UV-Vis Spectrophotometric Measurements Research Articles

High-resolution temporal variations of nitrate in a high-elevation pond in alpine tundra (NW Italian Alps)

High-resolution temporal measurements in remote, high-elevation surface waters are required to better understand the dynamics of nitrate (NO3−) in response to changes in meteoclimatic conditions. This study reports on the first use of a UV–Vis submersible spectrophotometric probe (UV–Vis probe) to measure the hourly concentration of nitrate nitrogen (NO3−-N) in a pond located at 2722 m a.s.l. in an alpine tundra area (NW Italian Alps), during two snow-free seasons (July–October) in 2014 and 2015. Weekly analyses of NO3−-N and stable isotopes of water (δ18O and δ2H), together with continuous meteorological, water temperature, and turbidity measurements, were performed over the same period. The integration of in-situ UV–Vis spectrophotometric measurements with weekly samples allowed depicting the role of summer precipitation, snow melt, and temperature (air and water) in influencing NO3− dynamics. Short-duration meteorological events (e.g., summer storms and rain-on-snow events) produced rapid variations of in-pond NO3− concentration, i.e., fivefold increase in 18 h, that would not be detectable using the traditional manual collection of discrete samples. The observed seasonal variability of NO3− concentration, negatively correlated with water temperature, highlighted the important role of in-pond biological processes leading to an enhanced N uptake and to the lowest NO3− concentration in the warmer periods. The occurrence of heavy rainfall events critically altered the expected seasonal NO3− trends, increasing the N supply to the pond. The comparison of N dynamics in two years characterised by extremely different meteoclimatic conditions allowed us to obtain insights on the potential effects of climate changes (e.g., high air temperature, heavy rainfalls, and rain-on-snow events) on sensitive aquatic ecosystems as high-elevation ponds.

Controlling Electronic Coupling of Acene Chromophores on Quantum Dot Surfaces through Variable-Concentration Ligand Exchange.

Controlling the binding of functional organic molecules on quantum dot (QD) surfaces and the resulting ligand/QD interfacial structure determines the resulting organic-inorganic hybrid behavior. In this study, we vary the binding of tetracenedicarboxylate ligands bound to PbS QDs cast in thin films by performing solid-state ligand exchange of as-produced bound oleate ligands. We employ comprehensive Fourier-transform infrared (FTIR) analysis coupled with ultraviolet-visible (UV-vis) spectrophotometric measurements, transient absorption, and Density Functional Theory (DFT) simulations to study the QD/ligand surface structure and resulting optoelectronic properties. We find that there are three primary QD/diacid structures, each with a distinct binding mode dictated by the QD-ligand and ligand-ligand intermolecular and steric interactions. They can be accessed nearly independently of one another via different input ligand concentrations. Low concentrations produce mixed oleate/tetracene ligand structures where the tetracene carboxylates tilt toward QD surfaces. Intermediate concentrations produce mixed oleate/tetracene ligand structures with ligand-ligand interactions through intramolecular hydrogen bonding with the ligands perpendicular to the QD surface and weaker QD/ligand electronic interactions. High concentrations result in full ligand exchange, and the ligands tilt toward the surface while the QD film compacts. When the tetracene ligands tilt or lie flat on the QD surface, the benzene ring π-system interacts strongly with the p-orbitals at the PbS surface and produces strong QD-ligand interactions evidenced through QD/ligand state mixing, with a coupling energy of ≈700 meV.

Investigation of the Real-Time Release of Doxycycline from PLA-Based Nanofibers

Electrospun mats of PLA and PLA/Hap nanofibers produced by electrospinning were loaded with doxycycline (Doxy) through physical adsorption from a solution with initial concentrations of 3 g/L, 7 g/L, and 12 g/L, respectively. The morphological characterization of the produced material was performed using scanning electron microscopy (SEM). The release profiles of Doxy were studied in situ using the differential pulse voltammetry (DPV) electrochemical method on a glassy carbon electrode (GCE) and validated through UV-VIS spectrophotometric measurements. The DPV method has been shown to be a simple, rapid, and advantageous analytical technique for real-time measurements, allowing accurate kinetics to be established. The kinetics of the release profiles were compared using model-dependent and model-independent analyses. The diffusion-controlled mechanism of Doxy release from both types of fibers was confirmed by a good fit to the Korsmeyer–Peppas model.

