YSI 556 MPS - Manual (Page 101)

Maintenance Section 11
YSI Incorporated YSI 556 MPS Page 95
1. Soak the sensor for 30-60 minutes in one molar (1 M)
hydrochloric acid (HCl). This reagent can be purchased from
most distributors. Be sure to follow the safety instructions
included with the acid.
2. GENTLY clean the glass bulb and platinum button by rubbing
with a cotton swab soaked in the acid.
3. Rinse the sensor in clean water, wipe with a cotton swab
saturated with clean water, and then re-rinse with clean water.
To be certain that all traces of the acid are removed from the
sensor crevices, soak the sensor in clean water for about an
hour with occasional stirring.
NOTE: If biological contamination of the reference junction
is suspected or if good response is not restored by the above
procedures, perform the following additional cleaning step:
1. Soak the sensor for approximately 1 hour in a 1 to 1 dilution
of commercially available chlorine bleach.
2. Rinse the sensor with clean water and then soak for at least 1
hour in clean water with occasional stirring to remove residual
bleach from the junction. (If possible, soak the sensor for
period of time longer than 1 hour in order to be certain that all
traces of chlorine bleach are removed.) Then re-rinse the
sensor with clean water and retest.`
11.1.4 Temperature/Conductivity Sensor Cleaning
The single most important requirement for accurate and reproducible results
in conductivity measurement is a clean cell. A dirty cell will change the
conductivity of a solution by contaminating it. The small cleaning brush
included in the YSI 5511 Maintenance Kit is ideal for this purpose.
To clean the conductivity cell:
1. Dip the brush in clean water and insert it into each hole 1520
times.
2. Rinse the cell thoroughly in deionized or clean tap water.