Applying fluorescence spectroscopy coupled with Gaussian band fitting to reveal dynamic variation process of humus fractions from riparian soils along an urbanized river.

Humus, an important fraction of soil organic matter, play an environmental role on nutrients, organic and inorganic pollutants in riparian zones of urbanized rivers. In this study, dynamic variation process of humus fractions from riparian soils was revealed along Puhe River. Composite soil samples of four depths were collected from four land-uses, i.e., eco-conservation area (ECA), industrial area (INA), urban/town area (UTA), rural/agricultural area (RAA). Based on synchronous fluorescence spectra coupled with Gaussian band fitting, fulvic/humic acid predominantly contained tyrosine-like (TYLF), tryptophan-like (TRLF), microbial-like (MLF), fulvic-like (FLF) and humic-like (HLF) substances within each soil profile. TRLF, MLF and FLF (89.43-90.30 %) are the representative components in fulvic-acid, while MLF and HLF (52.81-59.97 %) in humic-acid. Phenolic, carboxylic and humified materials were present in both humus. According to 2-dimensitonal correlation spectroscopy and canonical correlation analysis, fulvic/humic acid within the ECA soil profile could be mainly derived from the degradations of terrestrial plant metabolites and residuals. Within the INA, fulvic-acid could be associated with treated/untreated wastewater, which entered the river and flew into the riparian during high flow period; whereas humic-acid could be relative to the terrestrials. Fulvic-acid had the same source as humic-acid in the UTA, which might be concerned with scattered domestic sewage and livestock wastewater, rather than the fluvial water. Furthermore, the source of fulvic/humic acid in the RAA was the crop metabolites and residuals, apart from the livestock wastewater. Noticeably, the variations of humus fractions in the ECA and RAA roughly occurred in 0-60 cm, while approximately in 20-80 cm in the INA and UTA. This proved that humus fractions in the former were referred to the plant/crop residuals, whereas humus fractions in the latter were those the terrestrials and fluvial water. This study could provide a key support for the construction and restoration of the urbanized riparian zone.

A novel derivative synchronous fluorescence method for the rapid, non-destructive and intuitive differentiation of denitrifying bacteria.

It is challenging to differentiate bacteria residing in the same habitat by direct observation. This difficulty impedes the harvest, application and manipulation of functional bacteria in environmental engineering. In this study, we developed a novel method for rapid differentiation of living denitrifying bacteria based on derivative synchronous fluorescence spectroscopy, as exemplified by three heterotrophic nitrification-aerobic denitrification bacteria having the maximum nitrogen removal efficiencies greater than 90%. The intact bacteria and their living surroundings can be analyzed as an integrated target, which eliminates the need for the complex pre-processing of samples. Under the optimal synchronous scanning parameter (Δλ = 40 nm), each bacterium possesses a unique fluorescence spectral structure and the derivative synchronous fluorescence technique can significantly improve the spectral resolution compared to other conventional fluorescence methods, which enables the rapid differentiation of different bacteria through derivative synchronous fluorescence spectra as fast as 2 min per spectrum. Additionally, the derivative synchronous fluorescence technique can extract the spectral signals contributed by bacterial extracellular substances produced in the biological nitrogen removal process. Moreover, the results obtained from our method can reflect the real-time denitrification properties of bacteria in the biological nitrogen removal process of wastewater. All these merits highlight derivative synchronous fluorescence spectroscopy as a promising analytic method in the environmental field.

Synchronous Front-Face Fluorescence Spectra: A Review of Milk Fluorophores.

Milk is subjected to different industrial processes, provoking significant physicochemical modifications that impact milk's functional properties. As a rapid and in-line method, front-face fluorescence can be used to characterize milk instead of conventional analytical tests. However, when applying fluorescence spectroscopy for any application, it is not always necessary to determine which compound is responsible for each fluorescent response. In complex matrixes such as milk where several variables are interdependent, the unique identification of compounds can be challenging. Thus, few efforts have been made on the chemical characterization of milk' fluorescent spectrum and the current information is dispersed. This review aims to organize research findings by dividing the milk spectra into areas and concatenating each area with at least one fluorophore. Designations are discussed by providing specific information on the fluorescent properties of each compound. In addition, a summary table of all fluorophores and references cited in this work by area is provided. This review provides a solid foundation for further research and could serve as a central reference.

