B. Socas-Rodríguez 1, Á. Santana-Mayor 2, R. Rodríguez-Ramos 2, M.Á. Rodríguez-Delgado 2

1Institute of Food Science Research (CIAL, CSIC) (SPAIN)
2Universidad de La Laguna (SPAIN)
The development of analytical methodologies requires the study and performance of different steps which, in most cases, cannot be avoided due to the complexity of the analysed samples and the requirements in terms of sensitivity, especially when the evaluation of contaminants is carried out. Such methods involve sample collection, sample preparation and analysis. In general terms, sample preparation constitutes the largest and most complex step which, in addition, has an important influence on the success of the subsequent analysis. Based on that, the evaluation of each task and variable affecting sample preparation constitutes an aspect of great importance for the adequate development of any analytical procedure.

In this regard, different approaches have been explored to evaluate the influence of each parameter and obtain the best conditions to carry out the preparation, extraction and clean-up processes commonly applied during sample preparation. The use of experimental designs (DoEs) by using statistical approaches that allow the evaluation and effect of different parameters simultaneously, as well as their interactions, is common. This strategy is preferred within the scientific community since, apart from providing an optimal point with the most suitable conditions, also enable decreasing the number of experiments carried out in this part of the method development. However, the bases of DoE are not easy to understand for undergraduate students and its correct application at this stage results very difficult. In addition, when novel procedures are carried out, involving the application of new extraction sorbents, innovative devices or materials, the application of DoEs is controversial and the application of “one variable at a time” (OVAT) approaches provides a clearer and more general view of the influence of each parameter on the method performance, especially for novel scientists.

Considering all above mentioned, in this work, a practical approach has been carried out to initiate undergraduate students in the development of an OVAT strategy for the optimisation of a microextraction procedure based on the application of innovative green solvents for the evaluation of organic contaminants in complex food samples. With this aim, the students carried out the selection and evaluation of different parameters including, type and volume of solvent and sample pH, using the extraction recovery as response variable. This approach provides an effective learning based on practical training, and a clear view of the relevance of sample preparation in analytical methods.