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Add 9.5 mL of scintillation cocktail
Optiphase ’Hisafe’3 (LKB, Wallac). Shake well. Measure after ½ hour with a liquid scintillation counter.
To be able to calculate
55Fe radioactivity, counting efficiency need to be determined
(efficiency calibration). Counting efficiency is determined from a
55Fe standard series using
Fluorescein (C
20H
12O
5) as a quenching agent.
A quenching standard series
Add reagents into plastic scintillation vials as follows:

55Fe (X Bq/ml)

MQH2O

HF

Fluorescein

Scintillation cocktail

1

0.5 ml

2 ml

1 drop

0 ml

9.5 ml

2

0.5 ml

1.9 ml

1 drop

0.1 ml

9.5 ml

3

0.5 ml

1.8 ml

1 drop

0.2 ml

9.5 ml

4

0.5 ml

1.6 ml

1 drop

0.4 ml

9.5 ml

5

0.5 ml

1.0 ml

1 drop

1.0 ml

9.5 ml

Shake well. After ½ hour measure the samples in a liquid scintillation counter.
Draw a quenching standard quenching curve. Determine the counting efficiency for
55Fe from the curve.