The spatial distribution of calcium in alginate gel beads analysed by synchrotron-radiation induced X-ray emission (SRIXE)

The spatial distribution of calcium ions in alginate gel spheres was investigated by synchrotron radiation induced X-ray emission. X-ray emission spectra were obtained from 1 mm spherical calcium alginate beads gelled either in the presence or in the absence of sodium ions. Evidence was found for an inhomogeneous distribution of calcium ions with the highest concentration at the surface, and the lowest concentration in the core of the spheres, which reflected the spatial distribution of alginate in the gel spheres. The form and the steepness of the calcium concentration gradient was strongly affected by the presence of sodium ions. © 1997 Elsevier Science Ltd.