AUTOMATED-METHOD FOR SULFATE DETERMINATION IN SOIL-PLANT EXTRACTS ANDWATERS

A segmented flow system is described for a simple and sensitive automa ted method for measuring sulphate in several acidic and neutral matrix es. The procedure was based on the turbidimetric measurement of barium sulfate (BaSO4) precipitation. Gelatine is included in the barium chl oride (BaCl2 . 2H2O) solution to stabilise the suspended precipitate. Taking into consideration the nature of the matrix, this method can be used to measure sulphate concentration in water, in acid extracts of soils (phosphoric or acetic acids), and in very acid digestion of plan t material (perchloric acid). The ranges of concentrations are also va riable: (i) up to 10 mg/L without a dilution step, and (ii) up to 100 mg/L with automatic dilution of the sample. To reduce sensitivity or o vercome interferences, a dialyser must be included in the system for h igher concentrations and/or coloured samples.