Ya-Feng GUAN

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Name: 关亚风; Guan, YaFeng

Organization: Chinese Academy of Sciences , China

Department: Dalian Institute of Chemical Physics

Title: (PhD)

TOPICS

Polymer

Polyimide

Chemicals
References

A facile and high sensitive micro fluorimeter based on light emitting diode and photodiode

Co-reporter:Xuhui Geng, Yan Gao, Chunbo Feng, Yafeng Guan

Talanta 2017 Volume 175(Volume 175) pp:

Publication Date(Web):1 December 2017

DOI:10.1016/j.talanta.2017.07.022

•A high sensitive micro fluorimeter was developed employing LED and photodiode.•The amplifier of PD was investigated to achieve high sensitivity and low noise.•Theoretical analysis and experimental result were well matched.•LOD of 0.004 ppb FITC was near to the lowest among literatures and products.•A portable fluorimeter was developed to detect fungimycin, with LOD of 0.1 ppb.A facile and high sensitive micro fluorimeter was developed and evaluated. It employed light emitting diode (LED) as light source, cuvette as detection cell, and photodiode (PD) as optoelectronic detector. Optical and electronic parameters were optimized and demonstrated. A high power LED was chosen, which could irradiate the inner area of the cuvette completely at the same time with divergence angle as small as possible. The optimum LED brought 2.5 times signal-to-noise ratio (SNR) enhancement. Using reflector at the opposite direction of excitation light path doubled SNR. The amplifier circuit of PD was deeply investigated to achieve high sensitivity, low noise, and good stability. The limit of detection (LOD) of fluorescein isothiocyanate (FITC) and chlorophyll at SNR = 3 were 10 pM ~ 0.004 ppb and 0.05 ppb, respectively. Basing on the principle structure, a portable fluorimeter for fungimycin detection was developed using a low power UV LED as light source. The LOD for aflatoxin B1 was 0.1 ppb.Download high-res image (145KB)Download full-size image

One-step preparation of zirconia coated silica microspheres and modification with d-fructose 1, 6-bisphosphate as stationary phase for hydrophilic interaction chromatography

Co-reporter:Zhihua Song, Chunfeng Duan, Meng Shi, Shenghong Li, Yafeng Guan

Journal of Chromatography A 2017 Volume 1522(Volume 1522) pp:

Publication Date(Web):3 November 2017

DOI:10.1016/j.chroma.2017.09.046

•One-step surfactant-free synthesis of ZrO2/SiO2 microspheres is proposed.•d-Fructose modified ZrO2/SiO2 is useful stationary phase for HILIC.•The new stationary phase can separate polar biomolecules with high efficiency.In this study, ZrO2 layer coated silica microspheres (ZrO2/SiO2) were successfully prepared by a facile one-step surfactant-free hydrothermal route under low pH condition. The synthesized ZrO2/SiO2 material was then modified with d-fructose 1, 6-bisphosphate (FDP) to improve the chromatographic separation property of the material. Fused-silica capillary columns were prepared with the modified material for evaluation. Phenolic, nucleobases and alkaloids compounds in hydrophilic interaction chromatographic (HILIC) mode showed symmetrical peaks. The FDP-ZrO2/SiO2 stationary phase showed better performance than ZrO2/SiO2 packing material and demonstrated great potential for application in HILIC mode.

Ultrasensitive quantification of endogenous brassinosteroids in milligram fresh plant with a quaternary ammonium derivatization reagent by pipette-tip solid-phase extraction coupled with ultra-high-performance liquid chromatography tandem mass spectrometry

Co-reporter:Ting Deng, Dapeng Wu, Chunfeng Duan, Yafeng Guan

Journal of Chromatography A 2016 Volume 1456() pp:105-112

Publication Date(Web):22 July 2016

DOI:10.1016/j.chroma.2016.06.026

•A simple and ultra-sensitive PT-SPE-UPLC-MS/MS method was established for BRs.•A quaternary ammonium derivatization reagent was first developed.•A pipette-tip solid-phase extraction strategy was proposed.•MDA of 27–94 amol was achieved for BRs.•Endogenous BRs were quantified in 0.5 mg FW of rice leaf segments.Determination of endogenous brassinosteroids (BRs) in limited sample amount is vital to elucidating their tissue- and even local tissue-specific signaling pathway and physiological effects on plant growth and development. In this work, an ultra-sensitive quantification method was established for endogenous BRs in milligram fresh plant by using pipette-tip solid-phase extraction coupled with ultra-performance liquid chromatography tandem mass spectrometry (PT-SPE-UPLC-MS/MS), in which a quaternary ammonium phenyl boronic acid, 4-borono-N,N,N-trimethylbenzenaminium iodide (BTBA) was first developed for chemical derivatization of BRs. Due to the cationic quaternary ammonium group of BTBA, the ionization efficiencies of the BRs chelates with BTBA (BTBA-BRs) were enhanced by 1190–448785 times, which is the highest response enhancement factor among all derivatization reagents reported for BRs. In addition, PT-SPE packed with C18 sorbent was first used for purifying BRs from plant extracts, so the required sample amount was minimized, and recoveries higher than 91% were achieved. Under the optimized conditions, the minimal detectable amounts (MDA) of five target BRs were in the range of 27–94 amol, and the correlation coefficients (R2) were >0.9985 over four orders of magnitude. The relative recoveries of 75.8–104.9% were obtained with the intra- and inter-day relative standard deviations (RSDs) less than 18.7% and 19.6%, respectively. Finally, three BRs were successfully quantified in only 5 mg fresh rice plant samples, and 24-epiBL can even be detected in only 0.5 mg FW rice leaf segments. It is the first time that the BRs content in sub-milligram fresh plant sample has been quantified.