Development of a highly sensitive and green first-derivative synchronous fluorescence spectroscopic method for the simultaneous quantification of telmisartan and rosuvastatin: Greenness metric assessment and application to a pharmacokinetic study in rats.

Hypertension and hyperlipidemia frequently coexist and are correlated with elevated cardiovascular adverse outcomes. Fixed dose combination tablets containing antihypertensive and antihyperlipidemic drugs have the potential to improve patient compliance. Telmisartan and rosuvastatin fixed dose combination tablet has been recently formulated. This study provided the first fluorescence spectroscopic method for simultaneously quantifying telmisartan and rosuvastatin in tablet dosage form and plasma. The native fluorescence spectra of telmisartan and rosuvastatin completely overlapped, making direct measurement unachievable. However, through the implementation of synchronous fluorescence measurements of telmisartan and rosuvastatin at a Δλ = 60, distinct narrow bands were observed at 358 nm and 375 nm, respectively. Regrettably, the challenge of overlapping remained unresolved. Nevertheless, by converting these synchronous spectra into first-order spectra, the problem of overlapping was completely resolved. This conversion also allowed for the selective quantification of telmisartan and rosuvastatin at 374 nm and 358 nm, respectively. The validity of this method was confirmed in accordance with ICH guidelines, yielding satisfactory results in terms of the validation characteristics. The method demonstrated linear relationships between the response and the studied drugs concentrations in working range of 50-1000 ng/mL for telmisartan and 100-2000 ng/mL for rosuvastatin. The described methodology was applied for the pharmacokinetic study of telmisartan and rosuvastatin in rat plasma after a single oral dose of 4 mg/kg telmisartan and 50 mg/kg rosuvastatin. Pharmacokinetic analyses revealed a moderate drug-drug interaction between the two drugs, which was not considered to be clinically significant. Moreover, the described method was assessed in terms of sensitivity and environmental sustainability against three previously documented methods. The comparison effectively underscores the supremacy of the proposed technique over the documented techniques.

Fast concurrent determination of guaifenesin and pholcodine in formulations and spiked plasma using first derivative synchronous spectrofluorimetric approach.

Guaifenesin and pholcodine are frequently co-formulated in certain dosage forms. A new fast first derivative synchronous spectrofluorometric method has been used for their simultaneous analysis in mixtures. Here, first derivative synchronous spectrofluorometry enabled the successful simultaneous estimation of guaifenesin at 283 nm and pholcodine at 275 nm using a wavelength difference (Δλ) of 40 nm. The method was fully validated following International Council of Harmonization guidelines. For guaifenesin and pholcodine, linearity was determined within the corresponding ranges of 0.05-0.30 and 0.10-6.0 µg/ml. The two drugs were effectively analyzed using the developed approach in their respective formulations, and the results showed good agreement with those attained using reference methods. The method demonstrated excellent sensitivity, with detection limits down to 0.007 and 0.030 µg/ml and quantitation limits of 0.020 and 0.010 µg/ml for guaifenesin and pholcodine, respectively. Therefore, the procedure was successful in determining these drugs simultaneously in vitro in spiked plasma samples and syrup dosage form. The developed methodology also offered an environmentally friendly advantage by utilizing water as the optimal diluting solvent throughout the whole work. Different greenness approaches were investigated to ensure the method's ecofriendly properties.

Eco-friendly synchronous fluorescence spectrofluorimetric method for simultaneous determination of montelukast sodium and fexofenadine hydrochloride in their antiallergic rhinitis fixed-dose combination tablets.

