Comparison between modified acid digestion and a novel fusion method for determination of 54 elements in nano-soil samples with ICP-MS

Nano-soils are a type of layered silicates with nonmetric thickness and diameter of 50–200 nm. These nanoplates have many applications such as antibacterial activity, sterilizing effect, adsorption of toxins, and membrane coating [1]. Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) was employed to determine the concentration of trace elements in different samples. In this work, modified acid digestion and fusion techniques were investigated to obtain a simple, rapid and safe method for the simultaneous determination of 54 trace elements in nano-soil samples. Soil samples were collected, air dried, grinded, sieved and subjected to digestion. Subsequently, the digests for metal content by inductively coupled plasma-mass spectrometry (ICP-MS) were analyzed. Various combinations and volumes of hydrofluoric, nitric and hydrochloric acids were evaluated for the acid digestion efficiency. The modified fusion digestion with a mixture of Tetraborate and metaborate produced the fastest, safest and accurate analytical results with a recovery of 97–105% and a precision better than 5% in most cases. Very low limits of detection were obtained, below 0.05 μg g−1, for all elements, except. Detection limits, reproducibility, accuracy and possible interference were also studied for both methods. ICP-MS provided extremely low detection limits (0.1–10 ng L-1). Precision was typically better than 6% RSD. The potential of the method was evaluated by analysis of standard reference materials of soils and plants. Three certified reference materials (GSD 9, GSD 6 and GSD 110) were used in the comparison of these digestion protocols and good agreement between the two procedures and the certified values was found.