STUDIA CHEMIA - Issue no. 4 / 2022 - Table of contents

Professor Teodor Hodisan graduated the Faculty of Chemistry of "Babeş-Bolyai" University from Cluj-Napoca in 1966 and was assigned as a scientific researcher at the Institute of Chemistry of the Romanian Academy from Cluj-Napoca. On February 1, 1968, he was appointed by competition as an assistant at the Department of Analytical Chemistry, Faculty of Chemistry, "Babeş-Bolyai" University in Cluj-Napoca. Afterwards, he ascended through all the steps of the university hierarchy: lecturer (1975), associated professor (1990) and professor (1997). In 1973, he defended his doctoral thesis under the scientific supervision of the renowned emeritus scientist Prof. Docentus Candin Liteanu. From the beginning he worked under the guidance of eminent professor Candin Liteanu in the field of analytical chemistry, specialization chromatographic analysis, a field in full expansion at that time. Thus, the research directions approached were focused on the development and application of chromatographic methods and he became a follower of the illustrious professor, managing to preserve the reputation of the Cluj chromatography school along with his colleague Prof. Simion Gocan. The research carried out resulted in the elaboration, as author or co-author, of 8 published books and 2 treatises on chromatographic analysis. He elaborated a number of 80 scientific works, published in renowned journals from the country and abroad. He was co-author of 3 invention patents and 5 innovator certificates. He participated in most of the analytical chemistry scientific events organized in the country as well as abroad. He participated to the finalization of 10 scientific research contracts with various industrial and research units, as grant director or co-participant, in the field of liquid chromatography. He guided numerous students in the preparation of their doctoral theses and contributed to the training of many researchers and teaching staff members. During the period 2002-2007, he was the head of the Analytical Chemistry department. Also, he was a member of the Analytical Chemistry Society, and he was the president of this society, Transylvanian subsidiary between 1992 and 1994. The research carried out by professor Hodisan became a fundamental basis for many of us who are currently working in the field of chromatography and in the name of all colleagues who had the opportunity to work along with him, I want to address my special thanks for everything he did and for imparting inspirations with a positive impact on our scientific careers.

22.12.2022

Prof. dr. Claudia Cimpoiu
"Babeş-Bolyai" University
Faculty of Chemistry and Chemical Engineering

Keywords:

Coffee is rich in phytochemicals that give its fingerprint and differentiate it from other plant based food. Due to its widespread use and high cost price, it happens that some manufacturers counterfeit it with various additions of cheaper products. This study exhibits a new approach in evaluating of roasted coffee based on high-performance thin-layer chromatography (HPTLC) method. The separation of compounds was performed on silica gel 60 F254 HPTLC plates using a mixture of chloroform – methanol – acetonitrile, 6 : 1.5 : 2.5 v/v/v as mobile phase. The images of the plate were statistically analysed in order to find the most representative featurings for each samples

Keywords: coffee, adulteration, HPTLC, UV-Vis spectrophotometry, chicory, soybean, wheat

A new analytical procedure for rapid and selective derivatization of rosuvastatin directly in plasma into their corresponding methyl esters was developed for gas chromatography-mass spectrometry analysis. This work is the first method of selective derivatization of the carboxyl group from rosuvastatin to methyl ester. The lipids from plasma were extracted with heptane before derivatization. The methyl esters were obtained by reaction with methyl iodide in solution of dimethyl sulfoxide and in the presence of anhydrous potassium carbonate. The optimal conditions for selective methylation have been established. The derivatization was carried out in 2 min. The method was validated for the analysis of rosuvastatin in plasma. The methyl ester of rosuvastatin was identified by electron ionization mass spectrometry. The electron ionization mass spectrometer detector response was linear up to 300 ng/mL. The limit of detection and limit of quantification values in total ion chromatogram method were 0.4 ng/mL and 1.2 ng/mL, respectively.

