Pure and Applied Chemistry

Abstract: The characterization of iodine species in the microalgae Chlorella vulgaris after cultivation with different potassium iodide concentrations was performed using the coupling of multidimensional chromatography (size exclusion chromatography, SEC, and anion exchange chromatography, AEC) with inductively coupled plasma-mass spectrometry (ICP-MS) detection. Two iodine fractions, water-soluble and macromolecular fractions, were obtained using a sequential extraction scheme based on chemical reagents. Most iodine species separated from the water-soluble fraction with SEC-ICP-MS (mass range from 0.5 to 100 kDa) are present in inorganic forms (peak III), although the other two peaks were detected (peaks I and II). The application of AEC to the isolated peak III fraction allows the characterization of IO₃^– (about 25 %) and I^– (about 75 %). The application of SEC-ICP-MS (mass range from 10 to 1200 kDa) to the macromolecular fraction reveals the presence of four peaks from the void volume to about 67 kDa, a peak is located about 600 kDa. The mass balance of iodine in the different fractions obtained from the microalgae raw stuff shows that the water-soluble fraction represents 66.7 % of total iodine in microalgae, but the macromolecular fraction only contains 13.3 %, both summing up for 79.9 % of the total amount of iodine, which confirms the suitability of the separation scheme. Further studies have to be focused on the purification of the isolated fractions and their identification by tandem MS.