Agilent 7700 series icp ms

500 mg freeze-dried P. tetrastromatica was subjected to wet hydrolysis in a high-pressure polytetrafluoroethylene vessel, containing 6 mL of 65% HNO₃ and 2 mL of 35% H₂O₂ and digested in an Anton Paar microwave. After digestion, filtered samples are diluted to a final volume of 50 mL and analysed in an Agilent 7700 series ICP-MS (Agilent Technologies, Inc., Santa Clara, CA, USA) for multi-mineral elements based on the protocol of Aroyehun et al. (2020) [6 (link)].

To 0.5 g infant formula sample in a polyfluoroalkoxy digestion vessel, we added 1 mL deionized water (Milli-Q, Millipore, Bedford, MA, USA), 5 mL of HNO₃ (65%, Suprapur, Merck, Darmstadt, Germany) and 2 mL of H₂O₂ (30%, Suprapur, Merck, Darmstadt, Germany). Following an overnight pre-digestion at room temperature, the mixture was digested in a microwave-assisted reaction system (CEM MARs 6, Charlotte, NC, USA) according to the program shown in Table 2. Once cooled to room temperature, the digest was diluted with deionized water to 25 mL and analyzed by inductively coupled plasma mass spectrometry (ICP-MS; Agilent 7700 Series ICP-MS, Agilent Technologies, Santa Clara, CA, USA) after filtration through a 0.22-μm membrane.
We developed standard five-point calibrations for each of the toxic elements. The correlation coefficients were >0.999 and the limits of detection for Pb, As, Cr and Cd in infant formula was 0.2, 0.5, 2.0 and 0.1 μg/kg, respectively. To assess the accuracy of the method, milk powder certificate reference material (CRM, Code: GBW 10117, National Institute of Metrology, Beijing, China) were analyzed. The recovery of the elements from milk powder CRM is shown in Table 3. The recovery of these four toxic elements was 92.3%–104.3%.