Goal:

To measure oxygen concentration is measured in the headspace of organic solvents such as Acetonitrile) using a phase fluorometer systemMethod:
O2 Sensing

Hardware Used:
Phase Fluorometer Electronics (MFPF)
Bifurcated Fiber Optic Cable
Hioxy-R Sensor

Feasibility Test Procedure
The MFPF electronics is an instrument platform for measurement of fluorescence lifetime and phase. This frequency domain electronics uses a blue LED excitation and a photodiode for detection. A fluorescence method is used to measure the partial pressure of dissolved or gaseous oxygen. A bifurcated optical fiber carries excitation light produced by the blue LED to the thin-film coating of the Hioxy-R sensor.. Fluorescence generated at the tip of the probe is collected by the probe and carried by the optical fiber to the detector of the MFPF. The phase shift between the blue LED excitation and emission signal of fluorescence is used to calculate the lifetime.  The Lifetime is an essential parameter for the calculation of oxygen.

To test the feasibility of the Hioxy sensor in the Acetonitrile headspace, the Hioxy Sensor is evaluated for its performance before exposure to the acetonitrile vapor.
The Hioxy sensor is exposed to Nitrogen and then to Air as show in Figure 1. The ratio of the lifetime from Nitrogen to Air is noted to be approximately 4.01. Now the sensor is exposed to the vapors of acetonitrile for about 2 hours. After the exposure the sensor is pulled out from the vapors and left in ambient conditions. The ratio of Nitrogen to air is measured again in terms of lifetime. The ratio after this exposure has changed to 4.27. The sensor is again exposed to acetonitrile vapor and the ratio is measured after exposure to be the same at 4.27.

Results
As shown in Figure 1, the Hioxy Sensor looks very stable in the headspace of the Acetonitrile container. The ratio of Nitrogen to Air has changed after the first exposure to Acetonitrile vapor. After the first exposure the ratio stays the same. This means there is a one time effect on the sensor when exposed to acetonitrile vapor.

Conclusion
The Hioxy sensor can be used to measure oxygen in the headspace of Acetonitrile. When a sensor is sold for this application, the sensor needs to be cured with acetonitrile vapor before calibration.

Note:
The sensor needs to be placed in acetonitrile vapor for at least 2 hours before use.

This entry was posted on Wednesday, December 9th, 2009 at 5:01 pm and is filed under Chemistry, Consumer Products, Oxygen. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.