吹扫捕集-气相色谱-质谱法测定水中苦味酸

Determination of picric acid in water by GC- MS with purge and trap

目的建立水中苦味酸的吹扫捕集-气相色谱-质谱检测方法。方法水中苦味酸与衍生剂次氯酸钠反应生成挥发性的氯化苦(三氯硝基甲烷),经ENCON Evolution吹扫捕集仪取样、加氟苯内标、吹扫、捕集和热解析后,进入气相色谱-质谱联用仪进行分离和检测,全扫描监测,内标法定量。结果苦味酸的衍生化产物分离良好,衍生化后72 h内测试稳定,在1.0μg/L^40.0μg/L范围内,苦味酸的浓度与氯化苦/氟苯内标峰面积比呈现良好的线性关系,相关系数>0.999。方法检出限为0.5μg/L。实际水样加标10.0μg/L 7次平行测定RSD为2.8%。不同浓度加标回收率在90%~106%之间。结论:该方法简化了样品的前处理程序,避免了有毒萃取溶剂的使用,具有简便、环保、准确、灵敏的优点,适用于水中苦味酸的常规监测。

Objective To develop an analytical method for picric acid in water by GC - MS with purge and trap concentrator. Methods Picric acid in water reacted with derivatizing agent sodium hypochlorite to produce volatile chloropicrin（nitrotrichlo- romethane）. With fluorobenzene as internal standard, the sample solution containing chloropicrin was purged, trapped and ther- mally desorbed by ENCON Evolution purge and trap concentrator, then separated and detected by GC - MS, finally quantified by internal standard method. Results The derivative product of picric acid was separated well and tested stably within 72 hours. In the concentration range of 1.0 μg/L - 40.0μg/L, picric acid showed good linearity with peak area ratio of chloropic- rin / fluorobenzene （ r 〉 0. 999）. The detection limit of the method was 0.5 μg/L. The recoveries of picric acid at different lev- els were between 90% - 106%, and the RSD was 2.8% with standard addition concentration of 10.0μg/L in practical water sample（n = 7）. Conclusion This method has simplified the sample pre - treatment procedures and avoided the use of toxic solvent, it was convenient, environmental friendly, accurate and sensitive for routine monitoring of picric acid in water.