Quantitative analysis of Pb2+ ion in liquid by laser induced breakdown spectroscopy using chelating agent for sample preparation.

Lead is a highly toxic element which poses a serious threat to human health when it dissolves in water. Laser induced breakdown spectroscopy is a simple and fast element detection method which can be used to detect liquid samples. In order to improve the limit of detection of Pb²⁺ in water, chelating agent assisted LIBS is investigated in this work. Sodium diethyldithiocarbamate (DDTC) is a commonly used Pb²⁺ chelating agent which can chelate Pb²⁺ bidentately. In experiments, sodium DDTC is used to chelate Pb²⁺ and deposits at the bottom of liquid sample by centrifugation. The precipitate is dried and concentrated on the graphite substrate. Under the optimal conditions, such as optimal concentration of sodium DDTC (0.25 mg/mL) and centrifugation time (5 min), the limits of detection of Pb²⁺ are 2.82 ng/mL for tap water and 3.64 ng/mL for river water are achieved. Without using sodium DDTC, the limits of detection of Pb²⁺ for tap water and river water are 18.20 ng/mL and 23.00 ng/mL respectively. Sodium DDTC can improve the limit of detection by more than 6 times. The work in this paper proposes a fast, simple and cost-effectively method to quantitatively measure heavy metallic elements in water samples.