112
8.2.11 Methanol
This is a direct reading of Methanol in solution at the enzyme sensor. The enzyme Alcohol Oxidase is immobilized in the
enzyme membrane.
Methanol + O
2
Alcohol Oxidase
H
2
O
2
+ Formaldehyde
Solution A
Solution B
Color
Location
Tube Holder
Range
Point
Point
15 µL
(CV,n=10)
whichever is
greater
(0.1 to Cal Point)
±5%
(Cal Point to Range
Max)
Life
Note: See Appendix B – Concentration
Unit Conversion if concentration unit
conversion is required.
• The linear range of methanol 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 a methanol
concentration close to your sample concentration.
• If you prepare your own methanol calibrator, prepare a
solution with ionic strength. Level sensing at the Tube
Holder depends on a conductive solution. A 0.1%
K2EDTA solution as a diluent acts as both a conductive
solution and a preservative. Normal saline solution
(0.9%) is also an acceptable diluent.
• Since methanol requires a unique buffer and sample
size, a different chemistry cannot be assigned to the
other probe in the methanol module.
• Your sample should be ethanol-free. Ethanol 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 methanol 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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