Optimization of Bulk Heterojunction Photovoltaic Structures with Heterocyclic Derivatives

Photovoltaic structures of the bulk heterojunction type were fabricated, in which derivatives of N,N-diethylamine-3-Methyl-1-Phenyl-1H-pyrazolo[3,4-b]quinoxalines were used as the active layer. The compounds differed in the position of the electron-donating substituent in the carbocyclic ring. Four isomers were subjected to UV-Vis spectrophotometric measurements in solvents of different polarities. The absorption characteristics were experimentally determined for the tested derivatives. The values of HOMO-LUMO levels were determined by means of quantum chemical calculations using the HyperChem software. The current–voltage and dispersion characteristics of the produced OPV were determined. The spectral characteristics of the refractive indices and extinction coefficients of the active layers were determined using the spectroscopic ellipsometry method. These results were used in the analysis and optimization of photovoltaic structures. It was shown that the location of the N,N-diethylamine substituent affects the photophysical properties of the structure and the photovoltaic properties. The optimization of the OPV_2 photovoltaic structure using the coherent model and the 2 × 2 matrix method can be successfully used in modeling optical multilayer structures, including photovoltaic structures.

Structural and optical properties of mist-CVD grown MgZnO: Effect of precursor solution composition

This study aims to investigate the effect of precursor solution composition by changing the acetic acid (AA) ratio on the growth and physical properties of MgZnO structures by mist-CVD under ozone enriched O2 atmosphere. The MgZnO structures have been grown on soda-lime as the function of the Acetic acid (AA) in the precursor with different ratios as 12.5%, 25%, and 50%. According to X-ray diffraction (XRD) measurements, the (0002) diffraction peak is shown as a highly dominant peak in the grown MgZnO with 25% and 50% of AA ratio in the precursor. The surface morphology of MgZnO samples grown by precursor with different AA ratios has been examined via Atomic Force Microscope (AFM) and Scanning Electron Microscopy (SEM). As increased AA ratio in the precursor, the growing MgZnO density on the surface is decreased according to AFM and SEM images. The optical properties of MgZnO nanostructures have been investigated by means of UV–visible spectrophotometer measurements. For each MgZnO sample, the optical absorbance and transmittance properties have been determined. The optical band gap of MgZnO samples with different AA ratios in solution has been calculated by Tauc formula.

Silver films on glass with very thin chromium adherence interlayers; reflectance and adherence at film-glass interface

Silver (Ag) thin films deposited on glass are proficient in their visible range reflectance at both Ag/air and Ag/glass interfaces. However, the film adherence onto glass is feeble due to a surface free energy disparity between the materials. Issues such as peeling, pitting, and detaching of Ag films on glass used as mirrors and prisms in various optical instruments are common. Very thin and intermittent adherence interlayers of chromium (Cr), titanium (Ti), etc, between Ag and glass resolves the issues to a substantial level. With least possible net surface area of the interlayer and a sufficient adherence of the film system the reflectance at the film/glass interface may be affected only insignificantly. This study presents an adherence optimization of Ag thin films on glass using very thin Cr interlayer with an attempt to retain its Ag/glass interface reflectance at useful levels. Adherence layers of Cr at various thicknesses from 0.4 nm to 5.0 nm and overlayer Ag films around 120 nm on silica glass were deposited by thermal evaporation in vacuum. Then the adherence and reflectance of the film system at the glass interface were evaluated using Scratch and Scotch Tape Tests and UV–visible spectrophotometric measurements. Amount and distribution of the intermittent adherence layers have been evaluated by energy dispersive X-ray photoelectron spectroscopy. 0.7 nm thick intermittent chromium interlayer between the pure silver film and the glass were found to be useful as resolving the adherence issues with a loss about 4–5% in reflectance.

