An innovative thermally reduced graphene (TRG) modified silica-supported 3-aminopropyltriethoxysilane (SiO2-APTES) composite was synthesized and characterized using Fourier transform-infrared ...spectroscopy (FT-IR) and scanning electron microscopy SEM techniques. The adsorbent was then used in the solid phase extraction (SPE) of Cr (VI) as the Cr (VI)-diphenylcarbazide (DPC) complex with the subsequent measurement by UV–vis spectrophotometry. The adsorbent surface was activated by adding sodium dodecyl sulfate (SDS) to the sample solution. The effect of the main experimental parameters such as type and volume of the extraction solvent, pH, dosage of DPC, SDS, the adsorbent, time of the extraction, and salt concentration on the extraction efficiency were investigated and optimized. A linear dynamic range of 1.3-40ngmL−1 with a satisfactory determination coefficient (R2) of 0.9930 was obtained. A detection limit of 0.4ngmL−1 Cr (VI) was attained when a sample volume of 25mL was used. Intraday and inter-day precisions were obtained equal to 2.3% and 7.9%, respectively. The enrichment factor (EF) was calculated to be equal to 167. The technique was applied successfully to the determination of Cr (VI) at trace levels in tap, river, sewage and ground water samples and the relative recoveries of the added chromium were in the range of 92.6–109.9%.
Schematic of the TRG modified SiO2 solid phase extraction process
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•A new adsorbent for SPE and determination of Cr(VI) at trace levels was applied.•The sensitivity was higher compared with other SPE methods for Cr(VI) detection.•Selectivity of detection was improved for Cr (VI) using diphenylcarbazide ligand.•High EF with lower initial sample volume compared with other studies was achieved.
•Spectrophotometric assays to assess the major phenolic classes were discussed.•Chemical reactions, pros and cons of these quantitative methods were debated.•A criticism was made on some methods that ...tentatively estimate the content of phenolics, o-diphenols, flavonoids, anthocyanins, flavonols, flavanols.•Experimental protocols for determination of those phenolic classes were described in details.
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Consumers have sought for functional foods aiming to decrease the risk of various non-communicable diseases, such as diabetes, hypertension, overweight/obesity and principal cardiovascular diseases. Epidemiological and clinical studies are continuously corroborating the fact that individuals with higher intake of (poly)phenolic compounds present lower risk of incidence of non-communicable diseases, especially those related to the cardiovascular system. In this sense, food companies and regulatory health agencies together with academic bodies are investing in analytical methods to screen and typify the phenolic content of food extracts and beverages. In this scenario, this review focuses on the chemical perspective of some methods used to assess the total content of phenolic compounds, flavonoids, anthocyanins, ortho-diphenols, flavonols, and tannins (flavanols), by UV-Vis spectrophotometry, giving emphasis on the structures, reactions, overall positive aspects and limitations of the most used quantitative assays.
This article presents a new and sensitive method for the determination of trace amounts of fungicide carbendazim by dispersive liquid–liquid microextraction (DLLME) combined with UV–vis ...spectrophotometry. The method is based on the reduction of Fe(III) to Fe(II) by carbendazim, its reaction with potassium ferricynide to form a blue product and extraction into CCL4 by DLLME technique using methyltrioctylammonium chloride (Aliquat 336) as a disperser agent. Under the established optimum conditions, the calibration graph was linear in the range of 5–600ngmL−1 of carbendazim with a limit of detection of 2.1ngmL−1. The relative standard deviations for eight replicate determinations of 50 and 300ngmL−1 of carbendazim were 3.9% and 1.0%, respectively. The proposed method was successfully applied to determination of carbendazim in soil and water samples.
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•A new dispersive liquid-liquid microextraction method for fungicide carbendazim.•First combination of preconcentration and spectrophotometric method for carbendazim.•Micro-volume UV–vis spectrophotometric was used for the detection of carbendazim.•Methyltrioctylammonium chloride (Aliquat 336) was used as a disperser agent.•The method was applied to determination of carbendazim in soil and water samples.
This study presents an original nano-sorbent using activated nanodiamonds@Bi2WO6 to separate and enrich nickel ions from water and food samples. FTIR, XRD, FE-SEM, FE-SEM-EDX, EDS-TEAM, TGA, and BET ...were used to characterize the nanocomposite. It has a large surface area, active functional groups, and better reactivity. Ni(II) ions were determined as Ni(II)-PADAP chelates using UV-VIS spectroscopy. The parameters were studied and optimized, including pH (6), eluent type and volume (1 mL), ligand quantity (10 μg), sorbent dosage (20 mg), and contact time (1 min). The method has a low limit of detection (LOD) of 1.6 μg L−1, a limit of quantification (LOQ) of 5.3 μg L−1, a relative standard deviation of 4.5%, and a preconcentration factor of 10. The method was validated by applying to certified reference materials (BCR estuarine water 505 and 1573a NIST). The method was successfully applied to tap waters, industrial waste waters, and vegetables.
