Conventional Spectrophotometric Method Research Articles

Application of different chemometric assisted models for spectrophotometric quantitative analysis of velpatasvir and sofosbuvir

Four chemometric assisted spectrophotometric models were developed for the quantitative analysis of velpatasvir and sofosbuvir, in their newly FDA approved pharmaceutical dosage form. Due to the existed overlap of the scanned absorption spectra between velpatasvir and sofosbuvir, this resulted in degree of difficulty of the possibility of the conventional spectrophotometric methods to quantify and analyze the cited drugs simultaneously. Classical least squares, principal component regression, partial least squares and genetic algorithm partial least squares were designed and compared for the quantitative analysis of velpatasvir and sofosbuvir in their binary mixture. Experimental design for different concentrations of the studied drugs was done based on the spectral sensitivity of velpatasvir and sofosbuvir and the confirmed ratio of the two drugs in the commercial pharmaceutical dosage form. Optimization of the described models was adopted with the aid of five-levels, two factors experimental design. Successfully quantitative assay of the drugs in Epclusa® tablets was done by the proposed models. Statistically comparative analysis for the obtained models results with another published capillary electrophoresis quantitative analytical method was performed. It is noteworthy mentioning that there was no significant difference between the proposed models and the published method with respect to the accepted statistical parameters.

Glutathione system in the blood of gastric cancer patients with various tumor histotypes and prevalence of the disease.

e16534 Background: The role of oxidative stress in tumor growth and the multifaceted functional significance of glutathione have led to an interest in studying the components of the glutathione-dependent system in gastric cancer (GC), which occupies a leading position in cancer incidence and mortality. The aim of this work was to study the functioning of the glutathione system in the red blood cells of patients with gastric cancer in a comparative aspect depending on the histotype of the tumor and the prevalence of the disease. Methods: The study included 89 patients with GC divided into 6 groups depending on the histotype of the tumor. Separately, the results of the study were analyzed in patients with T4 status according to TNM and in patients with stage IV cancer. The content of reduced glutathione and the activity of glutathione-dependent enzymes were studied by conventional spectrophotometric methods in the red blood cells of patients. Statistical processing of the results was performed using the Statistika 6.0 program with Student’s t-test for two independent groups. Results: An increase in the content of glutathione in patients with GC compared with the group without oncopathology was revealed. The maximum increase was observed in patients with low-grade adenocarcinoma - by 42.5%, while in signet ring cell cancer (SRCC) there was only a tendency to increase by 17.8%. Glutathione reductase activity was reduced in adenocarcinoma by 23.4-26.2% and did not change in SRCC. The activity of the antioxidant enzymes glutathione peroxidase and glutathione transferase was increased in all groups and especially in SRCC - by 76% and 23-29%, respectively. In patients with T4 status and at stage 4 of the process, lower activity of the studied glutathione-dependent enzymes was revealed compared with all other groups of patients. Conclusions: The data indicate a greater functional potential of the glutathione system in SRCC. A significant increase in the activity of glutathione transferase with a sufficiently high level of reduced glutathione contributes to the development of treatment resistance in patients with SRCC.

Flow-through optical device based on silicone optical technology (SOT) for determination of iron in drinkable tap water

We propose a new concept “silicone optical technology (SOT)”, with low noise and simple integration of all optical components, and use a common matrix of polydimethylsiloxane (PDMS) as a prototype for rapid digital fabrication. This work involves the rapid design and fabrication of SOT optical modules designed to be coupled with a flow injection analysis system (SOT-FIA module), and their use in combination with a handheld photo absorbance meter “picoExplorer™” is also demonstrated. A digital fabrication method, by casting PDMS on the three-dimensional printed mold/frame, is developed. A simple structure of transparent PDMS mixed with the white pigment of titanium dioxide (TiO2) rutile particle (W-PDMS) optical core with a cladding of carbon black dispersed PDMS (K-PDMS) is fabricated. This structure performs as a tiny and straightforward optical filter and shows the ability to trap tilted incident light. The addition of the white pigment into PDMS results in a special enhancement of the optical sensitivity by increasing the amount of scattered light. This module is directly mounted on a white light emitting diode (LED) and the red-green-blue (RGB) sensor device from the picoExplorer at 45° to the flow channel to increase the detection length. The optical properties of the SOT-FIA module, which arise from the presence of white PDMS (W-PDMS) and the effect of the detection length, are investigated and show a dramatically enhanced sensitivity (30–45 times) of the optical detection compared with the calculation using Beer-Lambert's law. Moreover, lower than 1% of crosstalk is observed, which indicates the low noise level detection of the proposed SOT-FIA optical device. This proposed SOT-FIA module integrated with an LED detection system is developed to be combined with a flow injection analysis system for the colorimetric detection of iron in drinkable tap water samples. The results show excellent linearity, the ability for a wide range of chemical analysis, low detection limit, high percentage recovery, high precision and good agreement with the conventional spectrophotometric method. Furthermore, the tilted and tilt-shifted coupling alignments are newly developed and evaluated.

