A Vacuum Ultraviolet (UV) Photoreactor-Based Flow Droplet Digestion for Determination of Arsenic and Mercury in Blood by Atomic Fluorescence Spectrometry

It is still challenging to perform a high-throughput digestion on limited amounts of sample prior to elemental analysis by atomic spectrometry. Herein, a photochemical reactor consisting of a quartz tube inserted into a low-pressure mercury lamp was used to fabricate a flow droplet photodigestion (FD-PD) device for the high-throughput digestion of small amounts of samples. A mixture containing 20 μL of blood sample, 20 μL of H2O2, and 10 μL of HNO3 was pumped and passed through the reactor before its online analysis by hydride generation atomic fluorescence spectrometry (HG-AFS). The developed photochemical reactor provides significantly higher oxidation capability than conventional ultraviolet (UV) photochemical reactor since the vacuum UV irradiation below 200 nm from the mercury lamp directly irradiates samples with high transmittance, enabling complete digestion within 2 min. Compared to conventional digestion methods, the proposed method retains several unique advantages of higher sample throughput (57 pcs h–1), lower sample, mineral acid, and oxidant consumption, and shorter digestion time, facilitating painless blood analysis for children. Limits of detection (LODs) of 0.25 and 0.15 μg L–1 were obtained for As and Hg, respectively, with precisions (relative standard deviations (RSDs), n = 11, 2.0 μg L–1) better than 4%. The practicality of FD-PD-HG-AFS was confirmed by detecting As and Hg in one blood and two urine certified reference materials (CRMs), as well as several children's blood samples with satisfactory recoveries (93%–109%).