YSI 2700 SELECT - Simultaneous Dextrose and Sucrose

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You must have a dual channel version of the 2700 SELECT in order to perform this
measurement. Refer to the sections above on DEXTROSE and SUCROSE for theoretical and
special considerations. Then follow the instructions below to set up your instrument for
simultaneous determination.
Since the Sucrose Membrane (2703) utilizes a chain of enzyme reactions and the final reaction
is a “dextrose measurement”, free dextrose in a sample will be measured at the Sucrose Sensor.
By using the information at the Dextrose Sensor, this free dextrose is automatically subtracted
in the instrument software. The algorithm looks basically like this:
(“Total Dextrose” - “Free Dextrose”) x (1.9) = Sucrose
Total Dextrose is the combined sucrose and dextrose probe signal. Free Dextrose is the dextrose
not derived from sucrose hydrolysis. The constant 1.9 corrects for the weight of fructose that is
not sensed at either probe, and the water of hydrolysis.
System Buffer YSI 2357
Calibrator Std YSI 2776 and YSI 2780
Linearity Std YSI 1531 and YSI 2778
Black Membrane YSI 2703
White Membrane YSI 2365
Sample Size 25 µL
Cal Station Two Station, # 1 (dex), #2 (suc)*
Black Probe Parameters White Probe Parameters
Chemistry Sucrose Chemistry Dextrose
Unit of Conc g/L Unit of Conc g/L
Cal value 5.00 Cal value 2.50
End Point 30 sec End Point 30 sec
* Since sucrose calibrator is at the Test Tube Holder, you must sample at the Manual Station
(#3). The Turntable position (#4), and the Monitor Station (#5) may also be used on units
equipped with these accessories.
Special Considerations:
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The combined total of dextrose + sucrose cannot exceed 25 g/L. The dextrose
concentration cannot exceed 10 g/L if the combined total is near 25 g/L, since a
dextrose concentration that high combined with 15 g/L sucrose will saturate the
Sucrose probe. If either of these conditions occur, you should dilute your sample to
bring it into a reasonable range.
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The ability to select sample size (5 to 65 µL) may help you optimize your system,
especially if very high or very low concentrations of one or the other of these
substrates is a problem. The optimal probe current for a calibrator is about 10 nA. See
Menu Diagnostics, Section 5.4, to learn more about measuring your probe signal
before entering Run mode.
Special Considerations continued on other side....