Preparation of alumina nanoshell coated porous silica spheres for inorganic anions separation

Co-reporter:Zhihua Song, Dapeng Wu, Kun Ding, Yafeng Guan

Journal of Chromatography A 2016 Volume 1433() pp:85-89

Publication Date(Web):12 February 2016

DOI:10.1016/j.chroma.2016.01.008

•Alumina nanoshell coated porous silica microbeads were prepared.•A complete alumina nanoshell coating could be obtained in the mesopore of silica.•NanoAl2O3/mesoSiO2 particles were successfully applied to anions separation.•The column efficiency of 3.8 × 104 plates per meter was obtained for I−.It had been reported that alumina nanoshell coating could be obtained on the external surface of various substrates in one-nanometer precision in aqueous solution. In this work, alumina nanoshell coated mesoporous silica microbeads (nanoAl2O3/mesoSiO2) were prepared with the similar method, and were successfully applied to inorganic anions separation. As the mass transfer speed is largely constrained in the mesopore compared with that on the open surface, it was found that a complete alumina nanoshell coating could be obtained within the mesopore until the five-time coating was carried out. After characterization by BET, SEM and FTIR, it was found that the obtained nanoAl2O3/mesoSiO2 particles are smooth and well dispersed, and the mesopores are well reserved. In addition, the full coverage of nanoAl2O3 shell in mesopores was also confirmed by the binding capacity experiments with berberine. Finally, the nanoAl2O3/mesoSiO2 particles were packed in silica capillary for the separation of inorganic anions I−, SCN−, Br−, NO2− and NO3− with ion chromatography (IC), and a column efficiency of 3.8 × 104 plates per meter was obtained for I−.

Further investigation of a peptide extraction method with mesoporous silica using high-performance liquid chromatography coupled with tandem mass spectrometry

Co-reporter:Yan Du;Dapeng Wu;Yafeng Guan

Journal of Separation Science 2016 Volume 39( Issue 11) pp:2156-2163

Publication Date(Web):

DOI:10.1002/jssc.201501354

Mobil Composition of Matter No. 41 (MCM-41) was the most frequently used mesoporous silica material to extract peptides from complex biological samples. However, there were confusing extraction conditions and large extraction efficiency variance among related reports, which resulted from unclear understanding about the interaction between the material and peptides. In this study, the extraction mechanism was investigated with one set of tryptic peptides by using high-performance liquid chromatography coupled with triple quadrupole mass spectrometry. Generally, hydrophobic interaction and electrostatic attraction were two major driving forces for extraction of peptides, while electrostatic repulsion greatly weakened the interaction between the material and peptides with isoelectric points below the pH. With most peptides positively charged and MCM-41 slightly negatively charged, most efficient extraction was obtained at pH 3, and it was proved that electrostatic and hydrophobic interaction acted in synergy for extraction of all the peptides. A mixed solution of acetonitrile with buffers of high pH or ion strength was demonstrated to be favorable for elution, which performed much better than the commonly used eluate (mixture of acetonitrile with 0.1% trifluoroacetic acid). Finally, under optimum conditions, it was found that extraction efficiency of MCM-41 for protein digest and human serum was greatly improved.

Preparation and Application of Polyimide Coated Stir Bar for Extraction of Phenols in Environmental Water Samples

Co-reporter:Sheng-Hong LI, Da-Peng WU, Ya-Feng GUAN

Chinese Journal of Analytical Chemistry 2016 Volume 44(Issue 6) pp:842-849

Publication Date(Web):June 2016

DOI:10.1016/S1872-2040(16)60935-0

A polyimide coated stir bar for sorptive extraction (SBSE) was prepared by immersion precipitation method and evaluated by using 5 phenols and chlorinated phenols as model samples. The highest extraction efficiency was achieved among all commercial extraction phases of SBSE reported. Experimental parameters including stirring speed, ionic strength, extraction temperature, extraction time, desorption temperature and time were optimized. Under the optimal conditions such as 100 mL of sample, 30% NaCl, extraction time of 30 min, stirring speed of 800 rpm and extraction temperature of 25 °C, the target compounds were recovered by thermal desorption at 300 °C for 4 min. More than two orders of magnitude of linearity were obtained (R ≥ 0.9995). LOQs (S/N = 10) were 0.028–0.123 μg L−1, and RSDs were in the range of 1.6%–9.7%. The polyimide SBSE coupled with gas chromatography-mass spectrometry was applied to the extraction and analysis of phenols in real samples, including tap water, sea water, and waste water. It was found that the polyimide SBSE showed high selectivity towards polar compounds and high thermostability up to 350 °C.Polyimide coated stir bar for sorptive extraction (SBSE) was prepared by immersion precipitation method, and its performances were evaluated with 5 phenols as model analytes. It was found that the polyimide SBSE had high selectivity towards polar compounds and high thermostability up to 350 °C.

