Spectrophotometric Measurements Research Articles

A novel method for Ion Exchange Capacity characterization applied to Anion Exchange Membranes for Water Electrolysers

Hydrogen production from water electrolysis, hydrogen fuel cells and redox flow batteries are the right approach for the renewable energy sector because the electricity generated by solar, wind, photovoltaic, hydroelectric can be managed with a carbon-free approach. These technologies all have in common one fundamental component: the membrane. Different types of membranes have been developed for both cationic and anionic exchange, and recently, research activity focalized on improving their performances is very fervent. One fundamental characteristic of a membrane is its Ion Exchange Capacity (IEC), i.e. the density of charged functionalizing groups. Within our research project NEMESI, funded by EU-PNRR (ID: RSH2B_000002), and dedicated to Anion Exchange Membrane Water Electrolysis, we studied and validated a novel alternative method to measure IEC. The present titration methods have limitations for the need of dedicated hardware or qualitative inspection of their color-turning endpoint. The proposed method, based on the redox titration of potassium ferricyanide with ascorbic acid, allows a quantitative and independent assessment based on both potentiometric and spectrophotometric measurements, along with the usually adopted visual observation, as the yellow-colored ferricyanide is reduced to colorless ferrocyanide. Moreover, if compared to the classical Mohr titration with silver nitrate, the new method can be carried out at variable ferricyanide concentrations during the addition of the ascorbic acid, so a complete curve of the redox reaction can be constructed: the initial ferricyanide ion load of the membrane (IEC) can thus be derived in a more precise way than with a single-point evaluation. Only one Ag/AgCl reference electrode and a platinum working electrode are required without any power supply/potentiostat. The proposed method was validated using Anion Exchange Membranes with known IEC.

LOW-COST AND EASY ACCESS MATERIALS FOR A LABORATORY CLASS: A PROPOSAL OF LIQUID CHROMATOGRAPHY FOR FOOD COLORING SEPARATION AS AN EXPERIENCE OF MEANINGFUL LEARNING

The experimental activities for undergraduate chemistry students play an important role to develop skills and expertise in that science thus, the practice-experimental classes are so important to achieve this purpose. This work deals with a demonstrative experience for dye separation from food coloring sample using liquid column chromatography. Beyond the experimental practice and the facility in visualizing the separation, this demonstration shows how a simple experiment involving alternative and easy access materials can promote a meaningful learning once it is possible to handle the acquired data, trace and analyze the results themselves, thus developing skills rather than the operational procedure. This proposal could be implemented in initial chemistry classes in Brazilian universities. Sea and river sands were used as stationary phases and aqueous ethanolic solutions were used as mobile phases. A food coloring (a mixture of 3 dyes) was chosen as sample to be studied. Chromatographic separation was followed by spectrophotometric measurements. A set of analyses were carried out to discuss the solubility of the food coloring, granulometric studies of the stationary phases used and electronic microscopy images of the sands studied here. As alternative materials were used in this work, a chromatographic column was also constructed with low-cost materials.

Spectrophotometric quantification of paracetamol and tramadol hydrochloride by chemometric calibration methods.

The results of UV spectrophotometric analysis were analysed using partial least squares (PLS) and principal component regression (PCR) techniques to allow simultaneous evaluation of tramadol hydrochloride (TRA) and p-acetaminophen (PAR) in tablets. A calibration set of 16 mixtures, each containing PAR and TRA in various amounts, was created using a 24-full fractional design. The absorbance data set for the calibration set were obtained between 215-280 nm (Δλ = 0.1 nm). Subsequently, the concentration and absorbance sets were used to generate PCR and PLS calibrations. The ratio spectra- first derivative method was devised as a solution to the same problem to compare the outcomes of the chemometric methods used for the same experiment. After the proposed methods were shown to be accurate in the testing of validation samples, they were used in analysing commercial tablet samples. The analytical results showed that PCR and PLS methods can be used as alternative methods to high-performance liquid chromatography (HPLC). Correlation coefficients were determined for the working concentration range of 6-36 g.mL-1 for PAR and 4-22 g.mL-1 for TRA. The limits of detection and quantification were calculated as 0.9104 μg.mL-1 and 3.0347 μg.mL-1, respectively. The test results of the chemometric analyses and ratio spectra- first derivative method of the commercial tablet form are in agreement with the results of the one-way ANOVA with a confidence interval of 95%. This study shows that the ratio spectra- first derivative method, PCR and PLS models based on spectrophotometric measurements are very useful and straightforward techniques for the quantitative resolution of a two-component pharmaceutical preparation, requiring little sample preparation and little time for analysis.

