基于分子络合的分散液液微萃取与高效液相色谱联用检测环境水样中2种苯氧羧酸类除草剂

建立了基于分子络合的分散液液微萃取(DLLME)方法,以磷酸三丁酯为萃取剂,以甲醇为分散剂,与高效液相色谱联用检测了环境水样中麦草畏和2,4-二氯苯氧乙酸(2,4-D酸)2种苯氧羧酸类除草剂,对影响前处理效果的因素(包括水样的pH值、萃取剂的种类和体积、分散剂的种类和体积、反萃液的pH值、反萃液的体积和盐浓度等)进行了详细考察,在最佳萃取条件下(水样体积10 mL,水样的pH值为0~1.0、100μL磷酸三丁酯萃取剂、1 000μL甲醇分散剂、0.01 mol/L的氢氧化钾反萃液的体积为80μL),2种苯氧羧酸类除草剂在0.50~1 000μg/L范围内具有良好的线性,相关系数不小于0.998 5,麦草畏和2,4-D酸的检出限分别为0.44μg/L和0.49μg/L,富集倍数分别为85和90,在实际样品中的加标回收率为75.7%~104.0%。该方法基于分子络合反应机理,将新型萃取剂磷酸三丁酯应用于分散液液微萃取,与HPLC联用实现了麦草畏和2,4-D酸的富集与检测,为环境水样中苯氧羧酸类除草剂的检测提供了新的前处理方法。

Dispersive liquid-liquid microextraction based on molecular complexation followed by high performance liquid chromatography for the determination of two phenoxy carboxylic acid herbicides in environmental water samples

A dispersive liquid-liquid microextraction (DLLME) method based on molecular complexation was developed for the determination of 2,5-dichloro-6-methoxybenzoic acid (dicamba) and 2,4-dichlorophenoxyacetic acid (2,4-D) in environmental water samples by high performance liquid chromatography-ultraviolet detection (HPLC-UV). Tri-n-butylphosphate (TBP) and methanol were selected as the extraction solvent and dispersive solvent, respectively. Parameters affecting the extraction efficiency, including the type and volume of the extraction and dispersive solvents, pH of the sample solutions, pH of the backward extraction solution, and salt addition, were optimized. Under the optimized conditions, the linear range was 0.50-1000 μg/L for the two target herbicides. The limits of detection (LODs, S/N=3) were 0.44 μg/L and 0.49 μg/L for dicamba and 2,4-D, respectively. The enrichment factors (EFs) of dicamba and 2,4-D were 85 and 90, respectively. The recoveries were in the range 75.7%-104.0%. The proposed microextraction involved molecular complexation, and the Lewis acid-base interactions between TBP and the acidic herbicides gave satisfactory extraction results. Thus, the method is expected to be a powerful tool for the determination of acidic herbicides in environmental water samples