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2.3 Operating tips
Clean your probe regularly during use. For cleaning instructions see section 3.
Ensure samples or buffers are well mixed to obtain correct measurement values. This may be
done by a magnetic stirrer or by stirring with the probe for at least 5 seconds. Stop stirring and
record results when the read-out is stable.
Make sure that the medium which is being measured, is providing a “bridge” between the ISFET
and the diaphragm. Without a proper fluid (or semi-solid) connection between these both, no
(stable) measurement can be performed. A good rule of thumb is to have at least the first 10
mm from the probe tip to be immersed during measurements and calibrations.
When using CupFET or MicroFET probes, especially when performing single droplet
measurements, make sure the medium is in contact with both the ISFET and the diaphragm
simultaneously. The CupFET should contain the medium within the “cup” shaped tip of the
probe.
When using ConeFET or LanceFET probes with semi-solids, insert probe to desired depth, then
rotate left and right several times and tilt to ensure sample contact.
Buffer-handling: pH 7.00 buffers (phosphate-based) and pH 4.00 buffers (biphtalate-based) are
less susceptible to carbon dioxide contamination than pH 10.00 buffers (borax or carbonate
based). When slope errors occur, it usually indicates a failing probe or a contaminated buffer. If
slope errors occur when using a pH 10.00 buffer, try calibrating with pH 7.00 and pH 4.00 buffer.
If a good slope is achieved, try a new bottle of pH 10.00 buffer. Buffers in a convenient twin-
neck bottle are available from Sentron or our dealers.
When testing in direct sunlight or on a bright reflecting surface, please use brown, opaque or
shielded sample containers. Very bright light might influence the performance of the sensor.
Tris buffers and samples containing proteins form impermeable layers on surfaces, and require
special attention when being used. These types of samples should be measured quickly and the
probe should be rinsed thoroughly with deionized water between samples. Avoid prolonged
immersion in samples containing Tris or proteins. When testing is complete, first clean the probe
with water and a laboratory detergent and subsequently rinse with deionized or distilled water.
Avoid prolonged immersion in samples expected to have pH-values at the ends of the specified
pH-range. When prolonged exposure to very high or very low pH values does take place rinse
the probe with neutralizing agents and distilled water when the measurement is completed.
Summary of Contents for ConeFET
Page 5: ...5 1 3 Specifications...