•A novel nanocomposite (activated nanodiamonds@Bi2WO6) was synthesized and characterized.•It was used for Ni(II) extraction as Ni(II)-PADAP chelates from water and food samples.•Achieved low LOD (1.6 μg L−1) and LOQ (5.3 μg L−1) using a UV-VIS spectrophotometer without any interference from other ions.•Recovery rates in water samples are within an acceptable range.•This method is a valuable contribution to Ni(II) separation-preconcentration research.
The major bioactive component of black pepper (
) is piperine which has demonstrated beneficial therapeutic properties. The purpose of this research was to investigate the effects of different ...irradiation doses on the content of piperine in black pepper. Samples were irradiated with
Co γ-rays (at absorbed doses of 0.5, 1, 3, 5, 7, 10, and 12 kGy). Thin-layer chromatography (TLC) and UV–Vis spectrophotometry methods were used for measuring the piperine content in the samples. TLC was performed using three mobile phases (1. toluene:ethyl acetate, 7:3 v/v; 2. acetone:
-hexane, 6:4 v/v; 3. toluene:methanol, 8.5:1.5 v/v) and the retention factor (
) value for piperine was equal to 0.66, 0.94, and 0.67, respectively. The content of piperine in γ-irradiated samples of black pepper was found to be between 0.04 and 1.05% w/w from the spectrophotometry analyses. Irradiation slightly decreased the piperine content of black pepper. It was found that piperine crude yield from black pepper was from 1.10 (the unirradiated sample) to 1.69, 1.07, 0.60, 0.90, 0.30, 1.20, 0.80% for irradiated samples, respectively. Microbiological analyses were performed with standard plate count method, which resulted in a decreasing number of the total cell count of microbial cells with increasing the radiation dose. Treatment with irradiation reduced the population of bacteria by 4 logs.
•Data fusion of three instrumental techniques to classify virgin olive oils.•Objective instrumental analysis to distinguish different categories of virgin olive oils.•PLS-DA models are used to ...discriminate the samples based on the presence of sensory defects.
Three instrumental techniques, headspace-mass spectrometry (HS-MS), mid-infrared spectroscopy (MIR) and UV–visible spectrophotometry (UV–vis), have been combined to classify virgin olive oil samples based on the presence or absence of sensory defects. The reference sensory values were provided by an official taste panel. Different data fusion strategies were studied to improve the discrimination capability compared to using each instrumental technique individually. A general model was applied to discriminate high-quality non-defective olive oils (extra-virgin) and the lowest-quality olive oils considered non-edible (lampante). A specific identification of key off-flavours, such as musty, winey, fusty and rancid, was also studied. The data fusion of the three techniques improved the classification results in most of the cases. Low-level data fusion was the best strategy to discriminate musty, winey and fusty defects, using HS-MS, MIR and UV–vis, and the rancid defect using only HS-MS and MIR. The mid-level data fusion approach using partial least squares-discriminant analysis (PLS-DA) scores was found to be the best strategy for defective vs non-defective and edible vs non-edible oil discrimination. However, the data fusion did not sufficiently improve the results obtained by a single technique (HS-MS) to classify non-defective classes. These results indicate that instrumental data fusion can be useful for the identification of sensory defects in virgin olive oils.
In this work, a method based on UV–VIS spectrophotometry using the molybdenum blue reaction is described to monitor hypophosphite and phosphite levels in nickel electroless baths. Nickel is one of ...the most employed metals in the electroless coating industry and during the deposition process the metal is reduced from Ni (II) to Ni (0). Hypophosphite is a widely employed reducing agent, which is oxidized to phosphite. Therefore, the hypophosphite concentration should be monitored in order to replenish the bath while it is being consumed maintaining an optimum concentration in order to guarantee the desired coating. Phosphite, which could interfere with the coating process, must be monitored to ensure it does not exceed a certain concentration after which the bath stops working. Although iodometric titrations are the most commonly used methods to control hypophosphite and phosphite concentrations, these are time- and reagent-consuming. Thus, with the aim of developing a more appropriate methodology a colorimetric determination was carried out in this work. In certain conditions, the hypophosphite reacts with molybdenum, giving rise to a blue compound that can be measured between 390 and 1100 nm. The phosphite presence modifies the obtained spectra and that effect allows individual Partial Least Square (PLS) models to be built for each analyte. In this study, the calibration, cross-validation and external prediction relative error were always lower than 8 %, and the relative standard deviation lower than 12 %. The models were applied to real samples from two different nickel electroless baths, and the results were compared and validated using ion chromatography (IC). No significant differences were observed between the proposed and the reference methods for either of the two analytes. Therefore, the colorimetric method could be an improvement over the methods currently used for the control of the two anions in coating baths in term of saving time, money and reagents, making the coating process more efficient.