Effect of Annealing Time on Structural and Optical Properties of ZnGa2O4: Cr3+ (2.0mol %) Nanostructure Prepared by Sol Gel Method

ZnGa2 O4 : Cr3+ (2.0mol %) nanopowders annealed at annealing times (AT) of = 1, 2, 3, and 4H (hour) were synthesized by the sol-gel method. X-ray diffraction (XRD) results confirmed that the prepared ZnGa2 O4 : Cr3+ samples were cubic structures. In this study we showed that the annealing time has no pronounced influence on the ZnGa2O4: Cr3+ crystallite size at annealing times in the range of 1H to 3H. A significant change in the crystallite size was observed for the sample annealed for a relatively long time (4H). Scanning electron microscopy (SEM) images show the morphology of the prepared nanopowders influenced by annealing time. UV-visible spectrophotometer measurements showed that the energy gap of the prepared nanoparticles could be tuned from 4.50 to 4.12 eV as the annealing time changed from 1H to 4H. Photoluminescence (PL) measurement showed that the annealing time increased, and the PL intensity also increased reaching the maximum value for the sample annealed at AT=3H. Energy dispersive X-ray spectroscopy (EDS) measurements confirmed the presence of Zn, Ga, O and Cr ions.

A recent overview of surfactant-drug interactions and their importance.

This review focuses on the self-aggregation properties of different drugs, as well as on their interaction with anionic, cationic, and gemini surfactants. The interaction of drugs with surfactants has been reviewed concerning conductivity, surface tension, viscosity, density, and UV-Vis spectrophotometric measurements, and their relation with critical micelle concentration (CMC), cloud point, and binding constant. The conductivity measurement technique is used for the micellization of ionic surfactants. Cloud point studies can be used for the non-ionic, and also for certain ionic surfactants. Usually, surface tension studies are mostly employed for non-ionic surfactants. The degree of dissociation that is determined is used to evaluate thermodynamic parameters of micellization at various temperatures. The effect of external parameters like temperature, salt, solvent, pH, etc., is discussed for thermodynamics parameters using recent experimental works on drug-surfactant interactions. Consequences of drug-surfactant interaction, condition of drugs during interaction with surfactants, and applications of drug-surfactant interaction are being generalized which reflects current and future potential uses of drug-surfactant interactions.

Observation of protonation-induced intra-molecular metal-to-metal charge transfer in cyano-bridged [Fe-CN-Mn/Ni] dinuclear complexes.

A key challenge in the design of magnetic molecules with intramolecular charge transfer behavior is to obtain reversible magnetic bistability triggered by external stimuli. Here, we show that two dinuclear metal complexes, [(bbp)Fe(CN)3Mn(Py5Me2)]·2.5CH3OH (4) and [(bbp)Fe(CN)3Ni(Py5Me2)]·2.5CH3OH (5) (Py5Me2 = 2,6-bis(1,1-di(pyridine-2-yl)ethyl)pyridine, H2bbp = 2,6-bis(benzimidazole-2-yl)pyridine), were self-assembly synthesized by (Bu4N)2[(bbp)FeIII(CN)3] and [Mn(Py5Me2)(OH2)](ClO4)2 or [Ni(Py5Me2)(OH2)](ClO4)2, respectively. Complexes 4 and 5 exhibited intramolecular metal-to-metal charge transfer with the addition of acids or bases in solution by UV-visible spectrophotometric measurements and electrochemistry studies, and concomitant switching of the {FeIII(μ-CN)MnII/NiII} state to the {FeII(μ-CN)MnIII/NiIII} state.

One-Step Fabricate of Copper Nanoparticles via Pulsed Laser Ablation in Liquid: Influence of Energies on Physical Characterization

Pulsed laser ablation in liquid (PLAL) is considered a relatively fast, simple to manipulate, cost-effective abraoch, and enables the fabrecation of multiscale micro-nanostructures in one step, facilitating the fabrication process. Copper nanoparticles solution was prepared by PLAL technique using Nd:YAG laser in deionized water at (532 nm), (1000 pulse), and the energies (700 mJ, 800 mJ, 900 mJ, and 1000 mJ) with a fixed distance between the laser source and the sample, fixed amount of liquid, and the liquid rise above the copper was (5 mm). The effect of the excess of the laser energy in the preparation process was tested by analyzing the optical properties of the fabrecated samples by UV-Visible spectrophotometer, SEM, XRD, and EDX measurements.

