gas at temperatures above 25°C.
Whatever temperature the sterilization process is operating at will affect the saturation point of a chemical, meaning that depending on the temperature, only certain percentages of the sterilant will become a gas. The higher the temperature, the more sterilant can go into the gas phase before it saturates. The lower the temperature, the less you can create in a gas.
4. What have you learned about the penetration and half-life of VPA?
MS: We have learned through rigorous testing that VPA can achieve a 6-log reduction in a .015mm diameter, 1M length of tubing. How did we achieve this? At 50°C, the half-life of a peracetic acid (PAA) molecule is 30 minutes and the half-life of a hydrogen peroxide (H2O2) molecule is 10 seconds. The longer half-life enables the VPA time to travel through the tubing as an effective molecule.
5. Traditional sterilization methods have the advantage because of their history of FDA approvals verses “novel” sterilization methods. How does REVOX Sterilization Solutions address customers’ regulatory concerns since it is a new technology?
MS: REVOX Sterilization Solutions VPA technology is classified as a “novel” sterilization method, so it is likely that a new, full FDA clearance would be required for a device using VPA sterilization. Fortunately, as a medical device manufacturer, Cantel Medical has a strong track record of regulatory compliance and a team of experienced regulatory affairs professionals who work with our clients to find the best path forward to ensure all regulatory submissions are thorough and comprehensive. In one case, the REVOX Sterilization Solutions team helped a customer gain its FDA 510(k) clearance for using VPA within nine months after submission.
6. Sterilization can often add extra days and costs to the manufacturing process because manufacturers have to outsource their sterilization services. How does REVOX Sterilization Solutions address scalability issues for manufacturers?
MS: Our new 3000L chamber line—which is 10X larger than our first set of machines—is now in place and operational in our Minnesota facility. It brings the VPA sterilization process to a large-scale, commercial practice. More importantly, though, the rollout of the 3000L has demonstrated that chamber size options are only limited by operational efficiency considerations, and not the scalability of the technology itself.
This is an important consideration because vaporized hydrogen peroxide (VHP), another room-temperature sterilization technology—is not scalable because of half-life issues. We see VHP room decontamination systems that use fans strategically placed around the room, not only to ensure sterilant contact in all areas of the room, but to get it there quickly—within the 10–20 seconds so that the molecule remains effective. Within a closed chamber, the same constraints exist. A larger chamber volume will require numerous vaporization sources, large quantities of sterilant, and added dispersion mechanisms.