Combined Use of Laser-Induced Breakdown and X-Ray Fluorescence Spectroscopies for Elemental Analysis of Aquatic Organisms

Elemental chemical analysis of aquatic organisms is necessary for biochemical and ecological studies and pollution monitoring. Most analytical methods suitable for this require dissolution of solid samples. However, nondestructive analysis is possible by x-ray fluorescence spectroscopy (XRF) and laser-induced breakdown spectroscopy (LIBS), the analytical capabilities of which are complementary. Results from XRF and LIBS for determination of several macro- and microelements (P, Cl, K, Ca; B, Mn, Fe, Cu, Zn, and Sr) in organs and tissues of fishes and aquatic plants (bream, pike, horsetail, and hornwort) were compared using calibration curves. Signals of elements were normalized to the intensity of incoherently scattered radiation (in XRF) and to that of the Balmer H alpha emission line (in LIBS) to account for matrix effects. A comparison of the results with data from an independent analysis by inductively coupled plasma optical emission spectroscopy showed that LIBS was superior to XRF with respect to accuracy for relatively light elements (P, K, Ca, Mn, Fe, and Cu). The advantage switched to XRF for heavier elements (Zn and Sr). The combination of XRF and LIBS made it possible to broaden the range of measurable elements. In some cases (P, K, Mn, Fe, Zn, and Sr), chemical destruction of the sample was unnecessary, which was important for simplification of the analytical procedures.