An innovative, simple, accurate, sensitive, and eco-friendly synchronous fluorescence spectrofluorimetric method has been developed for the simultaneous analysis of montelukast sodium (MON) and fexofenadine hydrochloride (FEX). The method relies on measuring the relative synchronous fluorescence intensity of both drugs using Δλ of 60 nm in methanol at 405 nm for MON and 288 nm for FEX. The experimental parameters influencing the developed method were investigated and optimized. The method was linear over the ranges 0.1-2.0 and 2.0-20.0 µg/ml for MON and FEX, respectively. The limits of detection were 0.018 and 0.441 µg/ml, and the limits of quantitation were 0.055 and 1.336 µg/ml for MON and FEX, respectively. The developed method was applied successfully for the determination of the two drugs in their newly released fixed-dose combination prescribed for the treatment of allergic rhinitis. The mean per cent recoveries were found to be 100.680 ± 0.890 and 100.110 ± 0.940 for MON and FEX, respectively. Furthermore, the method was found to be eco-friendly green as was evaluated according to the Green Analytical Procedure Index tool guidelines and analytical eco-scale.

Characterizing dissolved organic matter and bacterial community interactions in a river network under anthropogenic landcover.

Anthropogenic landcover could rise nutrient concentrations and impact the characteristics and bioavailability of dissolved organic matter (DOM) in a river network. Exploring the interactions between DOM and microbials might be conducive to revealing biogeochemistry behaviors of organic matter. In this study, synchronous fluorescence spectra (SFS) with Gaussian band fitting and two-dimensional correlation spectroscopy (2D-COS) were employed to identify DOM fractions and reveal their interactions with bacterial communities. DOM was extracted from a river network under eco-agricultural rural (RUR), eco-residential urban (URB), eco-economical town (TOW), and eco-industrial park (IND) regions in Jiashan Plain of eastern China. The overlapping peaks observed in the SFS were successfully separated into four fractions using Gaussian band fitting, i.e., tyrosine-like fluorescence (TYLF), tryptophan-like fluorescence (TRLF), microbial humic-like fluorescence (MHLF), and fulvic-like fluorescence (FLF) materials. Across all four regions, TRLF (44.79% ± 7.74%) and TYLF (48.09% ± 8.85%) were the dominant components. Based on 2D-COS, variations of TYLF and TRLF were extremely larger than those of FLF in RUR-TOW. However, in URB-IND, the former exhibited lower variations compared to the latter. These suggested that FLF be likely derived continuously from lignin and other residue of terrestrial plant origin along the river network, and TYLF and TRLF be originated discontinuously from domestic wastewater in RUR-TOW. By high-throughput sequenced OTUs, the number of organisms in RUR-TOW could be higher than those in URB-IND, while genes associated with carbohydrate metabolism were lower in former than those in the latter. According to co-occurrence networks, microbes could promote the production of TYLF and TRLF in RUR-TOW. In contrast, microbial communities in URB-IND might contribute to decompose FLF. The obtained results could not only reveal interactions between DOM fractions and bacterial communities in the river network, but this methodology may be applied to other water bodies from different landscapes.

Green approach for tracking the photofate of ciprofloxacin and levofloxacin in different matrices adopting synchronous fluorescence spectroscopy: a kinetic study.

First derivative synchronous fluorescence spectroscopy (FDSFS) was applied to detect and quantify either ciprofloxacin (CIP) or levofloxacin (LEV) simultaneously with their photodegradation products, where the photolytic pathway for each analyte was found to be pH dependent. Under the guidance of early published articles, the structure of the produced photolytic products could be concluded, and further related to their resultant fluorescence spectra. The proposed method was subjected to full validation procedure which enables its application in investigating the photodegradation kinetics for both drugs. The obtained kinetic parameters were in accordance with previous reports and could be linked to predict the antibacterial activity of the resultant photodegradation products. These facts prove the suitability of the suggested FDSFS to serve as a stability-indicating assay method and to trace the photofate of CIP and LEV in the ecosystem as potential contaminants. Furthermore, the greenness of the suggested analytical methodology was evaluated via 'Green Analytical Procedure Index' (GAPI), which classifies it as an eco-friendly assay. Eventually, no extraction, treatment or preparation steps were needed during all analysis steps, which renders the proposed assay an appealing tool in environmental analysis.

