微波消解-气相色谱法测定罗汉参中硒的含量

Determination of the content of selenium in rohan ginseng by microwave digestion-gas chromatography

建立了微波消解-气相色谱法测定罗汉参中硒的方法。称取0.300 0 g经粉碎的罗汉参于封闭的聚四氟乙烯消化罐中,加入6.00 mL HNO3和2.00 mL 30%H2O2,经微波消解后,在酸性条件下,将消化液中的Se（Ⅵ）全部还原成Se（Ⅵ）;加入1%4-硝基邻苯二胺（NPDA）溶液,在酸性溶液中选择性地与Se？反应生成稳定性高的5-硝基-2,1,3-苯并硒二唑（苤硒脑）;该物质经甲苯萃取,微量进样后,通过毛细管色谱柱分离,用电子捕获检测器测定,以保留时间定性,由硒含量与峰高成正比绘制标准曲线,曲线方程为y=744.925x＋0.217相关系数R=0.998 3,在0.005~0.025μg/mL硒含量范围内线性关系良好;相对标准偏差（n=5）小于1.1%,加标回收率在98.0%~100.7%范围内,低检出限为0.003 mg/L。方法准确度高、精密度好、实用性强,结果令人满意。

A new method to determine the content of selenium in rohan ginseng using microwave digestion-gas chromatography is established.The detect conditions are as following： in a PTFE digestion jar,0.300 0 g of crushed rohan ginseng is mixed with 6.00 mL nitric acid and 2.00 mL 30% hydrogen peroxide.After microwave digestion, the Se（ VI） in digestive juice is reduced to Se（ IV） under acidic conditions.Then,1% 4- nitro phthalic diamine（ NPDA） solution is applied to react selectively with Se（ IV） to form highly stable 5-Nitro-benzo（ 1,2,5） selenadiazole.After extraction by toluene,the substance is separated by capillary gas chromatography.In order to retain the qualitative time,electron capture detector was used.The standard curve with relationship between Se content and the peak height is linearly proportional,with equation of y = 744.925x ＋ 0.217 and correlation coefficient of R = 0.998 3.The linear relationship is valid when the selenium content is within the range of 0.005 to 0.025μg/mL.The relative standard deviation（ n = 5） is less than 1.1%.The recovery rate is in the range of 98.0% to 100.7%.The lowest detection limit is 0.003 mg/L.This method is accurate,sensitive and practical.