Metrohm 833 IC Liquid Handling Unit - Manual (Page 82)

8 833 IC Liquid Handling Ultrafiltration Unit
833 IC Liquid Handling Unit / Instructions for Use 8.833.1003
74
8.4 Filtration
8.4.1 Selection of possible sample types
Each filtration process using a filtration membrane with a small pore
size could be subject to a membrane blockage.
The following table lists some types of sample that have been filtered
with the 833 IC Liquid Handling Ultrafiltration Unit with the standard
6.2714.020 Filtration membrane (0.15 µm) or a second filter membrane
(0.2 µm) and then analyzed on a Metrohm IC system. The
concentrations of the following 7 anions were determined: F - , Cl - , NO
2
- ,
Br - , NO
3
- , HPO
4
2- , SO
4
2- .
Sample type Pore size
of membrane
No. of samples
per filter
Orange juice with fruit pulp 0.15 40
Surface water 0.15 500
Drinking water 0.15 1000
Ground water 0.15 500
Wastewater 1 0.15 1000
Wastewater 2 0.15 130
Wastewater 3 0.15 40
Wastewater 4 0.15 80
NaCl solution (1%) 0.2 5000
Schöninger digestion soln. 0.2 100
Acidic soil extracts 0.2 1000
Aqueous soil extracts 0.2 200
The given number of samples that can be filtered on a filter membrane
without any loss of quality being observed are empirical values. They
have been determined at Metrohm AG and by various customers and
should be used as an orientation guide for estimating the application of
the ultrafiltration cell for sample preparation. These values must be
determined individually for each new application.
8.4.2 Filter working life
A reduction in the recovery rate when analyzing standard solutions can
be used as a possible indicator for the early recognition of an
impending blockage. Ideally these solutions should be made up in the
sample matrix being analyzed.
This means that if a large number of samples are to be analyzed then it
is advisable to measure standard solutions at regular intervals, for
example after every 5th or 10th sample for sample with a high particle
load. However, it is not possible to make any general prediction about
the number of possible filtration processes. The development of the
recovery rate with the number of samples may also be subject to large
variations. While with one sample matrix the recovery rate may remain