Applying synchronous fluorescence spectra with Gaussian band fitting and two-dimensional correlation to characterize structural composition of DOM from soils in an aquatic-terrestrial ecotone.

Dissolved organic matter (DOM), the primary participant of carbon and nitrogen cycle, has a great impact on the behavior and fate of organic pollutants and heavy metals in eutrophic lakes. The dynamic spectral properties of DOM fractions were revealed in an aquatic-terrestrial ecotone under the different types of land use. Composite soil samples of different depths (0-20, 20-40 and 40-60 cm) were collected from four different land uses along a disturbed-impact gradient in Taihu Lake, China, i.e., grassland (GRL), forest land (FOL), paddy field (PAF), and vegetable field (VEF). DOM mainly consisted of tyrosine-like material (TYLF), tryptophan-like material (TRLF), microbial humic-like material (MHLF), fulvic-like material (FLF) and humic-like material (HLF) within all soil profiles, where TRLF was the dominant component (61.30 %) using synchronous fluorescence spectroscopy (SFS) combined with principal component analysis and Gaussian band fitting. Based on two-dimensional correlation spectroscopy with SFS and Fourier transform infrared, the variation order of DOM fractions was FLF → MHLF → HLF → TRLF → TYLF within the GRL soil profile, and MHLF exhibited an oppositive change with aliphatic OH and amide I in protein. The order of DOM fractions was MHLF → FLF → HLF → TYLF → TRLF within the FOL soil profile, and the change trend of MHLF remained oppositive with aliphatic OH and CO in ester. The order of DOM within the PAF soil profile fractions was TRLF → MHLF → HLF → TYLF → FLF, and changing trends of TYLF were oppositive to aliphatic OH, CH bending vibration, CH bending vibration and CO in ester. The order of DOM fractions was HLF → TYLF → TRLF → FLF → MHLF within the VEF soil profile, where the changing trend TYLF remained oppositive to aliphatic OH, CH deformations in lignin and aliphatic group and amide I in protein. This study may provide important support for alleviating lake water eutrophication or pollution.

Spectrofluorimetric quantitative analysis of favipiravir, remdesivir and hydroxychloroquine in spiked human plasma.

Favipiravir, remdesivir and hydroxychloroquine have been suggested in COVID-19 Treatment Guidelines Panel of many countries. Synchronous spectrofluorometric measurement provides sensitive tool for resolving the overlapped spectra of multicomponent drugs through converting the wider spectra to narrower sharp spectra. This work introduces the first fluorescence spectroscopic method for quantitative analysis of favipiravir, remdesivir and hydroxychloroquine in spiked human plasma. Testing the fluorescence spectra of favipiravir, remdesivir and hydroxychloroquine shows severe overlap, which hinders the direct quantification of the cited drugs. To overcome the overlapping issue, the drugs under the study have been measured in the synchronous mode at Δλ = 60 nm. Favipiravir could be measured directly at 423 nm without interference of remdesivir or hydroxychloroquine. Synchronous measuring the cited drugs at Δλ = 130 nm with mathematical transforming to the first order derivative spectra allowing remdesivir and hydroxychloroquine at 384 nm and 394 nm, respectively without interference from favipiravir. Different factors affecting the spectrofluorometric measurement process have been verified. The drugs under the study have been successfully quantitatively analyzed in the spiked plasma using the proposed method.

Tracing the influence of caffeine on the pharmacokinetic parameters of three headache relieving pharmaceuticals applying synchronous fluorescence spectroscopy.

