The paper is devoted to the development of a version of the fingerprint method based on the effect of analytes on the shape of the fluorescence spectrum of a fluorophore mixture. The model analytes were medicinal substances (amikacin, sulfamethoxazole, pyracetam, and chloramphenicol) and binary to quaternary mixtures of these substances in equal concentrations. The mixtures were recognized using a fluorophore whose fluorescence was quenched to different extent by different model analytes (CdSe/CdS/ZnS quantum dots, Schiff base prepared from o-phthalic dialdehyde and polyethyleneimine, and also rhodamine B and fluorescein immobilized on silica nanoparticles to increase the degree of quenching – Rhod/SiO2 and Fluor/SiO2). The fluorophores were used as mixtures (“fluorescent reagents”) containing from one to four fluorophores. The classes of analytes were distinguished by calculating Mahalanobis distances on score plots of the principal component analysis method. It was found that it was more difficult to distinguish analyte mixtures in the presence of blood plasma than in a buffer solution and that the best fluorescent reagent was the mixture of all four fluorophores, which ensured the subdivision of 15 mixtures of 2–4 model analytes into seven classes. An alternative fingerprint method based on the use of UV absorption spectra allowed distinguishing of only five classes.

An approach to optimizing conditions of acquiring Electrospray Ionization Fourier Transform Ion Cyclotron Resonance mass spectra (ESI FTICR MS) was suggested. This method was employed to study the influence of cone voltage and the composition of the solution on peak intensity in ESI FTICR mass spectra of natural water humic substances. A presence of water in methanol solution was shown to reduce signal intensity significantly. The highest integral intensity of peaks selected was reached on 110 mg/l sample solution in acetonitrile and cone voltage 3.0 kV. The number of peaks to which molecular formulas were assigned, including doubly-charged peaks, was increased using these conditions.

Approximate equations were derived for predicting the height and position of a jump in the sigmoidal curve of compexometric titration with the formation of an MR n complex involving low-dentate ligands. The inflection point was shifted relative to the equivalence point with decreasing the stability and the concentration of the complex. Criteria of the applicability of the corresponding titrants were proposed. Predictions and recommendations were supported by a computer-aided experiment.

Parameters are proposed to describe the distribution of the effective electrophoretic mobilities of various anionic polyelectrolytes such as poly(styrene-4-sulfonates) and humic substances of different origins analyzed by capillary zone electrophoresis, The first step of the data treatment is a baseline correction and conversion of the electrophoretic raw time data to effective electrophoretic mobilities (mu-scale), taking into account the electroosmotic flow. With this new mu-scaling, the electropherograms are more representative of velocity-based separation phenomena than those using migration times, and a direct comparison of electropherograms is possible. Four different average electrophoretic mobilities were defined: the number-average effective mobility (mu(n)), the weight-average effective mobility (mu(w)), the z-average effective mobility (mu(z)), and the peak-average electrophoretic mobility (mu(p)). The polydispersity of the mobility of mixtures was described by the mu(w)/mu(n), mu(z)/mu(w) and mu(p)/mu(w) ratios. These parameters were used to describe the electrophoretic mobility distributions of different fractions of restricted molecular size: those obtained by ultrafiltration from a soil humic acid at neutral pH and reference humic substances of the International Humic Substances Society at different values of pH and ionic strength. The data clearly show the influence of both molecular size and charge distribution of the analyzed mixtures on the mobility distributions.