EN 14880:2005 – Surface active agents – Determination of inorganic sulphate content in anionic surface active agents – Potentiometric lead selective electrode titration method
1 Scope
This European Standard specifies a method for the determination of the content of inorganic sulphate in anionic surface active agents. It can be applied to α-olefin sulphonates and n-olefin sulphonates, alcohol sulphates, alcohol ether sulphates, alkyl benzene sulphonates and other alkyl sulphonates. This method is used also for the determination of inorganic sulphate in alkyl benzene sulphonates or other alkyl sulphonates in their acid form. This method also applies to deep-coloured samples.
NOTE Sulphate can be present as sulphuric acid, ionic salts of this acid or mixture of these.
2 Normative references
The following referenced documents are indispensable for the application of this European Standard. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
EN ISO 3696, Water for analytical laboratory use – Specification and test methods (ISO 3696:1987)
ISO 607, Surface active agents and detergents – Methods of sample division
3 Principle
Potentiometric titration of the test sample containing inorganic sulphate is performed in non-aqueous medium with a lead nitrate standard volumetric solution. The reaction is the following:NO 2 PbSO SO ) NO ( Pb Lead sulphate precipitate is formed during the titration and the non-aqueous medium decreases its solubility. Nitric acid is added to remove possible interference from carbonates. The endpoint is related to an increase in lead ion activity, as measured by a lead-selective electrode.
4 Reagents
During the analysis, unless otherwise specified, use only reagents of recognised analytical grade that have been checked in advance as to not interfere with the analytical results.
4.1 Water, complying with grade 3 as defined in EN ISO 3696.
NOTE If the water is purified via ion-exchange resins, ensure that no cationic or anionic species from the resins cause interference.
4.2 Nitric acid, solution c(HNO 3 ) = 1 mol/l.
4.3 Lead nitrate standard volumetric solution, c(Pb(NO 3 ) 2 ) = 0,01 mol/l.
Weigh 3,312 g of lead nitrate, previously dried at 150 °C in a vacuum oven, dissolve in water, by using a small beaker. Quantitatively transfer the solution into a 1 000 ml volumetric flask and add water up to the mark.
4.4 Lead nitrate standard volumetric solution, c(Pb(NO 3 ) 2 ) = 0,005 mol/l.
Weigh 1,656 g of lead nitrate, previously dried at 150 °C in a vacuum oven, dissolve in water, by using a small beaker. Quantitatively transfer the solution into a 1 000 ml volumetric flask and add water up to the mark.
EN 14880:2005 – Surface active agents – Determination of inorganic sulphate content in anionic surface active agents – Potentiometric lead selective electrode titration method