Dissolved Oxygen Manual 5 Version 1.7
Reporting dissolved oxygen in mg/L :
If you prefer to get your data in units of mg/L of dissolved oxygen, you can convert your %
saturation values. You need to know what value of mg/L DO corresponds to 100% saturation DO.
This number depends on several factors, including the conductivity (or “salinity”) of the wine, its
alcohol content, temperature, and the ambient barometric pressure. For most wines, only the latter two
are significant. At room temperature (72 F or 22.5 degrees C) and ordinary air pressure (sea level on a
clear day), the saturating oxygen level is about 8.5 mg/L. For most purposes, this value will be close
enough to give you the accuracy needed to make decisions. Be aware, however that this value
decreases about 10% for every 5ºC (8ºF) increase and for every 3000 feet (1000m) of elevation
increase.
Once you have a value for 100% (saturating) dissolved oxygen for your wine in ambient
conditions, calculate your dissolved oxygen from the data you have.
DO, mg/L = saturating oxygen level (mg/L) x % saturation
In the above example, assuming we are at sea level and 72 degrees, the DO is 8.5 x 14% = 1.2 mg/L
Finishing Up:
1. Turn off your pH meter and rinse the vials and the electrode with DI water. Replace the black
rubber cover over the end of the electrode to prevent damage to the membrane.
2. Electrode Storage: The electrode may be stored with its tip submerged in water for a few weeks
at a time, but make sure the electrode is disconnected from the meter during storage. For long
term storage you should store the electrode dry (unscrew the membrane cap, drain the
electrolyte, rinse everything with distilled water and let dry in air).
3. Cleaning and Maintenance: After the electrode has been used for a period of time the residual
current may rise, which shows up as an increasing value of 0% DO, and/or you may see a
decrease in 100%DO values. First, try replacing the electrolyte as described on page 2 under
“Setup”. If normal responses still aren’t seen within 15 minutes, the electrode may need
servicing. To recondition the electrode, gently unscrew the membrane cap from the electrode
body and rinse the inside of the cap with DI water; allow to air dry. Soak the silver-gray
cylindrical zinc anode in 0.1N HCl (1 ml 2M HCl, or the Vinmetrica Acid Solution for SO2, in
20 ml DI water) for 15 to 20 minutes. Rinse the zinc anode with DI water, blot dry with tissue
paper. If necessary, use fine sandpaper or similar fine abrasive to remove any grey or white or
other deposits from the anode, and restore a shiny appearance. Rinse with DI water and blot dry
with clean cloth or tissue paper. Refill with fresh electrolyte and replace membrane cap as
directed in the Setup section. It may take an hour or so for normal responses to stabilize.
To estimate changes in saturating oxygen level with temperature and pressure, see the dissolved oxygen
calculator at http://water.usgs.gov/software/DOTABLES/ . Set the specific conductivity of the wine to 3000
microsieverts/cm. To calculate air pressure change with altitude, see http://www.altitude.org/air_pressure.php
