One-step microwave-assisted synthesis of fluorescent carbon quantum dots for determination of ascorbic acid and riboflavin in vitamin supplements.

The synthesis of carbon quantum dots (CQDs) using chemical precursors with different organic groups is a strategy to improve optical properties and expand applications in several fields of research such as Analytical Chemistry. Ascorbic acid and riboflavin are widely used in human food supplementation, making quality monitoring of these vitamin supplements relevant and necessary. In this work, disodium ethylenediaminetetraacetic, sodium thiosulfate and urea were applied to obtain CQDs through a single-step microwave-assisted synthesis. The CQDs were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray powder diffraction, infrared spectroscopy, zeta potential measurements, ultraviolet-visible spectroscopy and photoluminescence spectroscopy. The synthesized nanoparticles exhibited satisfactory and stable optical properties with luminescence at 430 nm, water solubility, and fluorescence quantum yield of 8.9 %. They were applied in the quantification of ascorbic acid and riboflavin in vitamin supplements. The fluorescence mechanisms observed were dynamic quenching for the CQDs/Cr(VI) sensor, followed by a return of fluorescence in the presence of ascorbic acid, and static quenching and inner filter effect in the interaction with riboflavin. Factorial designs 23 and 24 were used to optimize the analytical parameters. The CQDs/Cr(VI) sensor used in the determination of ascorbic acid, employing an on-off-on strategy, resulted in a linear range of 0.5 to 50 µg mL-1 and a limit of detection of 0.15 µg mL-1. The ratiometric fluorescence used in the determination of riboflavin resulted in a linear range of 0.1 to 7 µg mL-1 and a limit of detection of 0.09 µg mL-1. The analytical results for ascorbic acid were compared to the reference method of the Brazilian pharmacopeia, showing accuracy and precision according to the Brazilian Health Regulation Agency. Therefore, the synthesized CQDs were used to determine ascorbic acid and riboflavin in vitamin supplements, and the application of this nanomaterial can be expanded to different analytes and matrices, using simple and low-cost analysis techniques.

Exposure to Bisphenol F and Bisphenol S during development induces autism-like endophenotypes in adult Drosophila melanogaster.

Bisphenol F (BPF) and Bisphenol S (BPS) are being widely used by the industry with the claim of "safer substances", even with the scarcity of toxicological studies. Given the etiological gap of autism spectrum disorder (ASD), the environment may be a causal factor, so we investigated whether exposure to BPF and BPS during the developmental period can induce ASD-like modeling in adult flies. Drosophila melanogaster flies were exposed during development (embryonic and larval period) to concentrations of 0.25, 0.5, and 1 mM of BPF and BPS, separately inserted into the food. When they transformed into pupae were transferred to a standard diet, ensuring that the flies (adult stage) did not have contact with bisphenols. Thus, after hatching, consolidated behavioral tests were carried out for studies with ASD-type models in flies. It was observed that 1 mM BPF and BPS caused hyperactivity (evidenced by open-field test, negative geotaxis, increased aggressiveness and reproduction of repetitive behaviors). The flies belonging to the 1 mM groups of BPF and BPS also showed reduced cognitive capacity, elucidated by the learning behavior through aversive stimulus. Within the population dynamics that flies exposed to 1 mM BPF and 0.5 and 1 mM BPS showed a change in social interaction, remaining more distant from each other. Exposure to 1 mM BPF, 0.5 and 1 mM BPS increased brain size and reduced Shank immunoreactivity of adult flies. These findings complement each other and show that exposure to BPF and BPS during the development period can elucidate a model with endophenotypes similar to ASD in adult flies. Furthermore, when analyzing comparatively, BPS demonstrated a greater potential for damage when compared to BPF. Therefore, in general these data sets contradict the idea that these substances can be used freely.

The Amazonian Camu-Camu Fruit Modulates the Development of Drosophila melanogaster and the Neural Function of Adult Flies under Oxidative Stress Conditions.