Rapid solid-phase microextraction of polycyclic aromatic hydrocarbons in water samples by a coated through-pore sintered titanium disk

Co-reporter:Yanggang Zhang, Dapeng Wu, Xiaohui Yan, Yafeng Guan

Talanta 2016 Volume 154() pp:400-408

Publication Date(Web):1 July 2016

DOI:10.1016/j.talanta.2016.03.094

•A novel SPME method based on through-pore sintered titanium disk was established.•Water sample of 100 mL was extracted in 2 min with high absolute recoveries.•PAHs at ng/L level in real water sample were quantified by this method.A novel solid-phase microextraction device based on a through-pore sintered titanium disk (ST-SPME) was prepared and evaluated for the rapid extraction of organic pollutants from aqueous samples. The through-pores embedded in a sintered titanium disk were enlarged by HCl etching, yielding more Ti–O functional groups and a rough surface that should benefit the covalent binding of extraction phase with the disk. The large inner surface area (850 mm2) of the disk and narrow through-pores (100 µm) significantly increase the extraction capacity and mass transfer rate. In addition, the resistance to water flow of the ST-SPME disk is rather low, yielding a back pressure of only 100 kPa at a flow rate of 50 mL/min. The extracted target compounds are thermally desorbed by a thermal desorption unit and transferred to a GC or GC–MS system. Taking polydimethylsiloxane as the extraction phase and 16 types of polycyclic aromatic hydrocarbons (PAHs) as model analytes, the extraction and desorption conditions were systematically investigated. The optimized extraction time was only 2 min for 100 mL of water sample. Absolute recoveries were between 5.93% and 23.02%, which are similar to that of stir bar sorptive extraction. The LODs and RSDs were 0.06–3.20 ng/L (S/N=3) and 0.57–7.08%, respectively. The method showed good linearity in the range of 0.01–10 µg/L with a squared determination coefficient R2≥0.9939. As our method was suitable for the measurement of organic pollutants in the water phase, the ST-SPME/GC–MS method was assessed by analyzing three filtered real environmental samples. Some PAHs were detected at the ng/L level in river water and sea water.

Cu2O nanorods modified by reduced graphene oxide for NH3 sensing at room temperature

Co-reporter:Hu Meng, Wei Yang, Kun Ding, Liang Feng and Yafeng Guan

Journal of Materials Chemistry A 2015 vol. 3(Issue 3) pp:1174-1181

Publication Date(Web):13 Nov 2014

DOI:10.1039/C4TA06024E

In this work, Cu2O nanorods modified by reduced graphene oxide (rGO) were produced via a two-step synthesis method. CuO rods were firstly prepared in graphene oxide (GO) solution using cetyltrimethyl ammonium bromide (CTAB) as a soft template by the microwave-assisted hydrothermal method, accompanied with the reduction of GO. The complexes were subsequently annealed and Cu2O nanorods/rGO composites were obtained. The as-prepared composites were evaluated using various characterization methods, and were utilized as sensing materials. The room-temperature NH3 sensing properties of a sensor based on the Cu2O nanorods/rGO composites were systematically investigated. The sensor exhibited an excellent sensitivity and linear response toward NH3 at room temperature. Furthermore, the sensor could be easily recovered to its initial state in a short time after exposure to fresh air. The sensor also showed excellent repeatability and selectivity to NH3. The remarkably enhanced NH3-sensing performances could be attributed to the improved conductivity, catalytic activity for the oxygen reduction reaction and increased gas adsorption in the unique hybrid composites. Such composites showed great potential for manufacturing a new generation of low-power and portable ammonia sensors.

Acetone-activated polyimide electrospun nanofiber membrane for thin-film microextraction and thermal desorption-gas chromatography–mass spectrometric analysis of phenols in environmental water

Co-reporter:Shenghong Li, Dapeng Wu, Xiaohui Yan, Yafeng Guan

Journal of Chromatography A 2015 Volume 1411() pp:1-8

Publication Date(Web):11 September 2015

DOI:10.1016/j.chroma.2015.07.050

•Electrospun polyimide nanofiber membrane was prepared for TFME for the first time.•Activation by acetone rinsing could increase the extraction efficiency by 6–12 folds.•Thermal desorption after TFME could be performed up to 300 °C.•Phenols at ppt level in real water samples were quantified by TFME/TD–GC–MS.In this work, a polyimide nanofiber membrane was electrospun and applied as sorbent for thin film microextraction (TFME). After TFME of phenols in water samples, direct thermal desorption of the sorbent at 300 °C followed by gas chromatography-mass spectrometric (TD–GC–MS) analysis was carried out. The extraction efficiency of TFME was enhanced by 6–12 times for phenols after activation with acetone. The positive effect of acetone activation was correlated to the increased hydrophilicity of the membrane. Extraction parameters, including mass of nanofiber membrane, pH value, NaCl concentration and extraction time, were optimized. Under optimal conditions, the LODs and LOQs for analysis of phenols in spiked purified water were 0.0006–0.008 and 0.002–0.025 μg L−1, respectively. The linearity range was more than two orders of magnitude (R > 0.99). The RSDs of intra-batch and inter-batch were 4.3–7.4% and 2.7–10.6% (n = 3). Finally the method was applied to real samples, including tap water, sea water, and waste water. These results indicate that the polyimide nanofiber membrane is a promising candidate as TFME sorbent for determination of polar analytes in water samples coupled with TD–GC–MS.

