Search

Carbon dot-based fluorescence sensors have attracted research interest for the selective determination of anti-inflammatory drugs in biological fluids and environments. The overdose and accumulation of anti-inflammatory drugs in tissues can cause chronic side effects including abdominal pain, and renal damage. Herein, we report a new fluorescent probe, bamboo stem waste-derived carbon dots (BS-CDs) for highly sensitive detection of Flufenamic acid (FA), a hazardous anti-inflammatory drug. The UV-vis absorption spectra of BS-CDs show a redshifted absorption peak at 283 nm upon the addition of FA suggesting strong binding interaction between BS-CDs and FA molecule. The BS-CDs showed a fluorescence enhancement (∼2-fold) detection for FA (400 μM) in the linear concentration range (0.40 → 0.65 μM) with a limit of detection (LoD; 17 nM) and binding constant (K a  = 1.33 × 10 -3 M -1 ). The time-resolved fluorescence decay analysis showed that the average lifetime of BS-CDs has slightly changed (4.42 → 4.67 ns) by the interaction with FA through the aggregation-induced emission (AIE) process. The interference, pH, and effect of time results suggest that BS-CDs are highly selective probes for FA detection and do not show any interference involvement during FA detection. The confirmation of the structure and morphology changes of BS-CDs after interaction with FA was carried out by XRD, FESEM, HRTEM, FTIR, and Raman spectroscopy. The practicability of the BS-CDs probe was proved by the detection of FA in human urine samples with recovery of 103-109 %. This suggests that the proposed BS-CDs-based 'turn-on' sensor could be used to determine the FA in biological fluids., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Recent advances to utilize two or more nanoparticles for developing novel sensors with superior sensitivity have spurred advanced detection limits even at low concentrations. In this research, a blend of rutheniumdoped TiO 2 (Ru-TiO 2 ) nanoparticles and multiwalled carbon nanotubes (MWCNTs) loaded into carbon paste matrix to fabricate a novel Ru-TiO 2 /MWCNTs-CPE sensor was used for the detection and quantification of flufenamic acid (FFA) and mefenamic acid (MFA) drugs. The surface morphology of Ru-TiO 2 was assessed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray diffraction (XRD) and atomic force microscopy (AFM). Sensitivity and selectivity of the electrode was improved at the Ru-TiO 2 /MWCNTs modified CPE compared to nascent CPE due to the amazing surface distinctive characteristics of the modifier at pH 5.0. The effect of concentration of the modifier, pH, pre-concentration time, sweep rate and concentration on signal enhancement of FFA and MFA was studied. The square wave voltammetry (SWV) currents are linearly related in the concentration range of 0.01 μM-0.9 μM with the detection limit values of 0.68 nM for FFA and 0.45 nM for MFA, respectively. The developed electrode assembly was used for the quantification of both the drug analytes in human urine samples., (Copyright © 2018 Elsevier B.V. All rights reserved.)

This article describes a multicommutated flow injection-solid phase spectroscopy system implemented with photochemically induced fluorescence for the determination of flufenamic acid (FFA). A strongly fluorescent photoproduct is generated when FFA is irradiated online under UV light in a strong sulfuric medium. The photoproduct generated is retained on C(18) silica gel (which fills the detection area of the flow cell) and directly monitored on the active solid support at 258/442 nm (lambda(ex)/lambda(em)). After maximum signal recording, the sensing zone is regenerated by eluting the retained photoproduct with an appropriate H(2)SO(4)/MeOH solution. The sensor, completely automated, is based on the use of three-way solenoid valves conveniently operated by a homemade multicommutation software written in Java language. The system is calibrated at 10 and 60s for sampling time, showing detection limits of 1.28 x 10(-9) and 5.33 x 10(-10) molL(-1) and sampling rates of 38 and 28 h(-1), respectively, with relative standard deviations of 0.9 and 1.2%. The applicability of the method is demonstrated for the determination of FFA in human serum, human urine, and a pharmaceutical preparation without any pre-treatment. Good recovery levels were achieved between 90.5 and 103.7%.

