4-9
&
'
This is a direct reading of Ethanol in solution at the enzyme sensor. The enzyme Alcohol
Oxidase is immobilized in the enzyme membrane.
E O
2
Alcohol Oxidase
H
2
O
2
+ Acetaldehyde
System Buffer
YSI 2787
Calibrator Std
YSI 2390 (Solution A, 2.00 g/L)
Linearity Std
YSI 2390 (Solution B, 3.20 g/L)
Black Probe
YSI 2786 Alcohol Oxidase Membrane
White Probe
n/a *
Sample Size
10
µ
L (for best linearity)
Cal Station
Station #2 Test Tube Holder **
Black Probe Parameters
Chemistry
Ethanol
Unit of Conc
g/L
Cal value
2.00 g/L
End Point
45 sec
* If you have a dual channel unit, either Black or White, or both Black and White probes can be
configured for this chemistry.
** You may use Station #1 (Cal Well), but evaporation through plastic components may be a
problem. See the evaporation control information in special considerations.
Note: See Appendix A if concentration unit conversion is required.
Special Considerations:
»
The linear range of ethanol is quite limited. If you are concerned about linearity,
monitor the upper range of concentration on a regular basis. You may benefit by
preparing and using a calibrator with an ethanol concentration close to your sample
concentration .
»
If you prepare your own ethanol calibrator, prepare a solution with ionic strength.
Level sensing at Station #2 (Test Tube Holder) depends on a conductive solution. A
0.1% K
2
EDTA solution as a diluent acts as both a conductive solution and a
preservative. Normal saline solution (0.9%) is also an acceptable diluent.
»
Your sample should be methanol-free. Methanol can be a significant interference,
since it is a good substrate for Alcohol Oxidase. Propanol and butanol are very weak
substrates of Alcohol Oxidase and usually do not present an interference problem.
»
Controlling evaporation of ethanol from both sample and calibrator is important. The
use of some type of test tube cover (eg., prepunctured film) will help. Frequently
replacing the calibrator solution with fresh solution will also minimize the effects of
evaporation on measurement integrity.
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