Determination of Dicarboxylic Acids in Fine Atmospheric Particles by Micro-Pressurized Liquid Extraction Coupled with Gas Chromatography-Mass Spectrometer

Co-reporter:Liang HAO, Da-Peng WU, Ya-Feng GUAN

Chinese Journal of Analytical Chemistry 2015 Volume 43(Issue 10) pp:1526-1530

Publication Date(Web):October 2015

DOI:10.1016/S1872-2040(15)60869-6

The method of micro-pressurized liquid extraction (μ-PLE) coupled with gas chromatography-mass spectrometer (GC-MS) for analysis of 4 dicarboxylic acids (DCAs, including malonic acid, succinic acid, glutaric acid, and adipic acid) in fine atmospheric particles was developed. PM2.5 filter sample was extracted by μ-PLE at a pressure of 8 MPa and temperature of 80 °C using methanol as extraction solution. After two static 5-min extractions and a rinsing step with 100 μL methanol, about 500 μL of extraction solution was obtained. The extraction solution was then blown to dry with high purity nitrogen and submitted to a silylation reaction at 60 °C for 30 min. After internal standard (IS) was added, the derivatization solution was directly injected for GC-MS analysis. For quantification of 4 normally DCAs in fine atmospheric particles, the calibration curve was obtained with a good linear relationship in the range of 0.2–20 ng μL−1. The limits of quantification (LOQs, S/N = 10) were in the range of 0.15–0.47 ng m−3. The relative recoveries were between 92% and 122% with the RSDs between 2.6% and 11.8% for spiked filter samples. The method developed here was used to determine malonic acid, succinic acid, glutaric acid, and adipic acid in real PM2.5 samples collected from Xinghai Bay of Dalian city, and the results were determined to be 64.6, 50.0, 41.8 and 20.2 ng m−3, respectively.The method of micro-pressurized liquid extraction (μ-PLE), BSTFA/TMCS silylation and GC-MS was developed systematically for analysis of orgainc acids in PM2.5, and four dicarboxylic acids (malonic acid, succinic acid, glutaric acid and adipic acid) in real PM2.5 samples were quantified precisely.

Filtration efficiency validation of glass wool during thermal desorption–gas chromatography–mass spectrometer analysis of fine atmospheric particles

Co-reporter:Liang Hao, Dapeng Wu, Kun Ding, Hu Meng, Xiaohui Yan, Yafeng Guan

Journal of Chromatography A 2015 1380() pp: 171-176

Publication Date(Web):

DOI:10.1016/j.chroma.2014.12.069

Hybrid Titania–Zirconia Nanoparticles Coated Adsorbent for Highly Selective Capture of Nucleosides from Human Urine in Physiological Condition

Co-reporter:Qian Wu, Dapeng Wu, and Yafeng Guan

Analytical Chemistry 2014 Volume 86(Issue 20) pp:10122

Publication Date(Web):September 29, 2014

DOI:10.1021/ac502876u

Modified nucleosides are important biomarkers of cancers. For their analysis, boronate adsorbents were widely used to selectively capture them from urine, but often suffered from serious secondary hydrophobic interaction and harsh alkaline extraction condition. In this work, the hybrid titania–zirconia nanoparticles coated on porous silica spheres (TiO2–ZrO2/SiO2) were developed for the first time as a selective adsorbent for nucleosides under neutral conditions based on specific recognition of its Lewis acid sites to the cis-diol group. It was found here that TiO2–ZrO2 has higher binding constants than pure TiO2 or ZrO2, and a significant improvement of binding efficiencies was obtained by decreasing calcination temperature to 400 °C. Moreover, physiological pH of urine (pH 6–7) was found optimal to adsorb nucleosides and resist other Lewis base interferences. By self-assembly of TiO2–ZrO2 nanoparticles on silica, unprecedentedly high binding capacity (35 mg/g) for nucleosides was obtained due to high surface area (350 m2/g) and abundant Lewis acid sites on the surface. Due to efficient reduction of secondary hydrophobic interaction on the inorganic surface, cis-diol nucleosides could be captured from 500-fold non-cis-diol interferences. In the real sample application, nine nucleosides have been quantified with relative recoveries in 83%–126%, and 42 ribosylated metabolites had been identified with only 100 μL of urine at physiological pH. Among them, two nucleosides have never been identified in most previous studies using boronate adsorbents for capture.

