Elemental analysis of nanodiamonds by inductively-coupled plasma atomic emission spectroscopy

A 68-element survey study was carried out on micro-impurities from 20 commercial nanodiamond samples from eight international manufacturers. The measurements were made using inductively coupled plasma atomic emission spectroscopy with detection limits for most elements below 1 ppm. Various methods of sample preparation were compared: direct introduction of suspensions, ashing with microwave-assisted acid digestion, and microwave-assisted acid extraction, and their advantages and disadvantages evaluated. The work demonstrates the feasibility of nanodiamond analysis by direct slurry nebulization, which provides a multi-element, rapid, simple, and relatively low-cost route for nanodiamond purity estimation. Most of the samples contain relatively high amounts of Fe, Na, Ca, Si, Cu, Al, S, and Ti (>100 ppm), while Pb, Zn, K, Mn, B, Cr, Mg, Mo, Sn, W, Ba, Sb, Co, and Sr are at low but significant amounts. In addition, in several samples, we found some uncommon elements like Ag, Ce, Y, Hf, Zr, and Hg. This study provides new possibilities for certifying nanodiamond purity, understanding their properties and behavior, and advancing their production technology.