Metrohm 746 VA Trace Analyzer User Manual

Page 124

4.3 Lead determination with calibration curve

746 VA Trace Analyzer / 747 VA Stand

4-39

Start the determination

•

Press the red key.

•

The status display in the header of the dialog page "MONITORING"

switches to

* BUSY *

, the start time of the measurement is entered un-

der

Determination

and the determination is given a standard name,

also formed from the start time. Further, during the measurement the

measurement window is superimposed which shows the current pro-

gram line being executed and the remaining line time.

•

Shortly after the start of the determination, the screen shows the prompt

to add 10 mL sample to the measuring vessel:

Addition of sample

•

Remove stopper 25

25 on 747 VA Stand and use a pipette to add 10 mL of

drinking water to the measuring vessel through the pipetting opening.

Press the key.

•

The screen shows the prompt to add 1 mL acetate buffer to the measur-

ing vessel:

Addition of acetate buffer

•

Use a pipette to add 1 mL acetate buffer (1 mol/L, pH 4.6) to the

measuring vessel through the pipetting opening. Then close the pipet-

ting opening using stopper 25

25 and press the key.

Measurement of the sample solution

•

Measurement of the sample solution runs as follows (see also section

4.3.3):

−

Purging and stirring for 180 s.

−

Call-up of the segment

DPASV

for measured value recording. The

lead present in the solution is enriched at the hanging mercury

drop with stirring at a measurement voltage of –600 mV and then

determined anodically without stirring from –600

…

–200 mV. The

selected measurement mode DP leads to a current peak whose

maximum lies at ca. –400 mV.

−

The

DPASV

segment is then repeated twice. The three single

measurements are allocated the VR numbers

and

•

On completion of the last measurement, the lead mass concentration is

calculated using the coefficients of the calibration curve stored in the

method. The program is now at an end. The status display in the header

of the dialog page "MONITORING" switches back to

* READY *

, the in-

strument is ready for a new determination.

ЪДДД

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ДДДДДДДДДДДДДДДДДД¿

SMPL 10.000 mL > M

АДДД

ДДД : continue ДДДДДДДДДДДДДДДДДД

ДДДДДДДДДДДДДДДДДДЩ