Conventional Spectrophotometric Method Research Articles

On-Site Sensitive Colorimetry for Free Cyanide by Using Ion-Pair Solid-Phase Extraction with Sedimentable Dispersed Particulates and Mobile Photography Box.

We propose a sensitive and simple colorimetric method using dispersed particle extraction for the highly sensitive detection of free cyanide in water samples. The method involves the direct capture of the color-producing compound by dispersed microparticles in a sample vessel containing colorimetric reagents and an adsorbent. The color of the microparticles that have naturally settled to the bottom of the microtube can be directly measured by visual observation or image analysis. A mobile photography box (MPB) suitable for use with a smartphone was developed to ensure reproducibility in the lighting environment during image acquisition. The MPB was then used to develop a highly sensitive analytical method for cyanide. This newly developed method allows direct measurement of the color tone of the target component collected on particles by irradiating light from below and photographing it perpendicularly. The method offers excellent portability, sensitivity, and reproducibility and is less affected by interfering color components. When applied to cyanide analysis, the detection limit reached 0.005 mg/L and measurements could be completed within 10 min, significantly shorter than the conventional absorbance spectrophotometric method, which requires 30 min. Thus, this method achieves highly sensitive cyanide analysis.

Reduction with zinc — Impact on the determination of nitrite and nitrate ions using microfluidic paper-based analytical devices

We used a microfluidic paper-based analytical device (μPAD) to investigate the influence that zinc reduction exerts on the determination of nitrite and nitrate ions in natural water samples. The μPAD consists of layered channels for the reduction of nitrate to nitrite with zinc powder and the subsequent detection of nitrite with Griess reagent. The amount of zinc, number of layers, and reaction time for the reduction were optimized to obtain an intense signal for nitrate. Initially, the sensitivity to nitrate corresponded to 55% that of nitrite, which implied an incomplete reduction. We found, however, that zinc decreased the sensitivity to nitrite in both the μPAD and spectrophotometry. The sensitivity to nitrite was decreased by 48% in spectrophotometry and 68% in the μPAD following the reaction with zinc. One of the reasons for the decreased sensitivity is attributed to the production of ammonia, as we elucidated that both nitrite and nitrate produced ammonia via the reaction with zinc. The results suggest that the total concentration of nitrite and nitrate must be corrected by constructing a calibration curve for nitrite with zinc, in addition to developing curves for nitrate with zinc and for nitrite without zinc. Using these calibration curves, the absorbance at different concentration ratios of nitrite and nitrate ions could be reproduced via calculation using the calibration curves with zinc for nitrite and nitrate. Eventually, the developed μPAD was applied to the determination of nitrite and nitrate ions in natural water samples, and the results were compared with those using a conventional spectrophotometric method. The results of the μPAD are in good agreement with those of conventional spectrophotometry, which suggests that the μPAD is reliable for the measurement of nitrite and nitrate ions in natural water samples.

EVALUATION OF EFFICACY OF COLOUR CORRECTED LIGHT SOURCE IN DETERMINING THE ACCURACY OF SHADE MATCHING DONE WITH A COMMONLY USED SHADE GUIDE SYSTEM BY CONVENTIONAL VISUAL METHOD AND AN INTRA ORAL SPECTROPHOTOMETER

Aim: The objective of this study was to evaluate the efficiency of colour corrected light source in shade matching and to determine accuracies and inter-rater agreement of three shade matching methods (conventional visual method, visual method using colour corrected light source and spectrophotometric method). Methodology: In the conventional visual method and the visual method using colour corrected light source, four examiners with normal colour vision matched five target control shade tabs taken from the VITAPAN 3D MasterTM shade guide, with other full set of the same shade guide. Shade matching with the colour corrected light source was done under daylight mode simulating 5500K or natural daylight. Each tab was matched three times to determine repeatability of visual examiners. In the spectrophotometric method, two independent examiners matched the control tabs with three repetitions for each tab. The data was collected and statistical analysis was performed. Results: Visual method using colour corrected light source produced more accurate results (80%) than the conventional visual method (68.3%) and spectrophotometric method (0%), thus proving the efficacy of colour corrected light source (p<0.05). All three methods exhibited poor inter-rater agreement. Conclusion: The question is whether handheld light correcting devices and digital assessments are clinically useful or are they unreliable andunnecessary costly. Even though visual shade matching is subjective, it is not inferior and should not be underrated. The low accuracy value obtained for the spectrophotometer may be a misrepresentation of the machines capabilities due to its inability to measure any reading asclose to the correct value. If both analyses are combined, digital determination of the basic shade and visual determination of the effects, can provide the best possible esthetic outcome. Although human eye will be the finalarbitrator, success can best be achieved by combining traditional artistic techniques with advancements in technology, complemented with innovations in colour-related research, education, and training of dental professionals.

