Construction of a thermoresponsive molecularly imprinted biomimetic hydrogel-based virus sensor and non-invasive cyclable detection of EV71.

A thermoresponsive molecularly imprinted hydrogel sensor was constructed for the specific selective recognition of enterovirus 71 (EV71). Due to the introduction of the thermosensitive monomer N-isopropylacrylamide (NIPAM), when the imprinted hydrogel is incubated with the virus at 37℃, the surface specific imprinting cavity will specifically recognize and capture the target virus EV71. When the temperature rises to 45℃, the combined EV71 is rapidly released due to changes in the shape and function of the imprinted sites. The MIP hydrogel-based viral sensor developed recognized, captured, and released the target virus in a non-invasive way. The imprinting factor of the target virus was 5.2, suggesting high selectivity, and the detection limit was 7.1 fM, suggesting high sensitivity. Detection was rapid, as adsorption equilibrium was achieved within 30 min. This method provides a new sustainable avenue for the simple and rapid detection of viruses.

Ultrasensitive Fluorescence Platform Based on AgNPs In Situ-Incorporated Zr-MOFs for the Detection of Organophosphorus Pesticides.

Organophosphorus pesticides (OPPs) are extensively used in agricultural production, and the contamination caused by their residues has raised significant concerns regarding potential threats to human health. Herein, a novel fluorescence nanoprobe based on an enzyme-mediated silver nanoparticle-modified metal organic framework (AgNPs@PCN-224) was successfully prepared for the rapid detection of OPPs. Initially, AgNPs@PCN-224 were synthesized by reducing silver nitrate (AgNO3) using sodium borohydride (NaBH4) embedded into luminescent PCN-224. This triggered the inner filter effect, leading to fluorescence quenching. Meanwhile, under the catalysis of acetylcholinesterase (AChE) and choline oxidase (CHO), acetylcholine (ATCh) was decomposed to hydrogen peroxide (H2O2), which could destroy AgNPs to form Ag+ released from PCN-224 for fluorescence recovery. Instead, fenitrothion, an OPP, inhibited AChE activity, allowing the quenched fluorescence to be reactivated. Under the current optimum conditions, the fluorescence intensity had a good correlation (Y = -728.5370X + 2178.4248, R2 = 0.9869) over a dynamic range of fenitrothion concentrations from 0.1 to 500 ng/mL, with an LOD of 0.037 ng/mL. In addition, the anti-interference ability and robustness of the proposed sensor was verified for the monitoring of fenitrothion in tea with recoveries of 87.67-103.72% and the relative standard deviations (RSD) < 5.43%, indicating that the system has excellent prospects for OPP determination in practical applications. Furthermore, this work provides a universal platform for screening other enzyme inhibitors to detect OPPs.

Expeditious fluorimetric detection of bilirubin by simple imidazole derived luminophore and it's pragmatic applicability in spiked biological fluids.

Bilirubin is an indispensable biomarker for liver diseases. Utilizing organic molecules as sensor platform for effective detection of bilirubin are little. In addition, the reported fluorophores required longer incubation time for detection. Hence, herein we have attempted to design an imidazole derivative 4-(3H-imidazo[4,5-b]pyridin-2-yl)-N,N-diphenylaniline (IMI) from triphenylamine and pyridine units which could detect bilirubin swiftly without any incubation period. IMI manifested an instant quenching of emission in presence of bilirubin with limit of detection (LOD) 11.74 × 10-6 mol L-1. The mechanistic aspect of detection involves coexistence of both static and dynamic quenching which was suitably justified. Finally, the pragmatic application of IMI was performed in bio-fluids.

HPLC-Fluorescence Detection Method for Concurrent Estimation of Domperidone and Naproxen. Validation and Eco-Friendliness Appraisal Studies.

