Annex I
sample to a boil and adding sufficient KMn04
solution dropwise to give a persistent pink
colour while the solution is boiled for 10 min.
Cool extract an aspirate.
During extraction, if an emulsion forms at
the water-MIBK interface, add anhydrous
Na2S04 to obtain a homogeneous organic
phase.
Extraction period: partitioning time for
silver is critical (keep constant to within 30 s).
181
To avoid problems associated with instability of extracted metal complexes, determine metals immediately after extraction.
4. Calculations
Calculate the concentration of each metal ion
in micrograms per litre by referring to the
appropriate calibration curve.