Visible-Light-Initiated Multicomponent Reactions of α-Diazoesters to Access Organophosphorus Compounds.

A simple visible-light-initiated strategy has been established for the construction of organophosphorus compounds via aerobic multicomponent reaction of α-diazoesters, cyclic ethers, and P(O)H compounds under air. A number of phosphonates and phosphinates could be efficiently isolated in moderate to good yields without the use of photosensitizers and metal reagents. This multicomponent reaction has advantages of mild condition, simple operation, eco-friendly energy, good functional-group tolerance, and gram-scale synthesis.

Carbon quantum dots-functionalized silica stationary phase for pharmaceutical analysis by a green liquid chromatography mode.

Facing the trends of green chemistry, this work tries to find a novel material for per aqueous liquid chromatography (PALC) aiming to reduce the consumption of hazardous reagents. As a kind of green nanomaterials, the chromatographic performance of carbon quantum dots (CQDs) in PALC was rarely studied. Here, hydrophilic CQDs were prepared by a simple hydrothermal method using citric acid and ethylenediamine as carbon sources. The synthesized CQDs with functional groups of amino, carboxyl, and hydroxyl were decorated on silica gels forming a novel Si-CQDs stationary phase. This Si-CQDs column possesses the typical retention feature of PALC. Compounds with different polarities including hydrophobic pesticides, polar sulfonamides, ß-adrenoceptor blockers and agonists, as well as hydrophilic nucleosides and bases obtained satisfactory separation on this Si-CQDs column under PALC mode, even better resolution than in hydrophilic interaction liquid chromatography (HILIC) mode. A mixture of four sulfonamides can be separated within 6 min using a mobile phase containing only 5% acetonitrile, and the resolution achieves 2.39, 2.13, and 1.83 with an average column efficiency of 1400. For certain compounds, this Si-CQDs column showed better separation performance than commercial SiO2 column, NH2 column, and C18 column. The retention mechanism includes hydrophobic and electrostatic interactions due to the multifunctional groups of CQDs. This Si-CQDs column achieved the rapid detection of residual sulfonamides in milk with simplified sample pretreatment process and the detection of atenolol in commercial atenolol tablets. The developed Si-CQDs column has great prospects in low-cost and environmentally friendly separation and analysis.

Ratiometric fluorescence sensing of formaldehyde in food samples based on bifunctional MOF.

A new fluorescence strategy was described for ratiometric sensing of formaldehyde (FA) with bifunctional MOF, which acted as a fluorescence reporter as well as biomimetic peroxidase. With the assistance of H2O2, NH2-MIL-101 (Fe) catalyzes the oxidation of non-luminescent substrate o-phenylenediamine (OPD) to produce fluorescent product (oxOPD) with the maximum emission at 570 nm. Besides, intrinsic fluorescence of MOF (λem = 445 nm) was quenched by oxOPD through inner filter effect (IFE). However, FA and OPD reacted to generate Schiff bases, which competitively consumed OPD inhibiting the generation of oxOPD. Under the excitation wavelength of 375 nm, a ratiometric strategy was designed to detect FA with the fluorescence intensity ratio at 445 nm and 570 nm (F445/F570) as readout signal. This strategy exhibited a wide linear range (0.1-50 µM) and low detection limit of 0.03 µM. This method was confirmed for FA detection in food samples. In addition to establishing a new method to detect FA, this work will open new applications of MOF in food safety.

Lead halide perovskites with aggregation-induced emission feature coupled with gold nanoparticles for fluorescence detection of heparin.

Herein, a new kind of lead halide perovskite (LHP, (C12H25NH3)2PbI4) with aggregation-induced emission (AIE) feature is developed as a fluorescent probe for heparin (Hep). The LHPs exhibit high emission when they aggregate in water. Interestingly, a few picomoles of dispersed gold nanoparticles (AuNPs) can quench the emission of LHPs, but the aggregated AuNPs are invalid. When protamine (Pro) is mixed with AuNPs at first, the negatively charged AuNPs aggregate through electrostatic interaction, producing the AIE recovery. Nevertheless, Hep disturbs the interaction between AuNPs and Pro due to its strong electrostatic interaction with Pro. Therefore, the dispersed AuNPs quench the fluorescence of LHPs again. A response linear range of Hep of 0.8-4.2 ng ml-1is obtained, and the detection limit is 0.29 ng ml-1. Compared with other probes for determination of Hep with AuNPs, this strategy exhibits better sensitivity due to the small quantity of AuNPs used. Finally, it is also successfully applied to detect Hep in human serum samples with satisfactory recoveries.