A simple and green ion-pairing extraction colorimetric determination of chlorhexidine employing coconut oil as a natural solvent with image processing

A cost-effective, simple, and green determination of chlorhexidine is proposed. A commonly available bromothymol blue serves as a reagent. The ion-pairing of chlorhexidine and bromothymol blue in an aqueous solution can be extracted into an organic phase of coconut oil, which is proposed as an alternative natural green solvent, replacing the conventional toxic organic solvents. An investigation of the chlorhexidine-bromothymol blue ion pair was made spectrophotometrically and via image processing using a smartphone camera. Downscaling is operated for the extraction of 500 μL of an aqueous mixture containing chlorhexidine and bromothymol blue in phosphate buffer (pH 7.5, 5 mmol/L) with 500 μL of coconut oil for 3 min by hand-shaking. A set of 12 extraction tubes can be operated in one run. After phase separation by centrifuging (3000 rpm, 3 min), the 12 tubes are photographed in one shot using a smartphone. Images of both aqueous and organic phases are evaluated for red-green-blue (RGB) color intensity system. Linearity equations: R intensity = 1.205 [Chlorhexidine] – 23.6 (r2: 0.9795), and ΔB intensity = 1.525 [Chlorhexidine] – 36.75 (r2: 0.9907), are obtained for aqueous and organic phases, respectively. The limits of detection (LOD) and quantitation (LOQ) were 12 and 40 mg/L for aqueous, while 11 and 34 mg/L for organic phases, respectively. The proposed procedure was applied to real samples of active pharmaceutical ingredients (API), disinfectant cleaner, and mouthwash. The results obtained by the proposed procedure agree with the high-performance liquid chromatography (HPLC) reference method that utilizes a UV detector. In evaluations using the green analytical procedure index (GAPI) and analytical greenness (AGREE), the proposed procedure was found to be the greenest compared to the conventional spectrophotometric method and HPLC. The proposed procedure involved the UN-SDGs #3, #4, and #12 and scored the highest value of the need, quality, and sustainability (NQS) index. The proposed procedure encourages sustainable chemistry and pharmacy.

Indicators of free radical oxidation in neutrophils of patients with primary and recurrent soft tissue sarcomas

Purpose of the study. To carry out a comparative analysis of lipid peroxidation intensity and antioxidant system indices in blood neutrophils of patients with primary and relapsed soft tissue sarcomas (STS) depending on sex and age.Patients and methods. Of the 81 patients included in the study, 48 had primary STS, 5 patients with continued growth, and 28 patients with recurrent STS. The patients were divided by sex and age; the level of lipid peroxidation products, superoxide dismutase (SOD) activity, total peroxidase activity (TPA), glutathione peroxidase (GPx) activity and reduced glutathione (RG) content in blood neutrophils were investigated by conventional spectrophotometric methods. The comparison groups (donors) consisted of 12 men and 17 women divided into the same age subgroups: ≤ 45 years and > 45 years.Results. In donors, there was a multiple decrease in the SOD/TPA ratio with age, especially in women, and in men this was accompanied by an age-related decrease in GPx activity. In primary sarcomas in older women and in men with continued growth and recurrence, there was an increase in diene conjugates (DC). In men over 45 years of age, there was an increase in SOD, TPA, and GPx. Women of the older age group were characterized by activation of SOD and GPx, expressed in the relapsed process to a significantly greater extent than in men, and an increase in RG was observed in women. The increase in both components of the glutathione system and SOD activity was especially significant in the development of relapses in women for periods exceeding three years, which was accompanied by a decrease in DC content. Conclusions. Neutrophils are characterized by an increase in DC content in patients of both sexes in the older age group with primary and recurrent STS, with its highest content in men with continued growth and relapses. GPx activity, increased in both men and women in the older age group in all variants of STS development, may play an important role in the antioxidant protection of blood cells in STS. Thus, the most pronounced activation of GPx, accompanied by a maximum increase in reduced glutathione and activation of SOD, contributes to a decrease in the level of DC and the absence of MDA increase in women with slow development of recurrences.

