Headspace single drop microextraction based digital image colorimetry and ICP-MS for dual-mode analysis of sulfide in...

In this work, a headspace single-drop microextraction (HS-SDME) based digital image colorimetry and inductively coupled plasma mass spectrometry (ICP-MS) dual-mode sensing platform was developed for portable or sensitive detection of sulfide, based on the bifunctionality of MnO₂ nanosheets (NSs) as oxidant and chromogenic agent. MnO₂ NSs were suspended as droplets to headspace extract and react with H₂S generated by acidification of S^2-. The color change could be directly read by a smartphone with RGB value, followed by the sensitive Mn²⁺ detection with ICP-MS, thus successfully constructing a dual-mode S^2- sensing platform. Limit of detection for S^2- based on colorimetry was calculated to be 1.3 μmol L^-1, while it was as low as 1.2 nmol L^-1 by ICP-MS. This method shown excellent selectivity among more than 30 interferents, thus it has been successfully utilized to analysis of condiments and beverage rich in salinity or small molecule organics, with recoveries of 90-109 %.