Extraction of quinolones from milk samples using bentonite/magnetite nanoparticles before determination by high-performance liquid chromatography with fluorimetric detection

Creatine@SiO2 @Fe3 O4 nanocomposite as an efficient sorbent for magnetic solid-phase extraction of escitalopram and chlordiazepoxide from urine samples through quantitation via HPLC-UV

An efficient, cost-effective, and fast-synthesis method is presented in the current study to prepare magnetic nanoparticles covered by cheap and nitrogen-rich creatine. The hydrothermal method was used for the synthesis of the magnetic core. The prepared magnetic core was then covered by SiO₂ and subsequently functionalized using creatine. The prepared creatine@SiO₂ @Fe₃ O₄ was utilized as a sorbent in the magnetic solid-phase extraction of the selected antidepressants including escitalopram and chlordiazepoxide as the model drugs. The extracted drugs were desorbed by a suitable organic solvent and analyzed by high-performance liquid chromatography equipped with an ultraviolet detection system. The influence of different variables on the magnetic solid-phase extraction method was examined by the Plackett-Burman and Box-Behnken designs for screening and optimization, respectively. Under the obtained optimum conditions, the linear ranges of the method were found to be in the range of 1-500 µg L^-1 . The limits of detection and limits of quantification were in the range of 0.27-0.63 µg L^-1 and 0.89-1.93 µg L^-1 for the selected analytes, respectively. Furthermore, the enrichment factors were found to be 79.8 and 92.7 for chlordiazepoxide and escitalopram, respectively. The method was successfully employed for the analysis of selected drugs in urine samples.

A Ratiometric Fiber Optic Sensor Based on CdTe QDs Functionalized with Glutathione and Mercaptopropionic Acid for On-Site Monitoring of Antibiotic Ciprofloxacin in Aquaculture Water

A ratiometric fluorescence fiber-optical sensor system (RFFS) merging a Y-type optical fiber spectrometer and CdTe QDs composite functionalized with glutathione and mercaptopropionic acid (GMPA@CdTe-QDs) for highly selective and on-site detection of ciprofloxacin (CIP) in environmental water samples was designed. Our preliminary results suggested that the red fluorescence of the synthesized GMPA@CdTe-QDs was effectively quenched by CIP. Based on this, the RFFS/GMPA@CdTe-QDs system was successfully fabricated and used for highly selective and rapid detection of CIP on site in the concentration range from 0 to 45 μM with the detection limit of 0.90 μM. The established method exhibited good interference resistance to the analogues of CIP and provided a great potential platform for real-time detection of CIP residues in environmental water. In addition, the fluorescence quenching mechanism of GMPA@CdTe-QDs by CIP was also investigated by means of temperature effect, fluorescence lifetime, ultraviolet (UV) visible absorption, and fluorescent spectra. Our results suggested clearly that the red fluorescence of GMPA@CdTe-QDs was quenched by CIP via the photoinduced electron-transfer (PET) mode.

Ionic liquid-based dispersive liquid-liquid microextraction followed by magnetic solid-phase extraction for determination of quinolones

An ionic liquid-based dispersive liquid-liquid microextraction (IL-DLLME) combined with magnetic solid-phase extraction (MSPE) was developed for extraction of quinolones (quinolones) from honey and milk prior to high-performance liquid chromatography (HPLC) analysis. 1-Butyl-3-methylimidazolium hexafluorophosphate was used as the extraction solvent and an effective adsorbent based on chitosan modified magnetic core-shell functionalized multi-walled carbon nanotube (MWCNTs-Fe₃O₄@SiO₂-CS) nanoparticles was used to assist IL to adsorb quinolone residues in honey and milk samples. Extraction conditions were optimized through one-factor-at-a-time and response surface methodology using a Box-Behnken design. Under optimum conditions satisfactory linearity (R² > 0.999) and high sensitivity (method limits of quantification were 4-8 μg kg^-1 or μg L^-1 in honey or milk samples) was achieved. The recoveries of quinolones in honey and milk ranged from 81.2 to 109%. Based on this study, the proposed method was employed for the determination of antibiotic residues in honey and milk samples.

