A spectrofluorimetric method has been developed for the quantitative determination of mefenamic, flufenamic, and meclofenamic acids in urine samples. The method is based on second-order data multivariate calibration (unfolded partial least squares (unfolded-PLS), multi-way PLS (N-PLS), parallel factor analysis (PARAFAC), self-weighted alternating trilinear decomposition (SWATLD), and bilinear least squares (BLLS)). The analytes were extracted from the urine samples in chloroform prior to the determination. The chloroform extraction was optimized for each analyte, studying the agitation time and the extraction pH, and the optimum values were 10 minutes and pH 3.5, respectively. The concentration ranges in chloroform solution of each of the analytes, used to construct the calibration matrix, were selected in the ranges from 0.15 to 0.8 microg mL-1 for flufenamic and meclofenamic acids and from 0.25 to 3.0 microg mL-1 for mefenamic acid. The combination of chloroform extraction and second-order calibration methods, using the excitation-emission matrices (EEMs) of the three analytes as analytical signals, allowed their simultaneous determination in human urine samples, in the range of approximately 80 mg L-1 to 250 mg L-1, with satisfactory results for all the assayed methods. Improved results over unfolded-PLS and N-PLS were found with PARAFAC, SWATLD, and BLLS, methods that exploit the second-order advantage.
A colorimetric chemosensor CMF (N′‐[(E)‐(4‐oxo‐4H‐chromen‐3‐yl)methylidene]furan‐2‐carbohydrazide) was applied for detecting Cu2+. CMF showed colorimetric selectivity to Cu2+ through a color variation from colorless to yellow. Binding ratio between CMF and Cu2+ was analyzed by Job plot to be a 2:1. Limit of detection was found to be 0.38 μM. The practicality of CMF was illustrated by the quantification of Cu2+ in real samples. In particular, the CMF‐coated test kit was able to detect the copper ions at a concentration lower than the recommended concentration (31.5 μM) of the World Health Organization (WHO) for copper ion. The binding mode of CMF and copper ions was studied through UV–visible spectroscopy, 1H NMR titration, ESI‐mass analysis, and DFT calculations. Sensing mechanism of CMF to Cu2+ was proposed to be the ligand‐to‐metal charge transfer (LMCT) through DFT calculations.
A dinitrophenol-based colorimetric chemosensor sequentially sensing Cu2+ and S2−, HDHT ((E)-2-(2-(2-hydroxy-3,5-dinitrobenzylidene)hydrazineyl)-N,N,N-trimethyl-2-oxoethan-1-aminium), was designed and synthesized. The HDHT selectively detected Cu2+ through a color change of yellow to colorless. The calculated detection limit of the HDHT for Cu2+ was 6.4 × 10−2 μM. In the interference test, the HDHT was not considerably inhibited by various metal ions in its detection of Cu2+. The chelation ratio of the HDHT to Cu2+ was determined as 1:1 by using a Job plot and ESI-MS experiment. In addition, the HDHT–Cu2+ complex showed that its color selectively returned to yellow only in the presence of S2−. The detection limit of the HDHT–Cu2+ complex for S2− was calculated to be 1.2 × 10−1 μM. In the inhibition experiment for S2−, the HDHT–Cu2+ complex did not significantly interfere with other anions. In the real water-sample test, the detection performance of the HDHT for Cu2+ and S2− was successfully examined. The detection features of HDHT for Cu2+ and the HDHT–Cu2+ for S2− were suggested by the Job plot, UV–Vis, ESI-MS, FT-IR spectroscopy, and DFT calculations.
A new spectrofluorimetric method has been developed for the quantification of danofloxacin (DANO) and difloxacin (DIFLO), in the presence of the primary metabolite of difloxacin, with sarafloxacin (SARA) as interference, in chicken tissue samples. The method is based on second-order multivariate calibration, applying parallel factor analysis (PARAFAC), to the excitation-emission matrices (EEMs) of these compounds. High overlapping of the signals and influence of matrix effects were observed. To solve the problem, the standard addition method was used. Chemical variables were optimized. The measured EEMs of the analytes, as analytical signals, allowed their quantification in chicken tissue samples. Solid phase extraction was used for the extraction of the analytes in real samples. The range of concentration examined varied from 30 to 100 ng g(-1) for danofloxacin, and from 100 to 200 ng g(-1) for difloxacin. Both analytes can be analyzed individually, and the binary mixture can be resolved, with recoveries comprising between 88.7 and 106.6%.
We designed a rhodamine B‐based colorimetric chemosensor BHSO ((Z)‐3′,6′‐bis(diethylamino)‐2‐(2‐(((8‐hydroxy‐2,3,6,7‐tetrahydro‐1H,5H‐pyrido[3,2,1‐ij]quinolin‐9‐yl)methylene)amino)ethyl)spiro[isoindoline‐1,9′‐xanthen]‐3‐one) for detecting Cu2+. In the presence of Cu2+, BHSO caused a colour variation from colourless to bright orange. The limit of detection for Cu2+ towards BHSO was 0.73 μM. The binding of BHSO to Cu2+ was analysed as a 1:1 ratio through a Job plot and electrospray ionisation mass spectrometry. BHSO can detect readily Cu2+ with a test strip by colorimetric variation. The detecting process of Cu2+ by BHSO was represented by ultraviolet‐visible titration, electrospray ionisation mass spectrometry, proton nuclear magnetic resonance titration, Job plot and density functional theory calculations.
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