The State of the LPO-AOD System and the Relative Length of Telomeric Repeats in the Chromosomes of Blood Leukocytes in Obstructive Sleep Apnea Syndrome.

We analyzed the relative length of telomeric repeats in peripheral blood leukocytes and indicators of oxidative stress in 32 men (mean age 51.2±3.1 years) with obstructive sleep apnea syndrome (OSAS). The control group consisted of volunteers without OSAS. The relative length of telomeres was determined in a DNA sample isolated from venous whole blood samples. The length of telomeric repeats of chromosomes was determined using quantitative real-time PCR (3 times for each DNA sample); albumin served as an internal control. The intensity of LPO processes and antioxidant protection was assessed by conventional spectrophotometric methods. It was found that in patients with OSAS, the relative length of telomeric repeats was lower by 48%, the levels of substrates and products of LPO were higher (double bonds and diene conjugates by 34 and 19%, respectively), and antioxidant protection indicators were lower (concentrations of fat-soluble vitamins α-tocopherol and retinol by 18 and 19.3%, respectively, total antioxidant activity by 32.9%) than in volunteers of the control group. Thus, we can conclude that the nucleotide sequences are reduced in patients with OSAS under conditions of intensified free radical oxidation.

Blood glucose level, lipid profile and histopathology of alloxan induced diabetic rats fed Sesamum indicum compounded diet

The purpose of this study was to examine the blood glucose level, lipid profile, and histology of alloxan-induced diabetic rats fed compounded diet of Sesamum indicum. 36 male albino rats were divided into nine groups of four each for a period of 21 days: normal control, diabetic control, treated with the standard medication glibenclamide, diabetic rats fed with 15%, 30%, and 60% compounded diet, and normal rats fed with 15%, 30%, and 60% compounded diet and induced with diabetics after 14 days. single intraperitoneal injection of freshly produced alloxan (120 mg/kg b.wt.) was used to induce diabetes. Acu-check glucometer was used to measure the blood glucose level, and conventional spectrophotometric method was used to measure the lipid profile level. When compared to the diabetic control group, which had glucose level above 200, the groups fed the compounded diet had decreased level. Significant (p<0.05) reduction was observed for cholesterol, triglyceride, and low-density lipoprotein when compared with diabetic control while the compounded diets were able to increase HDL that was found to be low in diabetic control. When compared to the diabetic control group, which displayed a damaged pancreas, the results from the histopathology of the pancreas showed that the groups fed with the compounded diet had a repaired pancreas. According to the study's findings, Sesamum indicum has the ability to reduce excessive blood glucose and cholesterol levels as well as mend a diabetic rat's deformed pancreas.

Establishing Compliance between Spectral, Colourimetric and Photometric Indicators in Resazurin Reduction Test.

The resazurin reduction test is one of the basic tests for bacterial culture viability and drug resistance endorsed by the World Health Organisation. At the same time, conventional spectrophotometric and spectrofluorimetric methods demand rather bulky and expensive equipment. This induces a challenge for developing simpler approaches to sensor systems that are portable and applicable in resource-limited settings. In this work, we address two such alternative approaches, based on the colour processing of the microbiological plate's photographic images and single-channel photometry with a recently developed portable microbiological analyser. The key results consist of establishing a sequential linear correspondence between the concentration of resorufin produced due to the reduction of resazurin by viable bacteria as determined by the UV-Vis studies, the intensity of the a* channel of the CIE L*a*b* colour space and the transmitted light intensity registered by a luxmeter under the LED illumination with a yellow colour filter. This route is illustrated with the chemical system "Hydrazine hydrate - resazurin", isolating the target colour change-inducing reaction and the test of determining the minimal inhibition concentration of the antibacterial first-line drug isoniazid acting on the culture of the H37Rv strain of M. tuberculosis.

