Development and Validation of a Complexometric and Potentiometric Titration Method for the Quantitative Determination of Zinc Pyrithione in Shampoo

Most of the pharmaceutical and cosmetic products used for the treatment of dandruff have zinc pyrithione as an active ingredient; therefore; quantifying this component becomes necessary. The purpose of this study was the validation of two simple and fast methodologies in the quantification of zinc pyrithione for shampoo quality control to guarantee consumer safety. The first method comprised a manual complexometric titration, and the second comprised a potentiometric titration performed with an automatic titrator, obtaining sensitivity values of 0.0534% and 0.0038%, respectively, precision expressed in RSD% values below than 1%, and accuracy in recovery percentage greater than 99%. Additionally, both methods were robust when subjected to significant changes in working conditions (temperature and pH) and were selective even in the presence of interferences and degradation products. Finally, the methodologies were adequate to ensure the quality of shampoo to ensure the safety of consumers.

MODERNIZATION OF EQUIPMENT IN CHEMICAL LABORATORY OF VILNIUS COLLEGE

The authors share the experience of creating a modern chemical laboratory. Production of modern la-boratory equipment is developing in the direction of implementing measurement decrease, measurement pre-cision and microprocessor control of instruments. In the faculty of Agro technologies Vilnius College has equipped a modern chemical laboratory with up-to-date central tables, affinity cabinets of new construction, vibration-proof tables, analytical balance, central ventilation and air conditioning systems. Automatic Titrators „METTLER TOLEDO“ are used for classic volume analysis method – titration. „Thermo Spectronic“, spectrophotometer „Genesys”20 UV-VIS“, AAS model „Buck Scientific 210 VGP“ and spectrometer „Varian 640–IR“ are used to determine the molecular composition of a wide range of organic and inorganic materials (testing water, food products, soil and sewage). The authors of the article express special thanks to the administration of Vilnius College and social partner – Company “Fermentas” for help and support. This modern laboratory provides students of chemical biotechnological analysis with the opportunity to gain practical skills, which will make them sough-after on the labour market and which are essential for their career. Key words: chemical analysis technology, chemical laboratory, analytical balance, automatic titrator, spectrophotometer, spectrometer.

Thermodynamic of Transfer and Preferential Solvation of Antibiotic Cephradine in 1,4-Dioxane-Water Mixtures

The ionization constants of cephradine in 0, 10, 20, 30, 40, 50, 60, 70, 80 and 90% ( v/v ) 1,4-dioxane-water mixed solvents were determined using a potentiometric technique and an automatic titrator. The measurements were performed at four different temperatures and 0.1 M KCl, and thus the thermodynamic parameters of ionization and transfer were evaluated. The ionization of cephradine has been found to be endothermic and entropically unfavourable. A non-linear dependence of the ionization Gibbs energies (Δ