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 high-performance liquid chromatographic (HPLC) method for simultaneous determination of mefenamic acid (MFA), flufenamic acid (FFA) and tolfenamic acid (TFA) is presented for application to pharmaceuticals and human urine. Isocratic reversed-phase HPLC was employed for quantitative analysis using tetra-pentylammonium bromide (TPAB) as an ion-pair reagent. Urine samples were purified by solid-phase extraction using a silica-based strong anion-exchanger, Bond-Elut SAX cartridge. The HPLC assay was carried out using a Wakosil ODS 5C18 column (5 microm, 150x4.6 mm I.D.). The mobile phase consisted of 1.9 g of TPAB dissolved in 1:1 of a mixture of acetic acid-sodium acetate buffer solution, pH 5.0, and acetonitrile (11:9, v/v). The calibration curves of MFA, FFA and TFA showed good linearity in the concentration range of 33-167 microg/ml with a wavelength of 280 nm for pharmaceuticals, and in the low concentration range (1.7-30.1 microg/ml) with a wavelength of 230 nm for biological fluids. The correlation coefficients were better than 0.9999 in all cases. The lower limits of detection (defined as a signal-to-noise ratio of about 3) were approximately 2 ng for MFA, 3.5 ng for FFA and 2.5 ng for TFA. The procedure described here is rapid, simple, selective and is suitable for routine analysis of pharmaceuticals and pharmacokinetic studies in human urine samples.

The possibility of separating flufenamic, meclofenamic and mefenamic acids by capillary electrophoresis was studied. The best approach involved combining a suitable pH of the carrier electrolyte (pH 12.0) with the host-guest complexation effects of beta-cyclodextrin. A running buffer consisting of 30 mM phosphate buffer (pH 12.0), 2 mM beta-CD and 10% (v/v) acetonitrile was found to provide a very efficient and stable electrophoresis system for the analysis of fenamic acids by capillary zone electrophoresis. Responses were linear from 0.4 to 40 microg/ml for the three drugs with detection limits of about 0.3 ng/ml. Intra- and inter-day precision values of about 1-2% R.S.D. (n = 11) and 3-4% R.S.D. (n = 30), respectively, were obtained. The method is highly robust and no breakdowns of the current or capillary blockings were observed for several weeks. The general applicability of this rapid CZE procedure (migration times less than 12 min) is demonstrated for several practical samples, including serum, urine and pharmaceuticals.

Renal Elimination and Metabolism of Etofenamate after Intramuscular Administration of Different Doses to volunteers. Renal elimination of etofenamate (active substance of Rheumon i.m.) after i.m. injection of oily solution of etofenamate to volunteers was investigated by HPTLC and GC. After injection of 250, 500 and 1000 mg etofenamate, free and conjugated flufenamic acid (flu), 5-hydroxy- and 4'-hydroxy flufenamic acid (5-OH-flu, 4'-OH-flu) were found as main metabolites in urine. Besides that several minor metabolites were identified. The ratio of free to conjugated metabolites was 1:10 to 1:25. From the doses administered 30% were eliminated as main metabolites. Overall amounts (in mg) of the eliminated metabolites and the doses correlated with each other (r = 0.9334), whereas the percent ratio of 5-OH-flu and of 4'-OH-flu increased with dose. Half lives of renal elimination for flu, 5-OH-flu and 4'-OH-flu are largely independent of dose. The half life of flufenamic acid corresponds roughly to data from plasma levels (7-9 h), the two hydroxy derivatives are eliminated into urine with half lives from 15 to 24 h. The results show, that i.m. injection of an oily etofenamate solution follows a linear dose independent kinetic, while the amounts absorbed and renally eliminated are proportional to dose. The results correspond to plasma level studies.

NMR and HPLC have been used to investigate the rearrangements of 1-O-acylglucuronides in vitro and the occurrence of rearranged isomers in urine. Glucuronides of flufenamic acid, (S)- and (R)-benoxaprofen, salicylic acid, and delta 9-11-carboxytetrahydrocannabinol were synthesized, by use of immobilized enzymes, or purified from urine. Ester-linked isomers of these gluruconides were characterized, and isomers derived from flufenamic acid, (S)-benoxaprofen, and salicylic acid were purified for further study by NMR and HPLC. The positions of the new ester linkages could be identified by two-dimensional NMR. Shifts not only in the resonance of the proton adjacent to the esterified hydroxyl group but also in the resonance of the anomeric proton on carbon 1 of the glucuronic acid moiety could be correlated with the position of each isomeric ester bond. HPLC elution times also correlated with ester position in this small set of samples. The sequences of isomer formation were studied in situ by NMR and also at pH 8 by HPLC. These studies indicate that, for the three cases examined, the C-2 ester is formed first, followed by formation of C-3 and C-4 esters. The purified isomeric esters were found not to re-form the high-energy 1-O-acyl bond. All other rearrangement steps are reversible. In contrast to other glycosides and glycerol esters, no evidence could be found for rearrangements beyond nearest-neighbor hydroxyl groups in glucuronic acid. The sequence of formation and reversibility is consistent with an ortho ester intermediate, as has been proposed for rearrangements of other glycosides.(ABSTRACT TRUNCATED AT 250 WORDS)