## 1 Introduction  
According to the World Health Organization (WHO), pesticides are \"chemical compounds that are used to kill pests, including insects, rodents, fungi and unwanted plants (weeds)\". Over 1000 different pesticides are used around the world. Pesticides are used in public health to kill vectors of disease, such as mosquitoes, and in agriculture to kill pests that damage crops. Pesticides can be classified into different groups by target organism (e.g., herbicides, insecticides, fungicides, rodenticides, and pediculicides), chemical structure (e.g., organic, inorganic, synthetic, or biological), and physical state (e.g., gaseous, fumigants). Among the others, organochlorines and organophosphates represent two of the most prominent pesticide families. Organochlorine pesticides (OCPs) are chlorinated hydrocarbons, extensively employed in agriculture and insect control from the 1940s to the 1960s. OCPs have been banned in most of the technologically advanced countries and replaced by other synthetic insecticides, such as organophosphate pesticides (OPPs) in the 1960s and pyrethroids (PYRs) in the 1980s, due to their significant toxicity to plants and animals, including humans, and to their persistence and potential to bioaccumulation. OPPs are widely used: 50% of the killing agents used in agriculture belong to this compound class [1]. Several studies reported that prolonged exposure to OPPs can increase the risk of cardiovascular and respiratory disease, and promote cancer diseases [2]. For these reasons, OPPs have been banned in most residential uses, but they are still allowed as pesticides on fruits and vegetables. Pyrethroids are synthetic analogs of pyrethrins, natural insecticides produced by certain species of chrysanthemum. PYRs are commonly used in crop protection, veterinary medicine, and for indoor/outdoor pest control [3]. PYRs are generally less toxic toward humans than OCPs and OPPs, but their stability and persistence in the environment make possible their transfer along the food chain, becoming consequently a health and environmental concern. In the last decades, in the European Community, pesticide legislation in foodstuffs and animal feeds has been continuously revised, leading to a continued update of maximum residue levels (MRLs) admitted for pesticides, based on their toxicity and the consumption of potentially contaminated food products. Specific official documents (classified by pesticide class and type of food sample) and related updates are online available [4]. Risks related to pesticide contaminations and the consumption of large amounts of cereals and legumes worldwide have promoted the development of a variety of analytical methods for their determination. Due to their high volatility, the analytical determination of pesticides is usually accomplished by using gas-chromatography. Electron capture detector (ECD), nitrogen-phosphorus detector (NPD) and flame ionization detector (FID) have been usually employed for pesticide determination, but each of them is specific for determinate pesticide class, making the pesticide comprehensive determination unfeasible [5; 6; 7]. Consequently, their use has been largely replaced by mass spectrometry, due to its higher selectivity, sensitivity and applicability to high number of pesticides [8; 9].