Salivary Oxidative Stress Biomarkers in Thai Adolescents and Young Adults with Type 1 Diabetes Mellitus: A Cross-Sectional Study.

The primary objectives of this study were to compare salivary oxidative stress (OS) biomarker levels in patients with type 1 diabetes mellitus (T1DM) and without T1DM (non-T1DM) and evaluate the relationships between diabetes, periodontal status, and OS biomarker levels. Twenty patients with T1DM and 20 age-matched patients without T1DM were enrolled. All participants were 15-23 years of age and had permanent dentition. Unstimulated whole saliva was collected in a sterile test tube before examination of clinical periodontal parameters, including bleeding on probing (BOP). Salivary levels of OS biomarkers-malondialdehyde, protein carbonyl, total oxidant status (TOS), and total antioxidant capacity-were determined using oxidative and antioxidative assays followed by spectrophotometric measurement at 375-532 nm. The relationships between diabetes, periodontal status, and OS biomarkers were analyzed using multiple linear regression. TOS was significantly lower in the T1DM group compared with the non-T1DM group (5.06 ± 0.39 vs. 6.44 ± 0.51 µmol H2O2 Eq/l, P = 0.035). After adjusting for confounding factors (age, gender, BMI, clinical periodontal parameters, BOP, or diabetes status accordingly), the multiple linear regression showed that T1DM was significantly associated with a reduction of TOS level (P = 0.008). The BOP > 30% group showed a significant correlation with increased TOS levels compared with the BOP ≤ 30% group (P = 0.002). No relationship was found between OS biomarkers and HbA1c levels. Salivary TOS levels were related to both diabetes status and the extent of gingival inflammation. Further studies to elucidate the role of OS in relation of periodontal disease and T1DM are required.

A comparative analysis of ten milk samples with differential scanning calorimetry and Fourier transform infrared spectroscopy

Milk proteins occupy a prominent place in the nutrition of adults and children. Generally, some commercial dairy contains proteins, lactose, other sugar derivatives, and additives. The proportions of the components that make up the milk are different in commercial milk. For this reason, analyzing milk correctly is essential for determining these contents. In this research, analyses of the milk were made by taking differential scanning calorimetry measurements (DSC), and Fourier transform infrared spectrophotometer (FTIR) measurements. Specific heat values and specific values of temperature peaks were examined for ten kinds of milk. DSC curves revealed triacylglycerol dissolution, lactose crystallization, and protein denaturation peaks. Wide variations were observed with the same fat content from 10 milk powders. Most characteristic peaks were not observed when the samples were re-measured after a year at -20°C. The powder samples were compared in terms of protein, fat, lactose content, whey protein casein, and caseinate contents according to differences in FTIR spectra. The FTIR results confirm the DSC curves for most of the analyzed milk types.

Analysis of Some Phenothiazine Drugs and Their S-Oxides using Enzymatic Method of Cholinesterase Inhibition

In this work, a highly sensitive spectrophotometric method was developed for the determination of cholinesterase (AChE) inhibitors - phenothiazine derivatives (PhTs). The assay involves spectrophotometric measurement of a mixture of buffer, solutions of acetylcholine (Ach), a sample containing AChE, H2O2, and PhTs. The rate of the enzymatic hydrolysis of Ach reaction was determined by the tangent method of the linear part of the kinetic curve in the A (358 nm) – t-coordinate. Results from the determination of PhTs and S-oxide PhTs with the AChE regulated spectrophotometric system showed the limit of quantitation of 5 ng/mL (IE20) and a linear dynamic range from 5 to 30 ng/mL for Chlorpromazine, Promethazine and from 0.5 to 10 ng/mL for Chlorpromazine S-oxide, from 1 to 10 ng/mL for Promethazine S-oxide, 12 to 40 ng/mL for Thioridazine 2,5-disulfoxide respectively. RSD for concentrations of PhTs as low as 1.5·10-8 mol/L did not exceed 6.7 %, while their corresponding sulfoxides at 1.50·10-9 didn’t exceed +6.5 %. δ < +3.8 %. Findings in this work demonstrate that this method may be used for the determination of phenothiazine based drugs, and sensitive tests for rapid PhT monitoring without the addition of other exogenous catalysts

