Rapid analysis and classification of blue ballpoint pen inks using high-performance thin-layer chromatography and digital color analysis.

Despite the rise of digitalization, the scrutiny of paper documents with stamps and signatures remains crucial, constituting 55-60 % of document examination court cases. Developing accessible and robust ink analysis techniques is an ongoing challenge for forensic scientists. To tackle issues related to the identification and classification of dye components in blue ballpoint pens, we have proposed an advanced approach that integrates high-performance thin-layer chromatography (HPTLC), digital color analysis (DCA), and hierarchical cluster analysis (HCA) for a simplified yet effective procedure. The method encompasses multiple development of TLC plates. Initial separation employs methanol:ethanol (4:1, v/v), followed by a second separation using methanol:propan-2-ol:formic acid (1:1:0.1, v/v/v) to achieve cationic dye separation. This TLC development enhances separation selectivity, contributing to a more precise clustering of pen inks. Employing advanced DCA as a processing method for HPTLC, the optimal descriptor for ink classification is identified as the difference between red (R) and green (G) color components. The proposed clustering algorithm achieved 8 distinct ink clusters, showing improved discriminative capability and a reduced variable space compared to well-established or state-of-the-art methods. The approach's robustness was demonstrated across different readout devices, including smartphones and scanners. Reproducibility tests yielded consistent clustering results, confirming the method's reliability. Moreover, the method proved effective in clustering pen ink extracts from paper substrates, showcasing its potential for real sample analysis. This HPTLC-DCA approach presents a simple, cost-effective, and high-precision solution for clustering blue pen inks, significantly enhancing accessibility in high-throughput forensic applications.

Multilayer coatings based on gold nanoparticles and polymers with bovine serum albumin as a functional layer for the chiral separation in capillary electrochromatography.

In this study, we developed physically adsorbed multi-layer coatings using poly-l-lysine or poly(diallyldimethylammonium chloride) and gold nanoparticles, which were functionalized with bovine serum albumin for the chiral separation in electrochromatography. The approach involves sequentially depositing positively charged polymers and negatively charged citrate-stabilized gold nanoparticles. By repeating this modification cycle, we created two- and four-layer coatings, which were sequentially functionalized with albumin forming three- and five-layer coatings that were finally applied for the separation of enantiomers of dl-tryptophan. The formed coatings exhibit stability across a pH range of 2-10 and feature a dense, uniform surface, as confirmed by scanning electron microscope images. The number of layers impacted nanoparticle deposition density, with five-layer coatings being denser than three-layer ones. Five-layer coatings enable baseline separation of dl-tryptophan enantiomers, whereas three-layer coatings require the presence of albumin in the background electrolyte for separation. Therefore, increasing the number of layers and gold nanoparticles density enhances albumin active center concentration on capillary walls, improving the separation of dl-tryptophan enantiomers. The five-layer coatings can be easily fabricated and possess good repeatability of analytes migration time.

Hydrodeoxygenation of Lignin-Based Compounds over Ruthenium Catalysts Based on Sulfonated Porous Aromatic Frameworks.

Bifunctional catalysts are a major type of heterogeneous catalytic systems that have been widely investigated for biomass upgrading. In this work, Ru-catalysts based on sulfonated porous aromatic frameworks (PAFs) were used in the hydrodeoxygenation (HDO) of lignin-derived compounds: guaiacol, veratrole, and catechol. The relationship between the activity of metal nanoparticles and the content of acid sites in synthesized catalysts was studied. Herein, their synergy was demonstrated in the Ru-PAF-30-SO3H/5-COD catalyst. The results revealed that this catalytic system promoted partial hydrogenation of lignin-based compounds to ketones without any further transformations. The design of the Ru-PAF-30-SO3H/5-COD catalytic system opens a promising route to the selective conversion of lignin model compounds to cyclohexanone.

CE with Cu2+ ions and 2-hydroxypropyl-ß-cyclodextrin additives for the investigation of amino acids composition of the culture medium in a cellular model of non-alcoholic fatty liver disease.

CE method with CuSO4 and 2-hydroxypropyl-ß-cyclodextrin additives in sodium acetate background electrolyte pH 4.3 for the simultaneous determination of amino acids and lactic acid was adapted for the comparative study of metabolism in "healthy" and non-alcoholic fatty liver disease model cells HepG2. In vitro model of the disease was developed by exposure HepG2 cells with oleate and palmitate to simulate an excessive flow of fatty acids into hepatocytes. The model was proven to be consistent with the disease pathophysiology, since intracellular triglyceride and cytokine interleukin 8 levels were increased, while cells viability was decreased. In order to check whether the metabolism of amino acids changes in pathology, we proposed sample preparation of culture medium and characterized the CE method by evaluating linear dynamic range, repeatability and intermediate precision of peak areas and migration times, accuracy (recovery rate and trueness estimated by reference method), detection limits and quantitation limits. The method proved to be sensitive, reliable and highly accurate for the quantitation of amino acids and lactic acid. The concentrations of amino acids in the culture medium of healthy and the disease model cells were measured and altered levels of Arg, Ala, Glu, Gln and lactic acid have been found in comparison to health control.