•Hypophosphite and phosphite simultaneously determined in nickel electroless baths•The UV–Vis spectrophotometry method is an excellent alternative to titrations.•Development of an easily automatable method for electroplating industry•Improvement on NiP bath monitoring in order to upgrade the coating quality
This study introduces a novel group of acridinium salts, specifically 10-methyl-9-((phenylthio)carbonyl)acridin-10-ium trifluoromethanesulphonates (ATEs), which are the sulphur analogues of widely ...used acridinium esters in bioanalytics. We conducted comprehensive experimental and theoretical studies on the chemiluminescence (CL) properties of these ATEs, including emission efficiency and kinetics in various liquid environments. These findings provide insights into the unique chemiluminescence behaviour of ATEs and pave the way for their potential applications in luminometric assays.
All ATE compounds, regardless of the type and location of the substituent, exhibit an effective flash-type emission. The 2-methoxy and 4-nitro-substituted derivatives demonstrated the highest effectiveness in an organic environment (dimethylsulfoxide, ethanol). We further evaluated the analytical usefulness of selected ATEs by studying their interactions with biological antioxidants (AOs) in aqueous systems. These interactions were found to reduce the emission capability of CL in proportion to the AO concentration in the system. The linearity ranges of AO analyses were within the range 10−9–10−6 M, with detection limits at the level of 10−7 M. Quantum chemical (DFT) calculations on the thermodynamics and kinetics of ATE chemiluminescence disclosed that they are highly susceptible to nucleophilic addition of the OOH− ion, initiating the CL process. They also demonstrated the thermodynamic feasibility of producing specific adducts of the ATE-AO type. The above results were supported by differential UV–Vis spectroscopy measurements, which revealed the formation of new bands around 370 nm, attributed to the formation of the adducts mentioned above.
The presented work describes the first characteristics of chemiluminogenic acridinium thioesters and draws perspectives on their practical uses in the analytics of biological substances. These findings also contribute to our understanding of the reactivity of ATEs in solutions accompanied by light emission.
•Synthesis and spectroscopic features of new chemiluminogenic salts, acridinium thioesters (ATEs), are reported.•The efficiency and kinetics of chemiluminescence of ATEs were evaluated in various liquid environments containing H2O2/KOH.•Usefulness of the new family of compounds was demonstrated in luminescence analysis of biological antioxidants (AOs).•DFT studies indicated the mechanism of CL with the formation of ATE-AO adducts.•Differential UV–Vis spectroscopy proved the formation of ATE-AO adducts.
•The selectivity of the iron detection can be greatly enhanced at wavelength 740nm.•The present method has a good sensitivity with a detection limit of 1.5μgL−1.•The present method has a wider linear ...range in compared with other method reported.•The UV–vis detection with DLLME for Fe is simple, rapid and economical.
A novel microvolume UV–vis spectrophotometry method was proposed for the rapid determination of total iron coupling with an efficient pretreatment method known as dispersive liquid–liquid microextraction (DLLME). The basis of the method is a quantitative colorimetric reaction between ferrous iron and 2-(5-bromo-2-pyridylazo)-5-(diethyl amino) phenol (5-Br-PADAP) after the reduction of Fe(III) to Fe(II) by using ascorbic acid as reducing agent. Parameters related to the efficiency of microextraction, such as pH, complexant concentration, the volume ratio of disperser solvent and extraction solvent were discussed and optimized in detail. Under the optimized conditions, the absorbance was in proportion to iron concentration in the range of 5–400μgL−1 with a correlation coefficient (R) of 0.9993. The limit of detection (LOD) and limit of quantitation (LOQ) were 1.5μgL−1 and 5.2μgL−1, respectively. The relative standard deviation (RSD) for samples were 1.37– 4.42% (n=3). Good recoveries of iron were obtained in the range of 95.4–103.2% in food samples, 96.9–103.6% in water samples and 98.8–102.3% in Certified Reference Material. The proposed method was rapid, reliable and high-selective for the determination of total iron in food and water samples.
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