Evaluation of a carbon ink chemically modified electrode incorporating a copper-neocuproine complex for the quantification of antioxidants

A feasibility study on the use of a carbon ink chemically modified electrode to quantify antioxidants, containing [Cu(Nc)2](NO3)2. First, [Cu(Nc)2](NO3)2 was prepared and characterized, to demonstrate similarity with electrochemical response of CUPRAC solution. Then, the Chemically Modified Electrode (CME) was prepared with [Cu(Nc)2](NO3)2 and it was used to determine the total antioxidant content (TAC), employing Trolox, as a variation of the CUPRAC methodology in order to provide an alternative to the original methodology, which requires the preparation of several precursor solutions. CME also demonstrated reproducible results in the quantification of TAC for different antioxidants, where the anodic peak current of the cyclic voltammograms of the adsorbed [Cu(Nc)2]2+ showed a linear correlation with the antioxidant concentration. Those results resemble results obtained in CUPRAC solution, the characteristic calibration curve slopes can also be employed to determine the relative number of exchanged electrons. Analytical performance of the prepared CME referred to Trolox as probe lead to the following parameters: quantification limit of 2.10 × 10−4 mol L-1; detection limit of 6.29 × 10-5 mol L-1; and a linear range of 2.10–77.4 (x 10−4) mol L-1. Finally, analytical performance of this CME was also evaluated with Ascorbic Acid and Catechin as sample antioxidants. TAC determinations were performed in tea samples and the results were comparable to those obtained using the conventional spectrophotometric CUPRAC method. Obtained results suggest that this CME can be reused in consecutive determinations, as long as a previous calibration curve is prepared for the electrode on a regular basis.

A new formaldehyde optical sensor: Detecting milk adulteration

A sensor consisting of an optical fibre with the exposed tip coated with the polyoxometalate salt [(C4H9)4N]4H[PMo10V2O40], specially designed to be insoluble in water, which UV–Vis spectrum changed in contact with formaldehyde, is presented.The sensor limit of detection for formaldehyde was 0.2 mg L−1, and the limit of quantification was 0.6 mg L−1, which were close to the conventional spectrophotometric method values of 0.2 mg L−1 and 0.5 mg L−1, respectively, and lower than the tolerable limit for ingested food. The sensor was tested for formaldehyde quantification in milk, as its deliberate addition is a matter of concern. The results obtained analysing formaldehyde in milk samples by the optical sensor and by the conventional method were not statistically different (α = 0.05).

Compact and on-demand 3D-printed optical device based on silicone optical technology (SOT) for on-site measurement: Application to flow injection analysis

The current trend for analytical systems and devices is to be small, portable, and low in cost because of the flexibility required to ensure their availability for on-site measurement applications. Using the concept of silicone optical technology (SOT), we propose a fully flexible analytical system, and digital fabrication of a compact optical module for flow-injection analysis (FIA) is demonstrated. A simple structure composed of a transparent polydimethylsiloxane (PDMS) optical core with a carbon black-dispersed PDMS cladding acts as a tiny but straightforward optical filter and shows an ability to trap light at tilted incidence; this structure is embedded on a silicone 3D-printed optical module via a simple injection and coating method. The coating properties, the optical trapping performance, and the cross talk test performance of the device were evaluated. The SOT-FIA optical module successfully demonstrated a 99.8% undesired light trapping performance; cross talk of less than 0.5% was observed, illustrating the low-noise detection performance of the SOT-FIA optical system. Colorimetric determination of iron in natural water samples demonstrated excellent linearity, a wide chemical analysis range, and good percentage recovery performance. The results of the determination in real water samples using the proposed SOT-FIA optical device agreed well with the results from the conventional spectrophotometric method. With advantages that include simplicity, low cost, flexibility, portability, and high sensitivity, the proposed optical device will be potentially useful for on-site chemical analysis measurements.

