The staff at CEBTech Services has helped design and build many process sensors for the measurement of concentrations of various alcohols, and dissolved oxygen.
On the farthest left is a basic design for a galvanic dissolved oxygen probe used widely in Bioscience. They are inexpensive and relatively easy to build. They are steam sterilizable, stable, and have a linear millivolt electrical output range of 0-25 mv. They perform with the over-all electrochemical reactions as follows:
SILVER CATHODE: 1/2 O2 + H2O + 2e- ___> 2OH -
LEAD ANODE: Pb ___> Pb++ + 2e-
ANODE SURFACE: 1/2O2 + Pb + H2O ___> Pb(OH)2
(Electrolyte composition: Acetic acid 5.0 M, Sodium acetate 0.5 M, Lead acetate 0.1 M, pH 3.0)On the right is one of the many designs for steam sterilizable alcohol probes. This design has a constant flow of low-pressure air flowing through it and through the silicone tubing which is very permeable to alcohols. The air absorbs alcohols proportional to that present in the fermentation broth. The air/alcohol mix is then sent to a gas sensor with an electrical output, 2-20 VDC, such as the Model TGS822 made by Figaro USA, Inc. www.figarosensor.com.
These are two completed galvanic dissolved oxygen probes. They are steam sterilizable "in place" in a bioreactor. They are mounted in 316 stainless steel housings to withstand turbulence and to allow pressure compensation. The probe tips extend out of the housing approximately 5 cm to allow replacement of the teflon membrane (32, 136, 195, 199, 226).
Craig Bremmon
CEBTech Services
503 11 th Ave. SE, Suite 5
Aberdeen, SD 57401
bremm001@nvc.net Phone: 605 226-3595
Fax: 605 225-0467