M.H Sodeghi Moghaddam - Faculty of Sciences Department of Chemistry, Yazd University, ۸۹۱۵۸۱۳۱۴۹ , Yazd, Iran
A.M Haji Shabani - Faculty of Sciences Department of Chemistry, Yazd University, ۸۹۱۵۸۱۳۱۴۹ , Yazd, Iran
S Dadfarnia - Faculty of Sciences Department of Chemistry, Yazd University, ۸۹۱۵۸۱۳۱۴۹ , Yazd, Iran
M Nozohour - Faculty of Sciences Department of Chemistry, Yazd University, ۸۹۱۵۸۱۳۱۴۹ , Yazd, Iran

Lead is a highly toxic element for humans and other living organisms. Lead can cause great damage to the kidneys and brain and can interfere with the production of red blood cells [۱,۲]. Therefore, the determination of small amounts of lead in different samples is very important.۲The most common technique for measuring lead is flame atomic absorption spectroscopy. However, direct determination of the low concentration of this element in real samples is often not possible due to the low sensitivity and disturbance of the sample tissue with this technique and requires a separation and pre-concentration step [۳].This study describes the synthesis, identification, and application of a new composite including a metal-organic framework and sulfur functionalized graphene oxide as the sorbent for solid-phase extraction and preconcentration of Pb۲+ ions from aqueous samples. The preconcentrated analyte was determined by flame atomic absorption spectrometry. The prepared sorbent was characterized using Fourier transform infrared spectroscopy (FT-IR), field emission scanning microscopy (FESEM), X-ray diffraction (XRD), and nitrogen adsorption and desorption isotherm (BET analysis). The effect of important parameters such as the sample pH, amount of sorbent, extraction time, sample volume, and type, concentration, and volume of the eluent on the extraction of the analyte was investigated and optimized. At the optimal conditions, the calibration graph was linear in the concentration range of ۵.۰-۱۴۰.۰ μg L-۱ lead ions with a determination coefficient (R۲) of ۰.۹۹۹۸. The limit of detection (LOD) and the limit of quantification (LOQ) of the method were ۱.۱ and ۳.۵ μg L-۱, respectively. The relative standard deviations (RSDs) of ۱.۵ and ۲.۱% were obtained at ۱۲ μg L-۱ concentration level of Pb۲+ (n = ۶) for intra- and inter-day analysis, respectively. The developed method was successfully employed for the determination of lead in different water and food samples.