Preconcentration of carbamate insecticides in water samples by using modified stir bar with ZnS nanoparticles loaded on activated carbon and their HPLC determination: Response surface methodology

• The stir bar was coated with the ZnS nanoparticles loaded on activated carbon.
• The modified SBSE was used for extraction of NMCs.
• The best extraction condition of NMCs was investigated by experimental design.
• The developed SBSE method has very low detection limit and good precision.

In this paper, a zinc sulphide nanoparticles loaded on activated carbon (AC) (ZnS-AC) as well as 1-ethyl-3-methylimidazolium hexafluorophosphate ([EMIM][PF6]) ionic liquid using sol gel technique was used as the adsorbent for the stir bar sorptive extraction (SBSE) of N-methylcarbamates (NMCs) (carbofuran, carbaryl and promecarb) in water samples followed by high performance liquid chromatography-ultraviolet detection (HPLC-UV). The fractional factorial design (FFD) was used to find the most important factors, which were then optimized by the central composite design (CCD) and response surface methodology (RSM). At optimum conditions values of factors set as 2.75% (w/v) NaCl, 23 min extraction time, 300 μL methanol (as desorption solvent), natural pH, and 500 rpm stirring speed. Under the optimal experimental conditions, the proposed method has linear ranges over 0.002–30 μg mL− 1 with detection limit 0.0003–0.0005 μg mL− 1 and good RSDs (and n = 6) of 3.3–4.5% for NMCs. The developed method has been successfully applied to the determination of three NMCs in environmental water samples such as tap water, river water, and mineral water.