Camu-camu (Myrciaria dubia) is known for its antioxidant properties, although little is known about its developmental safety effects, particularly on adult neural function under basal redox and oxidative stress conditions. Therefore, this study sought to address this gap by conducting three complementary protocols using Drosophila melanogaster to investigate these effects. The initial assays revealed that second-stage larvae consumed diets supplemented with various concentrations of camu-camu uniformly, establishing a 50% lethal concentration at 4.799 mg/mL. Hence, non-lethal (0.1, 0.5, and 1 mg/mL) and sub-lethal (5 and 10 mg/mL) concentrations were then chosen to evaluate the effects of camu-camu on preimaginal development and adult neural function. Our observations showed that camu-camu impacts the expression of antioxidant enzymes, reactive species, and lipoperoxidation. Notably, sub-lethal concentrations decreased preimaginal viability and locomotor activity, negatively influenced geotaxis and acetylcholinesterase activity, and increased reactive species, catalase, and glutathione S-transferase activity in flies. Additionally, the protective effects of camu-camu against oxidative stress induced by iron (20 mM) were assessed. Flies supplemented with 0.5 mg/mL of camu-camu during the larval period showed improved neural viability and function, and this supplementation was found to protect against oxidative stress. These findings are instrumental in evaluating the safety and efficacy of commercial supplements based on camu-camu, offering significant insights for future research and application.

Video-based fractional order identification of diffusion dynamics for the analysis of migration rates of polar and nonpolar liquids: Water and oil studies.

Diffusion dynamics of water and oil are observed in real-time using video images. Savitzky-Golay derivative filtering ensures accurate localization of the liquid front. System identification demonstrates that a fractional-order model with only two parameters may be used to describe the dynamics of the diffusion process. The method paves the way for video-based cellulose filter paper microfluidics and lateral flow assays, which are low cost and have broad diagnostic applications.

Synthesis of highly fluorescent carbon dots from lemon and onion juices for determination of riboflavin in multivitamin/mineral supplements.

In this work, lemon and onion biomasses commonly found in street markets are for the first time used to develop a facile, fast and low-cost one-step microwave-assisted carbonization method for synthesis of highly fluorescent carbon dots (CDs). The structure and optical properties of CDs were investigated by TEM, XRD, XRF, UV-Vis, FTIR, and fluorescence spectroscopy. CDs displayed satisfactory optical proprieties, a high quantum yield of 23.6%, and excellent water solubility, and the particle size was 4.23-8.22 nm with an average diameter of 6.15 nm. An efficient fluorescent resonance energy transfer (FRET) between the CDs and riboflavin was achieved with CDs acting as donor and riboflavin as acceptor. A linear relationship between FRET and the riboflavin concentration from 0.10 to 3.0 µg/mL was observed, allowing the development of an accurate and fast analytical method to determine this vitamin in multivitamin/mineral supplements. Despite the potential interferences in these supplements, CDs were selective for riboflavin under optimized conditions. A paired t-test at a 95% confidence level indicated no statistically significant difference between the proposed and the reference methods. Recovery test presented values ranged from 96.0% to 101.4%. The limit of detection and relative standard deviation were estimated at 1.0 ng/mL and <2.6% (n = 3), respectively. CDs were successfully synthesized in a domestic microwave oven (1450 W, 6 min), presenting satisfactory parameters when compared with results of other studies reported in the literature, suggesting that the proposed method is a potentially useful method for the synthesis of CDs and determination of riboflavin.

A robotic magnetic nanoparticle solid phase extraction system coupled to flow-batch analyzer and GFAAS for determination of trace cadmium in edible oils without external pretreatment.

A lab-made magnetic-mechanical robotic (MMR) system coupled to a flow-batch analyzer (FBA) for magnetic nanoparticles solid phase extraction (MSPE) is presented. As an illustrative application, an NMR-FBA couple was connected to a graphite furnace atomic absorption spectrometer (GFAAS) for quantification of trace cadmium in edible oils. Factors affecting MSPE, such as the amount of adsorbent, the type, concentration and volume of the eluent and elution time were studied. Under the optimized experimental conditions, the interferents studied did not reveal a significant change in the analytical response, indicating that proposed method is selective. The sampling rate, characteristic mass, working linear range, limits of detection (LOD), and sensitivity were 10h-1, 0.18pg, 0.05-1.0µgkg-1, 0.006µgL-1, and 0.4197, respectively. An enrichment factor of 9 was achieved using a 2.5mL oil sample. In order to evaluate the accuracy, a certified reference material was analyzed by the proposed and a reference method. The values obtained were compared with the one provided from the manufacturer and no statistically significant differences were observed among three values at a confidence level of 95% using paired t-test. In addition, the precision intra-day and inter day of the proposed method and the robustness were assessed and again no statistically significant differences were observed at a confidence level of 95%. The use of a microcolumn to immobilize the MNPs is not needed with the proposed MMR-FBA-GFAAS system, thus avoiding the well-known problem of non-uniform packing of the MNPs presented in previous flow-based automatic methods. Despite a high organic load of edible oils, the method developed is simple, robust and presents satisfactory analytical features when compared with others that have been reported in the literature, suggesting that it is a potentially useful alternative to determine trace analytes in viscous matrices without external pretreatment.

