TN44: The Determination of Trace Anions in Concentrated Phosphoric Acid

Instrument Type: IC

The determination of trace anions in phosphoric acid is hampered by a large excess of phosphate ion. Diluting the concentrated sample overcomes the problem of a large concentration of the interfering matrix ion, but lacks the required sensitivity for the contaminant ions of interest. An improved method for determining trace anions in concentrated phosphoric acid has been developed to overcome this problem. This Technical Note describes the theory, set up, and analytical procedure for the determination of chloride, nitrate, and sulfate at sub-mg/L (ppm) levels in 85% (w/w) phosphoric acid.