Metrohm 757 VA Computrace Manuel d'utilisateur télécharger pdf (Page 170)

7 How to ...?

757 VA Computrace – Software

160

15. Use a pipette to add 100 µL Pb ion standard solution

(Pb) =

1 g/L (Metrohm No. 6.2301.100) into the measuring vessel

and click the

<OK>

button.

16. The sample solution spiked again with standard addition solu-

tion is measured three times. Then the

END OF DETERMINA-

TION

window appears.

17. Click the

<OK>

button. The determination is saved automati-

cally and the result report is printed out.

18. To assess the recorded lead determination, the results printed

out in the full report for the mass concentration of lead Mass

conc. and its total scatter MC.dev. are used. The limit val-

ues of these two results depend greatly on the care taken in

the preparation of the analysis solution and in the dispensing

of the standard addition solutions. When the procedure is car-

ried out properly and carefully, the following results should be

expected:

• Accuracy = 95 … 105 %

Final Results: Pb = 0.95 … 1.05 g/L

• Scatter ≤ ± 3 %

Res. dev ≤ ± 0.03 g/L (± 3 %)

19. If desired, the reproducibility can be determined by perform-

ing the Testpb method several times and comparing the

results obtained for the mass concentration Mass conc..

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Metrohm 757 VA Computrace Manuel d'utilisateur Page 170