A micro-flow-batch analyzer with solenoid micro-pumps for the photometric determination of iodate in table salt.

In this study, a micro-flow-batch analyzer (µFBA) with solenoid micro-pumps for the photometric determination of iodate in table salt is described. The method is based on the reaction of iodate with iodide to form molecular iodine followed by the reaction with N,N-diethyl-p-phenylenediamine (DPD). The analytical signal was measured at 520 nm using a green LED integrated into the µFBA built in the urethane-acrylate resin. The analytical curve for iodate was linear in the range of 0.01-10.0 mg L(-1) with a correlation coefficient of 0.997. The limit of detection and relative standard deviation were estimated at 0.004 mg L(-1) and<1.5% (n=3), respectively. The accuracy was assessed through recovery test (97.6-103.5%) and independent analysis by a conventional titrimetric method. Comparing this technique with the conventional method, no statistically significant differences were observed when applying the paired t-test at a 95% confidence level. The proposed microsystem using solenoid micro-pumps presented satisfactory robustness and high sampling rate (170 h(-1)), with a low reagents consumption and a low cost to build the device. The proposed microsystem is a new alternative for automatic determination of iodate in table salt, comparing satisfactory to the recently flow system.

Photometric determination of phosphorus in mineralized biodiesel using a micro-flow-batch analyzer with solenoid micro-pumps.

A method for the determination of phosphorus in mineralized biodiesel using a micro-flow-batch analyzer (µFBA) with solenoid micro-pumps was proposed. The samples were mineralized using an ashing procedure at 550 °C followed by dissolution of the residue. The determination of phosphorus was performed by employing the well-known molybdenum blue method. The measures of the absorbance were performed at 850 nm using an InfraRed LED integrated into the µFBA. Comparing with the reference method, no statistically significant differences were observed when applying the paired t-test at a 95% confidence level. Recovery study shows results between 97.9% and 105.8%. The proposed microsystem using solenoid micro-pumps presented satisfactory robustness and high sampling rate (190 h(-1)), with satisfactory reproducibility (relative standard deviation <4.5%, n=3), low reagents consumption (32 µL per analysis) and cost to build the device. Moreover, µFBA presents limit of detection (0.014 mg Kg(-1)), precision and accuracy compatible with the biodiesel regulations that establish a maximum concentration of 10 mg Kg(-1) (Brazil, USA, EU), suggesting that it is a good alternative for the determination of phosphorus in biodiesel.

A monosegmented flow-batch system for slow reaction kinetics: spectrophotometric determination of boron in plants.

This work introduces the monosegmented flow-batch (MSFB) analysis concept. This system combines favourable characteristics of both flow-batch and the monosegmented analysers, allowing use of the flow-batch system for slow reaction kinetics without impairing sensitivity or sampling throughput. The MSFB was evaluated during spectrophotometric determination of boron in plant extracts, which is a method that involves a slow reaction between boron and azomethine-H. All calibration solutions were prepared in-line, and all analytical processes completed by simply changing the operational parameters in the MSFB control software. The limit of detection was estimated at 0.008 mg L(-1). The measurements could be performed at a rate of 120 samples per hour with satisfactory precision. The proposed MSFB was successfully applied to analyse 10 plant samples and the results are in agreement with the reference method at a 95% level of confidence.

Turbidimetric and photometric determination of total tannins in tea using a micro-flow-batch analyzer.