This work demonstrates a simple and reliable HPLC method with fluorimetric detection for simultaneous estimation of domperidone (DOM) and naproxen (NAP). Successful chromatographic separation was accomplished using Inertsil ODS C18 column (5 µm, 4.6 × 150 mm) with gradient elution of the mobile phase consisting of 0.01 M phosphate buffer (pH 5.5) solution and acetonitrile. The gradient elution started with 25% acetonitrile increased linearly to 65% in 5 min, then kept at this percentage till the end of the run. The mobile phase was pumped at a flow rate of 1.0 mL/min. The excitation wavelength at 284 nm was found suitable for both DOM and NAP since it corresponds to a maximum for the minor component DOM and measurable excitation for NAP, while using 316 and 355 nm as emission wavelengths for DOM and NAP, respectively. Peaks eluted with excellent resolution at retention times 4.4 and 6.3 min for DOM and NAP, respectively. Performance of the proposed method was tested according to ICH guidelines in regard to linearity, ranges, precision, accuracy, robustness, detection and quantitation limits. Calibration curves were linear in the ranges of 0.8-3.6 and 1.0-2.5 µg/mL for DOM and NAP respectively with correlation coefficients not less than 0.9996. The validated method was successfully applied to the analysis of DOM and NAP in their laboratory prepared tablets resembling the commercial dosage form, and assay results were favorably compared with a published reference HPLC method. The method's greenness was assessed using the Analytical Eco-Scale and the novel Analytical Greenness metric (AGREE).

Water-soluble non-conjugated polymer dots with strong green fluorescence for sensitive detection of organophosphate pesticides.

Water-soluble non-conjugated polymer dots (PDs) have been synthesized using hyperbranched polyethyleneimine (PEI) and dihydroxybenzaldehyde (DHB) for the first time via the Schiff base reaction at room temperature. The yielded non-conjugated PDs of PEI-DHB could display the well-defined spheric structure and good water solubility. In contrast to the common PDs otherwise showing blue emission, the PEI-DHB PDs could give out strong green fluorescence in aqueous media. Especially, the fluorescence of the PEI-DHB PDs could be specifically quenched by MnO2 nanosheets through the inner filter effects and further restored by the thiocholine that could reduce MnO2 nanosheets into Mn2+. Herein, thiocholine could be produced in hydrolysis reaction of acetylthiocholine catalyzed by the acetylcholinesterase (AChE), of which the catalytic activity could be irreversibly inhibitted by the introduction of organophosphates. A highly selective fluorimetric method was thereby been developed for the detection of organophosphorus pesticides using dimethyl-dichloro-vinyl phosphate as a model. The linear concentrations ranges from 0.050 to 2.5 µM. Importantly, the non-conjugated PDs probes with strong green fluorescence and high water solubility may promise the extensive applications in the environmental, food, and clinical analysis fields.

Metal Ion Detection by Carbon Dots-A Review.

Development of economical, sensitive, selective and robust sensors for metal ion sensing is always fascinating for a chemist because traditional routs for their detection involve complicated instrumentation and critical sample preparation procedures. A large number of metal ion detectors including carbon dots (CDs) have been reported for sensitive and selective detection of metal ions. This review comprehensively explores the use of CDs as metallic cation sensors. CDs are being fabricated from variety of carbon sources by employing various synthetic channels. CDs are proved to be efficient colorimetric and fluorimetric detectors due to surface oxygen moieties which are responsible to co-ordinate with metal ions. Doping of CDs with hetero atom such as N, S, B etc. may further enhance their activity toward metal detection. Therefore, designing of CDs having selective sensing properties with low detection limits has gained significant interest.HighlightsCDs have gained much attention as chemical sensors due to their dynamic features i.e. less toxicity, stability, solubility in various solvents, absorption in UV/Vis. region, fluorescence and tunable physico-chemical properties.These are coast effective, sensitive and selective colorimetric and fluorimetric metal ion sensors.Detection of metal ions by CDs involves different mechanisms such as complexation, aggregation, electron transfer, inner filter effect etc.LOD data is an evidence of their greater efficiency.

Simultaneous evaluation of losartan and amlodipine besylate using second-derivative synchronous spectrofluorimetric technique and liquid chromatography with time-programmed fluorimetric detection.

This study is concerned with two sensitive, fast and reproducible approaches; namely, second-derivative synchronous fluorimetry (method I) and reversed phase high-performance liquid chromatography with fluorimetric detection (method II) for synchronized evaluation of losartan (LOS) and amlodipine besylate (AML). Method I is based on measuring second-derivative synchronous fluorescence spectra of LOS and AML at Δλ = 80 nm in water. The experimental factors influencing the synchronous fluorescence of the considered compounds were sensibly adjusted. The chromatographic analysis was executed on a Nucleodur MN-C18 column of dimensions; 250 × 4.6 mm i.d. and 5 µm particle size). The fluorimetric detection was time-programmed at λem = 440 nm for AML (0.0-7.5 min) and at λem = 400 nm for LOS (7.5-10 min) after excitation at λex = 245 nm. The mobile phase is a blend of acetonitrile with 0.02 M phosphate buffer in a proportion of 45 : 55, pH 4.0, pumped using a flow rate of 1 ml min-1. The calibration plots were established to be 0.1-4.0 µg ml-1 for both drugs in method I and 0.05-4.0 µg ml-1 for both drugs in method II. The study was extended to the evaluation of the two drugs in their co-formulated tablets.

