RESUMO
Chlorine is a common disinfectant used in water treatment. However, its reaction with organic matter can lead to the formation of harmful byproducts, such as trihalomethanes (THMs), which are potentially carcinogenic. To address this issue, the aim of this work was to enhance a colorimetric method capable of quantifying THMs in drinking water through UV/Vis Spectrophotometry, using cost-effective equipment, and validate this methodology for the first time according to established validation protocols. The method's innovation involved replacing the solvent pentane with the more common hexane, along with adjusting the heating ramp, elucidating the mechanisms involved in the process. This method involves the reaction between THMs, pyridine, and NaOH to produce a colored compound, which is then monitored through molecular absorption spectroscopy in the visible region. The method was thoroughly validated, achieving a limit of detection of 13.41 µg L-1 and a limit of quantification of 40.65 µg L-1. Recovery assays ranged from 86.1 % to 90.7 %, demonstrating high accuracy. The quality of the linear fit for the analytical curve exceeded R2 > 0.98. The method was applied to real samples, revealing concentrations ranging from 13.58 to 55.46 µg L-1, all way below the legal limit in Brazil (Maximum Contaminant Levels (MCL) = 100 µg L-1). This cost-effective and straightforward method is suitable for integration into water treatment plant laboratories.
Assuntos
Água Potável , Trialometanos , Poluentes Químicos da Água , Purificação da Água , Trialometanos/análise , Água Potável/análise , Água Potável/química , Purificação da Água/métodos , Poluentes Químicos da Água/análise , Limite de Detecção , Espectrofotometria Ultravioleta/métodos , Reprodutibilidade dos Testes , Colorimetria/métodosRESUMO
α-Bisabolol (α-BIS) is a sesquiterpene alcohol present in chamomile essential oil [Chamomilla recutita (L.) Rauschert]. Despite its numerous pharmacological effects, its pharmacokinetics remain understudied. An analytical method capable of quantifying α-BIS in plasma is crucial to enable pharmacokinetic analysis. Presently, only one study has quantified it using mass spectrometry. Administering α-BIS requires a nanoemulsion for intravenous injection. This study aimed to develop and validate a bioanalytical method using high-performance liquid chromatography with an ultraviolet detector to quantify α-BIS in rat plasma. The method employed acetonitrile and ultrapure water (80:20, v/v) as the mobile phase, with a flow rate of 1 ml/min and concentrations ranging from 465 to 29.625 µg/ml. All US Food and Drug Administration-designated assays were successful, indicating the method's precision, accuracy, sensitivity and linearity in determining α-BIS in rat plasma. The developed nanoemulsion, assessed through dynamic light scattering analysis, the ensemble collection of particles and polydispersity index evaluation, proved safe and effective for intravenous administration. The pharmacokinetic parameters such as volume of distribution, clearance and half-life indicated that α-BIS tends to persist in the body. This study provides a foundation for further research to explore α-BIS's potential pharmaceutical applications in the future.
Assuntos
Emulsões , Sesquiterpenos Monocíclicos , Animais , Cromatografia Líquida de Alta Pressão/métodos , Ratos , Emulsões/química , Reprodutibilidade dos Testes , Sesquiterpenos Monocíclicos/farmacocinética , Sesquiterpenos Monocíclicos/sangue , Sesquiterpenos Monocíclicos/química , Masculino , Projetos Piloto , Modelos Lineares , Limite de Detecção , Sesquiterpenos/farmacocinética , Sesquiterpenos/sangue , Sesquiterpenos/química , Ratos Sprague-Dawley , Espectrofotometria Ultravioleta/métodosRESUMO
Myrcene (ß-myrcene), found in essential oils from plant species such as hops and cannabis, has many advantageous properties, but its use is limited due to volatility and low solubility in water. One way to circumvent these limitations is to encapsulate the essential oils in a polymer matrix. However, these hydrophobic molecules are difficult to quantify when dispersed in water. Seeking to study the release of this terpene in drug release tests from polymeric matrices, this work aimed to develop an easy and cheap UV spectrophotometric method for the quantification of ß-myrcene in aqueous medium. To achieves this goal, samples were prepared in 0.05% (w/v) polysorbate 80 solution, with concentrations of ß-myrcene ranging from 0.01% to 0.1% (v/v), and were analyzed at 226 nm. Each sample was analyzed in triplicate and repeated on three different days, to evaluate the repeatability of the results. The results were subjected to Q, F and Student's t-tests. The regression parameters obtained for ß-myrcene were above 0.99 and through statistical analysis, it was possible to confirm the repeatability for the results. The values of the limits of detection and quantification indicated that the method is not affected by intrinsic factors of the equipment. The results of accuracy, robustness and selectivity showed recovery rates within acceptable limits. This demonstrates that the quantification of ß-myrcene in aqueous medium by UV spectrophotometry is feasible.