Phytochemical profile, mineral content, and antioxidant activity of Olea europaea L. cv. Cornezuelo table olives. Influence of in vitro simulated gastrointestinal digestion

The main goals of this study were to determine the phenolic composition and antioxidant activity of table olives from Olea europaea L. cv. Cornezuelo, as well as the effect caused by a simulated in vitro digestion to evaluate compounds bioavailability. High-performance liquid chromatography with diode-array and mass spectrometry detection (HPLC-DAD-MSn) was used to evaluate the phytochemical profile, whereas conventional spectrophotometric methods (ABTS·+ and DPPH) were used to determine the antioxidant activity. The mineral content was also quantified by inductively coupled plasma – mass spectrometry.Thirty compounds were identified, mainly polyphenols, quantifying the major compounds by HPLC-DAD. After the simulated digestion, the phenolic content suffered an important decrease – more than 50% – reaching losses of up to 75% for oleuropein and comselogoside isomers. This decrease also resulted in a loss of antioxidant activity, observing significant differences for all parameters. However, the analyzed extracts still retained considerable antioxidant potential.

A Rapid Method for Measurement of Nickel and Chromium at Trace Level in Aqueous Samples

A rapid, simple and portable technique to measure Ni(II) and Cr(VI) at trace level in aqueous samples has been proposed. Colored spots were developed by interacting micro-liter drops of metal solutions with suitable reagents on TLC plates. Soon after, TLC having spots was scanned to import the image into the computer. Color densities of spots were calculated with the help of homemade software. Simple regression was practiced on calibration between standards’ concentrations and their color densities. For both metals, correlation coefficients were approaching to one, which pointed out a good correlation between color densities and corresponding analyte concentrations. Real samples from electroplating unit were analyzed with the present and conventional spectrophotometric method (employed as reference), and the results were compared to evaluate the pertinence of the proposed technique in the real analysis.

Phenolic profile and antioxidant activity of Jasonia glutinosa herbal tea. Influence of simulated gastrointestinal in vitro digestion

In order to value J. glutinosa DC (rock tea), we characterised its phenolic profile and antioxidant activity. The study was performed in aqueous extracts before and after a simulated in vitro digestion to obtain data regarding phenolics bioavailability. Methanolic extracts were also analysed for comparison purposes. Phytochemical profiles were determined by high-performance liquid chromatography with mass spectrometric detection, whereas total phenolic content (TPC) and antioxidant assays were performed by conventional spectrophotometric methods. The most abundant compounds were dicaffeoylquinic acids, representing more than 90% of phenolics in tea infusions. Statistically significant differences were observed for all parameters except for TPC in methanol and aqueous extracts. Both phenolics amount and antioxidant activities were lower after the in vitro digestion of the infusions. However, although phenolics were lost during the simulated digestion, rock tea is still a good source of bioactive compounds with potential applications in the pharmaceutical or nutraceutical industries.

Comparative secondary metabolites profiling and biological activities of aerial, stem and root parts of Salvadora oleoides decne (Salvadoraceae)

In this study, different parts (aerial, stem and root) of Salvadora oleoides Decne were investigated in order to explore their phytochemical composition and biological potential. The bioactive contents were evaluated by conventional spectrophotometric methods. Additionally, the secondary metabolite compounds were identified by UHPLC-MS analysis. Biological potential was evaluated by determining antioxidant (DPPH, FRAP, and Phosphomolybdenum) and enzyme inhibitory (butrylcholinesterase and lipoxygenase) effects. Higher total bioactive contents were found in methanolic extracts which tend to correlate with higher radical scavenging and reducing potential of these extracts. LC/MS spectrum revealed the presence of 16 different secondary metabolites belonging to terpene, glucoside and sesquiterpenoid dervivatives. Glucocleomin and emotin A were the main compounds present in all three parts. The strongest butrylcholinesterase and lipoxygenase inhibitory activity was observed for root and stem DCM extracts. Demonstrated biological potential of S. oleoides plant can trace a new road map for developing newly designed bioactive pharmaceuticals.

