Why Monitor Sterilant Concentrations with NIR Spectroscopy?
Near-infrared spectroscopy provides a sterilization monitoring solution that operates in both a positive and negative atmosphere. Electrochemical sensors cannot operate in a vacuum and can also be damaged or poisoned by high sterilant concentrations. Because NIR spectroscopy uses light to monitor the chemical concentrations, a NIR Analyzer can monitor sterilant levels under non-condensing conditions.
Gas and Vapor G-SST Probe
For hydrogen peroxide or other vapor applications, the 50 cm G-SST Vapor Probe provides an efficient, simple and easy interface between the vapor chamber, and the NIR analyzers.
The G-SST Probe was designed to be installed directly into a vacuum sterilization chamber for process monitoring. The probe enables reaction chemistry and specific chemical concentrations to be monitored in environments where electrochemical sensors cannot operate.
The probe clamps into a standard 2 inch Tri-Clover® sanitary fitting and can be mounted in the vapor chamber, feed line, or return line. Since both source and return fibers are on the same end of the probe, and external to the process, there are no fiber cables to seal. The optical path is folded, providing 50 cm of interaction with the gas in a compact 25 cm probe body. This means more accuracy and stability for low vapor concentrations.
Advantages of 50 cm Pathlength G-SST Probe
The G-SST Vapor Probe has been sold for over 25 years and continual design improvements have enabled more precise measurements of hydrogen peroxide and water vapor.
The double pass beam design (folded path) provides twice of the beam interaction with the gases in the chamber. This increases the achievable signal-to-noise making for a more accurate and stable measurement. Since the absorbance of water and Hydrogen Peroxide vapor is very weak, this is a significant improvement in the measurement accuracy.
The optics are sealed behind a window which isolates the lenses from the sterilization chamber; thus the probe is not sensitive to index of refraction changes, This makes the measurements more stable under widely varying conditions of deep vacuum to high concentrations of water and hydrogen peroxide vapor.
As shown above the perforated cage around the beam path is an open structure which allows the G-SST Probe to be quickly serviced by a technician. With the lenses behind an o-ring sealed window, there is no adhesive degradation increasing the service life of the probe.
Easy Validation of Sterilization Cycle Performance
When sterilization cycle performance validation is required the G-SST Probe can be inserted inside of the isolation chamber to measure the concentration of sterilant during the vacuum (negative atmosphere) process. This makes validation of performance easy, at any time.
Vapor Probe Design Features
- Glass windows protect optical surfaces
- High optical efficiency, > 50% transmission
- Long pathlength, 50cm for greater accuracy and stability
- Rugged design
- SMA 905 fiber optic interface, all fiber sizes
- Single-sided design, no need for fiber cable feed-throughs
- Can be installed in vapor feed, return lines or sterilization chamber
- Works in vacuum (10-5 Torr) or up to 2 atm absolute
- Operates in an environment from 0°C to 90°C
- Compatible with any photometer or spectrometer, according to fiber diameter and spectral range
Vapor Probe Options
- 2 inch (50.8 mm) Tri-Clover port
- Electropolished 316 stainless steel or anodized aluminum body material
Vapor Probe Pathlengths and Operating Range
- Standard Pathlength: 50 cm, double pass 25 cm
- Temperature Range: 0 °C to 90 °C
- Pressure Range: 1 x 10-5 Torr to 1520 Torr (2 atm)