ИСТИНА

Detonation nanodiamonds (NDs) gain much attention for biomedical and clinical applications, and high-technology purposes due to their unique properties. However, many ND properties, which are relevant for such uses depend on their production and purification technology. In particular, it is very important to know, reliably and precisely, the ND impurity composition because some chemical elements may be hazardous even in small quantities, especially when they exist in nano-species. In addition, they also change the ND properties, e.g. thermal and oxidative resistance. Thus, the replicability of ND technology is a topical problem in the industry. The development of analytical techniques is the first and crucial step to make ND properties traceable and to improve the production technology. Usually, this means sensitive and selective multielement analysis because the impurities in ND have various nature including metal-oxide microparticles, carbides, silicon dioxide, insoluble salts, as well as adsorbed cations and anions [1,2]. They appear due to the interactions in the detonation reaction chamber (Fe and Cr) or from the explosion initiation (Cu, Pb, and Hg), or adsorbed [2] on already formed NDs from liquids (acids and water) used for their isolation from the detonation-chamber charge [3]. To the best of our knowledge, the problem of quantitative multielement analysis of NDs was not sufficiently investigated. In our opinion, analysis of NDs can be reliably solved using the state-of-the-art method of atomic spectroscopy — optical-emission analysis with inductively coupled plasma (ICP-OES). This method is de facto standard for various environmental, high-technology, clinical and pharmaceutical analysis. In this paper, we will discuss the analytical possibilities of ICP-OES for accurate and precise quantifications of various elements in NDs. We developed a technique for quantitative multielement analysis of ND impurities. We found out that the most of analysed NDs contain relatively high amounts of Fe, Na, Si; Cu, B, Ni, Al (>100 ppm), while Pb, Zn, K, Mn, B, Cr, Mg, Mo, Sn, W, Ba, Sb, Co, Sr are in low but significant amounts. Moreover, we measured generalised indicator property—the ash mass after combustion—and found that all incombustible impurities comprise 1–3% of the total ND mass. In commercially available «deeply purified» ND samples, we detected much lower impurities of Сu, Ni, Al and slightly lower amounts of Fe, while other elements were almost at the same average level as in not so thoroughly purified ND species. This means that the purification process is possible, but needs improvement. We have found that NDs from different manufacturers contain very different impurities and even for a single product type they change from lot to lot. This means that ND purity needs to be monitored, and additional purification might be made if necessary Acknowledgements. This work was supported by the RFBR, grants nos. 12-03-00653-а and 12-03-31569-mol_a and the MST of Russian Federation, contract no. 16.740.11.0471.