Determination of Hyoscine Butylbromide in Pharmaceuticals Using Ce(IV)–Na2SO3 Chemiluminescent System in Flow Injection Analysis

A flow injection method with chemiluminescence (CL) detection has been developed for hyoscine butylbromide (HBB) determination based on an enhancement of cerium(IV)–sulphite CL reaction in an acidic medium. The method enables HBB determination in the range of 0.005–15 ppm (R2 = 0.9990, n = 10), with relative standard deviation of 2.5% (n = 12) for 0.25 ppm of HBB. The limit of detection (3s × blank) was 0.001 ppm with an injection throughput of 180 h–1. The concentration of reagents involved in the CL reaction and the key physical variables were carefully studied and optimized. The proposed procedure offered high sensitivity, simplicity and rapidity, and was successfully applied to HBB determination in pharmaceutical preparations. The results obtained were in good agreement with the conventional spectrophotometric method. The mechanism of Ce(IV)‒Na2SO3‒HBB CL reaction is also discussed.

Comparative in vitro studies of the biological potential and chemical composition of stems, leaves and berries Aronia melanocarpa's extracts obtained by subcritical water extraction

Preparation of functional products as well as natural-based products requires non-toxic but effective extraction techniques. In this study, subcritical water extraction was used for the extraction of different aronia parts in order to explore their potential. Stems, leaves and berries of Aronia melanocarpa were extracted under the following conditions: temperature 130 °C; pressure 35 bar; time 20 min. The total phenols and flavonoid contents of the produced extracts were evaluated by conventional spectrophotometric methods. Additionally, the main phenolic compounds were also identified and quantified by high performance liquid chromatography with diode array detection (HPLC-DAD). The biological potential of the extracts was evaluated by determining their antioxidant (DPPH, ABTS and lipid peroxidation assays), antimicrobial, enzyme inhibitory (cholinesterase and elastase) and cytotoxic effects (HeLa, A-549, LS-174T, MRC-5 cell lines). The results indicate that leaves and berries extracts exhibited stronger antioxidant action when compared with stems. The strongest cholinesterase and elastase inhibitory activity was also found in berries extract. Similarly, the extracts obtained from leaves and berries showed considerable cytotoxic effects against tested cell lines. A moderate antimicrobial effects was observed too. Demonstrated biological potential of all three aronia parts can trace a new road map for developing newly designed functional products.

Capillary zone electrophoresis determination of fluoride in seawater using transient isotachophoresis.

We developed capillary zone electrophoresis (CZE) with indirect UV detection for the determination of fluoride (F-) in seawater using transient isotachophoresis (tITP) as an on-line concentration procedure. A method of correcting sample salinity effects was also proposed so that F- concentrations were obtained using a calibration graph. The proposed method is simple: it requires no sample pretreatment aside from dilution. The following optimum conditions were established: background electrolyte (BGE), 5mM 2,6-pyridinedicarboxylic acid (PDC) adjusted to pH 3.5 containing 0.03% m/v hydroxypropyl methylcellulose (HPMC); detection wavelength, 200nm; vacuum (50kPa) injection period of sample, 5s (254nL); and applied voltage, 23kV with the sample inlet side as the cathode. The limit of detection (LOD, S/N = 3) and limit of quantification (LOQ, S/N = 10) for F- reached 0.024 and 0.070mg/L, respectively. The respective values of the relative standard deviation (RSD) of the peak area, peak height, and migration time for F- were 2.5, 3.4, and 0.30%. The proposed method was applied for the determination of F- in seawater samples collected from coastal waters of western Japan during August 26-28, 2014. Both results obtained using standard addition method and a calibration graph agreed with those obtained using a conventional spectrophotometric method.