Coumarin based hydrazone as an ICT-based fluorescence chemosensor for the detection of Cu2+ ions and the application in HeLa cells.

We have constructed a new coumarin based fluorescence probe BENZPYR with ICT character through condensation of N, N-diethylamino-3-acetyl coumarin with 2-hydrazinobenzothiazole. The absorbance and fluorescence spectral characteristics of BENZPYR revealed that the chemosensor can specifically detect for Cu2+ ions over other different metal ions and the lowest limit of detection was found in nano molar range. The turn off sensor of BENZPYR is related to chelation enhanced quenching (CHEQ) and intramolecular charge transfer (ICT) processes were serve as excellent fluorescent detection of Cu2+ ions in DMF medium. Fluorescence microscopy experiments revealed that probe BENZPYR may have application as a fluorophore to detect the Cu2+ in living cells. The simulated DFT analysis of electronic and structural properties and also UV-vis absorption spectra are in well accordance with the experimental UV-vis absorption spectra.

Determination of enantiomeric excess of some amino acids by second-order calibration of kinetic-fluorescence data.

In this investigation a new non-separative kinetic-spectroflourimetric method is proposed for the determination of lysine (lys), leucine (leu) and phenylalanine (phe) enantiomers as their o-phthaldialdehyde (OPA) derivatives in the presence of an optically active chiral thiol compound, 1-mercapto-2-propanol (MP). At ambient temperature and in the borate buffer media of pH 9.6, MP, OPA, as highly selective fluorogenic reagents, and amino acid (AA) enantiomers reacts with each other to yield two fluorescent diasteriomers of D and L-AA with maximum difference in fluorescence intensity at about 450 nm. To achieve information from the small spectral changes, the data are analyzed by Multivariate Curve Resolution Alternating Least Squares (MCR-ALS) method. Linear calibration curves are achieved to distinct D and L-lys, leu and phe in different mole ratios by applying appropriate constraints in MCR-ALS procedures. This is the first application of MCR-ALS in determination of enantiomeric excess (ee) using OPA/MP adduct as chiral reagent, which benefits from direct time dependent-fluorescence spectral analysis and does not require prior separation of chiral analytes. Both the cross-validated correlation coefficient (Q2) and root mean squares error of prediction (RMSEP) indicated satisfactory prediction ability of this method.

Colorimetric and fluorimetric detection of Hg2+ and Cr3+ by boronic acid conjugated rhodamine derivatives: Mechanistic aspects and their bio-imaging application in bacterial cells.

Colorimetric and fluorimetric detection of toxic metal ions such as Hg2+ and Cr3+ has gained tremendous popularity over the conventional methods due to their operational simplicity, high selectivity, and speediness. Although numerous colorimetric and fluorescent receptors for Hg2+ or Cr3+ were reported in the literature, boronic acid-based receptors for these metal ions are rather scarce in the literature. Hence, in the present study dual function boronic acid conjugated rhodamine derivatives were developed, and their toxic metal ion detection abilities were studied by absorption, emission and visual detection methods. Absorption and emission spectral studies revealed that these derivatives displayed selectivity towards Hg2+, Cr3+ and Fe3+ among the other metal ions studied by forming new absorption band. Both the derivatives exhibited colorimetric response towards Hg2+ and Cr3+ by the change in color of the solution to pink and reddish pink with Fe3+. The detailed mechanism involved in the detection of Hg2+ was deduced by 1H NMR and ESI-MS studies. Further, these derivatives were used for fluorescence imaging of Hg2+ and Cr3+ in S. aureus bacterial cells. Thus the present manuscript demonstrated the use of boronic acid conjugated rhodamine derivatives as a dual function (colorimetric and fluorescent) probes and as imaging agents for Hg2+ and Cr3+, which are known for their toxic influence on bacterial cells.

A facile carbon dots based fluorescent probe for ultrasensitive detection of ascorbic acid in biological fluids via non-oxidation reduction strategy.

