2 wet tests, 3 maintenance and adjustment of the coulometer – Metrohm 756 KF Coulometer User Manual

Page 142

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7.3 Coulometer validation, GLP mode

756/831 KF Coulometer, Instructions for Use

134

7.3.2 Wet tests

GLP (Good Laboratory Practice) requires the periodic validation of the analytical instru-

ments. The reproducibility and accuracy of the instruments are checked.

An annual repetition of the procedure appears to be sensible. Depending on the require-

ments a more frequent check may be indicated, e.g. every 3 or 6 months.

Guidelines for the testing regulations (SOP, Standard Operating Procedure) are given in

Metrohm Application Bulletin

No. 273: Validation of KF Coulometers according to GLP/ISO 9001.

The validation interval can be checked by the Coulometer (set under <CONFIG>, moni-

toring). If the interval has elapsed the Coulometer displays the message

validate instru-

ment

.

The GLP mode can be used in order to carry out the validation. It contains the appropriate

calculation formulas:

1. content = H2O/C01/C00;3;mg/g

2. recovery = RS1/C22;2;

where

C01=1000

C22=id2= content according to the reagent manufacturer in mg/g

The second formula calculates the recovery rate and is therefore a measure of the accu-

racy. The limit control for the second result is switched on and the limits are 0.97...1.03.

These values apply for a 1.00 mg/g standard.

For a 0.10 mg/g standard the limits should be set to 0.90...1.10.

7.3.3 Maintenance and adjustment of the Coulometer

The Coulometer should be serviced and adjusted by Metrohm service at regular intervals.

The Coulometer can check the date of the next service with the help of the monitoring

function "Service" under <CONFIG>, monitoring. If this date has been passed then the

Coulometer will display the message

service is due

.

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