A simple, sensitive, and selective first derivative synchronous fluorimetric method was developed and optimized to track the influence of caffeine content in beverages on the pharmacokinetic parameters of three pharmaceuticals used in relieving headache namely, aspirin (ASP), ibuprofen (IBU), and ergotamine tartrate (ERG). A full validation procedure was carried out to impart validity to the proposed method to apply it to biological fluids. The unique dissolving power of micellar solutions was utilized to avoid multiple extraction steps for both thein vitroandin vivoexperiments, aiming to obtain acceptable recoveries and to accomplish sustainability, where 0.1 M sodium dodecyl sulphate (SDS) was used for this purpose. Moreover, the developed bioanalytical method was subjected to full validation to avoid interferences emerging from biological matrices. The greenness of the proposed method was assessed according to the Analytical Eco-Scale and proved to be excellent green carrying a score of 98%.

A feasibility study for rapid evaluation of emulsion oxidation using synchronous fluorescence spectroscopy coupled with chemometrics.

A rapid method based on three-dimensional synchronous fluorescence spectroscopy was developed for emulsion oxidation evaluation. This method was selected because of its high sensitivity to dissolved organic matter typically occurring in the lipid oxidation. Spectral signal and chemical reference measurements were recorded for each emulsion sample as input and output data for the model construction. Characteristic values were extracted from the spectral data by the application of parallel factor (PARAFAC) analysis. Partial least squares regression (PLSR) was then used to construct a regression model for the rapid determination of emulsion oxidation. The correlation coefficient of the calibration and prediction sets were used as the performance parameters for the PLSR models as follows: R = 0.929, 0.973 for emulsion samples stored at 25℃; R = 0.897, 0.903 for emulsion samples stored at 70℃. The overall results demonstrated that the fluorescence spectroscopy, coupled with PARAFAC and PLSR algorithms, could be successfully used as a rapid method for the emulsion oxidation evaluation.

Fluorescence quenching by competitive absorption between solid foods: Rapid and non-destructive determination of maize flour adulterated in turmeric powder.

Fluorescence quenching induced by competitive absorption between different components of solid foods was observed for the first time. By using front-face synchronous fluorescence spectroscopy (FFSFS) and fluorescence titration, competitive absorption between maize flour and turmeric powder was proven to occur between phenolic acids in maize flour and curcumin in turmeric powder. FFSFS was applied for the rapid and non-destructive determination of maize flour adulterated in turmeric powder. Prediction models were constructed by partial least square (PLS) regression based on unfolded total synchronous fluorescence spectra, and were validated by five-fold cross-validation and external validation, with the determination coefficient of prediction (Rp2) greater than 0.95, root mean square error of prediction (RMSEP) < 6%, relative error of prediction (REP) < 15% and residual predictive deviation (RPD) greater than 5. The limit of detection (LOD) of maize flour was approximately 9%. In addition, most relative errors for test samples were from -20% to 20%.

Green quantitative spectrofluorometric analysis of rupatadine and montelukast at nanogram scale using direct and synchronous techniques.

Two green-sensitive spectrofluorometric methods were investigated for assay of rupatadine (RUP) [method I] and its binary mixture with montelukast (MKT) [method II]. Method I depends on measuring native fluorescence of RUP in the presence of 0.10 M H2SO4 and 0.10%w/v sodium dodecyl sulfate at 455 nm after excitation at 277 nm. The range of the first method was 0.20-2.00 µg ml-1 with detection and quantitation limits of 59.00 and 179.00 ng ml-1, respectively. Method II depends on the first derivative synchronous spectrofluorometry. The derivative intensities were measured for the two drugs in an aqueous solution containing Mcllvaine's buffer pH 2.60 at fixed Δλ of 140 nm. Each drug was estimated at zero-contribution of the other. The intensity was measured at 261 and 371 nm for RUP and MKT, respectively. The method was linear over 0.10-4.00 and 0.20-1.60 µg ml-1 with limits of detection 31.00 and 66.00 ng ml-1 and limits of quantitation 94.00 and 200.00 ng ml-1 for RUP and MKT, respectively. The method was extended to determine this mixture in laboratory-prepared mixtures and combined tablets. Method validation was performed according to ICH guidelines. Statistical interpretation of data revealed good agreement with the comparison method. Method greenness was confirmed by applying three different assessment tools.