Keywords: Rosuvastatin, Plasma, Methyl esterification, Gas chromatography-mass spectrometry analysis

Nowadays, protein purification by the aid of affinity tags can be carried out with high speed and efficiency. However, in several cases, affinity tags can significantly alter the key properties of enzymes, especially activity and/or thermostability. This study focused on the purification of the non-tagged phenylalanine ammonia-lyase from Petroselinum crispum (PcPAL), as well as on the purification of the TEV (Tobacco Etch Virus) protease, the molecular scissors used to remove the affinity tag from the recombinantly expressed PcPAL. Removal of the 6xHis-tag led to a 1.5-fold increase in the specific activity of PcPAL, while the absence of the affinity tag did not significantly alter the thermostability of the protein. The purity and oligomerization state of the proteins of interest were also analyzed by size exclusion chromatography, both before and after the removal of the affinity tag, confirming the stability of the tetrameric fold of PcPAL.

Keywords: affinity tags, phenylalanine ammonia-lyase, TEV (Tobacco Etch Virus) protease, thermostability, specific enzyme activity, oligomerization state.

Geometry optimization of perpendicular, antiparallel and parallel dimers were employed in order to analyze the relative energy values. The weakest interactions are seen for the perpendicular structures; among those, the strongest are for π, 310, while the DeSantis structure affords no local minimum at all. The strongest interactions are seen with parallel structures – of which the largest interaction energies are with the DeSantis and the π monomers (up to 2.8 and 4.2 kcal/mol per unit of lactic acid, respectively).

Keywords: polylactic acid (PLA), supramolecular, computational

Models for dissociation and mixing of acids and bases are the main subject of many analytical chemistry textbooks. Preparing the solutions for any titration generally involves diluting acids and bases. The mathematics behind precise calculation of pH and pOH is treacherous even for monoprotic acids and bases, becoming mathematically complex when processes of chemical complexation are considered and one should consider any simplifying approximation when available.

Keywords: dilution, acids, bases, 3D visualization, simulation software

This research work has two sections. In first section, the equilibrium constant for protonation processes of DL-phenylalanine (K1, and K2) were determined in binary mixed solvents of water–methanol, containing 0, 10, 20, 30, 40, 50, 60, 70, and 80 % (v/v) methanol, at T = 298.15 K and constant ionic strength (0.1 mol.dm-3NaCl). The obtained data (K1, and K2) were analyzed using Kamlet, Abboud, and Taft parameters. In second section, for DL-phenylalanine in aqueous solution, the values K1, and K2 were determined at T = (298.15, 303.15, 308.15, 313.15, and 318.15) K and constant ionic strength (0.1 mol.dm-3NaCl). Using these K1, and K2, the thermodynamic properties (changes of enthalpy, ΔH, changes of entropy, ΔS, and changes of Gibbs free energy, ΔG) were calculated for DL-phenylalanine in aqueous solution. In both sections, the values of K1, and K2 were determined using the spectrophotometric and potentiometric methods.

Keywords: protonation constants, DL-Phenylalanine, potentiometric, spectrophotometric, changes of enthalpy, changes of entropy, and changes of Gibbs free energy.

Various lignocellulosic waste materials were assessed for their potential usage as biosorbents for Cd(II) removal from wastewaters. Sunflower seed shells, carrot peel, bean pods, eggplant peel, and orange peel in dry form and different grain sizes were evaluated. Contact time, initial Cd(II) concentration, and biosorbent amount were also tested. Eggplant peel was the most efficient biosorbent with an experimental biosorption capacity of 9.33 mg/g, a monolayer capacity (Langmuir) of 18.05 mg/g, and maximum % yield removal of 97.33%. Experimental data best fitted the Langmuir isotherm model (exception, orange peel) and the pseudo-second-order kinetic model (all materials).

Keywords: cadmium(II), biosorption, waste valorisation, circular economy, sunflower seed shell, carrot peel, bean pod, eggplant peel, orange peel

The ability of peanut husk in removing Methylene Blue (MB) dye solution was studied in this project. The influence of various factors such as contact time, initial dye concentrations, pH and adsorbent dosage were examined in this project in order to study their effects towards the adsorption process. The percentage uptake of MB increases with contact time, pH and adsorbent dosage while it decreases with increasing initial dye concentrations. The functional group on peanut husk was determined using Fourier Transform Infrared Spectrophotometer (FTIR) and its surface morphology was characterized using Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) analysis. The experimental data fitted well into the pseudo-second-order kinetic model with R2 values close to unity. The experimental data is best fitted with Freundlich isotherm model by having R2 of 0.9927. By using Plackett-Burman design, the factors that can bring significant impact towards the adsorption of MB by peanut husks were determined to be contact time, pH and adsorbent dosage. The optimum condition for the adsorption process was determined by Response Surface Methodology. It was found that the optimum condition was reached at 120 minutes of contact time, pH 10 and 0.035 g of adsorbent.

