Lopez-Avila V, Liu Y, Charan C
Midwest Research Institute, Mountain View, CA 94043, USA.
J AOAC Int. 1999 May-Jun;82(3):689-704.
The microextraction/ion chromatographic (IC) method developed in this study involves extraction of 9 haloacetic acids (HAAs) from aqueous samples (acidified with sulfuric acid to a pH of < 0.5 and amended with copper sulfate pentahydrate and sodium sulfate) with methyl tert-butyl ether (MTBE), back extraction into reagent water, and analysis by IC with conductivity detection. The separation column consists of an Ion Pac AG-11 (2 mm id x 50 mm length) guard column and an Ion Pac AS-11 (2 mm id x 250 mm length) analytical column, and the concentration column is a 4 mm id x 35 mm length Dionex TAC-LP column. Use of the 2 mm id Dionex AS-11 column improved detection limits especially for trichloracetic acid (TCAA), bromodichloroacetic acid (BDCAA), dibromochloroacetic acid (DBCAA), and tribromoacetic acid (TBAA). The peak interfering with BCAA elutes at the same retention time as nitrate; however, we have not confirmed the presence of nitrate. Stability studies indicate that HAAs are stable in water for at least 8 days when preserved with ammonium chloride at 100 mg/L and stored at 4 degrees C in the dark. At day 30, recoveries were still high (e.g., 92.1-106%) for dichloroacetic acid (DCAA), BCAA, dibromoacetic acid (DBAA), trichloroacetic acid (TCAA), BDCAA, and DBCAA. However, recoveries of monochloroacetic acid (MCAA), monobromoacetic acid (MBAA), and TBAA were only 54.6, 56.8, and 66.8%, respectively. Stability studies of HAAs in H2SO4-saturated MTBE indicate that all compounds except TBAA are stable for 48 h when stored at 4 degrees C in the dark. TBAA recoveries dropped to 47.1% after 6 h of storage and no TBAA was detected after 48 h of storage. The method described here is only preliminary and was tested in only one laboratory. Additional research is needed to improve method performance.
本研究开发的微萃取/离子色谱（IC）方法包括用甲基叔丁基醚（MTBE）从水样（用硫酸酸化至pH < 0.5，并添加五水硫酸铜和硫酸钠）中萃取9种卤乙酸（HAA），反萃取到去离子水中，然后通过带电导检测的离子色谱进行分析。分离柱由一根Ion Pac AG - 11（内径2 mm×长度50 mm）保护柱和一根Ion Pac AS - 11（内径2 mm×长度250 mm）分析柱组成，浓缩柱是一根内径4 mm×长度35 mm的戴安TAC - LP柱。使用内径2 mm的戴安AS - 11柱提高了检测限，尤其是对三氯乙酸（TCAA）、溴二氯乙酸（BDCAA）、二溴氯乙酸（DBCAA）和三溴乙酸（TBAA）。与一溴氯乙酸（BCAA）峰保留时间相同的干扰峰与硝酸盐峰同时洗脱；然而，我们尚未证实硝酸盐的存在。稳定性研究表明，当用100 mg/L氯化铵保存并在4℃黑暗中储存时，HAA在水中至少8天是稳定的。在第30天，二氯乙酸（DCAA）、BCAA、二溴乙酸（DBAA）、三氯乙酸（TCAA）、BDCAA和DBCAA的回收率仍然很高（例如92.1 - 106%）。然而，一氯乙酸（MCAA）、一溴乙酸（MBAA）和TBAA的回收率分别仅为54.6%、56.8%和66.8%。HAA在硫酸饱和MTBE中的稳定性研究表明，除TBAA外，所有化合物在4℃黑暗中储存48小时都是稳定的。TBAA在储存6小时后回收率降至47.1%，储存48小时后未检测到TBAA。这里描述的方法只是初步的，仅在一个实验室进行了测试。需要进一步研究以提高方法性能。
