Application of Box–Behnken design in the optimization of a simple graphene oxide/zinc oxide nanocomposite-based pipette tip micro-solid phase extraction for the determination of Rhodamine B and Malachite green in seawater samples by spectrophotometry

Abstract

In this study, a miniaturized graphene oxide/zinc oxide nanocomposite (GO/ZnO) is proposed as a new sorbent for the pipette tip micro-solid phase extraction (GO/ZnO PT-μSPE) method for the very efficient microextraction of two dyes, Rhodamine B (RhB) and Malachite green (MG), from seawater samples followed by spectrophotometry. Different parameters that affect extraction efficiency, including type and volume of eluent solvent, volume of sample, number of cycles of extraction and elution, pH and ionic strength of the sample solution and concentration of surfactant were studied and optimized using both the one-variable-at-a-time method and response surface methodology (RSM). For the RSM, the Box–Behnken experimental design was utilized using seven factors in three levels. The linear range of the proposed technique was between 5–250 μg L⁻¹ for both MG and RhB under the optimum extraction conditions. The detection limits for RhB and MG were 1.0 and 1.2 μg L⁻¹, respectively. Finally, this technique was successfully used for the extraction and determination of both dyes in seawater samples.