Physicochemical Study, Fatty Acid Profile and Antioxidant Potential of the Seed Oil of Polyalthia longifolia angustifolia

In the face of worsening malnutrition or undernutrition in poor countries, diversification of food resources remains a high priority for the World Health Organization (WHO). Thus, the present study aims to determine the phytochemical composition and antioxidant activity of the fat extracted from the seeds of Polyalthia longifolia angustifolia.
 The fatty acid profile of the oil, extracted from the seeds with hexane by the Soxhlet method, was determined by gas chromatography-mass spectrometry (GC/MS) analysis. The physicochemical parameters of the oil were measured according to AFNOR standards. The total phenol and flavonoid contents of the seeds were evaluated by UV-visible spectrophotometric measurement. Antioxidant activity of the oil was determined by the reduction test of ferric ions (Fe3+) of the TPTZ complex to ferrous ion (Fe2+). The results revealed that the oil contains a higher level of oleic acid (63.38%), followed by: palmitic acid (13.80%); linoleic acid (11.74%) and stearic acid (6.24%). The physicochemical parameters of the oil were: refractive index (1.499); acid value (87.69 mg KOH/g of oil); acidity (23.659 g oleic acid/100 g of oil); iodine value (78.26 g I2/100 g of oil); saponification value (179.741 mg KOH/g of oil) and peroxide number (10.85 meq O2 /kg of oil).
 In short, the seeds of P. l. angustifolia contain fat and phytochemicals with appreciable antioxidant activity. However, further studies are needed to evaluate the toxicity, nutritional and therapeutic properties of the oil before considering the different types of applications that can be made with this oil.

Spectroscopic and Kinetic Study of Sucrose Oxidation by Cr(VI) and Its Application in the Quantitative Analysis of Soil Organic Carbon

The percent organic carbon (%OC) is an important soil fertility measure that has important implications in agricultural productivity and food security. In this study, a UV-visible spectrophotometric technique was investigated and applied to quantify %OC from selected soil samples along a river basin that traverses agricultural farmlands, a forest and sewage treatment lagoons for a comparative survey purposes. The study was based on the measurement of absorbance of Cr(III) species that arise from oxidation of sucrose (which is 42.11% carbon) by dichromate ions which contain Cr(VI) species. The uv-visible spectrophotometric double beam wavelength scan measurements elucidated the conversion of Cr(VI) to Cr(III) ions and a calibration plot was developed with r2= 0.99. The analyte peak was identified in the region from 750 nm to 550 nm (the absorbing Cr(iii) species) with a turning point maximum at 576 nm. The kinetic profile of sucrose oxidation by the dichromate ions was studied via absorbance of Cr(III) and Cr(VI) as a function of the reaction time and was used to characterize the reaction model. The absorbance of Cr(III) as a function of reaction time fitted best into the non-linear Belehradek power function equation y=a(x-b)c,, where y = absorbance; x = time(s); a, b, c = are constants (r2 of 0.91). Kinetic analysis revealed that the reaction that leads to the formation of Cr(III) during sucrose oxidation proceeds via pseudo first-order kinetics (r2= 0.83). A comparative quantitative analysis indicated that the sewage treatment lagoons had the highest %OC content at about 5.5-6.6%OC. The soils sampled from the forest regions had about 4.6-5.8%OC whereas the river bank soils had the lowest levels at about 2.0-2.5%OC. A statistical t-test analysis showed that the %OC levels in sub-soils were significantly higher than those of the top-soils (p > 0.05 at 95% CI).

Comparative full-length transcriptome analysis by Oxford Nanopore Technologies reveals genes involved in anthocyanin accumulation in storage roots of sweet potatoes (Ipomoea batatasL.).