Quantification of endogenous brassinosteroids in sub-gram plant tissues by in-line matrix solid-phase dispersion–tandem solid phase extraction coupled with high performance liquid chromatography–tandem mass spectrometry

Co-reporter:Lu Wang, Chunfeng Duan, Dapeng Wu, Yafeng Guan

Journal of Chromatography A 2014 Volume 1359() pp:44-51

Publication Date(Web):12 September 2014

DOI:10.1016/j.chroma.2014.07.037

•In-line MSPD–tandem SPE method was developed for plant sample preparation.•Good compatibility of elution solvents was obtained in the MSPD–MAX–MCX system.•The time cost of sample preparation was reduced from days to a few hours.•Solvent extraction of plant tissues overnight was totally avoided.•Highly sensitive and selective analysis of trace brassinosteroids in rice plant was achieved.A matrix solid-phase dispersion (MSPD)–tandem mixed mode anion exchange (MAX)–mixed mode cation exchange (MCX) solid phase extraction-high performance liquid chromatography coupled with tandem mass spectrometry (HPLC–MS/MS) method was developed for quantification of six endogenous brassinosteroids (BRs) (24-epibrassinolide, 24-epicastasterone, 6-deoxo-24-epicastasterone, dolichosterone, teasterone and typhasterol) in rice plant tissues. Non-polar interferences were removed effectively by C8 dispersant used in MSPD, while the following tandem MAX–MCX process facilitated the elimination of polar and ionizable compounds. The weak reversed-phase retention feature of MAX–MCX leaded to good compatibility of the elution solvents in the in-line coupled MSPD–MAX–MCX system. This system was optimized for extraction and purification of BRs in plant samples. The effects of the type of solid phase, the elution solvent, the extraction temperature and the clean-up material were studied. Before HPLC separation, BRs purified were derivatized by m-aminophenylboronic acid to enhance the sensitivity of MS/MS to BRs. Compared with traditional liquid–liquid extraction and solid phase extraction (LLE–SPE), the proposed MSPD–MAX–MCX method showed higher extraction efficiency, lower matrix effect, and advantages of easy manipulation and time-saving. The in-line MSPD–MAX–MCX coupled with HPLC–MS/MS method provided a linear response over two orders of magnitude of BRs concentration with correlation coefficients above 0.9982, limits of detection between 0.008 and 0.04 ng mL−1, relative standard deviations (RSDs) below 29.4%, and recoveries above 77.8%. The proposed method has been successfully applied to analysis of endogenous BRs in rice plant at booting stage and maturity stage.

Polyaniline sheathed electrospun nanofiber bar for in vivo extraction of trace acidic phytohormones in plant tissue

Co-reporter:Qian Wu, Dapeng Wu, Yafeng Guan

Journal of Chromatography A 2014 Volume 1342() pp:16-23

Publication Date(Web):16 May 2014

DOI:10.1016/j.chroma.2014.03.055

•Polyaniline sheathed nanofibers were electrospun for the first time.•The compressed nanofiber bar was inserted in aloe leaf for in vivo extraction.•Four phytohormones were detected by in vivo extraction.•A 3–8 μL spatial resolution and 20-min temporal resolution were obtained.•The limit of detection was down to 60 pg/g.For in vivo extraction of trace and polar components in tissues, extraction materials should be biocompatible, highly permeable to matrix and have high extraction capacity for polar and ionic compounds. In this study, nanofibers (∼200 nm) with rough polyaniline (PAn) sheath were prepared successfully for the first time by coaxial electrospinning and coelectrospun polymer sacrificing method. The nanofibers (0.5 mg) were then compressed into tiny bar (Φ1 mm × 2 mm) and inserted directly into the aloe leaf for in vivo extraction of trace phytohormones. Due to the large surface area (13.97 m2/g) of nanofibers and large through pores formed between fibers, high extraction capacity (up to 10 μg/bar) and permeability to tissue matrix of the tiny bar can be obtained. Moreover, PAn sheath has high adsorption equilibrium constants (107–108 mL/mol) for acidic phytohormones in aloe leaf. Four phytohormones were detected by in vivo extraction with a spatial resolution of 3–8 mm3, temporal resolution of 20 min, and limit of detection down to 60 pg/g. The quantification results were well met with that by traditional in vitro organic solvent extraction.

Further investigation of array capillary in-tube solid-phase microextraction of trace organic pollutants in water samples

Co-reporter:Xiaohui Yan, Dapeng Wu, Hu Meng, Liang Hao, Kun Ding and Yafeng Guan

Analytical Methods 2014 vol. 6(Issue 3) pp:750-757

Publication Date(Web):06 Nov 2013

DOI:10.1039/C3AY41525B

Array capillary in-tube solid-phase microextraction (ACIT-SPME) was demonstrated to be a fast, reproducible and convenient extraction method for trace organic pollutants in water samples. In order to improve the extraction efficiency per unit of extraction time, ACIT-SPME cartridges with capillary tubes of different inner diameters (I.D.), from 0.1 mm to 0.5 mm I.D., were fabricated and compared systematically for the extraction of chlorobenzenes (CBs) and nitrochlorobenzenes (NCBs). The results indicated that the ACIT-SPME cartridges with the largest bore diameter were more suitable for rapid extraction of analytes in abundant water samples, while the ACIT-SPME with the smallest bore diameter resulted in the highest absolute recovery. Thus, ACIT-SPME capillary tubes of 0.5 mm I.D. were applied in the rapid extraction of CBs and NCBs from environmental water. Parameters such as sample volume, extraction time, ionic strength, and thermal desorption conditions were investigated to obtain the optimal operation conditions. The extraction was completed in 1.5 min under gravity using 250 mL of water sample. The desorbed analytes were analyzed by gas chromatography (GC) coupled with electron capture detection (ECD). A linear relationship between the peak areas and the concentrations of the analytes covered 2 orders of magnitude with correlation coefficients higher than 0.9961 for all the compounds being studied. The detection limits were between 0.00041 and 0.047 μg L−1 with a relative standard deviation (RSD) of between 1.4% and 4.8%. The proposed method was applied in the extraction and determination of CBs and NCBs in real water samples. Relative recoveries and RSDs for the analysis of real water samples were 87.1–116% and 1.8–9.4%, respectively. These results further proved that ACIT-SPME could be applied as a routine sample preparation method for water analysis both in the field and in the lab .