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.

Sunscreen Activity Determination on Hippobroma Longiflora Leaves Extracts Affected to Differences in Simplicia Treatments and Extraction Techniques

Various weeds in paddy rice fields could be utilized as natural polyphenols sources, one of them was kitolod (Hippobroma longiflora (L.) G.Don). Kitolod was widely utilized as traditional medicine by several community groups because of its polyphenols content. Recent trends showed kitolod could be valorized as additive matters in sunscreen products. Polyphenols content, especially flavonoids were able to absorb dangerous spectrum in sunray radiation and it is related to sunscreen activity. This study aimed to evaluate the differences in simplicia treatments and extraction techniques towards total polyphenols content and sunscreen activity on kitolod leaf extracts. Solvent-cold extraction techniques were deployed in this study that consist of water infusion and ethanolic maceration for 24 hours at ambient temperature. Extracts were analyzed by spectrophotometric measurement to determine total phenolics content (TPC), total flavonoids content (TFC), and sunscreen activity by deploying Folin-Ciocalteu assay, AlCl3 colorimetric assay, and Mansur approached assay, respectively. Dry kitolod leaves were extracted by ethanolic maceration techniques provided high yields (15.5±0.3%), high TPC (17.9±0.3 mg GAE/g of solids), high TFC (25.9±0.4 mg QE/g of solids), and moderate sunscreen activity (SPF 11.0±0.1). The results indicated kitolod could be valorized as natural polyphenols sources and additive matters in any cosmetical sunscreen products.

Colorimetric hydrogen peroxide and glucose sensors based on the destruction of micelle-protected iron(ii) complex probes

A new strategy for the simple spectrophotometric measurement of H2O2 and glucose was developed based on the destruction of micelle probes.

A Parafac Model of Kinetic Spectrophotometric Measurements for Monitoring the Oxidation of Ascorbic Acid and Quantifying its Content in a Food Supplement Product

A Parafac Model of Kinetic Spectrophotometric Measurements for Monitoring the Oxidation of Ascorbic Acid and Quantifying its Content in a Food Supplement Product

Assessment of color changes in teeth and composite resins under the influence of chlorhexidine with and without anti-discoloration system: An in vitro study.

The aim of this study was to assess color changes in teeth and two different composite resins under the influence of chlorhexidine (CHX) with and without anti-discoloration system (ADS). A total of 20 extracted human premolar teeth for periodontal and orthodontic purposes were selected for the study. Further, a total of 40 composite specimens comprising 20 each nanoceramic and nanohybrid composite disks of size 10-mm diameter and 0.5-mm thickness were prepared on a customized model for standardization using the composite filling instrument. The specimens were cured with light-curing unit for 20 s and polished with a composite polishing kit. Two mouthrinses comprising CHX and CHX with ADS were used. Baseline color values of natural tooth and two composite resins were recorded using an ultraviolet spectrophotometer. After baseline spectrophotometric measurements, all the samples were subjected to the mouthrinses. The postimmersion color values of the samples were then recorded, respectively, using the same spectrophotometer. The statistical analysis was done using paired t-test. Reflectance values showed a statistically significant difference between CHX and CHX with ADS among nanoceramic and nanohybrid composite samples. There was no statistically significant difference in reflectance values among natural teeth samples with either CHX or CHX with ADS. Within the limitations of the current study, CHX with ADS may aid in avoiding stains caused due to use of CHX mouthwash, thereby making it more acceptable for patients.

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.