A novel spectrofluorimetric method for determination of lomefloxacin adopting on zinc(II) chelation strategy: Application in human plasma

A new sensitive and instantaneous spectrofluorimetric method for efficient determination of lomefloxacin (LMX) in its pure, dosage form and human plasma was designed. The developed method depends on formation of a metal-chelation compound of LMX as a ligand with zinc(II) in a buffer of acetate (pH 5.5). The following parameters; type of metal, concentration of metal, pH, type of buffer and diluting solvent were optimized. After carefully investigation; 0.2 mM zinc, 2.0 ml acetate buffer (pH 5.5) and water as diluting solvent were set as optimum reaction conditions. Under these conditions, a large increase in the intensity of the fluorescence of LMX was attained at 450 after excitation at 284 nm. The limits of detection and quantification were 5.8 and 1.9 ng ml^-1 , respectively, with linearity range of 10.0 to 500.0 ng ml^-1 . The binding mode of LMX and zinc(II) ion (Zn²⁺ ) was found to be 2:1, respectively, and confirmed by Job's plot method. Furthermore, it extended to the analysis of LMX in the spiked plasma of humans with percentage recovery (98.70 ± 0.97 to 100.30 ± 1.69%, n = 3).

Silicon nanoparticles-based ratiometric fluorescence platform: Real-time visual sensing to ciprofloxacin and Cu2

In this work, a silicon nanoparticles (Si NPs)-based ratiometric fluorescence sensing platform was conveniently fabricated by simply mixing fluorescent Si NPs as co-ligands and reference signal with lanthanide metal ion Eu³⁺ as response signal. The introduction of ciprofloxacin (CIP) remarkably turned on the characteristic fluorescence of Eu³⁺ at 590 nm and 619 nm through the "antenna effect". At the same time, the blue emission of Si NPs at 445 nm kept comparatively stable. A good linear relationship between the ratio fluorescence intensity and CIP concentration in the range of 0.211-132.4 μM with a limit of detection (LOD) of 89 nM was obtained. In the presence of Cu²⁺, the fluorescence emission of Eu³⁺ was sharply turned off because of the stronger coordination ability of Cu²⁺ with CIP, which guaranteed the sequential detection of Cu²⁺. Meanwhile, the distinct fluorescent color change from bright blue to red, then back to blue, enabled naked-eye visual detection of CIP and Cu²⁺ in the solution phase and on paper-based test strip, and was successfully applied to determine the levels of CIP in complicated food samples with high sensitivity.

Glutathione-stabilized Fe3 O4 nanoparticles as the sorbent for magnetic solid-phase extraction of diazepam and sertraline from urine samples through quantitation via high-performance liquid chromatography

The synthesis and application of glutathione-coated magnetic nanocomposite were introduced with the purpose of developing a stable, cheap, operationally convenient, simple, fast, sensitive, and selective device for the microextraction of diazepam and sertraline for the first time. The prepared glutathione@Fe₃ O₄ nanocomposite was used as the sorbent in the form of magnetic solid-phase extraction. Afterward, the extracted analytes were desorbed by organic solvent and analyzed by high-performance liquid chromatography-ultraviolet detection. Several influential variables such as desorption time, desorption volume, sample pH, extraction time, and sorbent amount were screened through Plackett-Burman design and then optimized via Box-Behnken design. The obtained results showed that the above-mentioned method enjoys a good linear range (0.2-500 μg/L) with the coefficient of determination higher than 0.9927, low limits of determination (0.07-0.24 μg/L), acceptable limits of quantification (0.22-0.93 μg/L), good enrichment factors (128 and 153), and good spiking recoveries (95-105%) for diazepam and sertraline under the obtained optimized condition. Analyzing the real samples results in the confirmation of the presented method and it can be applied for the analysis of various organic compounds in biological samples.