Thermal Desorption-Gas Chromatography or Gas Chromatography-Mass Spectrometry for Analysis of Semi-Volatile Compounds on Atmospheric Particulate Matters

Co-reporter:Hu MENG, Jing-Hong ZHAO, Chun-Feng DUAN, Liang HAO, Ya-Feng GUAN

Chinese Journal of Analytical Chemistry 2014 Volume 42(Issue 7) pp:931-936

Publication Date(Web):July 2014

DOI:10.1016/S1872-2040(14)60749-0

A thermal desorption (TD) device was developed and coupled to gas chromatograph (GC) or gas chromatograph-mass spectrometer (GC-MS) for the qualitative and quantitative analysis of semi-volatile organic compounds on atmospheric particulate matters (PM). The TD was operated by direct heating and placed on the top of GC injector, leading to high heating rate and easy transfer of analytes to GC without re-focusing of analytes by cold trap. The materials used for supporting PM samples, desorption temperature and time, and types of sample injection were investigated for the detection of sixteen polycyclic aromatic hydrocarbons (PAHs) and nine n-alkanes. The limits of detection of the proposed TD-GC method were in the range of 0.014–0.094 ng for PAHs, and 0.016–0.026 ng for n-alkanes, with coefficients of correlation above 0.9975. The TD-GC method was applied to the determination of trace PAHs and n-alkanes on PM10 samples from three cities. The recoveries were in the range of 95%–135% (PAHs) and 95%–115% (n-alkanes). Finally, the TD was coupled to GC-MS for comparison of the contents of PAHs and n-alkanes on PMx with different particulate size (x = 10, 5, 2, 1, 0.5, 0.25, 0.1).A thermal desorption (TD) device was developed and coupled to gas chromatograph (GC) or gas chromatograph-mass spectrometer (GC-MS) for the qualitative and quantitative analysis of semi-volatile organic compounds on atmospheric particulate matters (PM). Then, the contents of polycyclic aromatic hydrocarbons and alkanes on PMx with different particulate size from three Chinese cities were compared in detail.

Selective Extraction of Low Molecular Weight Proteins by Mesoporous Silica Particles with Phenyl Modified Internal and Alkyl-diol Modified External Surfaces

Co-reporter:Yan-Xia QI, Qian-Cheng ZHAO, Zhi-Bo LI, Wei LI, Qiu-Kuan WANG, Ya-Feng GUAN

Chinese Journal of Analytical Chemistry 2014 Volume 42(Issue 8) pp:1083-1087

Publication Date(Web):August 2014

DOI:10.1016/S1872-2040(14)60756-8

Selective extraction of low molecular weight (LMW) proteins and peptides from complex biological samples plays an important role in the discovery of useful biomarkers and signaling molecules. It was demonstrated that the unique pore structure of mesoporous material made it efficient to enrich LMW proteins and peptides from complex matrixes. In this study, a mesoporous material with modified external (alkyl-diol group) and internal (phenyl group) surfaces (alkyl-diol@phenyl-SiO2) was prepared by co-condensation and post-grafting, and its characteristic was evaluated by Fourier transform-infrared spectra (FT-IR) and mass spectrometry (MS). The LMW proteins and peptides enriched by the alkyl-diol@phenyl-SiO2 mesoporous material could be easily eluted by organic solvents, which was compatible with the following detection by MS. This new mesoporous material exhibited good selectivity for the extraction of LMW proteins and peptides (less than 10 kDa) from complex biological samples.The alkyl diol-phenyl-SiO2 mesoporous material was applied to selectively extract low molecular weight proteins and peptides in plasma. MALDI MS spectra of human plasma (a) and its extracts (b) by alkyl-diol@phenyl-SiO2 were shown in the Figure. The material had good selectivity for the extraction of LMW proteins from biofluids.

