108
8.2.7 Glycerol
This is a direct reading of glycerol in solution at the enzyme sensor. The enzyme Galactose oxidase is immobilized in the
enzyme membrane.
Gl O
2
Gal Oxidase
H
2
O
2
+ Glycerol Aldehyde Derivative
System Buffer
YSI 2705
Calibrator Std
YSI 7141
Linearity Std
YSI 7142
Membrane
YSI 7140
Membrane
Color
Magenta
Detection
Range
0.75–40.0 g/L
Calibration
Point
25.0 g/L
Linearity Check
Point
40.0 g/L
Sample Size
10
µ
L
End Point
30 sec
Precision
(CV,n=10)
3%
at calibration
point
Linearity
±
5% or 0.75 g/L,
whichever is
greater
(0.75 to Range Max)
Typical Working
Life
10 days
Note: See
Unit Conversion if concentration unit
conversion is required.
Special Considerations:
•
If sample dilution is required, use reagent water.
•
The sample should be lactose-free. Lactose and other
galactosides such as galactose, raffinose and stachyose
are substrates for galactose oxidase. They may interfere
by producing artificially high glycerol readings.
•
The enzyme membrane integrity test involving the use of
YSI 2363 Potassium Ferrocyanide solution is not
informative since ferrocyanide exists in the 2705 system
buffer.
•
Always use fresh YSI 2705 Buffer in an opaque buffer
bottle, such as the YSI 2935, when installing a new YSI
7140 Glycerol Membrane. Do not expose the 2705 Buffer
to light any more than necessary before it is installed in
the 2935 Bottle.
•
For maximum performance on the first day the glycerol
membrane is installed, calibrate before every sample.
•
If membrane sensitivity drops below 5nA, increase
sample size as required.
•
Reduce loss in membrane sensitivity over time by
calibrating glycerol membranes every 2 to 4 hours while
the instrument is idle.
•
Decontaminate the 2735 Buffer bottle and cap at least
monthly with 1% hypochlorite.