Rapid detection of sulfamethazine and ofloxacin residues in duck meat using synchronous fluorescence spectroscopy coupled with chemometric methods.

Rapid detection of antibiotic residues in duck meat is of great significance for strengthening food safety and quality supervision of duck meat and fighting against inferior products in the duck meat market. The objective of the current paper was to evaluate the potential of synchronous fluorescence spectroscopy (SFS) coupled with chemometric methods for the rapid detection of sulfamethazine (SM2) and ofloxacin (OFL) residues in duck meat.The SFS spectral data from duck meat containing different concentrations of SM2 and OFL were preprocessed by baseline offset. The detection conditions, including the adding amounts of ß-mercaptoethanol solution and o-phthalaldehyde solution, as well as the reaction time, were optimized by a single factor experiment for obtaining a better detection effect, and their optimal values were 400 µL , 25 µL , and 40 min, respectively. By comparing 2 chemometric models based on peak-height algorithm and peak-area algorithm, the prediction model based on peak-height algorithm was a better quantitative model with correlation coefficient for the prediction set (Rp) of 0.9031 and 0.9981, the root mean error for the prediction set (RMSEP) of 7.9509 and 0.5267 mg/kg, recovery of 81.7 to 155.1% and 96.4 to 111.2%, and relative standard deviation (RSD) of 4.1 to 6.7% and 2.9 to 6.8% to predict SM2 and OFL residues in duck meat, respectively. Overall, the results of this investigation showed that SFS technique was an effective and rapid tool for the detection of SM2 and OFL residues in duck meat.

Organotrialkoxysilane-Functionalized Noble Metal Monometallic, Bimetallic, and Trimetallic Nanoparticle Mediated Non-Enzymatic Sensing of Glucose by Resonance Rayleigh Scattering.

Organotrialkoxysilanes like 3-aminopropyltrimethoxysilane (3-APTMS)-treated noble metal cations were rapidly converted into their respective nanoparticles in the presence of 3-glycidoxypropylytrimethoxysilane (3-GPTMS). The micellar activity of 3-APTMS also allowed us to replace 3-GPTMS with other suitable organic reagents (e.g., formaldehyde); this approach has significant advantages for preparing bimetallic and trimetallic analogs of noble metal nanoparticles that display efficient activity in many practical applications. The formation of monometallic gold, silver, and palladium nanoparticles, bimetallic Ag-Pd, and Au-Pd nanoparticles at various ratios of noble metal cations, and trimetallic Ag-Au-Pd nanoparticles were studied; their biocatalytic activity in non-enzymatic sensing of glucose based on monitoring synchronous fluorescence spectroscopy (SFS) was assessed. Of these nanoparticles, Au-Pd made with an 80:20 Au:Pd ratio displayed excellent catalytic activity for glucose sensing. These nanoparticles could also be homogenized with Nafion to enhance the resonance Rayleigh scattering (RRS) signal. In this study, the structural characterization of noble metal nanoparticles as well as bi- and tri-metallic nanoparticles in addition to their use in non-enzymatic sensing of glucose are reported.

A synchronous fluorescence spectrofluorometric method for the simultaneous determination of policresulen and cinchocaine hydrochloride in ointment and suppositories.