Classification and Antioxidant Activity Evaluation of Edible Oils by Using Nanomaterial-Based Electrochemical Sensors.

The classification of olive oils and the authentication of their biological or geographic origin are important issues for public health and for the olive oil market and related industries. The development of techniques for olive oil classification that are fast, easy to use, and suitable for online, in situ and remote operation is of high interest. In this study, the possibility of discriminating and classifying vegetable oils according to different criteria related to biological or geographical origin was assessed using cyclic voltammograms (CVs) as input data, obtained with electrochemical sensors based on carbonaceous nanomaterials and gold nanoparticles. In this context, 44 vegetable oil samples of different categories were analyzed and the capacity of the sensor array coupled with multivariate analysis was evaluated. The characteristics highlighted in voltammograms are related to the redox properties of the electroactive compounds, mainly phenolics, existing in the oils. Moreover, the antioxidant activity of the oils' hydrophilic fraction was also estimated by conventional spectrophotometric methods (1,1-diphenyl-2-picrylhydrazyl (DPPH) and galvinoxyl) and correlated with the voltammetric responses of the sensors. The percentage of DPPH and galvinoxyl inhibition was accurately predicted from the voltammetric data, with a correlation coefficients greater than 0.97 both in calibration and in validation. The results indicate that this method allows for a clear discrimination of oils from different biological or geographic origins.

Early detection of lipid oxidation in infant milk formula by measuring free oxylipins-Comparison with hydroperoxide value and thiobarbituric acid reactive substance methods.

Infant milk formula was used as a model food to compare the sensitivity of thiobarbituric acid reactive substances (TBARS) and hydroperoxide methods to UPLC-MS/MS oxylipin analysis for detecting early lipid oxidation. Two different infant milk formulas were tested during 21 days of storage at 4°C. Formulas 1 and 2 contained canola oil and canola oil + 1% docosahexaenoic acid ethyl ester, respectively. Formulas were sampled up to 21 days of storage. Formula 2 had higher peroxide values than Formula 1 across all time points. However, no significant differences over time in TBARS and peroxide values in either formula were observed. Several oxylipins increased in both formulas starting on day 7 (linoleic acid and alpha-linolenic acid-derived oxylipins in Formula 1 and DHA-derived oxylipins in Formula 2). These results indicate that free oxylipins are effective in detecting early lipid oxidation and distinguishing between formulations containing different fatty acids. PRACTICAL APPLICATION: We have recently shown that primary oxidation products known as oxylipins can be measured in their free form by ultra-high pressure liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) to detect early lipid oxidation. However, a head-to-head comparison of the sensitivity of this approach to conventional spectrophotometric methods has not been evaluated. Our results indicate that free oxylipin measurements are better than conventional methods in detecting early lipid oxidation in milk infant formula distinguishing between different formulations.

Assessment of the Antioxidant Activity of Catechin in Nutraceuticals: Comparison between a Newly Developed Electrochemical Method and Spectrophotometric Methods.