MOF@MnO2nanocomposites prepared usingin situmethod and recyclable cholesterol oxidase-inorganic hybrid nanoflowers for cholesterol determination.

In this work, through thein situgrowth of MnO2nanosheets on the surface of terbium metal-organic frameworks (Tb-MOFs), MOF@MnO2nanocomposites are prepared and the fluorescence of Tb-MOFs is quenched significantly by MnO2. Additionally, the hybrid nanoflowers are self-assembled by cholesterol oxidase (ChOx) and copper phosphate (Cu3(PO4)2·3H2O). Then a new strategy for cholesterol determination is developed based on MOF@MnO2nanocomposites and hybrid nanoflowers. Cholesterol is oxidized under the catalysis of hybrid nanoflowers to yield H2O2, which further reduces MnO2nanosheets into Mn2+. Hence, the fluorescence recovery of Tb-MOFs is positively correlated to the concentration of cholesterol in the range of 10 to 360µM. The limit of detection (LOD) of cholesterol is 1.57µM. On the other hand, the hierarchical and confined structure of ChOx-inorganic hybrid nanoflowers greatly improve the stability of the enzyme. The activity of hybrid nanoflowers remains at a high level for one week when stored at room temperature. Moreover, the hybrid nanoflowers can be collected by centrifugation and reused. The activity of hybrid nanoflowers can continue at a high level for five cycles of determination. Therefore, it can be concluded that the hybrid nanoflowers are more stable and more economic than free enzymes, and they show a similar sensitivity and specificity to cholesterol compared with free ChOx. Finally, this strategy has been further validated for the determination of cholesterol in serum samples with satisfactory recoveries.

A fluorescence strategy for monitoring α-glucosidase activity and screening its inhibitors from Chinese herbal medicines based on Cu nanoclusters with aggregation-induced emission.

Herein, the self-assembly of 1-dodecanethiol-capped Cu nanoclusters (DT-Cu NCs) is obtained by annealing of dibenzyl ether solution of nanoclusters. These aggregates are composed of small clusters and emit a high level of aggregation-induced emission (AIE) in water. Based on the quenching effect of 4-nitrophenol (4-NP) on DT-Cu NCs, a fluorescence strategy is developed to monitor α-glucosidase (α-Glu) activity and screen its inhibitors from Chinese herbal medicines. 4-Nitrophenyl-α-D-glucopyranoside (NGP) is selected as the substrate, which is further hydrolyzed to yield 4-NP through the catalysis of α-Glu. The quenching efficiency is positively correlated to the concentration of α-Glu. Furthermore, the inhibitory effects of the extracts from four Chinese herbal medicines (i.e., the rind of Punica granatum L., Momordica grosvenorii Swingle., Crataegus pinnatifida Bge., and Lycium barbarum L.) on the α-Glu activity have been studied. The IC50 values of extracts from the rind of Punica granatum L. and Momordica grosvenorii Swingle are 0.23 and 0.37 g/L, respectively, so they show obvious inhibitory effects on α-Glu. The extracts of Crataegus pinnatifida Bge. and Lycium barbarum L. exhibit relatively weak inhibitory effects. Hence, the proposed strategy can be applicable for screening α-Glu inhibitors from Chinese herbal medicines. Last but not the least, by immobilizing DT-Cu NCs into agarose hydrogels in polyethylene tubes, a visual device is fabricated to screen α-Glu inhibitors with high throughput and sensitivity.

pH-modulated aggregation-induced emission of Au/Cu nanoclusters and its application to the determination of urea and dissolved ammonia.