Validated Liquid Chromatography-Tandem Mass Spectroscopic Method for Simultaneous Determination of Certain Drugs Used in Cataract Surgery in Rabbit Aqueous Humor

A sensitive, selective, accurate and precise ultra-high performance liquid chromatography-Tandem mass spectrometry (MS/MS) method was developed and validated for the simultaneous determination of drugs used as eye drops in cataract surgery in aqueous humor. Cataract surgery requires a powerful mydriatic eye drops combination such as cyclopentolate hydrochloride and phenylephrine hydrochloride to dilate the pupil and facilitate eye lens replacement and also requires strong fluoroquinolone antibiotic such as lomefloxacin hydrochloride. The method was performed with positive ion electrospray ionization and the analytes were quantified and monitored on a triple quadrupole mass spectrometer using multiple reaction monitoring scanning mode. Liquid-liquid extraction was used for the purification and preconcentration of analytes from rabbit aqueous humor matrix. Chromatographic elution was performed using an Phenomenex Luna® C18 (150 mm × 2.1 mm, 1.6 μm) column and moxifloxacin hydrochloride as internal standard with a mobile phase consisting of methanol:water:formic acid (70:29:1, by volume) at flow rate of 0.2 mL/min. Satisfactory results regarding linearity, recovery, stability, accuracy and precision of the analytes were obtained. Full validation of the procedure was performed according to the US Food and Drug Administration guidance for industry: bioanalytical method validation and European Medicines Agency (EMA) guideline on bioanalytical method validation.

Use of a magnetic covalent organic framework material with a large specific surface area as an effective adsorbent for the extraction and determination of six fluoroquinolone antibiotics by HPLC in milk sample

A magnetic covalent organic framework material was synthesized with a core-shell structure using a simple solvothermal method. It was prepared with Fe₃ O₄ as the magnetic core, covalent organic framework as the shell, which synthesized from 1,3,5-triformylphloroglucinol and p-phenylenediamine by Schiff base reaction. Transmission electron microscopy, Fourier transform infrared spectroscopy, powder X-ray diffraction, vibrating sample magnetometry, and nitrogen adsorption-desorption were used to characterize magnetic adsorbent. It has showed a large specific surface area (505.6 m² /g), which can provide many adsorption sites. Moreover, the saturation magnetization value was 48.4 emu/g enough to be separated by external magnet. Six kinds of fluoroquinolones (enoxacin, fleroxacin, ofloxacin, norfloxacin, pefloxacin, and lomefloxacin) were extracted by magnetic solid phase extraction with the magnetic adsorbent. High-performance liquid chromatography detects the entire adsorption and desorption process to further evaluate the optimal extraction and desorption conditions. Under the optimal chromatographic conditions, this method showed a low detection limit (0.05 to 0.20 μg/L), good linearity in the range of 0.5 to 200 μg/L, and the enrichment factor reaches 115.5-127.3. The spiked recovery of the fluoroquinolones in milk sample ranged from 90.4 to 101.2%.

A ratiometric fluorometric ciprofloxacin assay based on the use of riboflavin and carbon dots

Carbon dots (CDs) were hydrothermally synthesized from selenious yeast. They were further coupled with riboflavin to form a dually emitting probe for ciprofloxacin (CIP). Under 370 nm excitation, the probe displays dual (blue and green) emissions with peaks at 443 and 510 nm. When CIP is added, the blue fluorescence of the CDs is enhanced while the green fluorescence remains unaffected. The ratio of the relative fluorescence intensities at 443 and 510 nm increases linearly in the 0.5-200 μM CIP concentration range. The fluorescent probe is selective and has a 0.13 μM detection limit. Satisfactory recoveries (97.9-101.1%) were received when the probe was used to quantify CIP in spiked water and human serum samples. Graphical abstractBlue-emissive carbon dots were prepared from selenious yeast via a hydrothermal method, and then coupled with riboflavin as a ratiometric fluorometric probe for ciprofloxacin determination.

Determination of fluoroquinolones in food samples by magnetic solid-phase extraction based on a magnetic molecular sieve nanocomposite prior to high-performance liquid chromatography and tandem mass spectrometry

