Amperometric determination of cholesterol using cholesterol oxidase immobilized on Pt,Ru-C nanocomposite and an ionic liquid-modified carbon paste electrode

Cholesterol as very important biomolecule is the precursor of many biologically significant compounds which give strength and flexibility to the biological membranes. It is also a crucial component in lipoproteins, and has an important role to transport hydrophobic molecules in hydrophilic media such as blood [1, 2]. The analytical performance of carbon paste electrodes (CPE) bulk modified with ionic liquid 1-allyl-3-methylimidazolium dicyanamide ([AMIM][DCA]), and surface modified with platinum on graphitized carbon (Pt-C) or platinum-ruthenium alloy on graphitized carbon (Pt,Ru-C) for analysis of hydrogen peroxide (H 2O2) were compared. The prepared working electrodes were characterized using scanning electron microscopy–energydispersive X-ray spectrometry, together with electrochemical impedance spectroscopic, cyclic voltammetric, and amperometric techniques. After method optimization, an enzyme cholesterol oxidase (ChOx) was immobilized on the surface of Pt,Ru-C/IL-CPE by Nafion®. The improved cholesterol amperometric determination was achieved in phosphate buffer solution pH 7.50 at a working potential of 0.60 V. Under the optimized experimental conditions, a linear relationship between oxidation current and cholesterol concentration was in the concentration range from 0.31 to 2.46 µM, with an estimated detection limit of 0.13 µM and relative standard deviation (RSD) below 4.2%. The optimized amperometric method in combination with the developed ChOx/Pt,Ru-C/IL-CPE biosensor showed good repeatability and high selectivity towards cholesterol biosensing despite the presence of possible interferences. The ChOx/Pt,Ru-C/IL-CPE was tested for the determination of the free cholesterol, by its enzymatic reaction product H 2O2, in a human blood serum sample. The percentage recovery ranged from 99.08 to 102.81%, while RSD was below 2.0% for untreated, as well as for spiked human blood serum sample.YISAC 2023 : 28th Young Investigators' Seminar on Analytical Chemistry : the book of abstracts; June 25-28, Belgrad

The potential role of metal-induced oxidative stress in human pancreatic cancer: Preliminary results.

Pancreatic cancer (PC) is one of the most aggressive types of cancer and a worldwide health treat. However, it is rather unclear which environmental pollutants can be linked to PC development. Exposure to toxic metals through various sources can be one of the risk factors, especially having in mind that some toxic metals can induce oxidative stress, which has already been associated with the pathogenesis of PC. The aim of this study was to investigate the levels of cadmium (Cd) and lead (Pb), toxic metals of great environmental concern known to induce oxidative stress, in the blood of PC patients and healthy control subjects, as well as to examine the following biomarkers of oxidative stress: superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR), glutathione S-transferase (GST), glutathione (GSH), sulfhydrylgroups (SH), and lipid peroxides (TBARS) in blood. Blood samples were obtained from 15 PC patients and 7 healthy subjects. The present study demonstrated a significant increase in Pb concentrations in patients with carcinoma when compared to healthy subjects (p<0.05), while no significant differences were observed in Cd levels. The activities of SOD and CAT, as well as the concentration of SH groups, were significantly higher in people with PC compared with controls (p<0.05) proving oxidative stress induction in the blood of PC patients. This work contributes to a better understanding of the potential role of metal-induced oxidative stress in PC aetiology. However, confirmation of these pilot findings in a larger study is needed

Facile immobilization of cholesterol oxidase on Pt,Ru–C nanocomposite and ionic liquid–modified carbon paste electrode for an efficient amperometric free cholesterol biosensing

