Real-time and specific monitoring of nitric oxide and evaluating of the oxidative stress in living cells and zebrafish under the pollutant exposure using a carbon dot-based composite fluorescent probe.

Nitric oxide (NO) functions as an essential signalling molecule in various physiological and pathological pathways. In vitro and vivo redox processes mediated by reactive oxygen species (ROS) and nitric oxide (NO) directly influence the intracellular state. In this study, a red-emitting fluorescent nanoprobe, N,S-CDs@Zn-ICA, was synthesized to monitor NO fluctuations in living cells and zebrafish under the exposure to various pollutants. Red-emissive carbon dots (N,S-CDs) were synthesized by a hydrothermal method using o-phenylenediamine and urea as carbon / nitrogen sources, and H2SO4 as sulfur source. Glutathione (GSH) was introduced to link N,S-CDs with metal organic complexes (Zn-ICA) through an amidation reaction to fabricate a carbon dot-based composite fluorescent probe, which greatly improved the selectivity, stability, and response time of the N,S-CDs. The composite probe has high selectivity and sensitivity with limit of detection (LOD) of 96.0 nM. Furthermore, the proposed probe was successfully used to monitor the dynamic changes in NO levels and evaluate oxidative stress in MCF-7 cells and zebrafish under the exposure to various pollutants, including seven heavy metal ions (such as Pb2+, Cd2+, and Hg2+) and nine organic pollutants at different concentrations and exposure times. This work provides a novel strategy for constructing highly selective and red-emitting fluorescent probe for real-time and dynamic monitoring of NO and further evaluating oxidative stress induced by pollutants in vitro and in vivo via fluorescence imaging.

Gelatinous lanthanide coordination polymer with aggregation-enhanced antenna effect for ratiometric detection of endogenous alkaline phosphatase.

Aggregation-induced emission (AIE) and antenna effect (AE) are two significant behaviors that have attracted increasing attention. However, it is challenging to achieve the synergistic effect of AIE and AE in luminescent materials for more extensive applications. Here, four gelatinous Ln3+ coordination polymers (Ln-CPs) are synthesized by self-assembly of ciprofloxacin (CIP), adenosine monophosphate (AMP), and Ln3+ ions in aqueous medium. Encouragingly, a remarkable increase in the characteristic fluorescence of Ln3+ and a significant decrease in CIP are observed along with increasing concentration of Ln-CPs, which is attributed to the large aggregates formed by self-assembly that strictly constrain the intramolecular motions of antenna ligands, thereby achieving the aggregation-enhanced AE. More meaningfully, Eu-CP not only shows a rice-like morphology at high aggregation state, but also provides an opportunity for the selective detection of alkaline phosphatase (ALP). A new flower-like polymer is formed upon incubating Eu-CP with ALP, accompanied by the fluorescence quenching of Eu3+ and recovery of CIP, a ratiometric determination of ALP in the range of 0.1-6.0 U·L-1 is thus achieved. Additionally, ALP assay in human serum and bioimaging in living cells have been successfully performed. This research opens a new horizon for the fabrication of Ln3+-based luminescent materials with promising applications.

Dual-response fluorescent probe based on nitrogen-doped carbon dots and europium ions hybrid for ratiometric and on-site visual determination of oxytetracycline and tetracycline.

Tetracyclines residues, particularly oxytetracycline (OTC) and tetracycline (TC), have raised extensive concern because of their serious adverse effects on human health. Herein, a dual-response fluorescent probe based on nitrogen-doped carbon dots (N-CDs) and Eu3+ hybrid (N-CDs-Eu3+) was developed to selectively determine OTC and TC. The N-CDs act as ancillary ligands of Eu3+ and recognition units of OTC/TC, while the Eu3+ ions chelated with N-CDs can also specifically recognize OTC/TC. Upon inclusion of OTC/TC, an enhancement in Eu3+ emission occurs due to the energy transfer from OTC/TC to Eu3+ and the efficient elimination of quenching effect caused by H2O molecule, which is attributed to the incorporation of N-CDs; while the blue fluorescence emitted by the N-CDs decreases under the inner filter effect and static quenching effect caused by OTC/TC. Based on the double and reverse response signals, the ratiometric detection of OTC and TC in the range of 0.1-45 µΜ and 0.1-30 µΜ is achieved with a detection limit of 0.017 and 0.041 µM, respectively. In addition, the noticeable variation in fluorescence color of the probe is integrated with a smartphone-assisted analysis device for the rapid on-site quantitative assay of OTC, where the detection limit is 0.15 µΜ. The results show that this probe performs with excellent specificity and anti-interference for both OTC and TC, and satisfactory detection results are obtained in lake water, milk, and honey samples, thereby confirming that the probe exhibits promising application in food safety and environmental monitoring.