Keywords: Adsorption, Methylene Blue, Peanut husk, Plackett-Burman Design, Response Surface Methodology

The aim of this paper consisted of the carbon nanotube nanocomposite testing for the removal of ampicillin from aqueous solutions. To determine the optimum experimental conditions for ampicillin adsorption on nanocomposite, several parameters were selected: the pH, initial concentration of pollutant, adsorbent dose and contact time. The high-performance liquid chromatography was used to determine the residual ampicillin concentration from aqueous solutions. The best removal of the antibiotic on the tested nanocomposite was obtained with an initial concentration of 40 mg L−1 with 1 g L−1, pH 2 in 20 min.

Keywords: ampicillin, adsorption, nanocomposite, carbon nanotubes, water decontamination

In this study, a comparison of walnut-based carbon materials (CM) obtained by hydrothermal carbonization (HTC) and HTC in combination with steam gas activation (SGA) was carried out. In order to study the effect of steam activation on the functional layer formation, the obtained materials were studied by SEM, nitrogen adsorption/desorption by Brunauer-Emmett-Teller (BET) method, Raman spectroscopy, X-ray diffraction spectroscopy (XRD), X-ray fluorescence elemental analysis (XRF). Functional groups (FG) were evaluated qualitatively and quantitatively by Fourier transform infrared spectroscopy (FTIR), acetone extract analysis of CM by gas chromatography-mass spectrometry (GC-MS), and potentiometrically Boehm titration. The described mechanism of the influence of the base nature on the surface functionality correlates well with the results of the powder addition method. The HTC or HTC+SGA treatment provides a wide range of possibilities for further controlled modification of the carbon sorbent surface for specific adsorption purposes.

Keywords: hydrothermal carbonization, carbon material, thermal carbonization, walnut shell, activated carbon, functional layer

As plastic production increases, new waste management methods are required. Chemical recycling, such as pyrolysis, has the potential to raise recycling rates taking into account that it can use more waste plastics than standard mechanical recycling. Four types of bits of plastic: polyethylene (PE), polypropylene (PP), polystyrene (PS), and biaxial-oriented polypropylene (BOPP) fractions from the printing plant were collected; the possibility of recycling them by batch pyrolysis was investigated. Characterization of the obtained pyrolysis oils was carried out by gas chromatography-mass spectrometry (GC-MS), the analysis showed a mixture of aliphatic (saturated and unsaturated) compounds, in the case of PE and PP, while in the case of PS, aromatics and low quantities of other hydrocarbons were detected. In the case of BOPP the distribution of the pyrolysis products is not as uniform as in the case of PE, PP, or PS plastic samples. The FT-IR results showed clear peaks of aliphatic compounds in two liquid oil samples of PE, and PP that further confirmed the GC-MS results. More than 60% monomer (styrene) can be recovered from the PS pyrolysis, besides other aromatic compounds in low concentration. The pyrolysis oils have a reasonable heating value (calorific value) in the range of 36–45 KJ/g, close to conventional diesel. Therefore, the pyrolysis oils has the potential to be used as an alternative source of energy as fuel, after blending with conventional fuel, or heating combustion products. The research results will contribute to the development of waste valorization via plastic upcycling from a printing press, without using an expensive catalyst or reactor system.

Keywords: thermochemical process, plastic upcycling, pyrolysis oil, GC/MS analysis, hydrocarbons

The article reports the AMS (accelerator mass spectrometry) radiocarbon dating results of the historic Emperor’s Beech (Fagul Împăra-tului) from Muncel, Baia de Arieş, Romania. Two wood samples were collected from the large tree, out of which four segments were extracted and analysed by AMS radiocarbon. The oldest dated sample segment had a radiocarbon date of 233 ± 18 BP, which corresponds to a calibrated age of 365 ± 5 years. This value suggests an age of 420 ± 20 years for the Emperor’s Beech. Thus, the historic beech started growing around the year 1600.