The analysis of antioxidants in different foodstuffs has become an active area of research, which has led to many recently developed antioxidant assays. Many antioxidants exhibit inherent electroactivity, and, therefore, the use of electrochemical methods could be a viable approach for evaluating the overall antioxidant activity of a matrix of nutraceuticals without the need for adding reactive species. Green tea is believed to be a healthy beverage due to a number of therapeutic benefits. Catechin, one of its constituents, is an important antioxidant and possesses free radical scavenging abilities. The present paper describes the electrochemical properties of three screen-printed electrodes (SPEs), the first one based on carbon nanotubes (CNTs), the second one based on gold nanoparticles (GNPs) and the third one based on carbon nanotubes and gold nanoparticles (CNTs-GNPs). All three electrodes were modified with the laccase (Lac) enzyme, using glutaraldehyde as a cross-linking agent between the amino groups on the laccase and aldehyde groups of the reticulation agent. As this enzyme is a thermostable catalyst, the performance of the biosensors has been greatly improved. Electro-oxidative properties of catechin were investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV), and these demonstrated that the association of CNTs with GNPs significantly improved the sensitivity and selectivity of the biosensor. The corresponding limit of detection (LOD) was estimated to be 5.6 × 10−8 M catechin at the CNT-Lac/SPE, 1.3 × 10−7 M at the GNP-Lac/SPE and 4.9 × 10−8 M at the CNT-GNP-Lac/SPE. The biosensors were subjected to nutraceutical formulations containing green tea in order to study their catechin content, using CNT-GNP-Lac/SPE, through DPV. Using a paired t-test, the catechin content estimated was in agreement with the manufacturer’s specification. In addition, the relationship between the CNT-GNP-Lac/SPE response at a specific potential and the antioxidant activity of nutraceuticals, as determined by conventional spectrophotometric methods (DPPH, galvinoxyl and ABTS), is discussed in the context of developing a fast biosensor for the relative antioxidant activity quantification.

Free radical processes in rat liver in experimental diabetes, malignant growth and their combination

Purpose of the study. To study the intensity of lipid peroxidation (LPO) and indicators of antioxidant protection in the liver of rats of different sexes with combined pathology – the growth of Guerin's carcinoma in presence of experimental type 1 diabetes mellitus.Materials and methods. The levels of malondialdehyde (MDA) and diene conjugates (DC), the activities of superoxide dismutase (SOD) and catalase, and the levels of vitamins A and D were studied by conventional spectrophotometric methods in liver tissue samples from males and females with alloxan‑induced diabetes mellitus (DM), transplanted Guerin’s carcinoma (GC) and in animals with combined pathologies (GC growth in presence of diabetes mellitus), as well as in intact rats.Results. The levels of both LPO markers in intact females were significantly higher than in males: MDA by 3 times, DC by 2 times. The development of DM led to an increase in the content of MDA and DC in the liver of males compared with intact animals, which indicated an intensification of LPO. At the same time, there was an almost twofold increase in SOD activity, a decrease in catalase activity, and an increase in the ratio of enzymes by 2.8 times. In females, there was no increase in LPO in the liver; there was only a less pronounced increase in SOD activity than in males. At the same time, SOD activity in males was 37 % higher than in females, and catalase activity, on the contrary, was lower by 33 %, which caused a twofold excess of the ratio of enzymes in males relative to females. Among animals with GC, only males had an increase in SOD by 2.5 times, a decrease in catalase activity, and an increase in the SOD/Catalase ratio by 3 times relative to intact animals, which may be due to pronounced sex differences the SOD activity and SOD/Catalase ratio in males were 3–4 times higher than that of females. The levels of MDA and DC in males with GC growing in presence of DM remained elevated, although to a somewhat lesser extent than in DM alone, while in females both indicators were reduced. The ratio of vitamins E and A increased only in males. SOD activity and SOD/Catalase coefficient in animals of both sexes with combined pathologies were significantly lower than in groups with only DM or GC.Conclusions. The data showed that diabetes mellitus changes the specificity of oncogenesis depending on the sex of the animals. Males with the growth of Guerin's carcinoma in presence of diabetes in conditions of inhibition of SOD activity and a decrease in the ratio of conjugated enzymes of the first line of antioxidant defense demonstrate an intensification of LPO accompanied by an increase in the non‑enzymatic unit of the antioxidant system, while there is no increase in LPO in females, and the indicators of antioxidant activity change to a lesser extent.

