Icp single element standard solutions

Placenta samples were previously mineralized by wet method in a sand bath (J.R. Selecta, Barcelona, Spain); they were placed in a resistant flask and dissolved using nitric acid followed by a mixture of HNO₃:HClO₄ (69%:70%, v/v; Merck KGaA, Darmstadt, Germany; ratio 1:4, v/v) until complete elimination of organic matter. Fe, Mn, Se, Ba, Cu, Zn were determined using an Agilent 8800 ICP-MS (Agilent, Santa Clara, CA, USA). All ICP-MS standards were prepared from ICP single element standard solutions (Merck KGaA) after appropriate dilution with 10% HNO₃. For calibration, two sets of multielement standards containing all the analytes of interest at five levels concentrations were prepared using Rhodium as internal standard.

Prior to being placed in a resistant flask and dissolved in nitric acid, placenta samples were previously mineralized by a wet method in a sand bath (J.R. Selecta, Barcelona, Spain) and were then mixed with HNO₃:HClO4 (69%:70%, v/v; Merck KGaA, Darmstadt, Germany; ratio 1:4, v/v) until all organic matter was completely removed. The following elements were measured with an Agilent 8800 ICP-MS: Ca, P, and Mg (Agilent, Santa Clara, CA, USA). After the proper dilution with 10% HNO₃, all ICP-MS standards were made from ICP single-element standard solutions (Merck KGaA). Using rhodium as the internal standard, two sets of multi-element standards were created for calibration that included all of the relevant analytes at five different concentration levels.

Elements present in PS9 and G30 as well as ALI water has been addressed by Inductively Coupled Plasma mass spectrometry (ICP-MS) measurements. Solid samples were prepared by acid digestion in strong acids (HNO₃ and HF at a 3:5 ratio) inside a Teflon reactor, thus the samples were subjected to high pressure and temperature by heating in a microwave oven (Milestone ETHOS ONE, Sorisole, Italy). The quantification of the elements was done by a NexION-300 ICP-MS spectrometer (Perkin Elmer, Waltham, MA, USA) equipped with a triple cone interface and a quadrupole ion deflector using argon for plasma formation. Standard solutions of 100 and 1000 ppb were prepared for each element (Multi-Element standards, Perkin Elmer, Waltham, MA, USA), and Rh was employed as an internal standard. All standards were prepared from ICP single-element standard solutions (Merck, Darmstadt, Germany) after dilution with 10% HNO₃. Ultrapurified water (Milli-Q^® grade, 18 MΩ·cm) was used during the whole experiment. The accuracy of the ICP-MS equipment used ranges between ±2 and ±5% for analyte concentrations between 50 and 5 ppm, respectively. The detection limits were <0.1 ppt for Ir and Ta; <1 ppt for Ba, Li, Cu, Mo, Sb, Sn, Ag, Au, Co, Ni, V, As, Cd, Pb, Zr, Be and Nd; < 10 ppt for Cr, Hg and Te; <1 ppb for P.