Lanthanide coordination polymer nanoparticles as a ratiometric fluorescence sensor for real-time and visual detection of tetracycline by a smartphone and test paper based on the analyte-triggered antenna effect and inner filter effect.

Lanthanide coordination polymer nanoparticles (LML-Eu3+-GMP CPNPs) were fabricated as a ratiometric fluorescence sensor for real-time and visual assays of tetracycline (TC). The LML-Eu3+-GMP CPNPs were prepared by spontaneous self-assembly of Eu3+, luminol (LML) and guanosine 5'-monophosphate (GMP) at room temperature, which only emitted blue fluorescence dominated by LML, and no red characteristic fluorescence of Eu3+ was observed. In the presence of TC, TC can trigger the antenna effect (AE) and inner filter effect (IFE), the blue fluorescence of LML-Eu3+-GMP CPNPs is quenched by TC via IFE, and the red characteristic fluorescence of Eu3+ can be turned on through AE. When sodium citrate (Cit) is added to the sensing system, it can further enhance the red fluorescence of Eu3+. The dual-ligand CPNP sensor has a rapid fluorescence response, noticeable fluorescence color change, good selectivity, and high sensitivity with a detection limit of 3.4 nM. It was successfully applied to detect TC in honey, milk, lake water and tap water. Meanwhile, the portable smartphone and test paper were applied to develop POCT devices for real-time and visual detection of TC, which could offer a promising application for real-time and semiquantitative assays of TC.

Silicon nanoparticles / gold nanoparticles composite as a fluorescence probe for sensitive and selective detection of Co2+ and vitamin B12 based on the selective aggregation and inner filter effect.

Cobalt as a transition metal ion is a biologically essential trace element, and plays an important role in various biological systems. The silicon nanoparticles (SiNPs) / gold nanoparticles (AuNPs) composite as a simple and efficient fluorescent probe was developed to detect Co2+ and vitamin B12 (VB12) based on the selective aggregation and inner filter effect (IFE). The green-emitting SiNPs were synthesized by one-pot hydrothermal method, and the AuNPs were synthesized and modified with thioglycolic acid and cetyltrimethylammonium bromide. The fluorescent probe was fabricated by simple mixing the SiNPs and AuNPs together. In the presence of Co2+/VB12, AuNPs are selectively aggregated, which results in the enhancement of the local surface plasmon resonance absorption centered at 520 nm and the green fluorescence of SiNPs is significantly quenched via IFE. The fluorescence quenching efficiency of the probe is linearly proportional to the concentration of Co2+ in the range of 0.1-80 µM with a low detection limit of 60 nM, which is far lower than the guideline value of Co2+ in drinking water (1.7 µM). For vitamin B12 (VB12), its linear relationship is in the range of 0.1-100 µM, and the limit of detection is 69 nM. Furthermore, the proposed method shows good selectivity for the detection of Co2+ and VB12, and does not need sophisticated pretreatment, only through simple filter. It has been applied in actual environmental water samples and drug tablets with satisfactory results.

Dual-functional lanthanide metal organic frameworks for visual and ultrasensitive ratiometric fluorescent detection of phosphate based on aggregation-induced energy transfer.

