Ultrapure nitric acid hno3 65

All the reagents used were of analytical grade. Ultrapure nitric acid (HNO₃ 65%) was purchased from Merck (Merck Co., Darmstadt, Germany). A Multielement Standard Solution 6), used to obtain the calibration curves, was purchased from Sigma Aldrich (St. Louis, MO, USA). All dilutions were performed with ultrapure water (18.2 MΩ·cm). The glassware used for these determinations was washed, decontaminated with 10% HNO₃ solution, and then dried in an oven at 105 °C.

The analyzed samples were purchased from various drugstores or health food stores in Bucharest, Romania, in 2018 and 2019, totaling 41 food supplements of vegetal (SV1–SV30), mineral (SM1–SM9), and animal (SA1–SA2) origin, presented in Table 1. All reagent used were of analytical grade. Ultrapure nitric acid (HNO₃ 65%) and hydrogen peroxide (H₂O₂) were purchased from Merck (Merck Co., Darmstadt, Germany). Calibration curves were obtained using a lead standard solution of 1000 mg/L Pb for atomic absorption (AA) (Pb(NO₃)₂ in 2% HNO₃) and a cadmium standard solution of 1000 mg/L Cd for AA (Cd(NO₃)₂ in 2% HNO₃) purchased from Scharlau (Scharlab, Barcelona, Spain). All dilutions were performed using ultrapure water (resistivity of 18.2 MΩ·cm), and all glassware used was cleaned and decontaminated with 10% HNO₃.