In present work, the enzyme cholesterol oxidase (ChOx) was immobilized by Nafion® (Naf) on Pt,Ru–C nanocomposite and an ionic liquid (IL)–modified carbon paste electrode (CPE) in order to create cholesterol biosensor (Naf/ChOx/Pt,Ru–C/IL-CPE). The prepared working electrodes were characterized using scanning electron microscopy–energy-dispersive spectrometry, while their electrochemical performance was evaluated using electrochemical impedance spectroscopic, cyclic voltammetric, and amperometric techniques. Excellent synergism between IL 1-allyl-3-methylimidazolium dicyanamide ([AMIM][DCA]), Pt,Ru–C, and ChOx, as modifiers of CPE, offers the most pronounced analytical performance for improved cholesterol amperometric determination in phosphate buffer solution pH 7.50 at a working potential of 0.60 V. Under optimized experimental conditions, a linear relationship between oxidation current and cholesterol concentration was found for the range from 0.31 to 2.46 µM, with an estimated detection limit of 0.13 µM and relative standard deviation (RSD) below 5.5%. The optimized amperometric method in combination with the developed Naf/ChOx/Pt,Ru–C/IL-CPE biosensor showed good repeatability and high selectivity towards cholesterol biosensing. The proposed biosensor was successfully applied to determine free cholesterol in a human blood serum sample via its enzymatic reaction product hydrogen peroxide despite the presence of possible interferences. The percentage recovery ranged from 99.08 to 102.81%, while RSD was below 2.0% for the unspiked as well as the spiked human blood serum sample. The obtained results indicated excellent accuracy and precision of the method, concluding that the developed biosensor can be a promising alternative to existing commercial cholesterol tests used in medical practice. Graphical abstract: [Figure not available: see fulltext.]. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature

Application of plasma induced by TEA CO2 laser for determining the concentration of magnesium in the aluminum alloys

Laserski indukovana plazma predstavlja široko korišćeni emisioni izvor za spektroskopiju. Ova analitička tehnika poznata je pod nazivom spektroskopija laserski indukovanog proboja – LIBS (Laser Induced Breakdown Spectroscopy). LIBS se može koristiti za analizu bilo koje vrste uzoraka (čvrstih, tečnih, gasovitih), najčešće bez prethodne pripreme a masa potrebna za analizu je vrlo mala1. Zbog svoje univerzalnosti i jednostavnosti, LIBS je našla veliku primenu kao metoda spektrohemijske analize u različitim oblastima: geologiji, biohemiji, arheologiji, monitoringu životne sredine, praćenju industrijskih procesa, svemirskim istraživanjima i mnogim drugim1-5. Brza i pouzdana analiza elemenata prisutnih u legurama veoma je važna za kontrolu kvaliteta proizvoda. Legure aluminijuma imaju veliku primenu u savremenoj industriji a jedan od glavnih legirajućih elemenata je magnezijum koji pojačava tvrdoću aluminijuma i otpornost na koroziju, ali istovremeno smanjuje formabilnost i provodljivost. Kvantitativna analiza legura aluminijuma LIBS-om često je bila predmet proučavanja6-8. Za ovu svrhu uobičajeno se koristi LIBS sistem koji se sastoji iz Nd:YAG lasera, spektrometra i detektora sa vremenskom rezolucijom. Primena TEA CO2 laserskog zračenja (λ=10,6μm) za analizu metala i metalnih legura mnogo je ređa zbog manje energije fotona u odnosu na Nd:YAG laser, kao i visoke reflektivnosti metala u infracrvenom delu spektra. Sa druge strane, TEA CO2 laser ima i prednosti zbog talasne dužine zračenja i vremenskog profila laserskog impulsa. Interakcija nanosekundnog laserskog impulsa sa metalnom metom dovodi do ablacije, isparavanja i jonizacije materijala, a pri dovoljno velikoj gustini snage i do stvaranja plazme iznad površine mete9. Indukovana plazma apsorbuje preostali deo TEA CO2 laserskog impulsa kroz proces inverznog zakočnog zračenja, što dovodi dodatnog zagrevanja i povećanja ekscitacije. Apsorpcioni koeficijent plazme proporcionalan je kvadratu talasne dužine laserskog zračenja zbog čega je ovaj proces mnogo efikasniji za TEA CO2 nego za Nd:YAG lasersko zračenje. Laboratorijski LIBS spektrometar na bazi TEA CO2 lasera uspešno je primenjen za analizu bakra i njegovih legura i postignute su zadovoljavajuća osetljivost i niske granice detekcije3,4. Cilj ovog rada je ispitivanje mogućnosti primene plazme indukovane TEA CO2 laserom za određivanje Mg u legurama aluminijuma.The analytical capability of plasma induced by nanosecond infrared TEA CO2 laser radiation under reduced air pressure for determination of Mg in aluminum alloys was investigated. Sharp and well resolved spectral lines of Mg, with negligibly low background emission, were obtained from a plasma region 3 mm above the target surface. A calibration curve for Mg was constructed using certified aluminium alloy samples. A linear relationship between LIBS signal and analyte concentration was obtained (r2 = 0.9957) in the range from 0,26 -1,10 % w/w, and used for determination of Mg in a control sample. As a reference method for quantification of Mg in the control sample inductively coupled plasma - optical emission spectroscopy (ICP-OES) was used. Good agreement between LIBS and ICP-OES results was obtained. The results confirm that TEA CO2 LIBS is an effective technique for quantitative analysis of Mg in aluminum alloy samples.53rd Meeting of the Serbian Chemical Society : Kragujevac, June 10-11, 2016

