离子色谱法测定氧化铁粉中痕量氯离子

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

用超声提取法在氧化铁粉样品中加入一定量的20 mmol·L^(-1)碳酸钠和15 mmol·L^(-1)碳酸氢钠溶液的混合溶液提取其中氯离子,或者用水蒸气蒸馏法馏出样品中的氯离子,馏出物吸收于碳酸钠-碳酸氢钠混合溶液中。色谱测定中,Dionex AS 4A型阴离子柱用于各阴离子的分离,并采用电导检测法进行检测。共存的阴离子F^-、NO_3^-、SO_4^(2-)、PO_4^(3-)等均得以有效分离而不干扰氯离子的测定。比较试验结果显示:超声提取法较水蒸气蒸馏法操作更简便。在称样量为0.5 g时,方法的检出限(3s/k)为0.51 μg·L^(-1)。对方法的回收率及精密度也作了试验,测得其回收率在91%～106%之间,测定值的相对标准偏差(n=10)为1.3%～5.0%之间。

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 15mmol.L-1 of NaHCO3, or by steam distillation and the distillate absorbed by the mixed solution of Na2 CO3 and NaHCCh. The Dionex AS 4A anion column was used for the separation of chloride ion, and conductivity detection was adopted in the determination. Coexisting anions （e. g. F-, NO3-, SO4^2- and PO4^2- 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 t%g ＂ 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 reeovery found were in the range from 91% to 106%, with values of RSD＇s （n=10） ranged from 1.3% to 5.0%.