Metrohm 746 VA Trace Analyzer - Manual (Page 128)

4.4 Lead determination with internal standard
746 VA Trace Analyzer / 747 VA Stand
4-43
5 Drinking water
• Water that has been in the supply system for a lengthy period of time
absorbs metals from the pipe and fittings materials and thus falsifies the
analysis results. Hence, before taking the water sample allow the water
to run out of the tap in a powerful stream for several minutes.
• The drinking water sample should be acidified immediately after the
sample has been taken by adding 10 µ L conc. hydrochloric acid per
10 mL drinking water.
Owing to the large temperature dependence of the measured values ( ≥ 2%/°C), we
recommend you to use the 6.1418.220 Thermostatable measuring vessel with
the internal standard method.
4.4.2 Loading the method INTSTD.mth
To load the method INTSTD.mth from the method memory into the working stor-
age, the following steps are necessary:
1 Switch on instrument
• Switch on the 746 VA Trace Analyzer with mains switch 11 11 at the rear of
the instrument. The instrument is initialized. If all is in order, the dialog
page "MONITORING" appears after a few seconds.
2 Switch to dialog page "METHODS"
• Press the yellow key. The "METHODS" dialog page ap-
pears showing the methods stored in the instrument.
3 Selection of the method INTSTD.mth
• Use the cursor keys to select the method INTSTD.mth , which then
becomes black-backed.
4 Copying the method INTSTD.mth to the working storage
• Press the softkey . The softkey bar changes and presents the
destinations for copying the selected method.
• Press the softkey . The method INTSTD.mth is
copied to the working storage.
4.4.3 Method specifications of the method INTSTD.mth
In this section the 5 dialog pages of the group "Method Specifications" associated
with the loaded method INTSTD.mth will be explained in detail. If you are interested
only in a rapid lead measurement, you can proceed directly to section 4.4.4.
1 Switch to dialog page "OPERATION SEQUENCE"
• Press the yellow key. The dialog page "OPERATION
SEQUENCE" appears with the main program for the lead determination: