4.13  Determination of sulphate in aerosol filters

4.13.1  Determination of sulphate ions by ion chromatography

The procedures after the extraction from the aerosol filter (Section 3.6.2) for Dionex systems and for Waters systems are described in Section 4.1.

4.13.2  Determination of sulphate spectrophotometric by the barium perchlorate – Thorin method

4.13.2.1  Field of application

This method is applicable for the determination of water-soluble particulate sulphate collected on a filter. The working range is within 1 to 80 µg S per filter.

4.13.2.2  Principle

Particulate sulphate collected on a filter is dissolved in water. The concentration of sulphate in the solution is determined spectrophotometrically as described in Section 4.2.1 or 4.2.2.

4.13.2.3  Instrumentation

Same as listed in Section 4.2.1. In addition: 50 ml Erlenmeyer flasks.

4.13.2.4  Chemicals

Same as listed in Section 4.2.1.

4.13.2.5  Reagents

Same as listed in Section 4.2.1.

4.13.2.6  Calibration

Proceed as described in Section 4.2.1.

4.13.2.7  Analytical procedure

Transfer the exposed filters and blank filters to 50 ml Erlenmeyer flasks. Add 20 ml of water, shake well and leave for 30 minutes. (For small filters and low concentrations of sulphate use only 10 ml of water). Proceed according to Section 4.2.1.7 or 4.2.2.6.

4.13.2.8  Expression of results

The concentration of water soluble particulate sulphate in the air sample expressed in micrograms of sulphur per cubic metre, is given by:

         

a  = concentration of sulphur, in milligrams per litre, read from the calibration curve.
b  = concentration of sulphur in the blank sample
v= the volume of water, in litres, used to extract the filter.


Last revision: November 2001