A rapid, facile and ultrasensitive fluorescence sensing system based on nitrogen-doped carbon dots (N-doped CDs) for the detection of ascorbic acid (AA) was developed. The highly photoluminescent N-doped CDs with excellent solubility in water and good biocompatibility were prepared by a one-step hydrothermal synthesis and gave the fluorescence quantum yield of 47%. The addition of AA can intensively suppress the fluorescence of the N-doped CDs through the synergistic effect of the inner filter effect (IFE) and the static quenching effect (SQE). Benefited from the remarkable synergistic effect of IFE and SQE, a facile and ultrasensitive sensor was constructed successfully for AA sensing. The detection procedure was achieved within 2min. The linear response range of AA was obtained from 10-3 to 10-8 M with a detection limit of 5nM. This developed method enjoyed many merits including more simplicity, lost cost, high sensitivity, good selectivity, rapid response and excellent biocompatibility. Notably, the proposed fluorescent sensor exhibits excellent performance and applicability for AA determination in human serum and rat brain microdialysate, and may provide a fast yet facile route for AA detection in physiological and pathological fields.

Development and validation of a HPLC method for the determination of benzo(a)pyrene in human breast milk.

A simple analytical procedure was developed for the quantitation of benzo(a)pyrene in human breast milk using solid phase extraction (SPE) combined with high performance liquid chromatography. Before the chromatographic process, SPE, including C18 functional groups in silicagel cartridges, was conducted for sample preparation. A C18 column (100×4.6 mm id, 3 µm particle size) was used with acetonitrile:water (80:20) as the mobile phase at a flow rate 1mL/min at 30°C. Fluorimetric detection was performed for excitation and emission at 290 and 406 nm, respectively. It was observed that the calibration curve was linear over the range of 0.5-80 ng/mL. The limit of detection and limit of quantitation were found to be 0.5 and 1.07 ng/mL, respectively. Intraday and interday relative standard deviation values were less than 5.15%. Moreover, the newly developed method provides a fast, simple, cost effective, and sensitive assay to detect an important carcinogen substance, benzo(a)pyrene, in human breast milk.

Micellar liquid chromatographic determination of metformin hydrochloride using fluorimetric detection after pre-column derivatization: application to pharmacokinetic parameters in immediate and sustained release formulations.

An accurate and selective method using micellar liquid chromatography was developed to determine metformin hydrochloride both in its pharmaceutical dosage forms and human plasma. Separation was conducted using a Zorbax SB-Phenyl (250 × 4.6 mm id) stainless steel column at ambient temperature after pre-column derivatization with 9,10-phenanthraquinone. A mobile phase composed of 0.1 M sodium dodecyl sulfate, 10% 1-propanol and triethylamine (0.3%) in 0.02 M phosphoric acid, adjusted to pH 2.5, was used at a flow rate of 1 ml/min with fluorimetric detection at 450 nm after excitation at 306 nm. The proposed method showed high sensitivity with limit of quantification of 0.35 µg/ml and limit of detection of 0.23 µg/ml, being linear from 0.5 to 3.0 µg/ml. Being highly sensitive, the method could be applied to spiked human plasma, and also to follow the pharmacokinetic parameters of the studied drug in healthy volunteers after administration of both its immediate and sustained release tablet formulations. Such procedures were carried out without any extraction steps, which improves the accuracy and precision of the proposed method when applied to human plasma. Detailed validation procedures were also carried out giving results in accordance with the comparison method. The proposed method has also the advantage of being environmentally safe, where the use of organic solvents is highly limited in comparison with other traditional chromatographic separation methods that depend mainly on a high proportion of organic modifiers. This concept, in turn, emphasizes the application of green chemistry in the analysis of pharmaceutical products. The simplicity, relatively low cost and short analysis time of the suggested method makes it a candidate for routine quality control work.

