# Returning to Nature for the Design of Sportive Phases in Solid-Phase Microextraction
## 1 Introduction  
The irrational fear of chemicals, called chemophobia, is caused by the negative perspective among the general public of the impact of chemistry in our health and environment [1]. While fighting this chemophobia by intensive teaching at different levels [2; 3] (including the general public as a target, too) of the benefits that chemistry provides to our societies, chemists must be aware of the potential risks they deal with, to design effective strategies for their control and minimization. In the environmental protection context, analytical chemistry plays a role, since it allows the detection of environmental pollution and permits the monitorization of the remediation protocols. However, this positive contribution must be complemented by the reduction of the collateral impact of analytical procedures, which is the primary goal of green analytical chemistry (GAC) [4; 5; 6].  
In 2012, Professor [PERSON] et al. theorized about the main guidelines of GAC, providing 12 general principles to be followed in order to reduce the potentially deleterious effects of analytical procedures [7]. The application of these principles is desirable as long as the main aim of analytical chemistry, providing useful and reliable information, is fulfilled. For example, the first principle recommends the direct analysis of samples avoiding in that way the sample treatment. Although thisprinciple identifies one of the trends of current research in analytical sciences, it is difficult to be applied when complex samples containing the analytes at very low concentrations are processed. In such scenarios, the simplification of the sample treatment and the reduction of the sources applied (reagents, energy) can be a more practical objective, at least currently. Microextraction techniques fulfill the latter criteria [8], and they are considered among the greenest sample treatment techniques [9].  
Microextraction techniques have evolved in the last decade following some key trends. Among them, the development of new extraction phases can be highlighted, considering the context of this review article. In this evolution, the tenth (use of renewable resources) and eleventh (replace or remove toxic reagents) principles of GAC are especially relevant [7]. In the liquid microextraction context, environmentally friendly solvents [10; 11] such as CyreneTM [12] and deep eutectic solvents [13] are clear examples of this progress.  
The paradigm of our production system, which up to now has been based on a linear \"take-make-dispose\" model, is progressively changed to a circular model [14] where reusing, repairing, refurbishing, and recycling appear as key terms. The use of surpluses of natural products as raw materials for the preparation of new sorbents is an interesting contribution of analytical chemistry for changing the production model. This review article, which combines the vision of two research groups working in the topic, tries to draw the general picture of the potential of natural products for the synthesis of new sportive phases in solid phase extraction and solid phase microextraction. The article will cover strategies with different green characteristics, as some of the natural materials can be used with minimal modifications, but others require a chemical adjustment depending on the analytes to be extracted.