A fluorescence platform is designed based on aggregation-induced emission of Au/Cu nanoclusters (Au/Cu NCs) driven by pH value. When pH increases from 6.0 to 7.0, Au/Cu NCs change from aggregation to dispersion, accompanied by the oxidation of Cu cores. Under the catalysis of urease, urea is hydrolysed to release ammonia, which further undergoes a hydrolysis reaction to produce OH-, causing the pH to increase. The fluorescence of Au/Cu NCs quenches linearly at 590 nm with the excitation wavelength at 320 nm when the concentration of urea varies from 5.0 to 100 µM. The limit of detection (LOD) and limit of quantification (LOQ) of urea are 2.23 and 7.45 µM, respectively. Combined with headspace single-drop microextraction technology, Au/Cu NCs are employed to monitor dissolved ammonia with low-cost and simple operation. The linear range of dissolved ammonia is from 20 to 300 µM. The LOD and LOQ of dissolved ammonia are 7.04 and 23.4 µM, respectively. The relative standard deviation (RSD) values of the intra-day and inter-day precision of urea are 2.4-3.0% and 3.0-3.7%, respectively, and those of dissolved ammonia are in the range 3.4-5.1% (intra-day precision) and 4.2-5.8% (inter-day precision). No interferences have been indentified in the determination of urea and dissolved ammonia. Finally, the proposed method has been applied to determine urea in human urine samples and dissolved ammonia in water samples with satisfactory results.Graphical abstract The pH increase produces the dispersion and decomposition of Au/Cu NCs, leading to the fluorescence quenching. Both urea and dissolved ammonia are detected successfully because they cause the pH change to alkaline.

Recent progresses of derivatization approaches in the targeted lipidomics analysis by mass spectrometry.

Lipidomics plays an essential role in the development of an improved understanding of lipids metabolism and the identification of new biomarkers or therapeutic targets of related diseases. The strong analytical power of mass spectrometry and its rapid developments in the respect of instruments and techniques have significantly accelerated the emerging lipidomics and related application fields in biology, medicine, and pharmacy. The strategy of chemical derivatization can remarkably improve the shortcomings of mass spectrometric analytical technologies of shotgun lipidomics and liquid chromatography mass spectrometry, and in the past decade many related studies have been reported for fatty acids, glycerophospholipids, sphingomyelins, monoglycerides, diacylglycerols, long-chain bases, steroids, and so on. Therefore, this review will focus on new chemical derivatization approaches about the research progresses of shotgun-based and liquid chromatography mass spectrometry-based targeted lipidomics (from 2005 to July 2019, most of reports emerged in the past 5 years), and put forward the problems and prospects in this field. It is expected to be helpful for the design and synthesis of new derivatization reagents, especially the outstanding stable isotope labeling derivatization reagents, and the development and application of new chemical derivatization strategies and matched mass spectrometric analysis methods.

Multiplexed derivatization strategy-based dummy molecularly imprinted polymers as sorbents for magnetic dispersive solid phase extraction of globotriaosylsphingosine prior to UHPLC-MS/MS quantitation.

A new series of 9-plex chemical isotope-labeling reagents, levofloxacin-based mass tags (LMTs) named as LMT359, 360, 361, 362, 363, 373, 375, 376, and 378, was firstly designed and synthesized for the high-throughput labeling of globotriaosylsphingosine (lyso-Gb3), a disease biomarker of Fabry disease. Creatively based on derivatization strategy-dummy template technique, dummy magnetic molecularly imprinted polymers (DMMIPs) were designed and prepared using LMT387-labeled lyso-Gb3 as a dummy template. The novel DMMIP material was used as sorbents for magnetic dispersive solid-phase extraction of 9-plexed LMT derivatives of lyso-Gb3 from equally mixed derivatization solutions. The enriched 8-plexed lyso-Gb3 derivatives from 8 real samples were quantified by ultra-high-performance liquid chromatography tandem mass spectrometry in a single run using simultaneously extracted LMT359-labeled standard lyso-Gb3 as internal standards. DMMIPs were characterized by using the transmission electron microscope (TEM), Fourier transform infrared, X-ray photoelectron spectroscopy, and some other characterization techniques. TEM micrograph showed that the prepared DMMIPs had an apparent imprinting layer. Triple-recognition abilities of DMMIPs towards LMT-lyso-Gb3 mainly rely on the hydrogen bonding, electrostatic attraction, hydrophobic interaction, and boronate affinity. The imprinting factor of DMMIPs towards LMT-lyso-Gb3 was 5.1. This method shows the advantages of high selectivity (triple recognition), high sensitivity, high accuracy (recovery 93.5-108.8%), and high throughput (8 samples in a single run). The proposed method was successfully applied to the determination of lyso-Gb3 in plasma samples with spiked recoveries in the range of 95.0-102.4%. This indicates that the method is promising in bioanalysis and medical testing of lyso-Gb3 in the future. Graphical abstract Synthesis of multiplexed derivatization reagents and its correlative molecularly imprinted polymers for magnetic extraction of globotriaosylsphingosine.