Subcritical water extraction as an environmentally-friendly technique to recover bioactive compounds from traditional Serbian medicinal plants

Subcritical water extraction (SWE) has become a popular green extraction technique for the isolation of different classes of compounds from natural matrices. Low price, safety and green character of water, good yields of target compounds and reduced energy consumption, make this technique favorable for potential industrial applications. The purpose of this study was to evaluate antioxidant, antimicrobial and cytotoxic activity of four medicinal plants traditionally used in folk medicine of Serbia. Black mulberry (Morus nigra L.), wall germander (Teucrium chamaedrys L.), wild geranium (Geranium macrorrhizum L.) and comfrey (Symphytum officinale L.) were extracted by subcritical water at different temperatures. Antioxidant activity of the extracts was defined by conventional spectrophotometric methods, such as the total phenolic content (TPC), DPPH-radical scavenging activity (DPPH-RSA), ferric reducing antioxidant power (FRAP) and total antioxidant capacity (TAC) assessed by a DNA-based sensor. Additionally, the main phenolic compounds contributing to the antioxidant activity of the produced extracts were also identified and quantified by high performance liquid chromatography with diode array detection (HPLC-DAD). Antimicrobial properties of extracts were evaluated against eight microbial strains. Furthermore, the cytotoxic activity was observed for two human cancer cell lines and a cell line derived from murine fibroblast.

Characterization of β-lactamase activity using isothermal titration calorimetry

BackgroundHydrolysis of β-lactam antibiotic by β-lactamase is the most common mechanism of β-lactam resistance in clinical isolates. Timely detection and characterization of β-lactamases are therefore of utmost biomedical importance. Conventional spectrophotometric method is time-consuming and cannot provide thermodynamic information on β-lactamases. MethodsA new assay was developed for the study of β-lactamase activity in protein solutions (Metallo-β-lactamase L1) and in clinical bacterial cells, based on heat-flow changes derived from enzymatic hydrolysis of β-lactams using isothermal titration calorimetry. Results(1) The thermokinetic parameters of three antibiotics (penicillin G, cefazolin and imipenem) and the inhibition constant of an azolylthioacetamide inhibitor were determined using the calorimetric assay. The results from the calorimetric assays were consistent with the data from the spectrophotometric assay. (2) The values of heat change in the calorimetric assay using two clinical Escherichia coli strains correlated well with their antibiotic susceptibility results from the broth dilution experiment. The subtypes of β-lactamase were also determined in the calorimetric assay. ConclusionsThe ITC assay is a reliable and fast method to study β-lactamase enzyme kinetics and inhibition. It can also provide thermodynamic information on antibiotic hydrolysis, which has been taken advantage of in this work to study β-lactamase activity in two clinical Escherichia coli isolates. General significanceAs the first calorimetric study of β-lactamase activity, it may provide a new assay to assist biomedical validation of new β-lactamase inhibitors, and also has potential applications on rapid antibiotic susceptibility testing and screening β-lactamase producing bacteria.

The activity of redox-regulatory systems in the primary and recurrence tumors in vulvar cancer

The activities of superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx), glutathione reductase (GR), glutathione transferase (GST), the content of reduced glutathione (GSH) and malondialdehyde (MDA) were investigated in the samples of the tumor, peritumoral zone and healthy tissue, taken at the line of resection, were obtained from 14 patients with primary squamous cell carcinoma of the vulva, and 13 patients with local recurrence appeared in the period from 3 months to 7 years. by conventional spectrophotometric methods. The content of GSH and the activity of SOD, GPx, GR, GST were significantly increased, while MDA was decreased in the tissue of the primary carcinoma of the vulva in compared with the healthy tissue. Differences in the functioning of the investigated system of enzymes in the peritumoral zone were also revealed in the primary and recurrent tumoral process. Similar but much less pronounced changes were also observed in the recurrent tumor. It is suggested that such dynamics of activity of the studied system with the progression of cancer process can be the result of adaptation to changes in the local biochemical status of healthy (nonmalignant) tissue of the organ carrying the tumor and reflect the metabolic features of the recurrent tumor.

