Metrohm 781 pH/Ion Meter - Manual (Page 133)

8 Troubleshooting – Messages – Maintenance
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8.4.2 Wet tests
Quality assurance standards such as GLP (Good Laboratory Practice)
require the regular validation of the analytical instruments. The repro-
ducibility and accuracy of the instruments are checked.
Repeating the test at yearly intervals is normally adequate. However,
depending upon the requirements, it may be necessary to carry out the
test more frequently, e.g. every 3 months or every 6 months.
A basis for a test procedure (SOP, Standard Operating Procedure) is
given in the following Metrohm Application Bulletin:
AB No. 271: Validation of Metrohm pH Meters.
The validation interval can be monitored by the pH/Ion Meter (see Sec-
tion 5.5). When the interval has expired the pH/Ion Meter will show the
following message:
validate instrument
8.4.3 pH/Ion Meter maintenance
In the same way as monitoring the validation interval, the pH/Ion Meter
can also remind you that maintenance is due, e.g. by Metrohm Service
(see Section 5.5).
service is due