Study Set Content:
a term used to indicate the determination of a metal in the presence of another metal
Masking
EDTA is a hexadentate ligand, which means that it binds six times. It binds twice at the
nitrogens
and four at the
Oxygens
- formation of insoluble substances to be used for assay
Precipitimetric method
- Precipitimetric example method
- Example methods:
- Fajan
- Mohr
- Volhard
- Liebig
- Gay-lussac
Determination of end point may be determined by the following:
- Cessation of precipitation or appearance of turbidity
- use of internal indicator instrumental methods
- ex. potentiometry or amperometry
The indicators used for volumetric precipitation methods:
Ferric ammonium sulfate
Potassium chromate TS
Adsorption indicators:
- Dichloro flourescein (DCF)
- Eosin Y
- Tetra bromo phenolphthalein ethyl ester (TEE)
Involves a change of color on the surface of the precipitate
Fajan Method
Standard solution used:
Silver nitrate
Positive indicators:
Eosin, TEE, DCF
Negative indicators:
Rhodamine
Sample assays:
Phenylephrine HCl, Tubocurarine HCl, Meperidine HCl
Involves the formation of a soluble red complex.
Volhard Method
Standard solution:
Potassium thiocyanate
Indicator used:
Ferric ammonium sulfate (FAS)
Sample assays:
Aminophylline for theophylline, Sodium chloride dextrose and NaCl injection
STEP OF VOLHARD'S METHOD
Involves the formation of a second precipitate which is of a different color from the primary precipitate. But the second precipitate must be more soluble than the first.
Mohr method
Standard solution:
silver nitrate
