“…In particular, we used: RF power, 1500 W; plasma gas flow rate, 15 L min −1 ; auxiliary gas flow rate, 0.9 L min −1 ; carrier gas flow rate, 1.1 L min −1 ; helium collision gas flow rate, 4 mL min −1 ; spray chamber temperature, 2 ∘ C; sample depth, 9 mm; sample introduction flow rate, 1 mL min −1 ; nebulizer pump, 0.1 RPS; extract lens 1 voltage, 1.5 V. The instrument was used in no-gas mode for Mn, Pb, Zn, Mg, Ca, Na, K, and in helium mode for Ni, As, Se, Cd, Fe, Cu, to remove spectral interference. Monitored isotopes, chosen to maximize sensitivity and to minimize interferences due to the matrix, were 24 Mg, 23 Na, 39 Calibration standards were prepared at concentration ranges suitable for the analytes investigated: from 0.020 to 5 μg g −1 for the elements As, Cd, Pb, Se Cu, Fe, Ni; from 0.050 to 20 μg g −1 for Na, Mn, Zn; from 0.5 to 100 μg g −1 for Ca, K, Mg, preliminarily diluted (1:50).…”