In biopharmaceutical development, reliable chromatography is essential for separating, collecting, and characterizing compounds. However, when aggressive process conditions and sensitive analytes are introduced, the surfaces of chromatography hardware can become a source of unexpected challenges. Stainless steel is commonly used in chromatography systems, but exposure to corrosive conditions can compromise the integrity of the hardware, shorten equipment lifetime, and introduce unwanted metal interactions that interfere with analytical results.
For one global biopharmaceutical company developing RNA interference (RNAi) therapies, these challenges were significantly impacting the performance and operational lifetime of its semi-preparative high-performance liquid chromatography (HPLC) columns. By applying SilcoTek's Dursan® coating to its existing stainless steel column hardware, the company was able to extend column lifetime by at least 100x, achieve more than 3x the previous loadability, and reduce daily column operating costs by 99%.
Semi-preparative HPLC plays an important role in separating and collecting compounds for further analysis and characterization. When working with sensitive materials, maintaining the integrity of the sample throughout the process is critical. Unfortunately, the materials used to construct chromatography hardware can sometimes introduce complications, particularly when exposed to aggressive chemical environments.
For this biopharmaceutical manufacturer, the corrosive nature of its injection material was causing rapid deterioration of its stainless steel semi-prep columns. Operating under conditions of 1 M sodium bromide (NaBr), a pH of 11, and a temperature of 60°C, the uncoated stainless steel columns lasted approximately three days of continuous operation before oxidation rendered them unusable. This created an ongoing need to discard and replace costly chromatography hardware, increasing operational expenses and disrupting workflows.
However, the problem extended beyond equipment lifetime. Corrosion of the stainless steel columns also introduced iron into the process solution, contributing to the oxidation of impurities, specifically phosphorothioate (PS) to phosphoroxo (PO) oxidation. This unwanted chemical interaction created additional challenges for accurate impurity characterization, making it necessary to address both the physical deterioration of the columns and the analytical interference caused by exposed metal surfaces.
When analytes encounter reactive metal surfaces, unwanted interactions can affect chromatography performance and compromise the integrity of the materials being collected. For sensitive biopharmaceutical applications, this becomes particularly important when transitioning between analytical and preparative chromatography systems, where differences in hardware materials can influence chromatographic behavior.
Polyether ether ketone (PEEK) hardware can provide an alternative to exposed metal surfaces, but size and pressure limitations can restrict its suitability for larger-scale chromatography applications. Stainless steel offers the mechanical robustness required for these systems, but its exposed surfaces may introduce unwanted interactions or corrosion under certain operating conditions.
An inert surface coating offers another approach by retaining the structural advantages of stainless steel while modifying the surface that comes into contact with process materials. For this customer, the goal was to achieve chromatography performance comparable to its existing PEEK-based analytical system while eliminating the corrosion problems associated with its stainless steel semi-prep columns.
Working with its analytical hardware manufacturer and SilcoTek, the biopharmaceutical company applied Dursan coating technology to its existing semi-prep column design. Dursan is a chemically protective, inert coating applied using SilcoTek's chemical vapor deposition (CVD) process. The coating creates a thin, functionalized silica-like barrier, approximately 400 to 1,600 nanometers thick, that separates the underlying stainless steel from the process environment.
By modifying the surface properties of the stainless steel hardware, Dursan helps protect against corrosion while reducing unwanted interactions between analytes and exposed metal surfaces. This approach allowed the customer to continue using its existing column design while improving the chemical compatibility of the surfaces exposed to its process. Rather than replacing the stainless steel hardware with an alternative material, the customer was able to maintain its existing equipment configuration while addressing the underlying surface-related challenges.
The results demonstrated that modifying the surface of chromatography hardware could provide benefits beyond corrosion resistance, including improvements in column lifetime, sample loadability, and chromatographic consistency.
Before applying Dursan, the customer's uncoated stainless steel columns lasted approximately three days before corrosion required replacement. Following the application of Dursan, the coated columns operated continuously for 100 days without showing signs of corrosion or performance deterioration. The evaluation was ultimately ended without experiencing a coating failure, meaning the coated columns' maximum operational lifetime was not established and could potentially extend beyond the 100-day testing period.
This improvement significantly reduced the frequency of hardware replacement and the interruptions associated with premature column failure. In addition to protecting the stainless steel from the aggressive operating environment, the Dursan coating reduced the iron interactions that had previously contributed to impurity oxidation and compromised the customer's analysis.
The extended column lifetime also translated into substantial operating cost savings. According to the customer's cost analysis, using Dursan-coated semi-prep columns reduced daily column operating costs by 99% compared to the uncoated hardware. The coated columns also eliminated the need for passivation downtime, providing an additional opportunity to improve workflow continuity and reduce time spent maintaining the chromatography system.
In addition to improving corrosion resistance and equipment lifetime, Dursan coating technology produced a significant increase in column loadability. When comparing coated and uncoated 22 mm inner diameter semi-prep columns, the customer observed more than three times the previous loadability with the Dursan-coated hardware.
This improvement increased the efficiency of concentrating impurities for downstream characterization, allowing the customer to streamline its production process and reduce the amount of work required to collect materials for subsequent analysis. Greater loadability provided an additional operational benefit beyond the savings associated with extended hardware lifetime, demonstrating how improvements to chromatography surface chemistry can affect multiple stages of an analytical workflow.
One of the most significant findings from this application involved the comparison between the customer's analytical-scale chromatography performed on PEEK hardware and its preparative chromatography using Dursan-coated stainless steel columns. The customer reported nearly identical chromatography, with essentially no differences in peak shape or retention between the two systems.
This consistency was particularly valuable because it allowed the company to scale up its chromatography process without redeveloping methods to account for interactions with stainless steel hardware. Maintaining comparable chromatographic performance across different hardware materials helped simplify the transition from analytical to preparative workflows while preserving the separation characteristics established during earlier development.
For applications where PEEK hardware is limited by size or pressure requirements, Dursan-coated stainless steel may provide an alternative that combines the mechanical advantages of stainless steel with the surface inertness needed for sensitive chemical analysis.
This application demonstrates how the surface properties of chromatography hardware can influence more than equipment durability. For this customer, addressing stainless steel corrosion also helped resolve issues associated with iron contamination, impurity oxidation, and differences between analytical and preparative chromatography.
The improvements were measurable throughout the workflow. Column lifetime increased from approximately three days to at least 100 days, daily column operating costs decreased by 99%, and loadability increased more than threefold. At the same time, the customer achieved nearly identical chromatography between its PEEK analytical hardware and Dursan-coated stainless steel preparative columns, reducing the need for method redevelopment during scale-up.
Although these results reflect one customer's specific process conditions, they illustrate the potential value of addressing surface interactions directly rather than treating frequent hardware replacement and analytical interference as unavoidable challenges. By protecting stainless steel surfaces from corrosive environments and minimizing unwanted metal interactions, inert coatings can help improve the reliability and efficiency of chromatography processes.
Corrosion and unwanted metal interactions can create significant challenges in biopharmaceutical chromatography, particularly when aggressive operating conditions and sensitive analytes are involved. SilcoTek's Dursan coating technology provides a way to modify stainless steel surfaces without sacrificing the structural advantages of the underlying hardware.
For this biopharmaceutical customer, the result was longer-lasting semi-prep columns, greater process efficiency, and more consistent chromatography performance. The application demonstrates how addressing surface-related challenges can help improve both analytical reliability and the overall economics of chromatography operations.
Experiencing corrosion or unwanted metal interactions in your chromatography system? Contact SilcoTek to discuss your application and explore whether Dursan coating technology may be suitable for your chromatography hardware.