AS 3580.13.1-1993

Sets out a method for the automated collection and separation of gaseous and acid-soluble particulate fluorides in ambient air. Determination of each form of fluoride by use of an ion-selective electrode is included.

This Standard sets out a method for the collection and separation of acidic gaseous and acid-soluble particulate fluorides from ambient air and their determination using a fluoride ion-selective electrode.This method is applicable to the measurement of acidic gaseous and acid-soluble particulate fluorides suspended in ambient air at concentrations of 1 mg/m3and greater.NOTES:1 This method is subject to certain interferences. Particulate metallic salts such as those of aluminium, iron, magnesium, calcium and rare-earths collected on the initial filter tape may retain some or all of the gaseous fluorides. The presence of fluorophosphates or fluoroborates could contribute varying amounts of fluorides as they dissociate unpredictably.Acidic aerosols or gases may neutralize or acidify the alkali-impregnated final-filter tape thus preventing the quantitative collection of acidic gaseous fluorides. Although a citric acid impregnated Whatman No. 52 initial filter tape has been shown to allow passage of gaseous hydrofluoric acid, it may permit passage of fluoride particles smaller than about 1 mm. Hence these may impinge on the alkali-impregnated final tape. If initial tapes of higher retentivity are required for removal of particles of size less than 1 mm, citric acid impregnated tapes of Whatman No. 42 filter paper or equivalent may be used.2 The addition of total ionic strength adjustment buffer (TISAB) eliminates a number of possible interferences. The effects of metallic ions are minimized by complexing agents. Variation in ionic strength is overcome by maintaining a high concentration of sodium chloride in the TISAB solution. The TISAB solution is buffered to pH 5 to 6 to avoid negative interference from the formation of complexes containing fluoride ions and positive interference from hydroxide ions being measured.

First published as AS 2618.1-1983.
Revised and redesignated AS 3580.13.1-1993.