Colorimetric determination of the activities of tyrosinase and catalase via substrate-triggered decomposition of MnO2 nanosheets.

The authors describe novel colorimetric assays for tyrosinase (TYR) and catalase (CAT) based on the substrate-triggered decomposition of MnO2 nanosheets (NSs). The MnO2 NSs can act as oxidase mimics that catalyze the oxidation of the substrate tetramethylbenzidine (TMB) to form a blue dye with an absorption maximum at 652 nm. The oxidase-mimicking activity of the MnO2 NSs is inhibited by dopamine (DA)/hydrogen peroxide (H2O2) due to their decomposition of the MnO2 NSs. TYR catalyzes the oxidation of DA while CAT can decompose H2O2 into water and oxygen. Therefore, the oxidase-mimicking activity of MnO2 NSs is restored in the presence of both enzymes and their substrates. Based on the competitive consumption of substrates between enzymes and MnO2 NSs, a colorimetric method for determination of enzyme activity and its substrate is developed. The detection limits for TYR and CAT are 6 mU·mL-1 and 33 mU·mL-1, respectively. Graphical abstractA colorimetric method for monitoring enzyme activity and its substrate is described. It is based on the substrate-inhibited oxidase-mimicking activity of MnO2 nanosheets.

Molecular beacon-templated silver nanoclusters as a fluorescent probe for determination of bleomycin via DNA scission.

The authors describe a molecular beacon-based fluorescent probe for the determination of the cancer drug bleomycin (BLM). The probe was tagged with DNA-templated silver nanoclusters (DNA-AgNCs) and guanine-rich sequences (GRSs) at two terminals serving as signal reporter with a loop. In the absence of the BLM-iron(II) complex [BLM-Fe(II)], the probe has a hairpin shape and displays strong fluorescence because the AgNCs are close to the GRSs. In the presence of the BLM-Fe(II) complex, it will selectively cleave the probe at the 5'-GC-3' scission site of the loop. This displaces the AgNCs away from the GRSs and causes a decrease in fluorescence, best measured at excitation/emission wavelengths of 565/623 nm. This effect enables BLM to be detected with a detection limit as low as 33 pM, which was 1-3 orders of magnitude more sensitive than most of the previous reports. The probe was applied for the determination of BLM in spiked human serum samples, and excellent performance was achieved. In our perception, the method described here represents a promising tool for highly sensitive and specific analysis of BLM during cancer treatment. Graphical abstract Schematic of a highly sensitive fluorometric assay forbleomycin. It is based on molecular beacon-templated silver nanoclusters and DNA scission.

Rapid and sensitive determination of multiple endocrine-disrupting chemicals by ultrasound-assisted in situ derivatization dispersive liquid-liquid microextraction coupled with ultra-high-performance liquid chromatography/tandem mass spectrometry.

