The response surface methodology (RSM) is a widely used mathematical and statistical method for modeling and analyzing a process in which the response of interest is affected by various variables [1] and the objective of this method is to optimize the response [2]. The parameters that affect the process are called dependent variables, while the responses are called dependent variables [3]. Solid phase extraction (SPE) is a technique designed for rapid, selective sample preparation and purification prior to the chromatographic analysis (e.g. HPLC, GC, TLC). In SPE, one or more analytes from a liquid sample are isolated by extracting, partitioning, and/or adsorbing onto a solid stationary phase [4] .Sample preparation by SPE changes the original matrix of a sample to a simpler matrix environment. This renders the sample more suitable for subsequent analytical chromatography, often simplifying and improving the final qualitative and quantitative analysis. The simpler sample matrix also lessons the demand placed on an analytical system, potentially extending the system’s lifetime.
