Development and validation of an inductively coupled plasma mass spectrometry (ICP-MS) method for the determination of cobalt, chromium, copper and nickel in oral mucosa cells

The oral cavity is an ideal environment for the corrosion of fixed orthodontic appliances, leading to the release of metal ions that, eventually, could derive in adverse effects. Therefore, it is necessary to evaluate the biocompatibility of these materials for patient's safety. In vivo, oral mucosa cells are a valuable sample for this aim, however, analytical methods to quantify the liberation of metal ions are very scarce. Thus, the purpose of this work is to optimize and validate a sample preparation procedure to determine cobalt (Co), chromium (Cr), copper (Cu), and nickel (Ni) in oral mucosa cells in patients with and without orthodontic appliances, based on the extraction and digestion of the samples and quantification of the elements by inductively coupled plasma mass spectrometry (ICP-MS). The method has been suitably validated: the regression equation was calculated from standards prepared in the same matrix without oral mucosa cells and the linear range was 2.0-100.0 ng mL− 1 for all elements. Limits of detection were 0.10, 0.38, 0.49 and 0.67 ng mL− 1 and limits of quantification were 0.20, 1.13, 0.98, and 1.81 ng mL− 1 for Co, Cr, Cu, and Ni, respectively. The recovery percentages (%) obtained ranged between 104 and 109 for Co, 103-107 for Cr, 106-113 for Cu and 84-110 for Ni. Intermediate precision (RSD%) data obtained were also adequate. The present method proved to be robust for the three factors considered: heating time, volume of deionized water, and volume of PlasmaPure 65% HNO3 used to dilute the samples. Thus, the proposed method passed in a satisfactory way the validation standards considered and could be used to evaluate in vivo the metal ion release in oral mucosa cells from orthodontic patients.