RATIONALE: Endocrine-disrupting chemicals (EDCs) in environment samples and food stuffs are an increasing serious public health issue due to their potency to interfere and deregulate several aspects of the endocrine system. Because of their extremely low abundance, it remains a challenging task to develop a sensitive detection method. METHODS: 4'-Carbonyl chloride rosamine (CCR) was used as a derivatization reagent for EDCs for the first time. A new ultrasound-assisted in situ derivatization/dispersive liquid-liquid microextraction (UA-DLLME with in situ derivatization) method for multiple EDCs including five estrogens, two alkylphenols, eight bisphenols, seven parabens and triclosan coupled with ultra-high-performance liquid chromatography/tandem mass spectrometry (UHPLC/MS/MS) has been developed and validated. RESULTS: The ionization efficiency of EDCs was greatly enhanced through the introduction of a permanent charged moiety of CCR into the derivatives during electrospray ionization (ESI)-MS analysis. The main variables potentially affecting the UA-DLLME with in situ derivatization process are optimized. The recoveries and matrix effects of 23 EDCs for the spiking samples were in the range of 83.0-116.0% and 85.8-114.6%, respectively. Good method reproducibility was achieved. CONCLUSIONS: The limits of detection (LODs) for 23 EDCs were 0.05-0.40 ng/L and 0.03-0.25 ng/g (dry weight, d.w.) for environment samples and food stuffs, respectively. The proposed method has been demonstrated to be suitable for simultaneous determination of multiple EDCs in real samples with high sensitivity, speediness, and good sample clean-up ability. Copyright © 2017 John Wiley & Sons, Ltd.

Rapid and sensitive determination of phytosterols in functional foods and medicinal herbs by using UHPLC-MS/MS with microwave-assisted derivatization combined with dual ultrasound-assisted dispersive liquid-liquid microextraction.

In this work, a hyphenated technique of dual ultrasound-assisted dispersive liquid-liquid microextraction combined with microwave-assisted derivatization followed by ultra high performance liquid chromatography tandem mass spectrometry has been developed for the determination of phytosterols in functional foods and medicinal herbs. Multiple reaction monitoring mode was used for the tandem mass spectrometry detection. A mass spectrometry sensitive reagent, 4'-carboxy-substituted rosamine, has been used as the derivatization reagent for five phytosterols, and internal standard diosgenin was used for the first time. Parameters for the dual microextraction, microwave-assisted derivatization, and ultra high performance liquid chromatography tandem mass spectrometry were all optimized in detail. Satisfactory linearity, recovery, repeatability, accuracy and precision, absence of matrix effect, extremely low limits of detection (0.005-0.015 ng/mL) and limits of quantification (0.030-0.10 ng/mL) were achieved. The proposed method was compared with previously reported methods. It showed better sensitivity, selectivity, and accuracy. The matrix effect was also significantly reduced. The proposed method was successfully applied to the determination of five phytosterols in vegetable oil (sunflower oil, olive oil, corn oil, peanut oil), milk and orange juice (soymilk, peanut milk, orange juice), and medicinal herbs (Ginseng, Ganoderma lucidum, Cordyceps, Polygonum multiflorum) for the quality control of functional foods and medicinal herbs.

Sensitive determination of cholesterol and its metabolic steroid hormones by UHPLC-MS/MS via derivatization coupled with dual ultrasonic-assisted dispersive liquid-liquid microextraction.

RATIONALE: Quantitative analysis of cholesterol and its metabolic steroid hormones plays a vital role in diagnosing endocrine disorders and understanding disease progression, as well as in clinical medicine studies. Because of their extremely low abundance in body fluids, it remains a challenging task to develop a sensitive detection method. METHODS: A hyphenated technique of dual ultrasonic-assisted dispersive liquid-liquid microextraction (dual-UADLLME) coupled with microwave-assisted derivatization (MAD) was proposed for cleansing, enrichment and sensitivity enhancement. 4'-Carboxy-substituted rosamine (CSR) was synthesized and used as derivatization reagent. An ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method was developed for determination of cholesterol and its metabolic steroid hormones in the multiple reaction monitoring mode. RESULTS: Parameters of dual-UADLLME, MAD and UHPLC-MS/MS were all optimized. Satisfactory linearity, recovery, repeatability, accuracy and precision, absence of matrix effect and extremely low limits of detection (LODs, 0.08-0.15 pg mL(-1) ) were achieved. CONCLUSIONS: Through the combination of dual-UADLLME and MAD, a determination method for cholesterol and its metabolic steroid hormones in human plasma, serum and urine samples was developed and validated with high sensitivity, selectivity, accuracy and perfect matrix effect results. Copyright © 2016 John Wiley & Sons, Ltd.