Assuntos
Quitosana , Espectrofotometria Ultravioleta , Água , Espectrofotometria Ultravioleta/métodos , Água/química , Quitosana/química , Monoterpenos Acíclicos/análise , Monoterpenos Acíclicos/química , Alcenos/análise , Alcenos/química , Polissorbatos/química , Polissorbatos/análise , Solubilidade , Reprodutibilidade dos Testes , Óleos Voláteis/análise , Óleos Voláteis/químicaRESUMO
BACKGROUND: Marbofloxacin (MAR) is an antimicrobial for veterinary use, and it does not have a monograph in an official compendium for the pharmaceutical form in tablets. OBJECTIVE: In this context, the objective of this work was to develop and validate an effective, eco-friendly, and indicative of stability method by spectrophotometry in the ultraviolet region (UV) for quantitative evaluation of MAR in tablets. METHOD: Purified water-ethanol (80:20, v/v) as a diluent, quartz cubette and 296 nm were used. RESULTS: The method was linear in the range of 3-9 µg/mL (0.9994) with detection and quantification limits of 0.39 and 1.18 µg/mL, respectively, selective in the comparison of standard and sample, precise in intraday (RSD 1.20%), interday (RSD 1.68%), and between analysts (RSD 3.26%) levels, exact with average recovery of 100.39% and robust against small changes in wavelength, diluent concentration, and the use of the ultrasound device. The forced degradation test (sample solutions prepared in 0.1 M HCl, 0.1 M NaOH, and neutral conditions and kept at 60°C during 2 h, and exposure to UV 254 nm lamp at ambient temperature during 2 h) showed that the proposed method is able to assess the susceptibility of MAR. CONCLUSIONS: The method can be reliably applied in routine analysis of MAR in tablets as well as being stable, eco-friendly, effective, accessible, and following the principles of green analytical chemistry. HIGHLIGHTS: MAR, an antimicrobial for veterinary use, does not have a monograph in an official compendium for final product evaluation. The use of MAR-based products with inadequate quality can leave residues in foods of animal origin and can also contribute to microbial resistance. So, an ecologically correct and reliable method was developed to evaluate MAR in a final product.
Assuntos
Antibacterianos , Fluoroquinolonas , Antibacterianos/análise , Excipientes , Reprodutibilidade dos Testes , Espectrofotometria , Espectrofotometria Ultravioleta/métodos , Comprimidos/análiseRESUMO
In this study, a background electrolyte capable to separate and quantify inorganic cations in high ionic strength samples by UV-absorption indirect detection was designed. In this regard, the four most abundant monovalent and divalent cations in earth crust (K+, Na+, Ca+2, Mg+2) were selected as model compounds. A group of small carboxylic acids and, several toluidines and pyridines were evaluated as mild strength complexing agents and chromophoric probes, respectively. The optimized background electrolyte was composed of 200 mM 2,4,6-trimethylpyridine as the chromophoric probe, 250 mM lactic acid as the weak complexing agent and pH buffering reagent (adjusted to pH 4.5), and 5% v/v methanol as organic solvent modifier. Based on a minimum number of components, it provided outstanding separation performance in less than 4 min in a wide linear dynamic range (10 - 2500 µg·mL-1). Performances were contrasted against a reference method based on conductometric detection. Furthermore, studies of separation efficiency and peak shape were carried out at different analyte concentrations in high electric conductivity solutions. The herein developed method demonstrated exceptional features in terms of limits of detection (~10 µg·mL-1), resolution, speed of analysis, sensitivity and peak capacity in high electric conductivity samples. Moreover, the method was successfully applied to high ionic strength samples such as rock digest, sea water, soy sauce and isotonic drinks.