Both turbidimetric and photometric determinations of total tannins in samples of green and black tea, using a micro-flow-batch analyzer (µFBA) were studied. The miniaturized system was formed using photocurable urethane-acrylate resin and ultraviolet lithography technique. The turbidimetric method was based on the precipitation reaction of Cu (II) with tannins in acetate medium at a pH of 4.5. The photometric method was based on the complexation reaction of tannins with ferrous tartrate. The turbidimetric µFBA was able to test 200 samples per hour. The photometric µFBA allowed 300 analyses per hour, generating 136µL of residue per analysis. The paired t test, at a 95% confidence level, showed no statistically significant differences between results obtained by both methods and the reference method. The urethane-acrylate µFBA maintained satisfactory physical and chemical properties, and represents an improvement over conventional flow-batch analyzer.

Flow-batch miniaturization.

This study introduces the first micro-flow-batch analyzer (µFBA). A simple, low-cost, deep urethane-acrylate photo-resist ultraviolet-lithographic technique was used in its development. Details of the microfabrication process are presented including; the use of two superimposed photo-masks to improve the micro-channel and stop chamber border definition, as well as integration of an LED/phototransistor photometric pair, while using an open nylon-thread (fishing line) micro-mixing system for solutions homogenization. The system was used for photometric determination of Fe(II) in oral solution iron supplements employing the well-known 1,10-phenanthroline method, with instantaneously prepared micro-chamber calibration solutions. All analytical processes were accomplished by simply changing the timing parameters in the control software. It must be emphasized here that there was no outside preparation of the standard calibration solutions; the mixing was all done in-chamber/in-line, with all solutions maintained flowing while being proportioned for the measurement processes. The µFBA results were acceptable when compared to the reference method, and comparable to normal flow-batch systems. It was possible both to project and build a low-cost probe with high sample throughput (about 120 h(-1)), low relative standard deviations (about 1.1%), and reduced reagent consumption (30 times less than the reference method). The µFBA system based on urethane-acrylate presented satisfactory physical and chemical properties while keeping the flexibility, versatility, robustness, and multi-task characteristics of normal flow-batch analyzers. The µFBA system contributes to the advance of micro-analytical instrumentation, while realizing the basic principles of "Green Chemistry".

A digital image-based method for determining of total acidity in red wines using acid-base titration without indicator.

This work proposes the use of digital image-based method for determination of total acidity in red wines by means of acid-base titration without using an external indicator or any pre-treatment of the sample. Digital images present the colour of the emergent radiation which is complementary to the radiation absorbed by anthocyanines present in wines. Anthocyanines change colour depending on the pH of the medium, and from the variation of colour in the images obtained during titration, the end point can be localized with accuracy and precision. RGB-based values were employed to build titration curves, and end points were localized by second derivative curves. The official method recommends potentiometric titration with a NaOH standard solution, and sample dilution until the pH reaches 8.2-8.4. In order to illustrate the feasibility of the proposed method, titrations of ten red wines were carried out. Results were compared with the reference method, and no statistically significant difference was observed between the results by applying the paired t-test at the 95% confidence level. The proposed method yielded more precise results than the official method. This is due to the trivariate nature of the measurements (RGB), associated with digital images.

A modification of the successive projections algorithm for spectral variable selection in the presence of unknown interferents.

This work proposes a modification to the successive projections algorithm (SPA) aimed at selecting spectral variables for multiple linear regression (MLR) in the presence of unknown interferents not included in the calibration data set. The modified algorithm favours the selection of variables in which the effect of the interferent is less pronounced. The proposed procedure can be regarded as an adaptive modelling technique, because the spectral features of the samples to be analyzed are considered in the variable selection process. The advantages of this new approach are demonstrated in two analytical problems, namely (1) ultraviolet-visible spectrometric determination of tartrazine, allure red and sunset yellow in aqueous solutions under the interference of erythrosine, and (2) near-infrared spectrometric determination of ethanol in gasoline under the interference of toluene. In these case studies, the performance of conventional MLR-SPA models is substantially degraded by the presence of the interferent. This problem is circumvented by applying the proposed Adaptive MLR-SPA approach, which results in prediction errors smaller than those obtained by three other multivariate calibration techniques, namely stepwise regression, full-spectrum partial-least-squares (PLS) and PLS with variables selected by a genetic algorithm. An inspection of the variable selection results reveals that the Adaptive approach successfully avoids spectral regions in which the interference is more intense.