Application of plasma induced by TEA CO2 laser for determining the concentration of magnesium in the aluminum alloys

Ispitivana je mogućnost analitičke primene plazme indukovane nanosekundnim infracrvenim TEA CO2 laserskim zračenjem za određivanje koncentracije Mg u aluminijumskim legurama, pri sniženom pritisku vazduha. Oštre i dobro razložene spektralne linije Mg, uz nisku emisiju pozadine, dobijene su posmatranjem plazme na rastojanju 3 mm od površine mete. Kalibraciona kriva za Mg konstruisana je korišćenjem sertifikovanih uzoraka aluminijumskih legura. Dobijena je linearna zavisnost između LIBS signala i koncentracije analita (r2=0,9957) u opsegu od 0,26-1,10 % m/m i korišćena je za određivanje koncetracije Mg u kontrolnom uzorku. Kao referentna metoda za kvantifikovanje Mg u kontrolnom uzorku korišćena je induktivno spregnuta plazma - optičko emisiona spektroskopija (ICP-OES). Dobijeno je odlično slaganje između LIBS i ICP-OES rezultata. Rezultati potvrđuju da je TEA CO2 LIBS efikasna tehnika za kvantitativnu analizu Mg u uzorcima aluminijumskih legura.The analytical capability of plasma induced by nanosecond infrared TEA CO2 laser radiation under reduced air pressure for determination of Mg in aluminum alloys was investigated. Sharp and well resolved spectral lines of Mg, with negligibly low background emission, were obtained from a plasma region 3 mm above the target surface. A calibration curve for Mg was constructed using certified aluminium alloy samples. A linear relationship between LIBS signal and analyte concentration was obtained (r2 = 0.9957) ) in the range from 0,26 -1,10 % w/w, and used for determination of Mg in a control sample. As a reference method for quantification of Mg in the control sample inductively coupled plasma - optical emission spectroscopy (ICP-OES) was used. Good agreement between LIBS and ICP-OES results was obtained. The results confirm that TEA CO2 LIBS is an effective technique for quantitative analysis of Mg in aluminum alloy samples.53. Savetovanje Srpskog hemijskog društva : Program i kratki izvodi radova : Kragujevac, Srbija, 29. i 30. maj 2015

Elemental analysis of aluminum alloys by Laser Induced Breakdown Spectroscopy based on TEA CO2 laser

The applicability of nanosecond infrared Transversely Excited Atmospheric (TEA) CO2 laser induced plasma for spectrochemical analysis of aluminum alloys was investigated. The plasma was generated by focusing a pulsed TEA CO2 laser that emits at 10.6 mu m on the Al target in ambient air at atmospheric pressure. The temporal profile of the laser pulse is composed of a 100 ns peak followed by a slowly decaying tail of about 2 mu s. The output pulse energy was approximately 160 mJ, thus the peak output power was estimated to be around 1.6 MW. Time-Integrated Space-Resolved Laser Induced Breakdown Spectroscopy (TISR-LIBS) was employed to obtain the emission spectra. The maximum intensity of emission, with sharp and well resolved spectral lines that were almost free of the background continuum, was obtained from plasma region 2 mm from the target surface. Linear calibration curves for Mg, Cr, Cu and Fe were obtained using aluminum alloy spectrochemical standards. The limits of detection for the investigated elements were in the 2-73 ppm range. Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) was used as a reference technique to estimate the accuracy of LIBS determination by use of control samples with known compositions. Comparison of the obtained results with those available in the literature confirms that LIBS system based on TEA CO2 laser, in combination with TISR spectral measurements, can be successfully applied to qualitative and quantitative determinations of minor elements in aluminum based alloys. (C) 2017 Elsevier B.V. All rights reserved

Electroanalytical performance of boron doped diamond electrode for the determination of solifenacin