Assuntos
Cátions/análise , Eletrólitos/química , Eletroforese Capilar/métodos , Espectrofotometria Ultravioleta/métodos , Ácido Láctico/química , Limite de Detecção , Metanol/química , Concentração Osmolar , Piridinas/químicaRESUMO
This work exploits the applicability of a chemically reduced graphene oxide (CRGO) modification on the electrochemical response of a glassy carbon electrode (GCE) for the first-time sensitive determination of furosemide in natural waters. The batch injection analysis (BIA) is proposed as an analytical method, where CRGO-GCE is coupled to a BIA cell for amperometric measurements. Acetate buffer (0.1 µmol L-1, pH 5.2) was used as the background electrolyte. The modification provided an increase in sensitivity (0.024 µA/µmol L-1), low limit of detection (0.7 µmol L-1), RSD (< 4%), and broad linear range (1-600 µmol L-1). Recovery tests performed in two different concentration ranges resulted in values between 89 and 99%. Recovery tests were performed and compared with high-performance liquid chromatography (HPLC) with UV-Vis detection using Student's t test at a 95% significance level, and no significant differences were found, confirming the accuracy of the method. The developed method is proven faster (169 h-1) compared with the HPLC analysis (5 h-1), also comparable with other flow procedures hereby described, offering a low-cost strategy suitable to quantify an emerging pharmaceutical pollutant. Graphical abstract.
Assuntos
Carbono/química , Diuréticos/análise , Técnicas Eletroquímicas/métodos , Eletrodos , Furosemida/análise , Grafite/química , Poluentes Químicos da Água/análise , Cromatografia Líquida de Alta Pressão/métodos , Limite de Detecção , Oxirredução , Reprodutibilidade dos Testes , Espectrofotometria Ultravioleta/métodosRESUMO
The azo dyes, Yellow 5 (Y5), Red 2 (R2) and Blue 1 (B1), quantified in solutions and in mixtures of binary dyes, were studied by means of UV-Vis spectroscopy. In this work was used a CIE algorithm developed in Visual Basic for Applications (VBA). The CIE algorithm is based on the tristimulus chromaticity diagram, as an alternative to the shielding effect that arises in dye mixtures, and it can also be applied to complex quantification methods such as HPLC (High Performance Liquid Chromatography). The results obtained through of the algorithm, showed a higher accuracy from 97 to 99% in relation with similar UV-Vis quantification methods. In contrast, linear methods only managed to reach an accuracy from 78 to 98%. Additionally, the algorithm yielded significant similar values to the UHPLC reference method. The results showed that the method CIE algorithm was accessible and reliable to quantify binary mixtures of the dyes used which suggests the possibility to apply this method on other dyes, within the limits of quantification obtained in this study (0.076-24.56 mg/L) and the pH values from 2 to 10.
