￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭
4 Handling and maintenance
807 Dosing Unit
￭￭￭￭￭￭￭￭
35
4.1.4.2 PETG housing
In contrast to the other components of the dosing unit, the transparent
housing has only limited resistance to chemicals.
Good resistance Aqueous solutions, diluted acids, alcohols and
hydrocarbons
Limited resistance Concentrated organic acids, diluted aqueous
alkalis (cold cracking), acetone, isopropanol, tet-
rahydrofuran, hot water
Non-resistant Concentrated inorganic acids and bases, bro-
mine, chlorinated solvents, phenol, water vapor
>100°C
The PETG housing is not dishwasher-safe, but it can be cleaned readily
with lukewarm water and a dishwashing detergent.
4.1.4.3
Materials
Housing PETG (polyethylene terephthalate, glycol-modi-
fied) or PVDF
Centering tube PETG or PVDF
Dosing piston PTFE (polytetrafluoroethylene)
Dosing cylinder Borosilicate 3.3 or ETFE
Valve disc Silicone carbide ceramic
Distributor disc Al
2
O
3
ceramic
Distributor chan-
nels
ETFE
4.2 GLP - Validation
Every dosing unit manufactured by the Metrohm company is subjected to
rigorous quality controls prior to shipment. Every dosing unit is issued a
quality certificate attesting to conformance with the strict quality criteria
of Metrohm GLP(Good Laboratory Practice) requires, among other
things, periodic inspection of analytical measuring devices with respect to
precision and correctness on the basis of standard operating procedures
Standard Operating P rocedure, SOP). This may also include an inspection
of dosing accuracy.
Recommended literature
￭ Metrohm brochure "Quality management with Metrohm", detailed
information concerning the principles and procedural methods of
Good Laboratory Practice
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