An improved Stöber method towards uniform and monodisperse Fe3O4@C nanospheres

Co-reporter:Xue-Bin Zhang, Hong-Wu Tong, Shao-Min Liu, Guo-Ping Yong and Ya-Feng Guan

Journal of Materials Chemistry A 2013 vol. 1(Issue 25) pp:7488-7493

Publication Date(Web):11 Apr 2013

DOI:10.1039/C3TA11249G

Significant progress has recently been made in the synthesis of Fe3O4@C nanospheres with uniform, monodisperse and tunable carbon shells. Fe3O4@C nanospheres were obtained by directly carbonizing Fe3O4@polymer which was synthesized by a versatile and economical Stöber method with resorcinol and formaldehyde as precursors. The synthesis conditions in the formation of Fe3O4@polymer were systematically investigated. It was found that the yield of the Fe3O4@polymer is highly influenced by the concentration of ammonium hydroxide, and the monodispersity is mainly affected by the concentration of ammonium hydroxide and the citrate group sites outside the surfaces of the Fe3O4 nanospheres. Interestingly, carbonization of Fe3O4@polymer at high temperature makes the grain sizes of Fe3O4 in Fe3O4@C samples larger than those in the Fe3O4 sample, which makes the saturation magnetization value for the Fe3O4@C samples higher than those of common obtained materials. The adsorption performance of Fe3O4@C for anthracene was tested both in water and in cyclohexane solution; it shows fast adsorption rates (about 1 h to reach equilibrium in water and 3 h in cyclohexane solution) and high adsorption capacities (31.5 mg g−1 in water and 2 mg g−1 in cyclohexane solution), which are ascribed to its high uniformity and monodispersity. These make Fe3O4@C an ideal adsorption and enrichment material, especially for polycyclic aromatic hydrocarbons in water and in organic solvents.

Fast Equilibrium Micro-Extraction from Biological Fluids with Biocompatible Core–Sheath Electrospun Nanofibers

Co-reporter:Qian Wu, Dapeng Wu, and Yafeng Guan

Analytical Chemistry 2013 Volume 85(Issue 12) pp:5924

Publication Date(Web):May 23, 2013

DOI:10.1021/ac4006974

Sample preparation methods with high temporal resolution and matrix resistance will benefit fast direct analysis of analytes in a complex matrix, such as drug monitoring in biofluids. In this work, the core–sheath biocompatible electrospun nanofiber was fabricated as a micro-solid phase extraction material. With the poly(N-isopropylacrylamide) (PNIPAAm) as sheath polymer and polystyrene (PS) as core polymer, the fiber membrane was highly hydrophilic and exhibited good antifouling ability to proteins and cells. Its complete expansion in aqueous solution and its nanoscale fiber (100–200 nm) structure offered high mass transfer rate of analytes between liquid and solid phases. The equilibration time of microextraction with this membrane was all shorter than 2 min for eight drugs tested, and the linear ranges covered more than 3 orders of magnitude for most of them. This membrane could be applied to monitor free drugs in plasma and their protein binding kinetics by equilibrium–microextraction with a 2 min temporal resolution. The results showed that the core–sheath electrospun nanofiber membrane would be a better alternative of solid phase material for microextraction with good matrix-resistance ability and high temporal resolution.

A Porous Membrane Extraction and Microtrap System for On-line Monitoring of Volatile Organic Compounds in Water

Co-reporter:Di ZHAO, Zheng SHEN, Xiao-Hui YAN, Da-Peng WU, Ding Kun, Ya-Feng GUAN

Chinese Journal of Analytical Chemistry 2013 Volume 41(Issue 8) pp:1153-1158

Publication Date(Web):August 2013

DOI:10.1016/S1872-2040(13)60670-2

Based on the membrane pervaporation extraction and microtrap method, a sample pretreatment device for volatile organic compounds in water was constructed and evaluated. The volatile organic compounds (VOCs) in water samples could be extracted, preconcentrated, desorbed thermally, and injected directly into a gas chromatograph automatically. Two kinds of porous hollow fiber membrane materials, polydimethylsiloxane (PDMS) and polyvinylidene fluoride (PVDF), were examined. Extraction parameters, such as extraction temperature, extraction time, and carrier gas flow rate, were investigated by using nine model compounds, including chloroform, 1,2-dichloroethane, carbon tetrachloride, trichloroethylene, tetrachloroethylene, toluene, ethylbenzene, styrene and chlorobenzene. Under the optimum conditions (extraction temperature of 60 °C and concentration time of 30 min with purge gas flow of 8 mL min−1), the detection limits of chlorinated hydrocarbons were in the range of 0.003–0.041 μg L−1, with RSD of 2.7% and 13.0%, using a flame ionization detector. Coefficients of correlation were all above 0.9936. This result demonstrated that this device was feasible for monitoring volatile organic compounds in water.With the membrane pervaporation extraction and microtrap device, the volatile organic compounds (VOCs) in water samples could diffuse spontaneously through hollow fiber membrane, be taken away by carrier gas, and then were extracted and preconcentrated by microtrap. These adsorbed VOCs could be desorbed thermally, injected directly into a gas chromatograph, and quantified precisely.