Keywords: AMS radiocarbon dating, Fagus sylvatica, dendrochronology, age determination, Romania

Pelargonium quercetorum Agnew extract affects activities of acetylcholinesterase (AChE) and carbonic anhydrase I-II enzymes (hCA I-II) was investigated under in vitro conditions. IC50 values of P. quercetorum Agnew on hCA I-II and AChE activity were determined as 0.144±0.0720, 0.209±0.0593, and 0.062±0.0097 mg/mL, respectively. Rutin and shikimic acid was found to be the main phenolic component in P. quercetorum Agnew flower extract from the results of LC-ESI-MS/MS analysis. Rutin was found to be the main phenolic component in P. quercetorum Agnew leaf extract from the results of LC-ESI-MS/MS analysis. ICP-OES analysis showed that the leaves of P. quercetorum Agnew were rich in potassium. The DNA protective effect on plasmid DNA was demonstrated by using extracts obtained from leaf and flower tissues. Consequently, based on the findings of the current study, it could be anticipated that clinical trials related to P. quercetorum Agnew could be completed and the plant could be used pharmacologically.

Keywords: Acetylcholinesterase; Carbonic anhydrase; DNA protection; ICP-OES; P. quercetorum Agnew

The aim of this study was to assess the influence of the distillation processes on the content of Al, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb and Zn in 18 home-brewed fruit spirits, originating from different locations of Romania, and 3 industrially-brewed spirits and 19 cognacs. Metals quantification was achieved by inductively coupled plasma optical emission spectrometry (ICP-OES) after sample digestion. The study revealed higher metals concentration in the home-brewed spirits, compared to the industrially-brewed ones, with concentrations of Cu, Fe, Al and Zn in most of the samples above the Alcohol Measures for Public Health Research Alliance (AMPHORA) project set threshold in recorded alcoholic beverages. However, no risk to human health was found by a moderate consumption of the analyzed alcoholic beverages (100 mL/day) as respects to long-term non-carcinogenic health risk. The Principal Components Analysis (PCA) indicated a wide dispersion of the analyzed alcoholic beverages according to their elemental composition. The two-dimensional PCA representation after Varimax rotation indicated a group of elements of natural origin (Ca, Mg, Al, Cd, Mn, Pb), and another of trace elements (Co, Cr, Ni, Zn, Fe) originating from the distillation equipment. Copper however, was associated both with the raw material and the distillation equipment.

Keywords: alcoholic beverage, human health risk assessment, Principal Component Analysis

A new micro-HPTLC method assisted by image analysis technique was proposed for rapid evaluation of the total antioxidant potential (TAP) of redox-active drugs using 2,2-diphenyl-1-picrylhydrazyl (DPPH•) and 2,2’-azinobis-3 ethylbenzothiazoline-6-sulfonic acid (ABTS*+) radicals. Colored compounds that can significantly influence the spectrophotometric and chromatographic measurements were revealed in case of selected drugs after their reaction with DPPH• and ABTS*+ radical respectively. The best chromatographic conditions were selected for accurate quantification of DPPH• and ABTS*+ radicals after their separation from the interfering compounds. The validation of the proposed method was performed in terms of linearity, limit of detection, limit of quantification, precision, and accuracy. Green and red color channel used for image processing were found to allow accurate quantification of DPPH•. For accurate quantification of ABTS•+ the red and gray channels were selected. A linear dependence of spot area/radical concentration was obtained in the range 0.78-2.76 μg⋅spot-1 and 0.21-2.49 μg/spot for DPPH• and ABTS*+ radicals respectively. The developed method was found to be accurate and precise according to values higher than 92% for recovery and less than 3% for relative standard deviation parameters (RSD%). A statistical significant correlation was obtained comparing the spectrophotometric results with the chromatographic ones obtained for selected adrenergic drugs.