Observing protein degradation in solution by the PAN-20S proteasome complex: Astate-of-the-art example of bio-macromolecular TR-SANS.

In the present book chapter we illustrate the state-of-the-art of time-resolved small-angle neutron scattering (TR-SANS) by a concrete example of a dynamic bio-macromolecular system, i.e., regulated protein degradation by the archaeal PAN-20S proteasome complex. We present the specific and unique structural information that can be obtained by this approach, in combination with bio-macromolecular deuteration and online spectrophotometric measurements of a fluorescent substrate (GFP). The complementarity with atomic-resolution structural biology techniques (SAXS, NMR, crystallography and cryo-EM) and with the advent of atomic structure prediction are discussed, as well as the respective limitations and future perspectives.

Flame retardancy and aspects of the vat dyes application on inherently flame retardant fabrics

The paper presents research on the application of vat dyes to inherently flame resistant fabrics, using the conventional screen-printing method. The composition of the fabrics are defined within a scope of a project conducted in partnership of Croatian textile factory Cateks d.d. and University of Zagreb Faculty of Textile Technology. Fabrics are screen printed by using a vat dye Indanthren® Olive R (DyeStar, Germany) in two concentrations. After printing, a coloristic analysis of the obtained colouration is performed, based on instrumental spectrophotometric measurement and objective evaluation of the colouristic parameters (L*, C*, h°) and colour depth (K/S). The samples are tested for resistance to surface burning, and the colour fastness to dry/wet rubbing and light exposure are also tested. Excellent results of fire resistance and dry/wet rubbing resistance are achieved, while resistance to light exposure is lower to optimal.

USE OF BI2S3 AS A PHOTOCATALYST FOR PHOTOCATALYTIC DEGRADATION OF TEXTILE AZO DYE REACTIVE BLUE 160 (RB160)

In apparel industries removal of the color of dye is one of the main problem. In the current work semiconductor photo-catalyst Bi2S3 utilized in photo catalytic decolorizing of textile azo dye Reactive Blue 160 under UV light. Spectrophotometric measurements of the reaction rate were made. It has been investigated how many variables, including dye concentration, photocatalyst quantity, and pH, affect reaction efficiency.

Caffeine in Tablet Dosage Form: Analytical Method Development and Validation by Using U.V. Spectroscopy

Abstract: Caffeine (1,3,7-trimethylpurine 2,6 dione) is a CNS stimulant. Caffeine is used as a drug having drug-addicted properties having a U.V. cutoff in the range of 272 nm to 297 nm in the U.V. spectrum. In this paper, we took a tablet with Caffeine as a single dose in solid dosage form with excipients that do not have a sharp peak in the U.V. spectrum range from 200 nm to 400 nm. The solvent used as a vehicle is a simple polar solvent with a U.V. cutoff at around 189nm to 191 nm. The U.V. spectrophotometer that we used is of Shimdzu having a double beam, which has two provisions to keep reference and sample at a time to complete sample analysis. Firstly we make a calibration curve of Caffeine with a polar solvent. For the research, development, and production of medicines, analytical technique related to creation and validation are essential. Therefore, in this study, a readily reproducible, straightforward, and quick technique of U.V. spectrophotometric quantitative measurement of Caffeine in the form of tablets is adopted. According to ICH criteria, the parameters to be examined include linearity, specificity, accuracy, precision, and robustness. Purified/deionized water was used as the diluent for the drug quantification at the wavelength of 248.5 nm. Beer-law Lambert's applies to Caffeine at concentrations between 10 and 50 g/ml. Recovery was used to test the method's accuracy, and the results ranged from 99.46 to 100.67%. This approach was used for routine analysis of Caffeine in tablet dosage form.

