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This brief article examines common questions about best practices for autoclaving Hamilton sensors.

Can Hamilton sensors be autoclaved?

Yes, Hamilton offers a wide variety of sensors that can be autoclaved. If a sensor has this feature then it will be denoted in the product specifications as shown below.

The list below includes sensors which can be autoclaved:

  • EasyFerm Plus pH or ORP (traditional, ARC, and Memosens products)
  • EasyFerm Bio pH or ORP (traditional, ARC, and Memosens products)
  • Polilyte Plus pH or ORP (traditional, ARC, and Memosens products)
  • VisiFerm Optical DO
  • OxyFerm FDA Polarographic DO
  • Conducell 4UxF 4-pole conductivity
  • Conducell UPW 2-pole conductivity
  • Cell Density (Incyte Arc, Incyte / Dencytee pre-amp versions (without the pre-amp))

NOTE - Some sensors with autoclave capabilities may have temperature limitations. It is best to verify the product specifications or manual prior performing an autoclave.

Can Wi Wireless Adapters be autoclaved?

No, Wi wireless adapters are not meant to contact process liquids so they do not need to be autoclaved. Autoclaving a Wi adapter will damage the internal electronics. Please remove it from the sensor prior to performing an autoclave.

How many autoclave cycles can a sensor withstand?

The amount of cycles a sensor can withstand is dependent on autoclave temperature / time and will vary from sensor type-to-type. Due to these criteria it is difficult to put a firm number on the autoclave cycles a sensor can withstand. Hamilton recommends typical autoclave temperatures of 121°C for no longer than 30 minutes. Autoclavation at elevated temperatures and longer times will degrade sensors more quickly.

Verification on known liquid buffers or standards should be done after autoclaving any Hamilton sensor to confirm the sensor is working to the end-user's expectations.

EFFECTS OF AUTOCLAVE ON PH SENSORS

Why is a protective cap used with some sensors but not others?

Caps that cover the sensor electrical connections protect against condensed moisture from the autoclave. Moisture is undesirable as it could cause corrosion or possibly short-circuit a sensor. Moisture is more of an issue with recessed electrical connectors such as the T82/D4 found on polarographic DO sensors and the S8 connectors found on pH / ORP sensors. Moisture is much less of a concern on VP and K8 connectors. These connectors have no recessed areas thus any residual condensation can be easily wiped off post-autoclave.

For T82/D4 style connectors use Ref 242000 autoclave cap (sold separately) to protect against moisture. For S8 and K8 connectors use the cap provided with the sensor.

NOTE - The yellow caps supplied with VP style connectors are NOT designed to withstand autoclavation and should be removed prior to exposure to temperature.


I do not have a cap, what alternatives are there?

Tin foil / aluminum foil is commonly used as an alternate cover in place of a cap. Remember, due to their design, VP and K8 style connectors require no cap and Hamilton suggests that these connectors remain exposed.

Gravity versus vacuum cycle steam sterilization: Which should I choose?

Gravity cycle sterilization of sensors is preferred. Vacuum cycle sterilization is undesirable as the process frequently uses a series of fluctuating pressure and vacuum loads that can shorten the life of sensors. Moisture should be present during the autoclave cycle (avoid dry heat as higher temperatures may be required). Even just a few droplets of water can help in this process.