Читать книгу Analytical Methods for Environmental Contaminants of Emerging Concern - Группа авторов - Страница 24

There are several hints and tips that should be considered in order to fulfill current legislation as well as to ensure reliable results:

 Sample collection: Apply a statistical-based sampling procedure to ensure spatial and/or time variation and collect representative samples. Avoid compound degradation, selecting suitable storage and transport conditions. For air or water sampling, in addition to active sampling procedures, passive sampling is an interesting alternative, which is easy to deploy and minimum maintenance is required.

 Extraction: Use sensitive and/or generic extraction procedures. Thus, for aqueous samples, SPE or SPME, selecting suitable sorbents, are the most widely extraction techniques to ensure lower LOQs as well as suitable recovery. For solid samples, such as biota and soils, although PLE, combining different sorbents depending on the target compounds, is a good option, nowadays, QuEChERS approach is the first choice, because of its versatility, wide range of application and simplicity. Depending on the complexity of the matrix, an additional clean-up step could be necessary. The final extract can be injected in both GC and LC equipment or it can easily be evaporated and redissolved in a GC solvent as ethyl acetate.

 Analytical determination: Select LC or GC depending on the characteristics of the monitored compounds (GC for non-polar compounds and LC for polar pesticides). Either LC or GC should be coupled to QqQ, providing reliable, sensitive, fast and wide-scope analysis.

 LRMS vs HRMS: Use QqQ (LRMS analyzer) for targeted analysis of pesticide residues in environmental samples, whereas HRMS ((Q)-Orbitrap or (Q)-TOF) must be utilized if suspect or unknown analysis is also required.

 Data treatment: Well-set workflows and software are available for targeted analysis whereas when suspect or unknown analysis is performed, large raw data files are obtained, and high expertise and suitable software is needed for data interpretation and pesticide identification.