Quantitation of Iron(III) Ions Complexed by Tetraphenylporphyrin and Its Effect on the Structure of Ultrafine Poly(3-Hydroxybutyrate) Fibers

We demonstrate a methodical approach to quantitation of iron ions on the surface and in bulk of ultrafine fibrous materials of poly(3-hydroxybutyrate) (P3HB), taking the tetraphenylporphyrin iron(III) chloride (FeClTPP) complex as an example. Ultrafine fibers based on the P3HB biopolymer and containing 1–5 wt % of FeClTPP are fabricated by electrospinning. As analytical techniques, UV spectroscopy and electron paramagnetic resonance (EPR) are successfully used for quantitation of iron(III) species. We identify the effect of the complex on the crystalline phase and segmental mobility of P3HB molecules in amorphous domains of the ultrafine fibers. Adding small amounts of FeClTPP (up to 5%) leads to a marked increase in the crystallite size and the degree of P3HB crystallinity and to densification of the amorphous regions. Our findings suggest that UV spectroscopy and EPR are promising analytical techniques for quantitation of iron ions in nonwoven fibrous sorbents designed for removal of oil products and heavy metals from waste waters.