In this study, a magnetic molecular sieve material (Fe₃O₄@MCM-48) was synthesized by a combination of solvothermal and self-assembly methods. The physicochemical properties of the magnetic molecular sieve material were characterized by scanning electron microscopy, energy-dispersive spectroscopy, magnetic hysteresis loop measurements, transmission electron microscopy, powder X-ray diffraction, N₂ adsorption-desorption analysis, and Fourier transform infrared spectroscopy. The as-synthesized nanocomposite showed various advantages, including easy magnetic-assisted separation, high specific surface area, and a highly interwoven and branched mesoporous structure. The Fe₃O₄@MCM-48 nanocomposite was then used as an effective adsorbent material for magnetic solid-phase extraction of fluoroquinolones (FQs) from water samples. The FQs in the extract were determined via liquid chromatography-tandem mass spectrometry. Adsorption and desorption factors that affected the extraction performance were systematically optimized using spiked purified water samples. Good linearity (with R² > 0.99) was shown by this FQ detection system for FQ concentrations from 5 to 1000 ng L^-1. Moreover, low detection limits (0.7-6.0 ng L^-1) and quantitation limits (2.5-20.0 ng L^-1) and satisfactory repeatability (relative standard deviation < 10%, n = 6) were achieved for water samples. The developed method was also validated for the analysis of FQs in meat and milk samples. Finally, FQs in food and drinking water samples were successfully determined using the developed method. Graphical abstract.

A nanocomposite optosensor containing carboxylic functionalized multiwall carbon nanotubes and quantum dots incorporated into a molecularly imprinted polymer for highly selective and sensitive detection of ciprofloxacin

A nanocomposite optosensor consisting of carboxylic acid functionalized multiwall carbon nanotubes and CdTe quantum dots embedded inside a molecularly imprinted polymer (COOH@MWCNT-MIP-QDs) was developed for trace ciprofloxacin detection. The COOH@MWCNT-MIP-QDs were synthesized through a facile sol-gel process using ciprofloxacin as a template molecule, 3-aminopropylethoxysilane as a functional monomer and tetraethoxysilane as a cross-linker at a molar ratio of 1:8:20. The synthesized nanocomposite optosensor had high sensitivity, excellent specificity and high binding affinity to ciprofloxacin. Under optimal conditions, the fluorescence intensity of the optosensor decreased in a linear fashion with the concentration of ciprofloxacin and two linear dynamic ranges were obtained, 0.10-1.0 μg L^-1 and 1.0-100.0 μg L^-1 with a very low limit of detection of 0.066 μg L^-1. The imprinting factors of the two linear range were 17.67 and 4.28, respectively. The developed nanocomposite fluorescence probe was applied towards the determination of ciprofloxacin levels in chicken muscle and milk samples with satisfactory recoveries being obtained in the range of 82.6 to 98.4%. The results were also in good agreement with a HPLC method which indicates that the optosensor can be used as a sensitive, selective and rapid method to detect ciprofloxacin in chicken and milk samples.

Fabrication of polymer-modified magnetic nanoparticle based adsorbents for the capture and release of quinolones by manipulating the metal-coordination interaction

Functional polymers with a metal-coordination interaction have been fabricated for sample pretreatment. Poly(N-4-vinyl-benzyl iminodiacetic acid-co-methacrylic acid-co-styrene)-modified magnetic nanoparticles were prepared and used as solid-phase extraction adsorbents for the analysis of quinolones by tuning the metal-coordination interaction. In the construction of the polymer-based adsorbents, functional monomer (N-(4-vinyl)-benzyl iminodiacetic acid) and comonomers (methacrylic acid and styrene) were fabricated onto the magnetic nanoparticles by free radical polymerization. Factors affecting the performance of the adsorbents were investigated, and the results revealed that Fe³⁺ played a vital role in the formation of metal-coordination adsorbents. Compared with other compounds, the resultant adsorbents displayed good selectivity to quinolones due to the metal-coordination complex (N-4-vinyl-benzyl iminodiacetic acid-Fe³⁺ -quinolones). Interestingly, the captured quinolones could be rapidly released by manipulating the metal-coordination interaction with Cu²⁺ . The linearity range for analysis of the test quinolones was 0.025-2.0 μg/mL (R²  > 0.999), and the recovery varied from 80.0 to 100.7%. Further, the proposed adsorbents were combined with high-performance liquid chromatography for the analysis of quinolones in real urine samples. The results demonstrated that the prepared adsorbents have good selectivity and sensitivity for quinolones, showing great potential for drug analysis in real samples.

Ratiometric fluorescence, solution-phase and filter-paper visualization detection of ciprofloxacin based on dual-emitting carbon dot/silicon dot hybrids

This study demonstrates the ratiometric fluorescence, solution-phase and filter-paper visual detection of ciprofloxacin based on dual-emitting carbon dot/silicon dot hybrids.