BackgroundStorage roots of sweet potatoes (Ipomoea batatas L.) with different colors vary in anthocyanin content, indicating different economically agronomic trait. As the newest DNA/RNA sequencing technology, Oxford Nanopore Technologies (ONT) have been applied in rapid transcriptome sequencing for investigation of genes related to nutrient metabolism. At present, few reports concern full-length transcriptome analysis based on ONT for study on the molecular mechanism of anthocyanin accumulation leading to color change of tuberous roots of sweet potato cultivars.ResultsThe storage roots of purple-fleshed sweet potato (PFSP) and white-fleshed sweet potato (WFSP) at different developmental stages were subjected to anthocyanin content comparison by UV-visible spectroscopy as well as transcriptome analysis at ONT MinION platform. UV-visible spectrophotometric measurements demonstrated the anthocyanin content of PFSP was much higher than that of WFSP. ONT RNA-Seq results showed each sample generated average 2.75 GB clean data with Full-Length Percentage (FL%) over 70% and the length of N50 ranged from 1,192 to 1,395 bp, indicating reliable data for transcriptome analysis. Subsequent analysis illustrated intron retention was the most prominent splicing event present in the resulting transcripts. As compared PFSP with WFSP at the relative developmental stages with the highest (PH vs. WH) and the lowest (PL vs. WL) anthocyanin content, 282 and 216 genes were up-regulated and two and 11 genes were down-regulated respectively. The differential expression genes involved in flavonoid biosynthesis pathway include CCoAOMT, PpLDOX, DFR, Cytochrome P450, CHI, and CHS. The genes encoding oxygenase superfamily were significantly up-regulated when compared PFSP with WFSP at the relative developmental stages.ConclusionsComparative full-length transcriptome analysis based on ONT serves as an effective approach to detect the differences in anthocyanin accumulation in the storage roots of different sweet potato cultivars at transcript level, with noting that some key genes can now be closely related to flavonoids biosynthesis. This study helps to improve understanding of molecular mechanism for anthocyanin accumulation in sweet potatoes and also provides a theoretical basis for high-quality sweet potato breeding.

Studying Kinetic and Thermodynamic Parameters of the Interaction of Ceftriaxone with Albumin Extracted from Healthy and Covid-19 Plasma

Because it has been well defined, bovine serum albumin (BSA) is highly suited to pharmacological effects, biotransformation, and bio-distribution of medicines initial research. Drug–protein interactions in the blood stream are known to have a significant impact on drug distribution, free concentration, and metabolism. Coronavirus disease 2019 (COVID-19) has spread globally as a severe pandemic. It is a serious threat to healthcare systems, economies, and is devastating to some populations, such as the elderly and those with comorbidities. Unfortunately, there is still no effective cure for COVID-19, especially the critically ill patients. The link between the mortality risk of patients hospitalized for COVID-19 and the function of blood albumin levels has been investigated. Because of albumin biological significance, the study goal conducted to apply spectroscopic methods to explore and comparing the kinetic and thermodynamic aspects of ceftriaxone's interaction with BSA, albumin isolated from healthy and covid-19 plasma. A pooled plasma from healthy and hospitalized covid-19 individuals (Karbala Province / Iraq) was used to purify albumin using HPLC technique. UV-vis spectrophotometric measurements of albumin‒ceftriaxone complex formation recorded at different pH ( 7, 7.2, 7.4, 7.6 & 7.8) in phosphate buffer solution, and at six different temperatures (298, 301, 304, 307, 310 & 313) K. The equilibrium constant and the thermodynamic parameter such as ΔG, ΔH and ΔS were calculated. The drug-albumin (BSA, healthy and Covid-19 albumin) complexes are stable in 60 to 300 minutes, as evidenced by the steady absorbance studies. The reaction is from the first false order for drug-albumin (BSA, healthy and covid-19 plasma) complexes. Our finding suggesting the reaction is from the first false order. In the case of plasma albumin from individuals infected with - Covid-19, the values of (R2) are closer together. This is because the medication dominates the formation of a more stable complex with albumin. The stoichiometric ratio (coordination number) of complex between ceftriaxone and albumin at 298 k and pH=7.4 is 1:1. The Gibbs free energy for albumin‒ ceftriaxone is negative, indicating that the reaction is spontaneous. The positive enthalpy of contact indicates that the process is endothermic, requiring energy input. Positive enthalpy and entropy change also refer to the hydrophobic association and electrostatic contact that occurs between albumin molecules and ceftriaxone. It is worth noting that the complex formed between bovine albumin and the medication has less absorbency at pH = 7.4. That is, the complex is more stable, and it prefers natural helical shapes. Additionally, as the pH value shifts away from physiological (> 7.4 <), the intensity of complex absorption increases. Keywords: Ceftriaxone, Bovine serum albumin, Covid-19 albumin, purification of albumin

