Magnetic solid-phase extraction combined with in situ slurry cold vapor generation atomic fluorescence spectrometry for preconcentration and determination of ultratrace mercury

Abstract

A simple and ultrasensitive magnetic solid-phase extraction method using gold nanoparticle modified Fe₃O₄ magnetic microspheres combined with in situ slurry cold vapor generation atomic fluorescence spectrometry was developed for determination of trace Hg²⁺. The main parameters affecting the extraction process such as the time of the sorption process, pH, amounts of gold nanoparticles and sorbent, enrichment factors, and reusability of the sorbent were optimized. Hg²⁺ could be adsorbed on the sorbent in 2 mmol L⁻¹ HCOOH medium, even when the Hg²⁺ concentration was as low as 0.02 μg L⁻¹. The complete extraction can be achieved within 15 min. Under the premise of accurate detection, the enrichment factors were 10, 30 and 80 each for 2 mg, 5 mg, and 10 mg sorbent. The reusable performance of the sorbent was obviously affected by the amount of loaded gold nanoparticles. When the weight ratio of gold reaches 9.5%, the modified magnetic nanoparticles can be reused three times without causing a considerable decrease in their adsorption efficiency. In addition, the potential interference was studied. Under the optimized conditions, the detection limit of Hg²⁺ was 1.5 ng L⁻¹, and a relative standard deviation of 3.7% was obtained for determination of 0.05 μg L⁻¹ Hg²⁺. The linear calibration range was 0.005–0.2 μg L⁻¹. The accuracy of the method was verified through analysis of certificated reference materials. The proposed method has been applied to the determination of Hg in environmental water samples.