内标法与外标法测定餐具洗涤剂中甲醇含量的分析比较

Comparison of analysis methods for determination of methanol content in dishwashing detergent adopting ISTD and ESTD

对GB 9985—2000中内标法测定餐具洗涤剂中甲醇含量的方法进行了改进,并比较了内标法和外标法在测定洗涤剂中甲醇含量的差异。通过向洗涤剂样品中加入异丁醇内标液,用75%乙醇定容到一定体积,经0.45μm针式微孔滤膜过滤,DB-FFAP色谱柱分离,火焰离子化检测器（FID）检测,内标法和外标法分别计算洗涤剂中甲醇的含量。实验得到方法的检出限为0.5 mg/L,内标法和外标法的相对标准偏差（RSD）分别为0.4%~0.9%和0.6%~1.2%,平均回收率分别为100%~102%和95%~99%。结果表明,采用内标法和外标法的定量方式获得的结果均能满足检测要求,但内标法的精密度和回收率优于外标法。

The method for determination of methanol content in dishwashing detergent adopting ISTD as specified in GB 9985--2000 was improved. Difference between ISTD method and ESTD method for determination of methanol content in dishwashing detergent was compared. Via the spiking of isobutanol and dilution with 75% ethanol up to the specified volume,then filtered through 0. 45 μm pinhole membrane, the prepared sample solution was separated by DB -FFAP chromatographic column and detected by FID detector, quantified separately with ISTD and ESTD. Results showed that the detection limit was 0. 5 mg/L, the relative standard derivation of ISTD and ESTD were 0. 4% -0. 9% and 0.6% - 1.2% respectively, and the average recovery were 100% - 102% and 95% - 99% respectively. Both the quantitative results with ISTD and ESTD can satisfy the requirement specified in the National Standard. However, the precision and recovery of ISTD method are better than that of ESTD method.