https://doi.org/10.1016/j.mex.2021.101428
“The aim of this work is the development of a suitable method to extract and detect zinc-bound compounds from cabbage, broccoli and kale (family Brassicaceae, species oleracea) using solid phase extraction (SPE) and size-exclusion chromatography inductively coupled plasma mass spectrometry (SEC-ICP-MS). Tris [2-Amino-2-(hydroxymethyl)-1,3-propanediol]/hydrochloric acid (Tris/HCl) or ammonium nitrate were used as extractants added to the freeze-dried samples, which were then sonicated and centrifuged. An enzymatic mixture was added to the extracts and then incubated for 5- and 18 h prior to analysis by SEC-ICP-MS. Results showed a good coefficient of variation (CV) of the elution time (0.06-0.9%), concentration (4.7–16.9%) and molecular size (0.4–5.4%). The limit of detection (LOD) and the limit of quantitation (LOQ) were 0.9 μg L−1 and 2.8 μg L−1, respectively. The proposed method is reliable and robust and can be applied to samples with difficult matrices like vegetables and soil.
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Good precision, stability and reproducibility.
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Samples were analyzed using an ICP-MS (PerkinElmer NexION300XX, Seer Green, Bucks, UK) equipped with a glass Meinhard nebulizer, a quadrupole mass spectrometer and a collision cell. The SEC-ICP-MS settings were as in Table 2. Ammonium nitrate (200 mM, pH 7.6), as mobile phase, was prepared daily by dissolving 16 g of ammonium nitrate in 1 L of Purite ultrapure water and the pH was adjusted with ammonium hydroxide before degassing by vacuum filtration using 0.2 μm filters (Millipore, Watford, UK). Samples (100 μL) were injected into the column at room temperature and the analysis was performed in isocratic mode. After five runs a series of five repetitive 20 µL aliquots of water was injected over 20 min, without delay between injections, followed by one 100 µL aliquot of ammonium nitrate (200 mM at pH 7.6) to re-equilibrate the column. The same series of five repetitive 20 µL aliquots of water was injected, at the end of the batch, using water as mobile phase. An average of seven replicates per sample was carried out.
Table 2. Instrumentation settings.
ICP-MS Gas flow 1 L/min Auxiliary gas flow 1.2 L/min Plasma flow 18 L/min RF power 1600 Watts Cell gas flow (He) 3.9 mL/min Mode Collision cell HPLC Column Superdex Peptide 10/300 GL Eluent NH4NO3 (200 Mm, pH 7.6) Flow rate 0.6 mL/min Mode isocratic Sample volume 100 µL Wavelength 280 nm “
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Easy to execute and suitable for analysis of vegetables and other samples with complex matrices, eg. soil.
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This method contributed to good maintenance of the instrument and to minimal cleaning time.
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