Solid-phase extraction of ultra-trace levels of lead using tannic acid-coated graphene oxide as an efficient adsorbent followed by electrothermal atomic absorption spectrometry; response surface methodology - central composite design

Herein, highly efficient and rapid solid-phase extraction technique was used for preconcentration of ultra-trace levels of lead (Pb2+) followed by electrothermal atomic absorption spectrometry (ETAAS). Tannic acid-coated graphene oxide (TA-GO) was used as a powerful adsorbent in solid-phase extraction for the first time. The results of scanning electron microscopy (SEM), atomic force microscopy (AFM), and Fourier transform infrared spectroscopy (FTIR) showed that the TA-GO adsorbent was synthesized successfully. To optimize the experimental conditions, response surface methodology (RSM) with four factors, i.e. pH, amounts of adsorbent, extraction time, and desorption time, was used. Based on the results of central composite design (CCD), pH 5.2, 4.2 mg of TA-GO adsorbent, 12.05 min extraction time, and desorption time of 2 min were selected as the optimum conditions. Under optimum conditions, the calibration curve was linear in the range of 0.05-1.5 ng mL(-1) Pb2+. The relative standard deviation (RSD) based on six replicate analyses of 0.4 ng ml(-1) Pb2+ and limit of detection (LOD) were 3.8% and 0.015 ng mL(-1), respectively. The accuracy of the proposed method was checked by analyzing the certified reference material CRM-TMDW. Finally, this technique was applied for the determination of ultra-trace levels of Pb2+ in various real samples.