Carboxylic-group-functionalized single-walled carbon nanohorns as peroxidase mimetics and their application to glucose detection.

Carboxylic-group-functionalized single-walled carbon nanohorns (SWCNHs-COOH) have been found to possess peroxidase-like activity for the first time. Similar to natural peroxidase, SWCNHs-COOH can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine by H2O2 to produce a blue color solution. Compared with horseradish peroxidase, SWCNHs-COOH exhibit higher activity and stability under harsh reaction conditions. The catalytic activity of SWCNHs-COOH depends on the concentration of H2O2. A colorimetric method for glucose detection was developed by combining the SWCNH-COOH catalytic reaction and the generation of H2O2 by the enzymatic oxidation of glucose with glucose oxidase. Taking into account the advantages of good stability, high biocompatibility in aqueous solutions, being metal-catalyst free, and high purity, SWCNHs-COOH are expected to have potential applications in biotechnology and clinical diagnostics as enzymatic mimics.

Determination of bisphenol A, 4-octylphenol, and 4-nonylphenol in soft drinks and dairy products by ultrasound-assisted dispersive liquid-liquid microextraction combined with derivatization and high-performance liquid chromatography with fluorescence detection.

A novel hyphenated method based on ultrasound-assisted dispersive liquid-liquid microextraction coupled to precolumn derivatization has been established for the simultaneous determination of bisphenol A, 4-octylphenol, and 4-nonylphenol by high-performance liquid chromatography with fluorescence detection. Different parameters that influence microextraction and derivatization have been optimized. The quantitative linear range of analytes is 5.0-400.0 ng/L, and the correlation coefficients are more than 0.9998. Limits of detection for soft drinks and dairy products have been obtained in the range of 0.5-1.2 ng/kg and 0.01-0.04 µg/kg, respectively. Relative standard deviations of intra- and inter-day precision for retention time and peak area are in the range of 0.47-2.31 and 2.76-8.79%, respectively. Accuracy is satisfactory in the range of 81.5-118.7%. Relative standard deviations of repeatability are in the range of 0.35-1.43 and 2.36-4.75% for retention time and peak area, respectively. Enrichment factors for bisphenol A, 4-octylphenol, and 4-nonylphenol are 170.5, 240.3, and 283.2, respectively. The results of recovery and matrix effect are in the range of 82.7-114.9 and 92.0-109.0%, respectively. The proposed method has been applied to the determination of bisphenol A, 4-octylphenol, and 4-nonylphenol in soft drinks and dairy products with much higher sensitivity than many other methods.

Ratiometric fluorescence detection of artemisinin based on photoluminescent Zn-MOF combined with hemin as catalyst.

Artemisinin (ART) is a type of frontline drug to treat drug-resistant falciparum malaria. Simple, accurate and selective determination of ART is significant to monitor its clinical pharmaceutical efficacy. Herein, a new ratiometric fluorescence method has been designed for the determination of ART with Zn-MOF as fluorescence reference and hemin as catalyst, respectively. Zn-MOF possesses intrinsic fluorescence at 443 nm owing to 2-aminoterephthalic acid ligand. When o-phenylenediamine (OPD) is mixed with hemin, a weak fluorescent signal at 570 nm ascribed to oxidized product of OPD (oxOPD) is observed. In the presence of ART, hemin can catalyze ART to break its peroxide bridge and release a large number of reactive oxygen species, which effectively oxidize OPD into luminescent oxOPD. Therefore, the fluorescence at 570 nm is enhanced significantly while the fluorescence of Zn-MOF remains basically unchanged. Thus, a ratiometric fluorescence sensing platform has been constructed for the detection of ART. This method exhibits wider linear range (0.15 µM-150 µM) with detection limit of 50 nM. This novel and selective method has been used to detect ART in compound naphthoquinone phosphate tablets.

Ratiometric fluorescence assay for sulfide ions with fluorescent MOF-based nanozyme.