Keywords: micro-HPTLC method; image analysis; total antioxidant potential; adrenergic drugs; DPPH• and ABTS•+ protocols

2,4-D is a herbicide that in certain doses can be used as a growth stimulator for various crops. Although it is forbidden in our country to use it for such purposes, tomato growers use it to obtain large and fast harvests, but unfortunately of poor quality (the well-known tomatoes with tassel). In this work, we present a modified Miniluke extraction method and a LC-MS/MS analysis method of this pesticide from tomatoes. The method was validated both on tomatoes (presented in this paper) and strawberries, and its efficiency was demonstrated by participating to interlaboratory European tests where very good Z-scores were obtained.

Keywords: 2,4-D, growth plant stimulator, LC-MS/MS, Miniluke, QuEChERS

The aim of the present study was the electrochemical investigation of the inhibition efficiency of aluminum-tripolyphosphate (ATPP) incorporated in silica (SiO2) and chitosan (Chit) coatings prepared on zinc substrates. Coatings were prepared by dip-coating method. Electrochemical characterization of the coatings was performed by using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves (PDP). Effect of ATPP on Zn was also determined in 0.2g/L Na2SO4 solution and its adsorption on zinc was studied. Results concluded that the ATPP adsorption on Zn obeys Langmuir isotherm. The best corrosion resistance was reached when Zn was protected by SiO2 coating, obtained from a precursor sol containing 10-3 M ATPP

Keywords: zinc; silicon dioxide; chitosan; Al-tripolyphosphate; anti-corrosion coating; adsorption

This paper purpose was to develop a sensitive and selective method for the determination of glyphosate, and aminomethylphosphonic acid (AMPA) residues in water and glyphosate from soil samples. The method involves a derivatization step with 9-fluorenylmethylchloroformate in borate buffer of these compounds and liquid chromatography separation with fluorescence detection (HPLC-FLD). Separation of derivatized glyphosate and AMPA compounds was performed on an Agilent ZORBAX C18 reversed-phase column. The mobile phase consisted of a mixture of acetonitrile and 0.05 M KH2PO4 solution [30:70 v/v]. Limits of detection (LOD) was 0.28 μg L-1 for glyphosate, and 0.35 μg L-1 for AMPA, and limits of quantification (LOQ) was 0.84 μg L-1 for glyphosate and 1.05 μg L-1 for AMPA. The method has been validated for surface water and soil by recovery studies with samples spiked at 25 and 5 μg L-1. In water samples, the mean recoveries values ranged between 86.44 - 103.9% for glyphosate, and 71.27 - 99.08% for AMPA. The mean recoveries values for glyphosate ranged from 57 - 81.5% in soil samples. The developed method has been applied for determination of these compounds in water and soil samples from agricultural and rural areas of Roma community from some Transylvania Counties.

Keywords: Glyphosate, aminomethylphosphonic acid, water, soil, FMOC-Cl, RP-HPLC-FLD.

This study aims to assess the pollution history of persistent organic pollutants (POP) in lake Muntinu, Carpathian Mountains, Romania. Gamma spectrometry was used to measure 210Pb and 137Cs radionuclides in order to determine the age of sediment layers. The target compounds were isolated from sediment samples by ultrasound-assisted extraction method, followed by purification of extracts using open-column chromatography. 16 polycyclic aromatic hydrocarbons (PAHs), 20 organochlorine pesticides (OCPs) and 12 polychlorinated biphenyls (PCBs) were analysed in each dated sediment layer using gas chromatography coupled with mass spectrometry or electron capture detector. The results show that, over the past 100 years, POP concentrations from sediment samples ranged from 2.53 to 156.27 ng/g for PAHs, from 1.78 to 71.12 ng/g for OCPs, and from not detected to 76.03 ng/g for PCBs. PAHs diagnostic ratios such as ƩLMW/ƩHMW, ANT/(ANT+PHE) and FLT/(FLT+PYR) show that the main source of PAHs in the sediment is of pyrogenic nature, especially from biomass and coal combustion. The sources of OCPs and PCBs could not be determined due to the lack of data obtained. However, the study demonstrates that the analysis of POP residues in sediments is a suitable method for reconstructing the history of surface water pollution.