Influence of diabetes mellitus on free radical processes in the heart in rats with Guerin’s carcinoma and characteristics of malignant lesions depending on the gender of animals

To study the intensity of lipid peroxidation (LPO) and the activity of the main antioxidant protection enzyme: superoxide dismutase (SOD) in heart tissues and tumors in rats of both genders with Guerin’s carcinoma (GC) and the tumor growth against the background of diabetes mellitus (DM). Materials and methods. Our research work was carried out in 80 outbread albino male and female rats, divided into 4 groups, with 10 animals of each gender in a group. The animals of two groups, namely, an intact animal group and a group of rats treated with alloxan DM (with a 5-fold increase in glucose levels) were subcutaneously transplanted with the Guerin’s carcinoma (GC) strain cells, and at the same time we used one group of the intact rats and another group of the animals with DM as the references. The content of malondialdehyde (MDA), diene conjugates (DC), and the SOD activity in the heart and the tumor tissues were determined by conventional spectrophotometric methods. Results. The most pronounced changes were found in the heart in the female rats with isolated GC and GC growing against the background of DM: a more than threefold increase in MDA, with a significant increase in DC and a multiple increase in the SOD activity as compared with the intact animals. In the GC tissue, the dependence of the severity of the increase in the MDA content on the size of the tumor was traced: the maximum increase in both parameters was observed in males with GC tumor growing against the background of DM. In the males, the volume of the subcutaneous tumor nodes was 1.8 times greater than that in the reference group and in the females with combined pathology, while in the females with combined pathology the volume of their tumors was 1.3 times less than that in the reference group, although the area of tumor lesions in them was maximum due to extensive metastasizing. Conclusion. DM has changed the specifics of oncogenesis depending on the gender of the animals. The identified gender differences in the redox status of the heart and the tumor in rats with combined pathology contribute to specifics of oncogenesis in males and females and determines their life expectancy.

Metabolic Syndrome Associated with Polycystic Ovary Syndrome in Some Nigerian Women

Background: Polycystic Ovary Syndrome (PCOS) is a group of symptoms associated with endocrine disorders in women of reproductive age. Women with this syndrome is at increased risk of metabolic syndrome. This study described the metabolic syndrome and its associated components among women with PCOS in Nigerian populace. Methods: A total of 90 participants (50 PCOS and 40 controls) were recruited for the study. The diagnosis of PCOS was established using the criteria defined by International PCOS guidelines 2018. Demographic, anthropometric, and clinico-pathological data, including blood pressure, were obtained for each participant. Metabolic syndrome was diagnosed using the 2005 revised National Cholesterol Education Program Adult Treatment Panel-III (revised NCEP ATP_III) guidelines. Fasting blood glucose, insulin, total cholesterol, HDL, LDL, and triglycerides were evaluated with conventional spectrophotometric methods. Results: The prevalence of metabolic syndrome in PCOS women was 24%, with an odds ratio of 5.211, while the prevalence of 5.7% was observed in the control group. The prevalence of central obesity (waist circumference >88cm), FBS ≥100 mg/dl, HDL <50 mg/dl, triglycerides ≥150 mg/dl, and blood pressure ≥130/85 mmHg in PCOS women was 60%, 22%, 54%, 12%, and 20%, respectively. The most frequently observed individual components of metabolic syndrome were increased waist circumference and decreased HDL cholesterol. Conclusion: Metabolic syndrome and its components, especially obesity, are a major risk factor of PCOS in our population. Routine screening and modulating individual contributors of metabolic syndrome may support PCOS management.

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

Purpose of the study. Exploring the erythrocyte glutathione system functioning in patients with gastric cancer in a comparative aspect, depending on tumor histotype and disease prevalence.Patients and methods. The study included 89 patients with gastric cancer, 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 at stage 4. The content of reduced glutathione and the activity of glutathione-dependent enzymes in the erythrocytes of the patients' blood were studied by conventional spectrophotometric methods. Statistical processing of the results was carried out using the Statistika 6.0 software package according to the Student's t-test and the nonparametric Wilcoxon-Mann-Whitney test for two independent samples.Results. An increase in the content of glutathione was revealed in patients with gastric cancer compared with the group without oncopathology. The maximum increase was observed in patients with low-grade adenocarcinoma - by 42.5 %, while in signet ring cell carcinoma (SRCC) there was only a tendency to increase by 17.8 %. Glutathione reductase activity was decreased 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 the T4 status and at stage IV of the process, a lower activity of the studied glutathione-dependent enzymes was revealed in comparison with all other groups of patients.Conclusions. The data obtained indicate a greater functional potential of the glutathione system in SRCC. A significant increase in glutathione transferase activity at a sufficiently high level of reduced glutathione can contribute to the development of treatment resistance in SRCC patients.

