Development of a flow system for the determination of low concentrations of silver using Moringa oleifera seeds as biosorbent and flame atomic absorption spectrometry

In this study a method for the determination of low concentrations of silver in waters using solid-phase extraction with a flow injection analysis system and detection by flame atomic absorption spectrometry (FAAS) was developed. Moringa oleifera seeds were used as a biosorbent material. Chemical and flow variables of the on-line preconcentration system such as sample pH and flow rate, preconcentration time, eluent concentration and sorbent mass were studied. The optimum preconcentration conditions were obtained using sample pH in the range of 6.0-8.0, preconcentration time of 4 min at a flow rate of 3.5 mL min^− 1, 0.5 mol L^− 1 HNO₃ eluent at a flow rate of 4.5 mL min^− 1 and 35 mg of sorbent mass. With the optimized conditions, the preconcentration factor, precision, detection limit and sample throughput were estimated as 35 (for preconcentration of 14 mL sample), 3.8% (5.0 μg L^− 1, n = 7), 0.22 μg L^− 1 and 12 samples per hour, respectively. The developed method was successfully applied to mineral water and tap water, and accuracy was assessed through analysis of a certified reference material for water (APS-1071 NIST) and recovery tests, with recovery ranging from 94 to 101%.