Determination of native amino acids and lactic acid inLactobacillus helveticusculture media by capillary electrophoresis using Cu2+and ß-cyclodextrins as additives.

A capillary electrophoresis method for selective simultaneous determination and quantitation of native amino acids and lactic acid during cultivation of Lactobacillus helveticus D75 and D76 strains on the MRS-1 and milk nutrient media was presented. The method provided sensitive UV-detection of native analytes with minimum sample preparation and appeared to be extremely useful for the analysis of culture media. Native amino acids and lactic acid were separated and detected as complexes with Cu2+ ions, while proposed application of ß-cyclodextrin (ß-CD) and its charged and uncharged derivates (sulfated ß-CD and 2-hydroxypropyl-ß-CD) as pseudo stationary phases provided better separation selectivity. The effect of CDs, Cu2+, sodium acetate, ß-CDs concentrations and pH of background electrolyte (BGE) on the electrophoretic mobilities of AAs was thoroughly investigated. The composition of the BGE was found to be as follows: 20 mM acetate buffer solution, 50 mM CuSO4, 10 mM 2-hydroxypropyl-ß-CD, pH 4.3. The developed method possessed high analysis-to-analysis and day-to-day repeatability of migration times (RSD ≤ 1.0% and ≤ 2.5%, respectively). The differences in production of amino acids by D75 and D76 strains grown together and separately were found and concluded to be a consequence and/or one of the causes of synergism and syntropy of the strains. The developed method proved to be applicable for the analysis of culture media.

Nanosized cation exchanger for the electrophoretic separation and preconcentration of catecholamines and amino acids.

The first example of application of nanosized polystyrene-based cation exchanger (NSCE) with sulfo groups as a dynamic coating of capillary walls was demonstrated. The conditions of dynamic coating formation were optimized and ensured the long-term stability of the coating. Capillary-to-capillary and day-to-day repeatabilities were 4% and 3%, correspondingly. The NSCE coating stability at various pH and influence of pH on the EOF mobility were investigated. The developed NSCE-modified coated capillaries provided improved resolution (Rs = 0.9-3.2 for catecholamines and Rs = 1.7-2.8 for amino acids) and efficiencies (330-520 ×103 t.p./m) of basic analytes, which are 1.5 times higher compared to untreated capillary. The optimized conditions were as follows: 50 mM phosphate buffer solution at pH 2.2 with 5 µM NSCE. The effect of the NSCE concentration in BGE on the electrophoretic mobilities of the analytes was investigated. The various online concentration techniques were tested in order to decrease the LODs. The simultaneous application of NSCE capillaries and field-amplified sample stacking provided the lowest LODs of catecholamines and amino acids and allowed to determine these analytes in human urine.

Nano-sized anion-exchangers as a stationary phase in capillary electrochromatography for separation and on-line concentration of carboxylic acids.

Nano-sized anion-exchangers (NSAE) are promising materials in electrophoretic separation methods due to their high ion-exchange capacity, large surface-to-volume ratios, high adhesion to the quartz surface and pH-independent positive charge. In current research we describe a simple approach for NSAE synthesis, which includes two-step grinding of macroanionite followed by centrifugation. The synthesized stable aqueous suspension of NSAE particles was applied as physically adsorbed modifier of fused-silica capillary walls for CEC separation of carboxylic acids. We proposed fast and simple approach to formation of NSAE-based stationary phase on the internal fused-silica surface, which included 15 min rinsing of the capillary with diluted water suspension of NSAE. Formed physically-adsorbed coating turned out to be extremely stable in a wide range of pH (from 2 to 10). NSAE modified capillaries provided high separation efficiency (N = 148-732 *103 t.p./m) and selectivity (Rs = 1.2-5.7) of carboxylic acids. Simultaneous application of NSAE-modified capillaries with various on-line concentration techniques (such as field amplified sample stacking and field amplified sample injection) provided both low detection limits (up to 1-3 ng/mL) and high separation selectivity of carboxylic acids. It was useful for their quantitative determination in wines samples. Physically-adsorbed coatings based on NSAE exhibit higher selectivity and lower detection limits compared to commonly used dynamic modifier of fused-silica capillary walls - cetyltrimethylammonium bromide. NSAE-based coatings do not require equilibrium sustaining to maintain the surface coverage. It makes them appropriate for CE-MS application.