Phosphate (Pi) not only plays a significant role in physiological processes, but also is an important indicator for aquatic ecosystems. The dual-functional lanthanide metal organic frameworks (MOFs) were synthesized for visual and ultrasensitive ratiometric fluorescent detection of Pi based on aggregation-induced energy transfer. In the MOFs material, ciprofloxacin (CIP) functions as an energy donor and results in the fluorescence enhancement of Eu3+; the introduction of pyromellitic acid can cause the aggregation of the CIP-Eu3+ complex, and red characteristic fluorescence of Eu3+ at 614 nm is further enhanced (about 40 times). When Pi is added to the MOFs solution, CIP is released from the MOFs, red fluorescence of Eu3+ is quenched and blue fluorescence of CIP is simultaneously recovered, thereby a ratiometric fluorescent probe for the detection of Pi was fabricated. The fluorescent response based on intermolecular energy transfer of the CIP-Eu3+ complex is very sensitive to Pi. The limit of detection (3σ/K) of the probe is ultrasensitive and attains 4.4 nM. The possible interferential substances such as 17 common metal ions and 14 anions investigated do not interfere with the Pi detection. The ratiometric fluorescent probe has been successfully used in the determination of Pi in real human urine and lake water samples. This work may supply a new strategy for fabricating ratiometric fluorescent probe and a prospective application in biological and environmental samples.

Dual-Emission Fluorescent Probe for the Simultaneous Detection of Nitrite and Mercury(II) in Environmental Water Samples Based on the Tb3+-Modified Carbon Quantum Dot/3-Aminophenylboronic Acid Hybrid.

Nitrite (NO2-) and mercury (Hg2+) ions are recognized as two typical inorganic contaminations that can cause severe damage to the environment and humans. In this paper, the energy transfer from carbon quantum dots (CQDs) to Tb3+ by the antenna effect was found, which can promote the f-f transition of Tb3+ and emit strong characteristic fluorescence of Tb3+. Based on CQD-Tb3+ and 3-aminophenylboronic acid (APBA), which have respectively sensitive and specific fluorescent response to NO2- and Hg2+ with different fluorescent signals, a dual-emission fluorescent probe of the CQD-Tb3+/APBA hybrid was thus fabricated for the simultaneous detection of NO2- and Hg2+ in environmental water samples. They emit dual-emission fluorescence peaks centered at 373 and 545 nm, respectively. A good linearity between the quenching efficiency of (F0 - F)/F0 and the concentrations of NO2- and Hg2+ was in the range of 5.0-1200.0 nM for NO2- and 0.1-6.0 µM for Hg2+. The limit of detection (LOD, 3σ/K) is ultrasensitive for NO2- (2.0 nM), and the LOD for Hg2+ is 38.1 nM. The dual-emission fluorescent probe was successfully applied for the determination of NO2- and Hg2+ in various environmental water samples. The possible luminescence and fluorescence quenching mechanisms of the probe are also discussed in detail. This study provides a new approach for fabricating a multifunctional fluorescent probe or sensor and a prospective application in environmental monitoring.

[Synthesis of magnetic graphene oxide modified with dodecylamine and its application for the determination of seven endocrine-disrupting chemicals in environmental water samples].

Magnetic graphene oxide (MGO) modified with dodecylamine (DDA) was synthesized in this work. The as-prepared MGO-DDA was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and vibrating sample magnetometer measurements. The material was used as the absorbent in magnetic solid-phase extraction (MSPE) for seven environmental endocrine-disrupting chemicals (EDCs):estrone (E1), ß-estradiol (E2), estriol (E3), 17α-ethynylestradiol (EE2), hexoestrol (HEX), androstendione (AND), and bisphenol A (BPA). MSPE combined with HPLC-UV was developed for the determination of EDCs in environmental water samples. The effects of the amount of adsorbent, adsorbing time, and the type and volume of eluents on the recoveries of the EDCs were investigated. Under the optimal conditions, good linear relationships between the UV signals and the EDC concentrations were obtained, with R2 greater than 0.999. The limits of detection for all the EDCs were between 0.10 and 0.23 nmol/L. The MSPE-HPLC-UV method was successfully applied to the analysis of the seven EDCs in environmental water samples such as lake water and sewage water samples. The recoveries of all the EDCs in spiked lake water and sewage water samples were between 73.9% and 114.7%, and the RSDs ranged from 0.7% to 11.8%. Thus, the proposed MSPE-HPLC-UV method is simple, reliable, sensitive, and low-cost.

Ratiometric fluorometric determination of silver(I) by using blue-emitting silicon- and nitrogen-doped carbon quantum dots and red-emitting N-acetyl-L-cysteine-capped CdTe quantum dots.

