Challenge #1: Sample Preparation
Sample preparation is always a bottleneck between specificity and the range of chemical properties of the different analytes to be analyzed. [1]

Challenge #2: Standards Some practical problems are related with a huge standard solutions production such as (1) the availability of some pesticides, (2) use of different solvents to dissolve them, and (3) fast degradation of some of them. Recently, to avoid all these disadvantages and to permit the nontarget analysis, the need for screening methods is growing up (Romero-Gonza´lez et al., 2011). These methods provide a qualitative binary response, and samples can be classified as negative and nonnegative, considering nonnegative samples as those containing one or more analytes above a preestablished concentration level. Then, nonnegative samples must be reanalyzed by an identification/quantification method to determine the final concentration in the positive samples (Romero-Gonza´lez et al., 2011).[1]

[1] p132, Applications in High Resolution Mass Spectrometrey Food Safety and Pesticide Residue Analysis, edited by Roberto Romero-González, ©2017 ELSEVIER.