Selective Heavy Atom Effect-Promoted Photosensitization Colorimetric Detection of Ag+ in Silver Ore Samples

Analytical methods capable of facile screening of silver ore samples are of vital importance for resource exploration and ore mining. Due to its extreme simplicity, colorimetric detection is desired for silver ore screening, but the analytical sensitivity of existing approaches is typically not sufficient. Here, an Ag+- selective heavy atom effect-promoted photosensitization colorimetric assay was developed. Specifically, Ag+ and dsDNA-staining dye (photosensitizer) were spatially adjoined in close proximity in dsDNA bearing several cytosine (C) mismatches, leading to enhanced 1O2 generation for photosensitized oxidation of chromogenic substrate 3,3 ',5,5 '-tetramethylbenzidine (TMB). Due to the stable C-Ag(I)-C metallo-base pair, the C-C mismatches in dsDNA can selectively capture Ag+, thus allowing highly selective colorimetric detection of Ag+ with a visual limit of quantification (LOQ) as low as 0.2 ng/mL. For ore sample analysis, the visual LOQ was about 2 g/t, which was suitable for colorimetric screening analysis of ores of different values. The accuracy of the proposed method was verified through analyzing both certified reference material and real ore samples, the results of which agreed well with those obtained by electrothermal atomic absorption spectrometry (ET-AAS). To facilitate field silver ore screening, acid leaching of the samples was also adopted, and satisfactory analytical accuracy was also obtained at a rough leaching efficiency of 20%.

Automated summary

Development of an important and easy analytical method for screening silver ore samples is crucial for resource exploration and mining. A selective Ag+-promoted photosensitization colorimetric assay was developed, which allowed highly sensitive colorimetric detection of Ag+ with a visual limit of quantification as low as 0.2 ng/mL. The accuracy of the method was verified through analyzing certified reference material and real ore samples, showing good agreement with the results obtained by electrothermal atomic absorption spectrometry (ET-AAS).