A ratiometric fluorometric assay for silver(I) is described. The method makes use of a dually emitting quantum dot hybrid, which is composed of (a) blue-fluorescent silicon- and nitrogen-doped carbon quantum dots (CQDs), and (b) of red-emitting CdTe quantum dots (QDs) capped with N-acetyl-L-cysteine. The red-emitting CdTe QDs undergo strong and specific quenching by Ag(I), whereas the blue-emitting N,Si-CQDs are not quenched. The two kinds of QDs are mixed and used as a ratiometric fluorescent probe. A linear relationship is found between the log of intensities [(I608/I441)0/(I608/I441)] and the concentration of Ag(I) in the range from 5.0-1000 nM, and the limit of detection (at S/N = 3) is 1.7 nM. Possible interferents (including 17 general metal ions, 12 anions and fulvic acid) do not interfere with the determination. The assay was successfully used for the determination of Ag(I) in surface water and wastewater samples. The fluorescence quenching mechanism of the ratiometric assay system was also discussed in detailed. Graphical abstract Schematic representation of a ratiometric probe composed of silicon- and nitrogen-doped carbon quantum dots (N,Si-CQDs) and CdTe quantum dots capped by N-acetyl-L-cysteine (CdTe QDs). This dual-emission QDs hybrid was fabricated for ultrasensitive and highly selective detection of silver(I) in water samples.

Nitrogen- and Sulfur-Codoped Carbon Dots for Highly Selective and Sensitive Fluorescent Detection of Hg2+ Ions and Sulfide in Environmental Water Samples.

Nitrogen- and sulfur-codoped carbon dots (N,S-CDs) with a fluorescence quantum yield of 16.1% and good photoluminescent properties were synthesized by a simple hydrothermal method. Cytotoxicity of the N,S-CDs was evaluated by the MTT assay, and human hepatoma HepG2 cells were chosen as the target. The cell viability was more than 85% after 24 h of incubation when its concentration was up to 300 µg/mL, suggesting low cytotoxicity and good biocompatibility of the N,S-CDs. The fluorescence spectra of the N,S-CDs are excitation-dependent in the excitation-wavelength range of 295-400 nm, and it emits bright blue fluorescence centered at 435 nm. Its selective fluorescence recognition for Hg2+ ions was found. When Hg2+ ions were added to the N,S-CDs solution, its bright blue fluorescence was obviously quenched and could be recovered by the addition of sulfide. Accordingly, a new strategy based on N,S-CDs-Hg2+ system as a highly selective and ultrasensitive "turn off-on" fluorescence sensing for the detection of sulfide was fabricated. The limits of detection (S/N = 3) are 83 nM for Hg2+ ions and 11 nM for sulfide. Almost no statistically significant interference for Hg2+-ion and sulfide detection was observed among possible coexisting substances in the water samples, including 17 common metal ions and 11 anions. This probe was successfully applied for the cellular imaging of Hg2+ ions in HepG2 cells by fluorescence microscopy.

A Specific Turn-On Fluorescent Sensing for Ultrasensitive and Selective Detection of Phosphate in Environmental Samples Based on Antenna Effect-Improved FRET by Surfactant.

Phosphate is not only an important indicator for aquatic ecosystems, but also plays vital roles in biosystems. A new strategy for ultrasensitive and selective detection of phosphate is fabricated based on a new insight found in this paper, in which a lower concentration of surfactant sodium dodecylbenzenesulfonate (SDBS) can greatly induce fluorescence resonance energy transfer (FRET) from ciprofloxacin (CIP) to Eu3+ in the CIP-Eu3+ complex. Surfactant SDBS does not act as a sensitizer for enhancing the fluorescence intensity of the system, but acts as a sensitizer of FRET and makes the native fluorescence of CIP quenched completely (switch off). Eu3+ ions can coordinate with the oxygen-donor atoms of phosphate, which weakens FRET from CIP to Eu3+ and results in the fluorescence recovery of CIP (turn on). The multicomplex of the CIP-Eu3+-phosphate has more sensitive fluorescent response than that of the reported coordination nanoparticle-based fluorescent probes. The LOD (S/N = 3) of this sensing system can attain 4.3 nM. The possible interferential substances existing in environmental samples, such as 17 common metal ions, 11 anions, and fulvic acid investigated, do not interfere with the phosphate detection. This sensing system has been successfully applied for phosphate detection in environmental samples such as wastewater, surface water, and atmospheric particulates. This work not only develops a fluorescent probe for the phosphate detection, but also provides a new strategy for designing fluorescent probes based on FRET or coordination nanoparticles.

