Laser-induced breakdown spectroscopy of γ-Fe2O3 nanoparticles in a biocompatible alginate matrix

An intensive multi-disciplinary research effort is underway at Wayne State University to synthesize and characterize magnetic nanoparticles in a biocompatible matrix for biomedical applications. The particular system being studied consists of 3–10 nm γ-Fe2O3 nanoparticles in an alginate matrix, which is being studied for applications in targeted drug delivery, as a magnetic-resonance imaging (MRI) contrast agent, and for hyperthermic treatments of malignant tumors. In the present work we report on our efforts to determine if laser-induced breakdown spectroscopy (LIBS) can offer a more accurate and substantially faster determination of iron content in such nanoparticle-containing materials than competing technologies such as inductively-coupled plasma (ICP). Standardized samples of α-Fe2O3 nanoparticles (5–25 nm diameter) and silver micropowder (2–3.5 μm diameter) were created with thirteen precisely known concentrations and pressed hydraulically to create solid “pellets” for LIBS analysis. The ratio of the intensity of an Fe(I) emission line at 371.994 nm to that of an Ag(I) line at 328.069 nm was used to create a calibration curve exhibiting an exponential dependence on Fe mass fraction. Using this curve, an “unknown” γ-Fe2O3/alginate/silver pellet was tested, leading to a measurement of the mass fraction of Fe in the nanoparticle/alginate matrix of 51 ± 3 wt.%, which is in very good agreement with expectations and previous determinations of its iron concentration.