“…Normally, an additional preconcentration step must be performed after acid digestion during the analysis of ultra-low gold contents in rocks. The commonly used enrichment methods use precipitation [26,80,81,82,83], ion exchange resins [5,71,81,84,85,86,87,88], solvent extraction [27,89,90,91,92,93,94,95,96,97,98], polyurethane foam (PUF) [99,100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,125,126,127,128,129,130], extraction chromatography [36,131,132,133], and solid adsorbents [134,135,…”