Quantification of Silicon in Rice Based on an Electrochemical Sensor via an Amplified Electrocatalytic Strategy.

Silicon plays a very important role in the growth of rice. The study of the relationship between rice and silicon has become a hot area in the last decade. Currently, the silica-molybdenum blue spectrophotometric method is mostly used for the determination of silicon content in rice. However, the results of this method vary greatly due to the different choices of reducing agents, measurement wavelengths and color development times. In this work, we present for the first time an electrochemical sensor for the detection of silicon content in rice. This electrochemical analysis technique not only provides an alternative detection strategy, but also, due to the rapid detection by electrochemical methods and the miniaturization of the instrument, it is suitable for field testing. Methodological construction using electrochemical techniques is a key objective. The silicon in rice was extracted by HF and becomes silica after pH adjustment. The silica was then immobilized onto the glassy carbon surface. These silica nanoparticles provided additional specific surface area for adsorption of sodium borohydride and Ag ions, which in turn formed Ag nanoparticles to fabricate an electrochemical sensor. The proposed electrochemical sensor can be used for indirect measurements of 10–400 mg/L of SiO2, and thus, the method can measure 4.67–186.8 mg/g of silicon. The electrochemical sensor can be used to be comparable with the conventional silicon-molybdenum blue spectrophotometric method. The RSD of the current value was only 3.4% for five sensors. In practical use, 200 samples of glume, leaf, leaf sheath and culm were tested. The results showed that glume had the highest silicon content and culm had the lowest silicon content. The linear correlation coefficients for glume, leaf, leaf sheath and culm were 0.9841, 0.9907, 0.9894 and 0.993, respectively.

Metal nanoparticles based lab-on-paper for phenolic compounds evaluation with no sample pretreatment. Application to extra virgin olive oil samples

In this work, a low-cost, disposable, and portable lab-on-paper device is proposed to simultaneously quantify total polyphenol content (TPC) and antioxidant capacity (AOC) in 15 min; the assay requires no pre-treatment of the samples. The lab-on-paper device fabrication has been carried out employing a xurography-based benchtop microfabrication technology using low-cost materials as chromatography paper and polymeric sheets. Extra virgin olive oil (EVOO) phenolic compounds' represents a nutritional added value, nevertheless, the high lipidic content hinders their direct and rapid analysis, resulting in an extremely challenging sample. The realized lab-on-paper allows to perform the dual TPC and AOC determination in three simple steps: (i) sample loading, (ii) analytes transport to the analysis spot, and (iii) double colorimetric analysis exploiting the growth of AuNPs and AgNPs on paper mediated by phenolic compounds. Signal acquisition is achieved using a standard digital camera. The dual colorimetric assay is able to detect phenolic compounds in the 25–500 mg L−1 range with limits of detection ≤6 mg L−1 and good reproducibility (RSDs ≤11%). Direct analysis of EVOO samples (n = 30) correlated well (r > 0.92) with conventional spectrophotometric methods for TPC and AOC determination.

In-vessel headspace liquid-phase microextraction

A new mode of headspace liquid-phase microextraction termed in-vessel headspace liquid-phase microextraction (IV-HS-LPME) has been developed. A plastic vessel was used as a holder for an extraction phase. Problems with drop stability, limitations in the stirring speed, and too little volume of the acceptor phase have been completely eliminated. The proposed approach is fully compatible with ordinary instruments and microcuvettes used in spectrophotometry. The potential of the method was evaluated by determining the iodide concentration in various samples. Iodide in the donor phase was converted to volatile I2 by oxidation with 1 mmol L−1 K2Cr2O7. The reaction mixture was agitated on a magnetic stirrer for 30 min at a stirring speed of 1200 rpm. A 1% (w/v) aqueous solution of KI was used as the acceptor phase. The absorbance of the I3− ion formed in the acceptor phase was measured in a 50 μL microcuvette at 350 nm. For the case of extraction from 10 mL donor solution into 50 μL of acceptor phase, the calibration graph is linear in the range of 20–400 μg L−1 (as I−) with a detection limit of 6 μg L−1. The developed method has a high precision comparable to conventional spectrophotometric methods (0.6–1.5%). The extraction efficiency obtained in the optimal conditions was 10.5%. The distribution constants for equilibria between the donor solution and the headspace and between the headspace and the acceptor solution are 0.8 ± 0.1 and 16 ± 2, respectively. The developed method was successfully applied to determine the iodine content in natural waters, medicines and algae.