Molecular interactions of benzophenone UV filters with human serum albumin revealed by spectroscopic techniques and molecular modeling.

Benzophenone (BP)-type UV filters have been widely used in many personal care products to protect human from UV exposure. Their dermal applications can cause direct human health risk following accumulation in bloodstream. Few studies have addressed whether BP-type UV filters could bind and alter the structure and function of human serum albumin (HSA), the major carrier protein in plasma. Four benzophenones, BP-1, BP-2, BP-3 and BP-8 were selected to investigate their potentially toxic interactions with HSA and the intrinsic binding mechanism using combined spectroscopies and molecular docking techniques. Four benzophenones significantly quench the intrinsic fluorescence of HSA via static mode. The competitive binding fluorescence assay and molecular docking both revealed that the benzophenones bind at site II of HSA. Their binding constants range from 1.91 × 10(4)M(-1) to 12.96 × 10(4)M(-1) at 296 K. BP-8 interacts with HSA mainly through hydrogen bonding interactions and van der Waals interactions, while hydrophobic interactions and electrostatic interactions are dominant for interactions between BP-1, BP-2, BP-3 and HSA. Molecular docking revealed that the changes in structural moiety and hydrophobicity of four benzophenones account for their different binding affinities. As further revealed by circular dichroism and time-resolved fluorescence decay, these benzophenones cause global and local structural changes of HSA, which illustrates their potential toxicity to cause structural damage of HSA. Two degradation products of BP-3 have higher binding affinities to HSA, suggesting higher potencies in causing adverse effects on human health.

Enrichment of steroid hormones in water with porous and hydrophobic polymer-based SPE followed by HPLC-UV determination.

There have been great concerns about the persistence of steroid hormones in surface water. Since the concentrations of these compounds in water samples are usually at a trace level, the efficient enrichment of steroid hormones is vital for further analysis. In this work, a porous and hydrophobic polymer was synthesized and characterized. The composition of solvent used as porogen in the synthetic process was shown to have an effect on the morphology of the polymer, which was successfully used as an SPE sorbent for simultaneously enriching steroid hormones in surface water samples. The recoveries of the steroid hormones on the custom-made polymer ranged from 93.4 to 106.2%, whereas those on commercialized ENVI-18, LC-18, and Oasis HLB ranged from 54.8 to 104.9, 66 to 93.6, and 77.2 to 106%, respectively. Five types of steroid hormones were simultaneously measured using HPLC-UV after they were enriched by the custom-made sorbent. Based on these findings, the SPE-HPLC method was developed. The LODs of this method for estriol, estradiol, estrone, androstenedione, progesterone were 0.07, 0.43, 0.61, 0.27, and 0.42 µg/L, respectively, while precision and reproducibility RSDs were <6.40 and 7.49%, respectively.

Probing the molecular interaction of triazole fungicides with human serum albumin by multispectroscopic techniques and molecular modeling.

Triazole fungicides, one category of broad-spectrum fungicides, are widely applied in agriculture and medicine. The extensive use leads to many residues and casts potential detrimental effects on aquatic ecosystems and human health. After exposure of the human body, triazole fungicides may penetrate into the bloodstream and interact with plasma proteins. Whether they could have an impact on the structure and function of proteins is still poorly understood. By using multispectroscopic techniques and molecular modeling, the interaction of several typical triazole fungicides with human serum albumin (HSA), the major plasma protein, was investigated. The steady-state and time-resolved fluorescence spectra manifested that static type, due to complex formation, was the dominant mechanism for fluorescence quenching. Structurally related binding modes speculated by thermodynamic parameters agreed with the prediction of molecular modeling. For triadimefon, hydrogen bonding with Arg-218 and Arg-222 played an important role, whereas for imazalil, myclobutanil, and penconazole, the binding process was mainly contributed by hydrophobic and electrostatic interactions. Via alterations in three-dimensional fluorescence and circular dichroism spectral properties, it was concluded that triazoles could induce slight conformational and some microenvironmental changes of HSA. It is anticipated that these data can provide some information for possible toxicity risk of triazole fungicides to human health and be helpful in reinforcing the supervision of food safety.