Application issue of anthraquinonoid vat dyes on inherently flame‐resistant fabrics

AbstractThe vat dyeing process of specific fabrics with protective, inherently fire retardant properties that have a high content of aramid fibres in their composition, is presented. The research was performed on fabric samples that differ in raw material composition and aramid content. The samples were dyed in raw form (group 1) as well as after pretreatment with alkaline scouring (group 2). Measured limiting oxygen index (LOI) values showed that the selected fabrics meet the properties of inherently fire retardant fabrics. Dyeing was performed with Indanthren® Olive Green HB (manufactured by DyStar) vat dye, in exhaustion process, with a bath ratio of 1:30. The dye concentration was 3%, and sodium‐hydrosulphite (Na2S2O4) was used as a reducing agent. The colouristic analyses were performed based on spectrophotometric measurement and results interpretation according to CIELab system. The evaluation of primary tactile properties was performed which show an increase of smoothness and softness after scouring and dyeing. Also, wash fastness as well as light fastness tests have shown satisfactory fastness properties.

The Role of Nucleases Cleaving TLR3, TLR7/8 and TLR9 Ligands, Dicer RNase and miRNA/piRNA Proteins in Functional Adaptation to the Immune Escape and Xenophagy of Prostate Cancer Tissue.

The prototypic sensors for the induction of innate and adaptive immune responses are the Toll-like receptors (TLRs). Unusually high expression of TLRs in prostate carcinoma (PC), associated with less differentiated, more aggressive and more propagating forms of PC, changed the previous paradigm about the role of TLRs strictly in immune defense system. Our data reveal an entirely novel role of nucleic acids-sensing Toll-like receptors (NA-TLRs) in functional adaptation of malignant cells for supply and digestion of surrounding metabolic substrates from dead cells as specific mechanism of cancer cells survival, by corresponding ligands accelerated degradation and purine/pyrimidine salvage pathway. The spectrophotometric measurement protocols used for the determination of the activity of RNases and DNase II have been optimized in our laboratory as well as the enzyme-linked immunosorbent method for the determination of NF-κB p65 in prostate tissue samples. The protocols used to determine Dicer RNase, AGO2, TARBP2 and PIWIL4 were based on enzyme-linked immunosorbent assay. The amount of pre-existing acid-soluble oligonucleotides was measured and expressed as coefficient of absorbance. The activities of acid DNase II and RNase T2, and the activities of nucleases cleaving TLR3, TLR7/8 and TLR9 ligands (Poly I:C, poly U and unmethylated CpG), increased several times in PC, compared to the corresponding tumor adjacent and control tissue, exerting very high sensitivity and specificity of above 90%. Consequently higher levels of hypoxanthine and NF-κB p65 were reported in PC, whereas the opposite results were observed for miRNA biogenesis enzyme (Dicer RNase), miRNA processing protein (TARB2), miRNA-induced silencing complex protein (Argonaute-AGO) and PIWI-interacting RNAs silence transposon. Considering the crucial role of purine and pyrimidine nucleotides as energy carriers, subunits of nucleic acids and nucleotide cofactors, future explorations will be aimed to design novel anti-cancer immune strategies based on a specific acid endolysosomal nuclease inhibition.

Characterization of a Ruthenium(II) Complex in Singlet Oxygen-Mediated Photoelectrochemical Sensing.

A water-soluble ruthenium(II) complex (L), capable of producing singlet oxygen (1O2) when irradiated with visible light, was used to modify the surface of an indium-tin oxide (ITO) electrode decorated with a nanostructured layer of TiO2 (TiO2/ITO). Singlet oxygen triggers the appearance of a cathodic photocurrent when the electrode is illuminated and biased at a proper reduction potential value. The L/TiO2/ITO electrode was first characterized with cyclic voltammetry, impedance spectroscopy, NMR, and Raman spectroscopy. The rate constant of singlet oxygen production was evaluated by spectrophotometric measurements. Taking advantage of the oxidative process initiated by 1O2, the analysis of phenolic compounds was accomplished. Particularly, the 1O2-driven oxidation of hydroquinone (HQ) produced quinone moieties, which could be reduced back at the electrode surface, biased at -0.3 V vs Ag/AgCl. Such a light-actuated redox cycle produced a photocurrent dependent on the concentration of HQ in solution, exhibiting a limit of detection (LOD) of 0.3 μmol dm-3. The L/TiO2/ITO platform was also evaluated for the analysis of p-aminophenol, a commonly used reagent in affinity sensing based on alkaline phosphatase.

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.