Simultaneous determination and variability over time of Cr, Cu, Zn, As, Se, Sr, Cd, Sb, Hg, Tl, Pb concentrations in fingernail samples by ICP-MS method

The aim of this study was to simultaneously quantify 11 metal(oid)s in fingernails by inductively coupled plasma-mass spectrometry (ICP-MS) and to demonstrate the intra-day reproducibility and time-dependent variability of the measurements. Fingernail samples without nail polish were taken from the female subject in the research team twice in 2020 and three times in 2023. The nails of both hands were combined in a nail pool. Each nail pool was considered as one sample (n= 5). Simultaneous determination of Cr, Cu, Zn, As, Se, Sr, Cd, Sb, Hg, Tl, and Pb was carried out with 3 consecutive intra-day readings. The ages of the samples were 1150 and 939 days (aged) and 9, 14, and 41 days (current samples), respectively. The mean relative standard deviation (RSD) of 3 consecutive intraday measurements was 5.26%, and Kendall's W value was 0.99. Kruskall-Wallis test showed no significant difference between the three measurements (p