固相萃取-液相色谱/紫外法测定地表水中百草枯和敌草快

利用固相萃取和液相色谱,建立地表水中百草枯和敌草快的分析方法。该方法不使用离子对试剂即可对目标物进行分离,百草枯和敌草快的回收率分别为107.6%±6.90%、100.5%±9.93%,在0.04~10μg/ml范围内,有很好的线性相关性,百草枯和敌草快的检出限均为0.05μg/L,定量限为0.2μg/L。水样需在7天内完成前处理。     

Sorption of the herbicides diquat and difenzoquat from aqueous medium by polymeric resins in the presence of sodium dodecylsulfate: Kinetic and mechanistic study

The goal of this work was to propose a novel method for the solid-phase extraction of the herbicides diquat (DQT²⁺) and difenzoquat (DFQT⁺) from aqueous medium using polymeric Amberlite XAD-2 and XAD-4 resins in the presence of sodium dodecylsulfate (SDS). The addition of SDS to the medium was of fundamental importance in order to allow the formation of a negatively charged surface able to sorb the cationic solutes. Several factors that could influence the sorption process, such as SDS concentration in the medium, sorbent mass, pH, ionic strength, and initial concentration of the solutes were investigated. Kinetic studies were also performed to model the system and to identify the mechanisms that operate the sorption process of the herbicides. SDS concentration in the medium presented remarkable influence on the extraction efficiency, achieving maximum values when the ratios [SDS]/[herbicide] were approximately 90, for XAD-2, and 22 and 11 for DQT²⁺ and DFQT⁺, respectively, for XAD-4. The sorption process followed a pseudo second-order kinetic in all cases studied. It was also found that an intraparticle diffusion process controlled exclusively the sorption of the herbicides by the Amberlite XAD-2 and XAD-4 resins in the first 15 min, becoming less active with time.