The determination of fluoride in sugar cane by using an ion-selective electrode

Abstract

A method is described for the determination of fluoride in sugar cane in which a fluoride ion selective electrode is used. Three methods for removing the interferences of silicon, aluminium and iron, which occur in high concentrations in sugar cane, were evaluated in detail: (1) direct complexation of the interfering elements with phosphoric acid; (2) separation of fluoride from the interfering elements by a microdiffusion technique; and (3) separation of fluoride from the bulk of the interfering elements by leaching from a sodium carbonate-zinc oxide fusion, followed by complexing residual trace elements with citrate.

The proposed method involves an adaptation of method (3) and yielded good accuracy and precision over a wide concentration range of fluoride (5 to 1000 p.p.m.) added to sugar-cane tissue. The method permits the analysis of six samples per working day per operator and can be applied to other types of plant tissues with which silicon, aluminium and iron cause interference.