X series 2 model

Hair samples were collected from only healthy men and women who had not dyed, permed, or discolored their hair in the last 3 months. Hair was collected (5–10 cm) as close to the skin of the head as possible using surgical scissors. The hair samples were then cut into 50-mg slices and washed according to International Atomic Energy Agency recommendations [14 ]. Specifically, they were rinsed once in acetone, twice in double deionized water, and once more in acetone for 10 min each time [14 ]. Fifty-milligram portions of pretreated hair samples were measured and hydrolyzed for 30 min using nitric acid and hydrogen peroxide in the Mars 6 microwave digestion system (Matthews, NC, USA). The hydrolyzed homogeneous aqueous solutions were diluted and analyzed with an inductively coupled plasma mass spectrometer (Model X series II, Thermo Fisher Scientific, Waltham, MA, USA). All chemicals were of reagent grade and obtained from Sigma Aldrich (St. Louis, MO, USA).
Statistical analysis in this study, including correlation and linear regression analyses, were performed using Minitab® software (Minitab Inc., State College, PA, USA), and sex differences were analyzed using the paired t-test.

The quantification of elements was performed using 250 mg of dried plant powder. Mineralization was carried out using 3.5 mL nitric acid (HNO₃, 65%, analytical grade, Optima) and 1 mL hydrogen peroxide, and samples were incubated in a heating block digestion system (DigiPREP, SCP Sciences, Courtaboeuf, France). A gradual heating mode was used to achieve a final temperature of 100 °C (total run of 265 min). Then, ultrapure water (18.2 MΩ/cm², Millipore Milli-Q Integral 3 system, Molsheim, France) was added to a final volume of 25 mL, and samples were filtrated to 1 μm. Elemental concentrations were determined by ICP-AES (Radial ICAP 6500 Model, Thermo Fischer Scientific, Courtaboeuf, France) or ICP-MS (X Series II Model, Thermo Fischer Scientific, Courtaboeuf, France) for REEs. Oriental basma tobacco leaves (INCT-OBTL-5, LGC Promochem, Molsheim, France) were used as certified reference material.