Chitosan nanoparticles as a potential drug delivery system attached to viscose cellulose fibers

Chitosan and its water-soluble N,N,N-trimethyl derivative were attached to cellulose fibers in the form of nanoparticle dispersions. The attachment of the chitosan nanoparticles to the fiber surface was studied by evaluation of the quantity of chitosan amino groups using a conventional spectrophotometric method supported by X-ray photoelectron spectroscopy. The desorption kinetics of the chitosan nanoparticles from the fiber surface was also examined indirectly by the spectrophotometric method. Additionally, a model drug was incorporated into the optimal chitosan nanoparticles for subsequent attachment to fibers to create a potential fibrous drug delivery system aimed at gynecological use, i.e., tampons as antimicrobial agents themselves or as drug reservoirs.

Monitoring the effect of transglutaminase in semi-hard cheese during ripening by hyperspectral imaging

Semi-hard cheese samples made from pasteurized 3.5% and 5% fat cow’s milk were partly enzyme treated with microbial transglutaminase (mTG). Cheese colour and yield was greatly affected by mTG at both fat levels. The cross-linking effect of mTG also led to improved protein content and hardness in cheese. As Texture Profile Analysis (TPA) could only distinguish according to enzyme treatment we studied hyperspectral imaging (HSI) to differentiate also according to fat level and ripening status. HSI was used on a weekly basis during 4–10 weeks period of ripening time. In case of uneven surface, using the spatial information and making proper normalization on the spectra of ROI pixels, the hyperspectral method can provide even better signal-to-noise ratio then the conventional spectrophotometric method. Statistical analysis with Partial Least Squares (PLS) regression and Monte Carlo Cross Validation (MCCV) led to determination of significant wavelengths both for the detection of enzyme treatment (1387 nm) and for fat content (1190, 1234 nm) independent of the actual age of examined semi-hard cheese. Hyperspectral measurement method allowed remote inspection of the product through transparent vacuum foil. The spectrum normalization allowed the elimination of effects originating from inhomogeneous illumination caused by cheese holes.

Determination of 5-hydroxymethylfurfural in honey, using headspace-solid-phase microextraction coupled with a polyoxometalate-coated piezoelectric quartz crystal.

High concentrations of 5-hydroxymethylfurfural (HMF) in honey provide an indication of overheating under inappropriate storage conditions or aging. Conventional methods for determining HMF are cumbersome and require expensive equipment or hazardous reagents. Hence the aim of this study was to propose a new analytical tool for HMF determination in honey, using a low cost acoustic wave sensor. Volatile organic compounds (VOCs) of honey samples were extracted, using the solid phase microextraction (SPME) technique, and HMF was quantified, using a piezoelectric quartz crystal with gold electrodes coated with a layer of decamolybdodivanado phosphoric acid, sensitive to HMF. The reliability of the proposed method was confirmed after comparing the results of HMF quantification with those obtained by the conventional spectrophotometric White method, and no statistical differences were found (α=0.05).

Comparative Study of the Spectral Resolution Efficiency of the Recently Developed and Conventional Spectrophotometric Methods in the Analysis of Severely Overlapped Zero-Order Absorption Spectra with the Same Geometrical Features

Simple, cost-effective, safe, accurate, precise and environmentally friendly spectro-photometric methods were developed and validated for the quantitative determination of valaciclovir (VAL) in the presence of its related impurity in bulk powder and in its pharmaceutical preparation. This related impurity namely guanine (GUA) is the potential and synthesis impurity of VAL. The spectra of VAL and GUA show the same geometrical features with different absorptivities, so their resolution is very challengeable. A Comparative study was conducted for the results of the conventional methods namely, dual wavelength (DW), first derivative of ratio spectra (1DD) and mean centering of ratio spectra (MCR) versus the recently developed methods namely, induced dual wavelength (IDW), ratio difference (RD) and constant center (CC). The optimized methods allow the estimation of VAL in the concentration range 5-50 μg/mL. The methods were validated as per ICH guidelines and the specificity was assessed by analyzing synthetic mixtures containing different percentages of the related impurity with the drug. The obtained results were compared with that of the official HPLC method by using one-way analysis of variance (ANOVA) and proved to be suitable for quality control laboratories.