Metrohm 750 Autosampler - Manual (Page 42)

4.1 Operating information
750 Autosampler
39
4 Notes – Maintenance –
Faults
4.1 Operating information
4.1.1 Loading sample vials
Load the vial with sample to within ≈ 6 mm (1/4 in.) of the top and push
the polyethylene cap (cup side down) into the vial. The cap has two
sealing rings on its periphery. The cap should be pushed into the vial
so that both rings engage and remain so. The maximum volume of
sample is 800 µ L, the minimum volume of sample is 300 µ L using a
loop size > 20 µ L and 150 µ L using a loop size ≤ 20 µ L.
Air trapped under the plastic caps is of no consequence. The first
stroke of the needle into the vial displaces enough liquid to force the air
completely through the injector valve loop and through the waste outlet
tube. Should any air remain in the vial, it will be above the needle
opening and will not enter the tubing. The first stroke also forces
enough sample through the tubing and loop to remove remnants of the
previous sample.
4.1.2 Sample preparation
It is important that samples be free of particulate matter which may plug
the needle or tubing. Metallic or gritty particles will cause damage to the
injection valve and may plug the chromatographic system. All samples
should be filtered therefore prior to filling the vials. This can be accom-
plished using a hand filtration device with a 0.45 µµm membrane filter
shown in Fig. 9.
Fig. 9: Manual sample filtering