Fluorescent lifetime imaging of atmospheric aerosols: a direct probe of aerosol viscosity.

The viscosity of atmospheric aerosol particles affects a number of key physical and chemical particle properties, such as composition and reactivity. However, determination of the microscopic viscosity of aerosol particles is a non-trivial task. We report a new method of imaging viscosity in a variety of model aerosol systems, based on a fluorescence lifetime determination of viscosity-sensitive fluorophores termed molecular rotors. We report the viscosity changes associated with the relative humidity dependent hygroscopicity of NaCI and sucrose aerosols, as well as reaction dependent changes in viscosity during ozonolysis of oleic acid aerosols. The Fluorescence Lifetime Imaging Microscopy (FLIM) of molecular rotors shows great promise in understanding important fundamental aerosol properties, which can be both time-dependent and spatially variable through the aerosol particle.

Occurrence and risk assessment of four typical fluoroquinolone antibiotics in raw and treated sewage and in receiving waters in Hangzhou, China.

A sensitive liquid chromatography-fluorescence detection method, combined with one-step solid-phase extraction, was established for detecting the residual levels of the four typical fluoroquinolone antibiotics (ofloxacin, norfloxacin, ciprofloxacin, and enrofloxacin) in influent, effluent, and surface waters from Hangzhou, China. For the various environmental water matrices, the overall recoveries were from 76.8 to 122%, and no obvious interferences of matrix effect were observed. The limit of quantitation of this method was estimated to be 17 ng/L for ciprofloxacin and norfloxacin, 20 ng/L for ofloxacin, and 27 ng/L for enrofloxacin. All of the four typical fluoroquinolone antibiotics were found in the wastewaters and surface waters. The residual contents of the four typical fluoroquinolone antibiotics in influent, effluent, and surface water samples are 108-1405, 54-429, and 7.0-51.6 ng/L, respectively. The removal rates of the selected fluoroquinolone antibiotics were 69.5 (ofloxacin), 61.3 (norfloxacin), and 50% (enrofloxacin), indicating that activated sludge treatment is effective except for ciprofloxacin and necessary to remove these fluoroquinolone antibiotics in municipal sewage. The risk to the aquatic environment was estimated by a ratio of measured environmental concentration and predicted no-effect concentration. At the concentrations, these fluoroquinolone antibiotics were found in influent, effluent, and surface waters, and they should not pose a risk for the aquatic environment.

Optical ammonia gas sensor based on a porous silicon rugate filter coated with polymer-supported dye.

An ammonia gas sensor chip was prepared by coating an electrochemically-etched porous Si rugate filter with a chitosan film that is crosslinked by glycidoxypropyltrimethoxysilane (GPTMS). The bromothylmol blue (BTB), a pH indicator, was loaded in the film as ammonia-sensing molecules. White light reflected from the porous Si has a narrow bandwidth spectrum with a peak at 610 nm. Monitoring reflective optical intensity at the peak position allows for direct, real-time observation of changes in the concentration of ammonia gas in air samples. The reflective optical intensity decreased linearly with increasing concentrations of ammonia gas over the range of 0-100 ppm. The lowest detection limit was 0.5 ppm for ammonia gas. At optimum conditions, the full response time of the ammonia gas sensor was less than 15s. The sensor chip also exhibited a good long-term stability over 1 year. Therefore, the simple sensor design has potential application in miniaturized optical measurement for online ammonia gas detection.

Metal ion mediated molecularly imprinted polymer for selective capturing antibiotics containing beta-diketone structure.