New Cu(II) and Zn(II) complexes with diethyl phenyl (N-phenylsulfamoylamino) methyl phosphonate: Synthesis, characterisation, DFT/M11 studies, NBO, DOS, QTAIM and RDG analysis

The stability constants (βij) and the thermodynamic parameters (ΔH°, ΔS° and ΔG°) of the complexes between diethyl phenyl (N-phenylsulfamoylamino) methyl phosphonate with Cu(II) and/or Zn(II) ions were determined by UV-visible spectrophotometric measurements in methanol at room temperature. The stable (1:2) solid-state mononuclear complexes were synthesised and characterised by FTIR, 1H-NMR, elemental analysis and magnetic moment measurements. In the DFT study, the predicted structural parameters with four exchange-correlation functionals were compared with experimental data. Their performance in predicting the vibration frequencies was also tested. Subsequently, with the best functionals thus obtained, calculations were performed on the most stable (1:2) complexes to obtain information on their structures and properties. The most stable geometrical structure, structural parameters, vibrational frequencies, UV-vis absorption spectra and global reactivity indices were carried out. The calculated results were in good agreement with the experimental findings. In order to gain further insights on the complexes properties non-linear optics (NLO), natural bond orbital (NBO), density of states (DOS) and quantum theory of atoms in molecule (QTAIM) analyses were performed. In addition, attractive bonds and van der Waals interactions were explored and visualized with reduced density gradient analysis (RDG). Finally, molecular docking was performed with Auto-Dock 4.2 to study the interactions between donors (DPSAMP or metallic complexes) and receptors [Escherichia coli (PDB code: 1HNJ) or Candida albicans (PDB code: 1H1W)].

Stability of UV-visible spectrophotometric measurements for investigating the adsorption of hexavalent chromium from wastewater

Stability of UV-visible spectrophotometric measurements for investigating the adsorption of hexavalent chromium from wastewater

Bifunctional 3-Hydroxy-4-Pyridinones as Potential Selective Iron(III) Chelators: Solution Studies and Comparison with Other Metals of Biological and Environmental Relevance.

The binding ability of five bifunctional 3-hydroxy-4-pyridinones towards Cu2+ and Fe3+ was studied by means of potentiometric and UV–Vis spectrophotometric measurements carried out at I = 0.15 mol L−1 in NaCl(aq), T = 298.15 K and 310.15 K. The data treatments allowed us to determine speciation schemes featured by metal-ligand species with different stoichiometry and stability, owing to the various functional groups present in the 3-hydroxy-4-pyridinones structures, which could potentially participate in the metal complexation, and in the Cu2+ and Fe3+ behaviour in aqueous solution. Furthermore, the sequestering ability and metal chelating affinity of the ligands were investigated by the determination of pL0.5 and pM parameters at different pH conditions. Finally, a comparison between the Cu2+ and Fe3+/3-hydroxy-4-pyridinones data herein presented with those already reported in the literature on the interaction of Zn2+ and Al3+ with the same ligands showed that, from the thermodynamic point of view, the 3-hydroxy-4-pyridinones are particularly selective towards Fe3+ and could therefore be considered promising iron-chelating agents, also avoiding the possibility of competition, and eventually the depletion, of essential metal cations of biological and environmental relevance, such as Cu2+ and Zn2+.

Observation of Protonation-Induced Spin State Switching in a Cyanido-Bridged {Fe2Co2} Molecular Square.

