The influence of selected polymers on the surface tension of solutions developed for the preparation of eye drops.

BACKGROUND: Many substances are used to increase the viscosity of eye drops and reduce their surface tension. Their function is to prolong the persistence of the product on the surface of the eyeball and to increase the bioavailability of the pharmacologically active ingredient. OBJECTIVES: To investigate the surface tension of substances added to the eye drops, with the main aim of modulating properties of the preparation. MATERIAL AND METHODS: Five substances contained in solutions proposed for the development of eye drops were studied: sodium hyaluronate macromolecular (H-Na W), sodium hyaluronate ultramolecular (H-Na UM), hyaluronic acid 4% (K-H), methylcellulose (MC), and polyacrylic acid (PA). The main method was to study the surface tension using the du Noüy ring tensiometer. RESULTS: The research presented in this paper shows the various effects of different eye drop ingredients on the surface tension of the solutions. The surface tension values of PA solutions are in the range of 48.89-56.03 mN/m, of MC in the range of 68.94-89.32 mN/m, of K-H 54.54-65.66 mN/m, of H-Na UM 67.18-70.97 mN/m, and of H-Na W 67.09-71.73 mN/m. CONCLUSIONS: The use of different polymers affects the surface tension of model solutions proposed for use in ophthalmic preparations. Compounds containing carboxyl groups and anionic polymers have a similar effect on reducing the surface tension of the solution as classical surfactant compounds.

Green Extractants in Assisting Recovery of REEs: A Case Study.

The recycling of REEs from the end of life (EoL) products, such as nickel metal hydride batteries (NiMH), offers great opportunities for their supply in Europe. In the presented paper, the application of 'green' extractants such as citric (CA), metatartaric (TA), and ethylenediaminedisuccinic acid (EDDS) (also with H2O2 addition) for the recovery of REEs was studied. The studies were conducted considering the effects of the phase contact time, the initial concentration of CA, TA, and EDDS, as well as H2O2, pH, and temperature. It was found that the addition of TA to the CA solution meant that higher rates of metal ion binding and, thus, leaching was observed. The optimal conditions were obtained in the system: CA-TA and H2O2 for the concentration 0.6M-0.3 M-2%.

Application of Ion Exchangers with the N-Methyl-D-Glucamine Groups in the V(V) Ions Adsorption Process.

The adsorption capacities of ion exchangers with N-methyl-D-glucamine (NMDG) groups (Amberlite IRA 743, Lewatit MK 51, Purolite S110 and Purolite S108) relative to V(V) ions were tested in a batch system, taking into account the influence of various parameters, such as the adsorbent mass (0.05-0.20 g), phase contact time (1-240 min), initial concentration (10-150 mg/L), and temperature (293-333 K), as well as in a column system where the variable operating parameters were initial concentration (50, 100 mg/L), bed volume (10, 100 mL) and flow rate (0.6, 6 mL/min). Pseudo-first order, pseudo-second order, intraparticle diffusion and Boyd models were used to describe the kinetic studies. The best fit was obtained for the pseudo-second order model. The Langmuir, Freundlich and Temkin adsorption models were used to describe the equilibrium data to acquire better knowledge about the adsorption mechanism. The thermodynamic parameters were also calculated, which showed that the studied processes are endothermic, spontaneous and thermodynamically favorable. The physicochemical properties of the ion exchangers were characterized by nitrogen adsorption/desorption analyses, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photo electron spectroscopy (XPS). The point of zero charge (pHPZC) was also determined.