The anticholinergic drug, solifenacin (SOL), is frequently used for the treatments in urological tract for urinary incontinence, and urinary frequency [1]. As an electroactive molecule, SOL can be an appropriate target analyte for voltammetric measurements. Boron doped diamond electrode (BDDE) was selected as a working electrode because of its unique electrochemical properties and emphasis on anodic measurements [2]. Prior to the voltammetric measurements of SOL, BDDE was electrochemically activated in the supporting electrolyte by anodic pretreatment (+2.0 V; 30 s) to achieve an oxygen terminated surface [3]. The voltammetric behavior of SOL was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in a model system. Based on the CV measurements it is proved that the certain electrooxidation process is diffusion controlled. Various experimental parameters were optimized including the pH of the aqueous Britton-Robinson (B-R) buffer as a supporting electrolyte (from pH 2.0 to 11.98) in the potential range from -0.3 V to 1.6 V vs saturated calomel electrode. Depending on the pH value of the B-R buffer one oxidation peak of SOL was obtained at maxima of peak potential around 1.1 V. The most intensive peak of the target analyte was at pH 11.0 which was chosen as an optimal pH value for further measurements. Based on the correlation of SOL peak intensity and different concentrations, the developed DPV method was characterized by a linear concentration range from 0.015 to 0.907 µg mL-1, coefficient correlation of 0.999, and relative standard deviation of 0.33%. Taking into account the sensitivity of the developed DPV method towards the electrochemical oxidation of SOL, a very low detection limit of 0.005 µg mL-1 in the model system is achieved. The BDDE showed adequate selectivity for SOL in the presence of investigated interferents. The obtained results indicate that BDDE with an optimized DPV method could be applied for the trace-level electroanalytical determination of SOL in real samples

Spectrochemical analysis of powdered biological samples using transversely excited atmospheric carbon dioxide laser plasma excitation

The aim of this study was to develop a simple laser induced breakdown spectroscopy (LIBS) method for quantitative elemental analysis of powdered biological materials based on laboratory prepared calibration samples. The analysis was done using ungated single pulse LIBS in ambient air at atmospheric pressure. Transversely-Excited Atmospheric pressure (TEA) CO2 laser was used as an energy source for plasma generation on samples. The material used for the analysis was a blue-green alga Spirulina, widely used in food and pharmaceutical industries and also in a few biotechnological applications. To demonstrate the analytical potential of this particular LIBS system the obtained spectra were compared to the spectra obtained using a commercial LIBS system based on pulsed Nd:YAG laser. A single sample of known concentration was used to estimate detection limits for Ba, Ca, Fe, Mg, Mn, Si and Sr and compare detection power of these two LIES systems. TEA CO2 laser based LIES was also applied for quantitative analysis of the elements in powder Spirulina samples. Analytical curves for Ba, Fe, Mg, Mn and Sr were constructed using laboratory produced matrix-matched calibration samples. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used as the reference technique for elemental quantification, and reasonably well agreement between ICP and LIBS data was obtained. Results confirm that, in respect to its sensitivity and precision, TEA CO2 laser based LIBS can be successfully applied for quantitative analysis of macro and micro-elements in algal samples. The fact that nearly all classes of materials can be prepared as powders implies that the proposed method could be easily extended to a quantitative analysis of different kinds of materials, organic, biological or inorganic. (C) 2017 Elsevier B.V. All rights reserved

Optimization of extraction yield and chemical characterization of optimal extract from Juglans nigra L. leaves

The extraction yield of Juglans nigra L. leaves was assessed at different ethanol concen-trations (0–96% (v/v)) and solvent-to-solid ratios (5–20 kg kg−1). The response surfacemethodology (RSM) and artificial neural network with genetic algorithms (ANN-GA) weredeveloped to optimize the extraction variables. The RSM and ANN-GA models determined50% (v/v) ethanol concentration and 20 kg kg−1solvent-to-solid ratio as optimal conditions,ensuring an extraction yield of 27.69 and 27.19 g 100 g−1of dry leaves. The phenolic com-pounds in optimal extract were quantified: 3-O-caffeoylquinic acid (2.27 mg g−1of dry leaves),quercetin-3-O-galactoside (10.99 mg g−1of dry leaves) and quercetin-3-O-rhamnoside (15.07mg g−1of dry leaves) using high-performance liquid chromatography (HPLC). The mineralsin optimal extract were quantified: macro-elements (the relative order by content was: K> Mg > Ca) using inductively coupled plasma optical emission spectrometry (ICP-OES) andmicro-elements (the relative order by content was: Zn > Rb > Mn > I>Sr > Ni > Cu > Co >V > Ag > Se) using inductively coupled plasma mass spectrometry (ICP-MS). The extrac-tion coefficients for minerals were determined and were highest for K (64.3%) and I (53.5%).Optimization of extraction process resulted in high extraction yield from J. nigra leaves andoptimal extract containing different phytochemical compounds