YSI 2700 Select Biochemistry Analyzer

Introduction

The YSI Biochemistry analyzer is a great and easy instrument for measuring many substances in liquid samples. Typically it can only measure one substrate at a time, but sometimes two at once. The system uses an enzymatic membrane specific to the sustance you're trying to detect and measures changes in current. The YSI can measure the following analytes (haha): Dextrose (D-Glucose), Ethanol, L-Glutamate, L-Lactate, Lactose, Sucrose, Choline, L-Glutamine, Methanol, Galactose, and Hydrogen Peroxide.

Simple Protocol for Everyday Use

There are a few things that you need to check first:

• Is the buffer the correct one?
  • Is there enough buffer to run all your samples?
• Is the membrane the correct one?
  • Has it passed its expiration date? (see manual section 1.4 for working lifelifetimes)
• Has my calibration standard expired?
• Is the concentration of what I'm trying to measure below the linearity check point? (see manual section 1.4)
• Are my samples at room temperature? (temperature can affect the readings significantly)

The simple procedure for running your sample is:

1. Turn on the instrument. The power supply is on the lower left hand side of the back panel (as you face the instrument).
2. Determine which electrode (white or black) is housing your membrane (to change a membrane see the next section).
3. Press Menu and then MeasParameter and then Select your electrode of interest (black or white) and your analyte of interest. Be sure to also set the other electrode (the one without your membrane of interest) to "none".
4. Return to the main menu by pressing Menu and then press Run to enter the run mode.
5. Wait for the machine to stabilize the base current and auto-calibrate.
6. Hit Run Sample. This will summon the manual injection needle from its housing and cause it to extend from the upper left front of the unit.
7. After the aspiration needle is still and fully extended, carefully hold your sample-containing test tube so that the needle tip is immersed in the sample. While holding the sample in this position, hit Aspirate Sample.
   1. on older units both Run Sample and Aspirate Sample are the same button, simply labeled Sample.
8. Hold your sample until the aspiration needle withdraws back into the unit’s housing.
9. Wait for the analysis of your sample to be completed and for the results to display on the LCD screen. (This should take 1-2 minutes)
10. Repeat sampling procedure as desired.
11. When you are finished, change the instrument to “Standby” mode in the front control panel.
12. Turn off the YSI 2700 Select Biochemistry Analyzer.

Special Notes:

• Every 5 – 6 samples, the machine will automatically recalibrate itself to make sure that the current measured for reference standards is not drifting too far from the previously established calibration. The autocalibration takes some minutes to complete. Be patient.
• Periodically, buffer tanks run low and enzyme electrodes need to be replaced. This is not very difficult, but see the manual for specific instructions.

Periodic Maintenance: Changing the Membrane Electrodes

1. Make sure you have purchased unexpired membrane electrodes from YSI, and have them ready at the instrument. Make sure the instrument in powered off.
2. For reference, some commonly used membranes:
   1. Glucose: YSI2392
   2. Lactate: ???
   3. Glutamate: ???
3. Open one of the four membrane compartments containing the new membrane.
4. Use salt solution (part YSI2392) to wet the surface of the membrane. Be careful not to touch the membrane during this process.
5. Open the YSI front casing by pulling on the left side of the instrument.
6. Unscrew the electrode (L=lactate, G=glucose) you intend to change.
7. Using tweezers, carefully remove the old membrane from the electrode.
8. Wash the electrode with salt solution, and blot dry with a kimwipe.
9. Repeat the previous step several times.
10. Carefully press the clean electrode tip onto the bead of salt solution which is wetting the new membrane. Capillarity will make the membrane stick to the electrode surface.
11. Turn the electrode over, making sure not to separate the membrane from the electrode in the process.
12. Carefully move the membrane into place by pressing with tweezers *only on the rubber septum which borders the membrane*. Do not touch the membrane directly.
13. Blot any excess droplets of salt solution away from the electrode casing.
14. Rescrew the electrode into the housing chamber.
15. Close the YSI and turn on its power.
16. Press Menu, Service, blah blah blah, and monitor the current.
17. Periodically press "flush" until the basal currents for each membrane are under 5 nA.
18. Exit from the "monitor" mode. The YSI is ready to put into run mode! After the machine autocalibrates itself, it will be ready to use.

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