A novel ratiometric fluorescence strategy for sulfide ions (S2-) analysis has been developed using metal-organic framework (MOF)-based nanozyme. NH2-Cu-MOF displays blue fluorescence (λem = 435 nm) originating from 2-amino-1,4-benzenedicarboxylic acid ligand. Besides, it possesses oxidase-like activity due to Cu2+ node, which can trigger chromogenic reaction. o-Phenylenediamine (OPD), as a common enzyme substrate, can be oxidized by NH2-Cu-MOF to form luminescent products (oxOPD) (λem = 570 nm). Inner filter effect occurs between oxOPD and MOF. Upon exposure to S2-, oxidase-like activity of MOF is depressed significantly because of the generation of CuS. On one hand, the amount of free Cu2+ decreases, affecting the yielding of oxOPD. On the other hand, CuNPs with larger size are obtained during the oxidation-reduction reaction between Cu2+ and OPD, which show weaker autocatalytic ability for OPD oxidation. These result in the decrease and increase of intensities at 570 and 435 nm, respectively. This method exhibits sensitive and selective responses towards S2- with LOD of 0.1 µM. Furthermore, such ratiometric strategy has been applied to detect S2- in food samples.

Simultaneous and dynamic measurement of Schisandrol A changes in rat blood and brain and its comparative pharmacokinetic study in control and Parkinson's disease rats by dual-probe in vivo microdialysis.

Schisandrol A (SchA) is the main active ingredient of Schisandra chinensis (Turcz.) Baill., which is a famous traditional Chinese herbal medicine. SchA can penetrate the blood-brain barrier and has a significant neuroprotective effect. A group of multiplexed stable isotope mass tags (MSIMTs, m/z 332, 338, 346, 349, 351, 354, 360, 363, 374 and 377) were synthesized to perform multiplexed stable isotope labeling derivatization (MSILD) of SchA in rat microdialysates and standards. A new magnetic molecularly imprinted polymer was prepared using MSIMT-375-SchA as dummy template. All the 10-plexed derivatives of MSIMTs-SchA can be efficiently and selectively enriched and purified using this adsorbent by magnetic dispersive solid phase extraction (MDSPE) before ultra high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) analysis. It should be pointed out that the MSIMT-346-SchA standard derivative was used as internal standard in the process of MDSPE and UHPLC-MS/MS. On these bases, 9 different rat microdialysate samples can be determined by UHPLC-MS/MS in a single run. The utilization of MSIMTs significantly increased the sensitivity, accuracy, selectivity and analysis throughput. Under the optimized conditions, satisfactory linearity (R2> 0.987), limit of detection (LODs, 0.15-0.26 pg/mL) and lower limit of quantitative (LLOQ, 0.8-2.0 pg/mL) were obtained. Intra- and inter-day precisions were in the range of 2.2% -12.5%, and recoveries 94.2% -106.2%. The matrix effects were very low, and the average derivatization efficiency of 10-plex MSIMTs to SchA was as high as 97.8%. Using the developed dual-probe in vivo microdialysis sampling technique, the proposed analytical method has been applied for comparative pharmacokinetics of SchA in the brain and blood of control and Parkinson's disease (PD) rats.

Terbium (III)-based Metallacrowns with aggregation-induced emission feature coupled with cu (II) for fluorescence detection of cysteine.

The Metallacrowns (MCs) composed of repeated [Metal-N-O] subunits are a type of new material, but the MCs have not been developed and utilized in analytical applications. This essay reports on a new kind of terbium(III)-based Metallacrowns (Tb-MCs) with aggregation-induced emission (AIE) feature to build a sensing platform. It is first time that Tb-MCs are able to aggregate to larger aggregates in water along with a bright green emission, so that the property makes it possible to apply in biosensing. Thereafter, the AIE of Tb-MCs can be quenched effectively by Cu2+. Based on the high affinity of thiol to Cu2+, cysteine (Cys) recovers the fluorescence of Tb-MCs in the presence of Cu2+. There is a good linear range varying from 0.02 to 20 µM with a low limit of detection (LOD) 9.67 nM of Cys. In the end, this novel probe is also successfully applied to the determination of Cys in human serum with satisfactory results.