16
Spectroquant
®
photometers
Release 06/2014
3 Sample Preparation
In the event that the sample to be analyzed is a highly contaminated ma-
terial (high proportion of organic substances) or water-insoluble samples,
decomposition using concentrated acids and other agents is in dispensible
.
Corresponding examples from the collection of applications for real sam-
ples are available on request.
The necessity for decomposition can be checked according to the follow-
ing diagram:
For wastewater with a consistent composition, this check as a rule need
be carried out only once. It is, however, advisable to check the result peri-
odically.
4 Pipetting System
Positive-displacement pipettes permit
•
an exact dosage of the sample volume
•
a precise measurement of sample and reagent volumes and of the
volumes of water for dilution purposes
.
Pipettes of varying volumes and also ones with a fixed volume are available.
Sources of error and hints on how to avoid them:
•
Closely follow the instructions for use contained with the pipette in
question.
•
Check the pipetted volumes
a)
by weighing using analytical scales (weighing ac cu racy ±1 mg),
1 ml of water at 20 °C = 1.000 g ±1 mg
b) using Spectroquant
®
PipeCheck;
this is a pho tometric check of the pipette, and scales are not
necessary (see section “AQA”).
•
Avoidance of spread effects by rinsing the pipette several times with
the solution to be pipetted.
•
Always exchange the pipette tip.
•
Draw up the liquid slowly and depress piston completely to discharge
the liquid.
Decomposition
Measurement
Result A
A and B
idential?
No decomposition
necessary
Yes
Procedure
Measurement
Result B
Procedure
No
Decomposition
necessary
To Next Page
Loading...