Determination of Quinolones in Spicy Soup Using Packed Fiber Solid Phase Extraction and High Performance Liquid Chromatography-Fluorimetric Detection / 分析化学

An analytical method for simultaneous determination of five quinolones in spicy soup was developed. Spicy soup samples were firstly extracted by EDTA-Mcllvaine buffer at pH 4, then purified and concentrated by a novel Packed fiber solid phase extraction ( PFSPE ) coulumn. The extracted liquid supernatant was loaded onto the column, rinsed with water, and then eluted with 2% ammoniated methanol. The mobile phase was methanol-water-phosphoric acid (25:75:0. 1, V/V, adjusting the pH to 2. 8 with triethylamine) . These analytes were quantified by high performance liquid chromatography-fluorimetric detector( HPLC-FLD) at excitation and emission wavelength of 280 nm and 450 nm respectively. Recoveries of spiked quinolone antibiotics in spicy soup were from 72 . 1% to 110 . 3% with intraday relative standard deviation (RSD) between 1. 6% and 4. 3% and inter-day RSD from 2. 0% to 4. 3%. Limit of detection (LOD) and limit of quantitation(LOQ) were from 1. 2 to 5. 4 μg/L and from 3. 9 to 18 μg/L, respectively. The method could be applied to determine the quinolones in spicy soup.

Rapid chromatographic determination of caseins in milk with photometric and fluorimetric detection using a hydrophobic monolithic column.

Reverse-phase liquid chromatographic methods using a hydrophobic C18 monolithic column and on-line photometric and fluorimetric detection for the determination of the major casein (CN) proteins in milk are presented. The separation of αs1-CN, αs2-CN, ß-CN and κ-CN was achieved in only five minutes. Fluorimetric detection enabled better analytical results than photometric detection. Thus, the dynamic ranges of the calibration graphs and detection limits obtained using fluorimetric detection were (mgmL(-)(1)): αs1-CN (0.74-10.0, 0.22), αs2-CN (0.15-10.0, 0.045), ß-CN (0.68-10.0, 0.20) and κ-CN (0.21-10.0, 0.06). The analytical features of the photometric method, which does not allow the quantification of ß-casein, were (mgmL(-)(1)): αs1-CN (1.5-9.0, 0.45), αs2-CN (1.4-10.0, 0.43) and κ-CN (0.4-9.0, 0.12). Precision data, expressed as relative standard deviation, ranged between 0.6% and 5.3% for the fluorimetric method and between 2.4% and 6.2% for the photometric method. Both methods were applied to the analysis of three different milk samples, obtaining recoveries in the ranges of 86.6-103.2% and 92.0-106.5% using fluorimetric and photometric detection, respectively.

Simultaneous Determination of Three Sulfonamides Residues in Vegetable by High Performance Liquid Chromatographic Method with Fluorimetric Detection / 分析化学

A high performance liquid chromatographic method with fluorimetric detector was developed for the simultaneous determination of three sulfonamides in vegetable samples. Vegetable samples were extracted with methanol for three times, and then the combined extracts were evaporated to dryness under reduced pressure at 45 ℃. The residue was dissolved in 0.1 mol/L HCl and the analytes were derivatized with fluorescamine. The chromatographic separation was performed on an ODS column with a gradient elution program using mobile phases based on mixtures of acetonitrile and 0.5% acetic acid aqueous solution. The derivatized compounds were detected with fluorimetric detector. The limit of detection was 1.02-1.29 μg/L and the limit of quantification was 3.4-4.3 μg/kg(fresh weight, F.W.) for three sulfonamides in vegetable. The average recoveries were higher than 87%, inter and intra RSDs were lower than 10% for all samples spiked with 0.2-1.0 μg/g of sulfonamides. The proposed method has been applied to the analysis of vegetables sold in Hefei markets. The result indicated that 3 SAs were found at different degree in the practical vegetable samples with the total concentrations between 0.0726-0.3709 μg/g(F.W.).

Determination of Quinolones in Soils Using Solid Phase Extraction and High Performance Liquid Chromatography-Fluorimetric Detection / 分析化学

An analytical method for the simultaneous determination of four quinolones in soil was developed. Soil samples were extracted by a mixture of 50% magnesium nitrate and 10% ammonia(96∶ 4, V/V)with an ultrasonic-assisted extraction, then purified and concentrated by HLB cartridge, and eluted with acetonitrile and 0.067 mol/L phosphoric acid(5∶ 1, V/V). Using acetonitrile and 0.067 mol/L phosphoric acid(pH=2.5) as the mobile phase, these analytes were quantificated by HPLC(fluorimetric detector) at excitation and emission wavelength of 280 nm and 450 nm respectively. The detective limits for four quinolones in soil were from 0.58 to 0.03 g/kg. The recoveries were 60.4% to 99.3% for soil samples. The method was successfully applied to determine the quinolones in soil samples from vegetable fields. Four quinolone compounds were detected to a different extent with total amounts of quinolones ranged from 27.84 to 129.26 μg/kg.