For the treatment of internal and external hemorrhoids, policresulen (POL) and cinchocaine hydrochloride (CIN) are used in combination. Using a new, simple, fast, and economical first-derivative synchronous fluorescence spectroscopic process, both drugs were simultaneously determined and validated. At Δλ60 nm and with a scanning rate of 600 nm/min, methanol was used as the solvent for both products. In the concentration ranges of 5.0-21.0 µg mL-1 and 0.5-6.0 µg mL-1 for POL and CIN, the amplitude-concentration plots were rectilinear. The detection limits were found to be 0.770 µg mL-1 and 0.118 µg mL-1 and the quantitation limits for POL and CIN were 2.541 µg mL-1 and 0.391 µg mL-1. To evaluate all compounds in synthetic mixtures and medicinal dosage types, the proposed method has been successfully applied. These findings were in line with the results obtained using high-performance thin layer chromatography, the comparison process.

Front-face synchronous fluorescence spectroscopy for rapid and non-destructive determination of free capsanthin, the predominant carotenoid in chili (Capsicum annuum L.) powders based on aggregation-induced emission.

Capsanthin is the major natural carotenoid pigment in red chili pepper possessing important bioactivity. Its conventional determination method is high performance liquid chromatography (HPLC) with complex and tedious sample pretreatment. In this study, synchronous front-face fluorescence spectroscopy (FFFS) was applied for the fast and non-invasive detection of free capsanthin in chili powders. Although capsanthin was only weak fluorescent in solution state, it showed strong fluorescence in two separated regions in front-face geometry which could also be clearly observed in chili powders. The mechanisms of these emissions are revealed to be aggregation-induced emission (AIE) and J-aggregate formation (JAF). The free capsanthin in 85 chili powder samples were determined by HPLC as in the range of 0.6-3.0 mg/g. The total synchronous FFFS spectra of these samples were scanned. Simple first-order models were built by partial least square regression (PLSR), and were validated by 5-fold cross-validation and external validation. The coefficients of determination (R2) were higher than 0.9, and the root mean square errors (RMSE) were less than 0.2 mg/g. The relative error of prediction (REP) was 9.9%, and the residual predictive deviation (RPD) was 3.7. The method was applied for the estimation of free capsanthin in several real-world samples with satisfactory analytical results. The average relative error to HPLC reference values was -11.8%.

Copper nanocluster-based sensor for determination of vancomycin in exhaled breath condensate: A synchronous fluorescence spectroscopy.

A synchronous fluorescence spectroscopy (SFS) nanoprobe is developed for the determination of vancomycin in exhaled breath condensate (EBC) samples. The synthesized nanoprobe is copper nanoclusters (Cu NCs) and its SFS peak is located at 405 nm with Δλ = 80. The affinity of Cu NCs to complex formation with vancomycin results in blocking non-radiative e-/h+ recombination defect sites on the surface of NCs and consequently enhancing the SFS signal intensity. Central composite design and response surface methodology is used for the optimization of reaction conditions. Under the optimized conditions, a linear relationship is found between the SFS intensity and the concentration of vancomycin in the range of 0.1-8 µg/mL. The validated method is applied for the determination of vancomycin in EBC of newborns receiving vancomycin treatment.

Novel spectrofluorimetric technique for determination of amoxicillin and ethopabate in chicken tissues, liver, kidney, eggs, and feed premix.

A new smart spectrofluorometric method was developed for the quantitation of amoxicillin and ethopabate simultaneously for the first time. The method is based on measuring their first derivative synchronous amplitudes in water at Δλ = 80 nm. The peak amplitudes were recorded at their crossing points; 240 nm for amoxicillin and 280 nm for ethopabate. The method is linear over the concentration ranges of 100.0-1,000.0 ng/ml for amoxicillin and 2.0-20.0 ng/ml for ethopabate. The limits of detection were 20.0 ng/ml and 0.58 ng/ml and limits of quantitation were 60.0 ng/ml and 1.92 ng/ml for amoxicillin and ethopabate, respectively. The method sensitivity permitted the determination of the two drugs below their maximum residue limit stated by the federal regulations. The developed method was applicable to the analysis of both drugs in the veterinary powders, feed premix, chicken tissues, liver, kidney, and eggs samples with percentage recoveries ranging 93.72-104.71%.