Minimizing the impact of sample preparation on analytical results: In-tube solid-phase microextraction coupled on-line to nano-liquid chromatography for the monitoring of tribenuron methyl in environmental waters.

The degradation kinetics and residual levels of the sulfonylurea herbicide tribenuron-methyl (TBM) in different environmental waters were studied using in tube-solid phase microextraction (IT-SPME) coupled on-line to nano-liquid chromatography (nanoLC) and UV diode array detection (DAD). This approach combines the high extraction efficiency of IT-SPME using polymeric coatings reinforced with metal oxide nanoparticles and the high sensitivity attainable by nanoLC, making possible the determination of TBM at low ppb levels (limit of detection, 0.25 ppb) without altering the sample matrix. The present study demonstrated that the preservation of the sample properties is essential to ensure accurate results at these concentration levels due to the high tendency of TBM to hydrolyze, particularly under the acidic conditions involved in most protocols used for sample treatment. The approach used in the present study was applied to evaluate the degradation of this herbicide under different conditions (UV radiation, pH), as well as to study the evolution of its concentration in different environmental waters, namely sea, river, ditch and transition waters. When the samples were exposed to identical conditions, significant differences in the degradation rate of TBM were found depending on the water matrix. The results obtained indicate that this herbicide can persist from several days to weeks depending on the type of water.