Single or multiple system peaks can be observed in ion-exclusion chromatography (IEC) based on whether the eluent is composed of single or multiple active eluent constituents. It was confirmed experimentally that the number of system peaks is always equal to or lower than (when co-elution occurs) the number of active eluent components. Positive and negative system peaks can be recorded in the IEC systems. Negative system peaks can be expected for each eluent component that is also present in the injected sample plug at a lower concentration than in the eluent. In the opposite case, where the eluent components in the injected sample plug are present at a higher concentration than in the eluent, positive system peaks will be recorded. The appearance of the system peaks in IEC is based on the column capacity which is analyte –depending. Variable column capacity was used to determine the absolute time window in which an individual system peak can be expected.
COBISS.SI-ID: 1609007
Multivariate data analysis methods were applied to the analysis and interpretation of micro-Raman spectra, collected from a broad set of historical iron-based ink samples, previously characterised for the content of organic acids (gallic acid, ellagic acid and protocatechuic acid).The obtained classification method for discrimination of historic inks and the regression method for determination of condensed tannic acid residuals supports the use of Raman analysis of fluorescing organic materials, and may provide information to scholars on ink composition and potentially on its provenance.
COBISS.SI-ID: 36976133
A partial distance-weighted variable anti-connectivity topological index was introduced for modelling pK a values of 31 aliphatic carboxylic acids and haloalkyl-carboxylic acids. The partial distance-weighted variable anti-connectivity index showed superior modelling capabilities compared with the index calculated from the complete graph, because it is capable of accounting correctly for the intramolecular interactions of unconnected vertices to specific bond strengths (active site), thereby improving the RMSCV error by about 30% (0.221 pKa units).
COBISS.SI-ID: 36863493
New insights into the functioning, i.e. electrochemical behaviour and analytical performance, of in situ prepared antimony film electrodes (SbFEs) under square-wave anodic stripping (SW-ASV) and cyclic (CV) voltammetry conditions are presented by studying several key operational parameters using Pb(II), Cd(II) and Zn(II) as model analyte ions. It was ascertained that HNO3 as supporting electrolyte yield nearly identical results in conducting ASV experiments with SbFE as so far almost exclusively used HCl. This is extremely important as HNO3 is commonly employed acidifying agent in trace metal analysis, especially in elemental mass spectrometry measurements. By carrying out a systematic CV and ASV investigation using a medium exchange protocol, we confirmed the formation of poorly soluble oxidized Sb species at the substrate electrode surface at the end of each stripping step, i.e. at the potentials beyond the anodic dissolution of the antimony film. Hence, the significance of the cleaning and initializing the surface of a substrate electrode after accomplishing a stripping step was thoroughly studied in order to find conditions for a complete removal of the adhered Sb-oxides and thus to assure a memory-free functioning of the in situ prepared SbFE. Practical use was tested for the determination of selected ions in drinking, surface and river water samples in ng/mL concentration range.
COBISS.SI-ID: 36731141