建立了多次高温裂解、富集-离子色谱检测己内酰胺(CPL)中痕量氯的分析方法.CPL样品在富氧环境下经3次高温(800 ℃)裂解后,痕量有机氯转化为氯气或氯化氢气体,经5 mL 10 mmol/L 的NaOH溶液吸收、富集,然后转化为氯离子,在阴离子抑制电导检测模式下进行离子色谱分析,检测其中氯离子(Cl-)的含量.在优化的条件下,Cl-在0.05~1.0 mg/L 范围内呈良好线性,相关系数为 0.999 7,方法检出限为0.37 μg/g.对0.8 mg/L 的Cl-标准溶液连续进样7次,其保留时间、峰面积、峰高的RSD分别为0.04%、0.24%和0.20%;分别对CPL样品进行处理和检测,得到痕量氯含量的RSD为1.52%(n=4);Cl-标准溶液的转化率为93.3%~104.0%, CPL样品的加标回收率为95.3%~113.1%.该方法操作简单、前处理条件可控、重复性好、检出限低,可满足实际样品中痕量氯的检测.
A method was developed for determination of trace chlorine in caprolactam samples by ion chromatography (IC) coupled with multiple pyrolysis and enrichment pretreatment.The caprolactam samples were treated by multiple pyrolysis at 800 ℃.Trace organic chlorine in samples was decomposed into chlorine or hydrogen chloride.The gas products of pyrolysis were absorbed and enriched in 5 mL 10 mmol/L NaOH solution, which was analyzed by IC with suppressed conductor.Under the optimum conditions, the linear relationship of Cl- was good in the range of 0.05-1.0 mg/L with correlation coefficient of 0.999 7.The method detection limit of chlorine in caprolatam samples was 0.37 μg/g.For 0.8 mg/L Cl- standard solution, the RSDs of retention time, peak area and peak height were 0.04%, 0.24%, and 0.20%, respectively (n=7).The RSD of the contents of chlorine in caprolactam samples was 1.52% (n=4).The conversion ratio of Cl-standard solution ranged from 93.3% to 104.0%, and the spiked recoveries of the samples ranged from 95.3% to 113.1%.The method was applied to determine the contents of chlorine in caprolactam samples with simple operation, controlled pretreatment, low blank, low detection limit, good reproducibility and satisfactory results.
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