Sequential injection analysis for determination of lead(ii) using extract of caesalpinia pulcherrima as a natural reagent

The lead(II)-contaminated aquatic environment may endanger humans and living organism. The maximum tolerable limit of lead(II) in river water is 1 mg/L. Therefore, the development of a sensitive and green analytical method to determine lead(II) is required. In this work, we developed a Sequential Injection Analysis (SIA) system equipped with a valve-mixing and a flow-based UV detector for highly sensitive detection of lead(II). In order to deal with the green chemistry system, the environmentally friendly natural reagent is prepared from the extract of Caesalpinia pulcherrima instead of a commercial synthetic reagent. The extract of Caesalpinia pulcherrima contains several flavonoid compounds which can bind lead(II) ion to form an orange complex compound at a wavelength of 672.4 nm. Various parameters affecting the sensitivity of the proposed method, which includes pH, reaction time, the flow rate to the detector, and stability of Caesalpinia pulcherrima extract, were investigated in detail. The optimum conditions for a complex formation of Pb-Caesalpinia pilcherrima extract were found at pH 4 along with a reaction time of 10s, and the product flow rate to the detector was 200 L/s. Under the optimum conditions, a linear calibration graph can be constructed in the lead(II) concentration range of 0-800 ppb with a detection limit of 8.9 ppb. The proposed method is successfully applied to determine lead(II) in industrial wastewater samples with satisfied results.