The self-assembly of [Co(MeTPyA)(CH3COO)]PF6 (1) and [Fe(bbp)(CN)3]2- affords a cyanido-bridged square-shaped {Fe2Co2} tetranuclear complex, [{Co(MeTPyA)(μ2-NC)2Fe(bbp)(CN)}2]·3H2O (2; MeTPyA = tris((3,5-dimethylpyrazol-1-yl)methyl)amine and H2bbp = bis(2-benzimidazolyl)pyridine). The possibility of inducing an intramolecular electron transfer coupled spin transition in 2 by employing protonation as an external stimulant is explored. UV-visible spectrophotometric measurements, electrochemical and 1H NMR studies establish that a reversible intramolecular electron transfer coupled spin transition can be triggered in 2 upon addition of either acid or base.

Phyto-Synthesized Silver Nanoparticle Toxicity Effect on Aquatic Plant Lemna minor L.

Silver nanoparticles (AgNP) are made up about 55% of all nanomaterials produced and are widely used in consumer products. Its is inevitable that these particles are released to the aquatic environment during production, use and disposal. In this study, subacute toxicity of AgNPs obtained by phyto-synthesis was investigated on Lemna minor L. (duckweed) plants. Plant stock cultures were grown in the climate room according to OECD 221 guidelines. After 8 weeks of acclimation, the plants were treated with AgNP concentrations ranging from 0.005 to 50 mg L−1 for 7- and 14-days. The formation of silver nanoparticles obtained from laurel (Laurus nobilis L.) extract was determined by UV-VIS spectrophotometric measurements. The AgNPs synthesized by the phyto-synthesis method were characterized by Fourier transform infrared spectroscopy (FT-IR), Zeta size and potential, Inductively Coupled Plasma Mass Spectrometry and Scanning electron microscopy (SEM-EDS) analysis. The analysis results show that AgNPs are homogeneously distributed, spherical in shape with an average size of 34 nm and coated with phyto-content. The increase in AgNP concentration caused a decrease in frond numbers. Growth inhibition data showed that the EC50 value of phyto-synthesized AgNP was 4.78 mg L-1 and the lowest observed effect concentration (LOEC) was 0.5 mg L-1 for 7-days. AgNP concentrations below LOEC level (0.05, to 0.5 mg L-1) caused a significant decrease in growth rate by 20.07% after 7 days of exposure while it was found 4.03% for 14-days treatment at the highest AgNP concentration (0.5 mg L-1). Similar trend was observed in fresh-and dry weight of plants indicating prolonged exposure time triggering tolerance mechanism which was corroborated by chlorophyll a/b and carotenoids content results. Based on higher NOEC, LOEC and EC50 values, phyto-synthesized AgNP usage may lead less environmental toxicity.

Coupling of spectrometric, chromatographic, and chemometric analysis in the investigation of the photodegradation of sulfamethoxazole

A workflow is proposed for the study of the photodegradation process of the sulfamethoxazole (SMX) based on the combination of different experimental techniques, including liquid chromatography, mass spectrometry, UV–Visible spectrophotometry, and the treatment of all the analytical data with advanced chemometric methods. SMX, which is one of the most widely used antibiotics worldwide and has been found at remarkable concentrations in various rivers and effluents over all Europe, was degraded in the laboratory under a controlled source of UV radiation, which simulates the environmental solar radiation (Suntest). Kinetic monitoring of the photodegradation process was performed using UV–Visible spectrophotometric measurements and by further Liquid Chromatography with Diode Array Detector and Mass Spectrometry analysis (LC-DAD-MS). Additionally, the acid-base properties were also investigated to see how the pH can affect the speciation of this substance during the photodegradation process. Based on the Multivariate Curve Resolution–Alternating Least Squares (MCR-ALS) application, the proposed chemometric method coped with the large amounts of data generated by the different analytical techniques used to monitor the evolution of the photodegradation process. Their simultaneous analysis involved applying a data fusion strategy and an advanced MCR-ALS constrained analysis, which allowed and improved the description of the complete degradation process, detecting the different species of the reaction, and identifying the possible transformation products formed. A total number of six species were resolved in the degradation process of SMX. In addition to the initial SMX, a second species corresponded to a conformational isomer, and the other four species represented different photoproducts, which have also been identified. Furthermore, three different acid-base species of SMX were obtained, and their pKa values were estimated.