The present research aimed to investigate the demineralizing effects of sulfuric acid on pig bone. Alterations in collagen and phosphate contents and changes in the elemental composition of the bone during the 14-day-long immersion in sulfuric acid solutions of different concentrations were estimated using ATR-FTIR, LIBS, and AAS. FTIR spectra at amide I (1800–1600 cm⁻¹) and phosphate ν₁/ν₃ (PO₄³⁻) (1300–900 cm⁻¹) domains were scrutinized using the deconvolution method for monitoring changes in the protein secondary structure and mineral content. The results implicated sulfuric acid as a powerful demineralization agent and effective in targeting mineral components, such as hydroxyapatite, while leaving the collagen matrix relatively preserved with a complex secondary structure. Collagen maturity marker values gave valuable insights into the structural integrity of the bone. LIBS and AAS indicated changes in bone hardness; phosphorous-to-carbon ratio; and calcium, phosphorous, and magnesium content in the solutions left after the immersion period. The changes in the ratio of ionic-to-atomic calcium lines in the LIBS spectra indicated hardening of the bone, with increasing acid concentration and prolonged action, due to the deposition of calcium sulfate on the surface. The calcium concentration in the solutions decreased with increased acid concentration, while the change in phosphorus and magnesium concentrations was reversed.

The composition of the plasma obtained by laser ablation of cermet WC–Cu is calculated under the assumption of local thermodynamic equilibrium. Special attention is paid to the effect of lowering the ionization potential, the influence of which in the Saha equations is reflected both through the exponential Boltzmann term and through the partition functions of atomic and ionic species present in the plasma. The effects of these two terms are separated and quantified. It has been shown that the correction to the partition functions due to the reduction of the ionization potential is of greater importance than the correction to the Boltzmann term at higher temperatures for atomic species. It is thus necessary for the precise determination of the plasma composition, especially at higher temperatures. The effect of lowering the ionization potential on different types of atoms as well as on different ionic states is analyzed. The change of the partition function due to the lowering of ionization energy also affects the concentration of single charged ions in an amount comparable to the correction of the Boltzmann term.

Laser induced plasma (LIP) is transient, the part of the time evolution of its emission used for the Laser induced breakdown spectroscopy (LIBS) technique corresponds to plasma pressures that are comparable to atmospheric, where a certain degree of mixing of the ablated material and air must be taken into account. The aim of this work was to discuss the influence of pressure change and air mixing of laser ablated material on the equilibrium composition of plasma obtained on an ODS steel target, which is a material of great interest for nuclear technology. Special care is devoted to the influence of pressure and mixing on the equilibrium relationship between the temperature T and the electron number density Ne, which is important for plasma diagnostics. The obtained results show that the concept of local thermodynamic equilibrium (LTE) can be used for the LIBS plasma diagnostics and the optimization of spectrochemical analysis parameters. The conclusion refers to the expected interval of plasma pressure during its evolution (10?0.1 bar) and the expected degree of mixing of the ablated material and air, in the temperature range 5,000?15,000 K, relevant for the LIBS technique.