Effect of <i>Thymus marschallianus</i> extract on lipid peroxidation processes <i>in vivo</i> and <i>in vitro</i> experiments

BACKGROUND: Currently, fundamental and experimental data confirming the role of free radicals in physiological and pathological processes have been accumulated. The literature describes conflicting information about the effect of antioxidants on the organism: they are able to protect not only normal cells from the alterative effect of free radicals, but also tumor cells, thereby supporting the survival and growth of the latter. Therefore, the study of the effect of Thymus marchallianus extract on the processes of lipoperoxidation in vivo against the background of the tumor process is relevant.
 AIM: To study the effect of Thymus marchallianus extract on the quantity of lipid peroxidation intermediates in the blood plasma of mongrel white rats with liver cancer PC-1 and compare with in vivo antioxidant activity.
 MATERIALS AND METHODS: The object of research was the dried Thymus marchallianus grass. Water and alcohol extracts were used in the experiment. Fifteen male white mongrel rats with a tumor were included in the experiment: the first group was intact, the second group received the water extract of Thymus marchallianus, and the third group received the alcohol extract of Thymus marchallianus. The activity of lipoperoxidation processes was evaluated, the content of intermediate lipid peroxidation intermediates malon dialdehyde, lipid hydroperoxides and medium-mass molecules in the blood plasma of experimental rats were estimated by means of conventional spectrophotometric methods. Determination of the antioxidant activity of the infusion and alcohol extraction in the in vitro experiment was carried out by the titrimetric method.
 RESULTS: In the control groups and the group of animals that received intraperitoneal water and alcohol extracts of Thymus marchallianus, increase in the intermediate products of lipid peroxidation was not revealed. The amount of malon dialdehyde, lipid hydroperoxides and medium-mass molecules in the blood plasma of experimental rats did not differ significantly from the level of similar indicators of intact animals. In the in vitro experiment, water and alcohol extracts from raw Thymus marchallianus showed antioxidant activity.
 CONCLUSIONS: For the first time, the experiment was conducted to study the effect of water and water-alcohol extracts of Thymus marchallianus on lipoperoxidation processes in mongrel white rats with alveolar liver cancer PC-1. The activity of formation of intermediate products of lipid peroxidation did not change, since their content in the blood plasma of experimental animals did not differ from the level of similar indicators of intact animals. In vitro the infusion and alcohol extract demonstrated antioxidant activity.

Development of a Digital Microscope Spectrophotometric System for Determination of the Antioxidant Activity and Total Phenolic Content in Teas

This work presents a simple, low cost, and portable spectrophotometer based on a digital microscope as a detector for the determination of the antioxidant activity and total phenolic content (TPC). The antioxidant activity was expressed as ascorbic acid equivalents (AAE) using the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) assay. The TPC value was measured using the Folin-Ciocalteu method. The color of the products was captured using a digital microscope powered through the USB output of a laptop. A digital microscope, held in a 3D printing device was used to take photos of the reaction product that was illuminated with the stable light source of the digital microscope. The pictures were analyzed for quantitation. For the DPPH assay, the developed method provided a working range from 0.6 to 6 mg L−1 of ascorbic acid with a limit of detection (LOD) of 0.2 mg L−1 and a relative standard deviation (RSD) of 2.2%. The TPC method provided a working range from 4.6 to 100 mg L−1 for gallic acid, with a LOD of 1.4 mg L−1 and a RSD of 1.3%. Results of the proposed system agree well with a conventional spectrophotometric method and have been successfully applied to measure the antioxidant activity and TPC of local Thai tea samples.