Keywords: Historical pollution, Polycyclic aromatic hydrocarbon, Organochlorine Pesticide, Polychlorinated biphenyl, radionuclides dated sediment

Two experimental procedures implying mechanochemical and ultrasounds assisted protocols were assessed as alternatives to the classical synthesis of the title MB analogue, based on the substitution of the phenothiazinium tetraiodide with diethanolamine nucleophile. These greener alternatives required a much shorter reaction time and consequently less energy consumption. The sonochemical procedure gave a crystalline reaction product demanding a facile purification. UV-vis spectroscopic analysis emphasized the optical properties of the 3,7-bis(N,N-(2-hydroxyethyl)amino)phenothiazinium dye characterized by an intense absorption maxima situated at 663 nm and weak fluorescence emission in aqueous solution (quatum yield 0.7% relative to methylene blue standard) with the emission maxima situated at 685 nm (Stokes shift 484 cm-1). The solid state structure of the dye was determined by X-ray diffraction.

Keywords: Phenothiazinium dye, mechanochemistry, sonochemistry, XRD, UV-vis absorption spectroscopy

A series of Pt-complexes of the type [Pt(DioxH)2L2], (DioxH= deprotonated diethyl-glyoxime, methyl-pentyl-glyoxime, methyl-propyl-glioxime, L=amine) were synthesized, described and characterized with thermoanalytical (TG-DTG-DTA), spectroscopical (FTIR, ESI-MS, UV-VIS and NMR), powder XRD and AFM methods. The biological activity, especially the antibacterial effect, was also studied. The complexes were tested against selected Gram-positive and Gram-negative bacteria. The thermoanalytical measurements revealed the stability of complexes until 200 °C, which then loose characteristic fragments of their ligands. The spectroscopic data are in accordance with the thermal properties of the samples, confirming their composition. The compounds exhibited antibacterial effect against the bacterial strain studied.

Keywords: Pt(II)-complexes, α-dioxime, amine ligand, thermal properties, spectroscopy, AFM, antimicrobial activity

A new route to obtain by regioselective acylation of cyclohexyl amine using N-phthaloyl-L-glutamic anhydride, followed by hydrolysis of phthaloyl group with hydrazine hydrate was performed in order to prepare γ-L-glutamyl-cyclohexyl amide. This one was used as ligand for a novel series of metal transition complexation like Cu(II), Co(II) and Ni(II). The ligand and its metal complexes were characterized via their spectral and thermogravimetric analysis. The thermal stability of the compounds was discussed in the 20-8000C temperature range. In all these complexes, the γ-L-glutamyl amide act as a bidentate ligand with coordination involving the carboxylate group and the nitrogen atom belonging to the amino group of glutamic acid fragment. The results indicate that their stability range obeys the Irving-Williams series.

Keywords: L-glutamic acid, glutamyl amides, metal complexes, thermal behavior

Origanum vulgare L., commonly known as oregano, is a woody, rhizomatous perennial plant. Oregano extracts are a complex mixture of different compounds, in which major constituents are terpenes (mono- and sesquiterpenes). The flavor of oregano oil is generally due to the presence of thymol and carvacrol. Carvacrol has multiple properties: antioxidant, antimicrobial, antitumor, antimutagenic, antigenotoxic, analgesic, antispasmodic, anti-inflammatory, angiogenic, antiparasitic, antiplatelet, insecticidal, antihepatotoxic and neuroprotective. The oregano extract was characterized by analyzing, the antioxidant activity, the total polyphenols content (obtaining 2.4 - 3 mg gallic acid/g), the content of phenolic acids and flavonols by HPLC chromatography, the content of carvacrol (21, 29% in essential oil and 19.78% in ethanolic extract) and thymol (2.59% in essential oil and 2.67% in alcoholic extract) by GC-MS chromatography. Oregano extracts were tested for antimicrobial activity against Staphylococcus aureus. The test results demonstrate the significant antimicrobial activity of these preparations.

Keywords: Oregano vulgare, antioxidant activity, polyphenols, HPLC, GC-MS