Assuntos
Compostos Azo/análise , Colorimetria/métodos , Colorimetria/normas , Espectrofotometria Ultravioleta/métodos , Espectrofotometria Ultravioleta/normas , Espectrofotometria/métodos , Espectrofotometria/normas , Algoritmos , Calibragem , Cromatografia Líquida de Alta Pressão , Limite de Detecção , Linguagens de ProgramaçãoRESUMO
Phytochromes are photosensitive proteins with a covalently bound open-chain chromophore that can switch between two principal states: red light absorbing Pr and far-red light absorbing Pfr. Our group has previously shown that the bacteriophytochrome from Xanthomonas campestris pv. campestris (XccBphP) is a bathy-like phytochrome that uses biliverdin IXα as a co-factor and is involved in bacterial virulence. To date, the XccBphP crystal structure could only be solved in the Pr state, while the structure of its Pfr state remains elusive. The aims of this work were to develop an efficient screening methodology for the rapid characterization and to identify XccBphP variants that favor the Pfr form. The screening approach developed here consists in analyzing the UV-Vis absorption behavior of clarified crude extracts containing recombinant phytochromes. This strategy has allowed us to quickly explore over a hundred XccBphP variants, characterize multiple variants and identify Pfr-favored candidates. The high-quality data obtained enabled not only a qualitative, but also a quantitative characterization of their photochemistry. This method could be easily adapted to other phytochromes or other photoreceptor families.
Assuntos
Fotoquímica/métodos , Fitocromo/química , Espectrofotometria Ultravioleta/métodos , Xanthomonas campestris/química , Cristalografia por Raios XRESUMO
Aminoglycosides are a relevant class of antibiotics widely used by medics and veterinaries. There are a variety of reasons that make their determination relevant, such as quality control, environment and food contamination assessment, drug-release studies, among others. The lack of a chromophore makes aminoglycoside spectrophotometric detection particularly challenging, often requiring derivatization. In this work, an indirect detection method, making use of imidazole as a probe, applying CZE was successfully tested. It did not require derivatization, which simplified the sample preparation. Suitable figures of merit were obtained; recoveries between 95 and 105%, adequate repeatability and precision, correlation coefficients (r) above 0.998, and limits of detection (LODs) of 3.2 and 11 mg/L for gentamicin and paromomycin, respectively. As a proof-of-concept, it was also applied in a simple controlled release experiment that was well fitted using the Hill equation.
Assuntos
Aminoglicosídeos/análise , Antibacterianos/química , Eletroforese Capilar/métodos , Espectrofotometria Ultravioleta/métodos , Formas de Dosagem , Imidazóis/química , Limite de Detecção , Modelos Lineares , Reprodutibilidade dos TestesRESUMO
Two analytical methods were developed using electrochemical and spectrometric techniques for the simultaneous determination of endocrine disruptors triclosan and methylparaben in the monitoring of personal care products. For the electroanalytical analyses, a sensitive electrode based on graphene quantum dots supported in chitosan was employed. Under optimized conditions and a working potential of typically + 0.60 V for triclosan and + 0.81 V (vs. Ag/AgCl) for methylparaben, the calibration plots obtained by differential pulse voltammetry were linear in the range 0.10 to 10.0 µmol L-1. The detection limits were 0.03 and 0.04 µmol L-1 for triclosan and methylparaben, respectively. For the spectrometric method, UV/VIS spectrometry was used with a mathematical processing of non-linear deconvolution. This processing was used to solve the problem of overlapping absorption bands of triclosan (282 nm) and methylparaben (257 nm), which enabled simultaneous determination. The calibration plots by UV/VIS spectrometry were linear in the range 1.0 to 14.0 µmol L-1 with detection limits of 0.42 and 0.37 µmol L-1, respectively, for triclosan and methylparaben. Similar results obtained from the calibration plots of individual analytes suggest that the methods can be applied for individual or simultaneous determination of these species. Both methods were employed in the analysis of five samples of personal care products: toothpaste, antiseptic soap, antiseptic deodorant, shampoo, and a bath kit (soap and shampoo). The statistical tests indicated that there were no significant differences regarding the accuracy and precision of the data provided by the two methods described herein. Graphical abstract Schematic representation for simultaneous determination of triclosan and methylparaben: electrochemical method employing an electrode modified with graphene quantum dots supported in chitosan and spectrometric method applying a non-linear deconvolution of spectrum.