Ion-chromatographic Determination of Trace Amounts of Chloride Ion in Ferric Oxide Powder

Trace amounts of chloride in ferric oxide powder were separated from the sample either by the ultrasonic extraction with mixed solution of 20 mmol·L-1 of Na2CO3 and 15 mmol·L-1 of NaHCO3,or by steam distillation and the distillate absorbed by the mixed solution of Na2CO3 and NaHCO3. The Dionex AS 4A anion column was used for the separation of chloride ion,and conductivity detection was adopted in the determination. Co-existing anions (e.g. F-,NO-3,SO2-4 and PO3-4 etc.) were effectively separated and did not interfere with the determination of chloride. As shown by the experimental results,the operation of ultrasoinc extraction was easier and simpler than the steam distillation operation. Detection limit (3s/k) of 0.51 μg·L-1 was attained when 0.5 g of sample was taken. Recovery and precision of the method were tested,and the values of average recovery found were in the range from 91% to 106%,with values of RSD′s (n=10) ranged from 1.3% to 5.0%.