Development of a method for the detection of zinc in Brassica oleracea using solid phase extraction and size-exclusion chromatography inductively coupled plasma mass spectrometry (SEC-ICP-MS)

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. • Good precision, stability and reproducibility. • Easy to execute and suitable for analysis of vegetables and other samples with complex matrices, eg. soil. • This method contributed to good maintenance of the instrument and to minimal cleaning time.