A new molecularly imprinted polymer (MIP) targeting to quinolones (Qs) and tetracyclines (TCs) was synthesized using itaconic acid (ITA) and ciprofloxacin (CIP) as a functional monomer and template molecule, respectively. Factors affecting the overall performance of MIP were investigated, and the results showed that Fe(3+) ion play a vital role in the formation of MIP with high molecular imprinting effect. Meanwhile, the chelating ability of monomer, species of template molecule, as well as the molar ratio of monomer and template also contribute to the performance of the obtained MIP. Cyclic voltammetry verified that, with the participation of Fe(3+) ions, a ternary complex of ITA-Fe(3+)-CIP could be formed before polymerization. Compared with conventional MIP prepared from commonly used monomer, methacrylic acid (MAA), the new MIP show significantly enhanced molecular imprinting effect and higher capacity for specific adsorption of target compounds as revealed by static and dynamic binding experiments. The MIP was successfully used as solid-phase extraction (SPE) adsorbent for enriching a broad spectrum of antibiotics containing beta-diketone structure from surface water sample. HPLC detection showed that high recovery rate (78.6-113.6%) was found in these spiked antibiotics, whereas recovery rate for the non structurally related drugs, epinephrine (EP) and dopamine (DOPA), was very low (4.7-7.6%) on the MIP cartridges. The results demonstrate that the MIP prepared by the strategy proposed in this work, could specifically target to a series of structurally related antibiotics containing beta-diketone structure.

Synchronous fluorescence measurement of enrofloxacin in the pharmaceutical formulation and its residue in milks based on the yttrium (III)-perturbed luminescence.

A simple, rapid and sensitive synchronous fluorescence method is put forward for the determination of enrofloxacin (ENRO) in the pharmaceutical formulation and its residue in milk based on the yttrium (III)-perturbed luminescence. When Y(3+) is added into the ENRO solution, the fluorescence of ENRO is significantly enhanced. The synchronous fluorescence technology is employed in the method to determine trace amount of ENRO residue in milks. The synchronous fluorescence intensity of the system is measured in a 1-cm quartz cell with excitation wavelength of 328 nm, Δλ=80 nm. A good linear relationship between the fluorescence intensity and the ENRO concentration is obtained in the range of 1.0 × 10(-9) to 2.0 × 10(-6)mol L(-1) (r(2)=0.9992). The limit of detection (LOD) of this method attains as low as 3.0 × 10(-10) mol L(-1) (S/N=3). The selectivity of this method is also very good. Common metal ions, rare-earth ions and some pharmaceuticals, which are usually used together with ENRO, do not interfere with the determination of ENRO under the actual conditions. The proposed method can be applied to determine ENRO residue in milks, and limit of quantification (LOQ) determined in the spiked milk is estimated to be 2.8 × 10(-8) mol L(-1) (10 µg L(-1)). Moreover, this method can be used as a rapid screening for judging whether the ENRO residues in milks exceed Minimal Risk Levels (MRLs) or not. In addition, the mechanism of the fluorescence enhancement is also discussed in detail.

Simultaneous determination of five nitroaniline and dinitroaniline isomers in wastewaters by solid-phase extraction and high-performance liquid chromatography with ultraviolet detection.

A high-performance liquid chromatography (HPLC)-ultraviolet detection method, combined with solid-phase extraction (SPE), was developed for the determination of five nitroaniline and dinitroaniline isomers including 2-nitroaniline, 3-nitroaniline, 4-nitroaniline, 2,4-dinitroaniline and 2,6-dinitroaniline in wastewater samples. Extraction of the five isomers was carried out with a hydrophile-lipophile balance cartridge, the Oasis HLB. The cartridge was washed by a mixed aqueous solution containing 10% (v/v) acetonitrile and 10% (v/v) ethyl acetate before the five isomers were eluted by a mixture of methanol and acetic acid. Separation of the five isomers was achieved by using an Agilent TC-C(18) column at 30°C, and using a mixture of acetonitrile/water 30/70 (v/v) as mobile phase under an isocratic condition at a flow rate of 1.0 mL/min. The analytes were detected by a UV detector at a wavelength of 225 nm. Recoveries of the five isomers in the spiked sewage sample were between 84.6% and 94.0% with a relative standard deviation of less than 4.7%. The limits of quantification (LOQ) determined in a spiked sewage sample of 500 mL were 2.0 x 10(-9)M for 2-nitroaniline, 3-nitroaniline and 2,6-dinitroaniline, and 4.5 x 10(-9)M for 4-nitroaniline and 2,4-dinitroaniline. The proposed method was applied to determine the five isomers in real samples of acidic wastewater and printing and dyeing wastewater.