Naked-eye sensor for rapid determination of mercury ion

Co-reporter:Jing Liu, Dapeng Wu, Xiaohui Yan, Yafeng Guan

Talanta 2013 Volume 116() pp:563-568

Publication Date(Web):15 November 2013

DOI:10.1016/j.talanta.2013.07.035

•A rapid naked-eye paper sensor was developed for trace mercury ions.•Color change from white to purple red was observed for 10 nM Hg2+.•The sensor can tolerate the common metal ions up to 140–80,000 folds.•Hg2+ in mineral water, tap water, and pond water was quantified.A naked-eye paper sensor for rapid determination of trace mercury ion in water samples was designed and demonstrated. The mercury-sensing rhodamine B thiolactone was immobilized in silica matrices and the silica matrices were impregnated firmly and uniformly in the filter paper. As water samples flow through the filter paper, the membrane color will change from white to purple red, which could be observed obviously with naked eye, when concentration of mercury ions equals to or exceeds 10 nM, the maximum residue level in drinking water recommended by U.S. EPA. The color change can also be recorded by a flatbed scanner and then digitized, reducing the detection limit of Hg2+ down to 1.2 nM. Moreover, this method is extremely specific for Hg2+ and shows a high tolerance ratio of interferent coexisting ions. The presence of Na+ (2 mM), K+ (2 mM), Fe3+ (0.1 mM), Zn2+ (0.1 mM), Mg2+ (0.1 mM), Ni2+ (50 μM), Co2+ (50 μM), Cd2+ (50 μM), Pb2+ (50 μM), Cu2+ (50 μM) and Ag+ (3.5 μM) did not interfere with the detection of Hg2+ (25 nM). Finally, the present method was applied in the detection of Hg2+ in mineral water, tap water and pond water.

Colorimetric sensing of anions in water using ratiometric indicator-displacement assay

Co-reporter:Liang Feng, Hui Li, Xiao Li, Liang Chen, Zheng Shen, Yafeng Guan

Analytica Chimica Acta 2012 Volume 743() pp:1-8

Publication Date(Web):19 September 2012

DOI:10.1016/j.aca.2012.06.041

The analysis of anions in water presents a difficult challenge due to their low charge-to-radius ratio, and the ability to discriminate among similar anions often remains problematic. The use of a 3 × 6 ratiometric indicator-displacement assay (RIDA) array for the colorimetric detection and identification of ten anions in water is reported. The sensor array consists of different combinations of colorimetric indicators and metal cations. The colorimetric indicators chelate with metal cations, forming the color changes. Upon the addition of anions, anions compete with the indicator ligands according to solubility product constants (Ksp). The indicator–metal chelate compound changes color back dramatically when the competition of anions wins. The color changes of the RIDA array were used as a digital representation of the array response and analyzed with standard statistical methods, including principal component analysis and hierarchical clustering analysis. No confusion or errors in classification by hierarchical clustering analysis were observed in 44 trials. The limit of detection was calculated approximately, and most limits of detections of anions are well below μM level using our RIDA array. The pH effect, temperature influence, interfering anions were also investigated, and the RIDA array shows the feasibility of real sample testing.Graphical abstractA colorimetric indicator-displacement assay (IDA) array has been developed for the determination of ten anions in water. The color changes in IDA array provide facile identification of these anions with no misclassification.Highlights► The RIDA array was developed to sense ten anions in aqueous solution. ► No complicated molecular synthesis is needed. ► The collected images were digitized for the semi-quantitative discriminations. ► Array technologies and pattern-recognition were combined. ► The transparency scan unit was used to avoid the light reflection.

Colorimetric and “turn-on” fluorescent determination of Cu2+ ions based on rhodamine–quinoline derivative

Co-reporter:Liang Feng, Hui Li, Yongjun Lv and Yafeng Guan

Analyst 2012 vol. 137(Issue 24) pp:5829-5833

Publication Date(Web):01 Oct 2012

DOI:10.1039/C2AN36215E

A novel rhodamine–quinoline derivative-based indicator for Cu2+ ion determination was designed and synthesized. It exhibited highly selective and sensitive colorimetric and “turn-on” fluorescent responses toward Cu2+ ions based on the ring-opening mechanism of the rhodamine spirolactam in aqueous solution. The colorimetric and fluorescent responses were recorded using a domestic scanner and camera-based home-made fluorescent imaging unit, separately. The images were digitized, and the red (R), green (G), and blue (B) values were investigated. Both colorimetric and fluorescent methods showed good selectivity, and the color/fluorescence changes were remarkable for the Cu2+ ion detection even in the presence of other metal ions. The good linear relationship was easily obtained between the color/fluorescence changes and the concentrations in the range of 20–120 μM.

Array capillary in-tube solid-phase microextraction: A rapid preparation technique for water samples

Co-reporter:Xiaohui Yan, Dapeng Wu, Hong Peng, Kun Ding, Chunfeng Duan, Yafeng Guan

Journal of Chromatography A 2012 Volume 1244() pp:69-76

Publication Date(Web):29 June 2012

DOI:10.1016/j.chroma.2012.05.015

A rapid sample preparation technique, namely array capillary in-tube solid-phase microextraction (ACIT-SPME) for direct extraction of organic pollutants from water samples, was developed and evaluated. The ACIT-SPME cartridge consisted of a bundle of glass capillary tubes of 0.5 mm I.D. × 30 mm contained inside a quartz liner of 4 mm I.D. The high ratio of cross-section area of channel-to-wall allowed water sample flow through the cartridge just under gravity. Both the internal/external surfaces of the array capillary tubing were coated with extraction phase of 2–5 μm in thickness, which provided large extraction surface area up to 30 cm2 for a cartridge containing 19 glass capillaries. The large surface area and thin extraction phase improved greatly both the mass transfer process of extraction and the thermo desorption process, leading to fast extraction and fast desorption. The extracted analytes were thermally desorbed in a homemade thermal desorption unit (TDU), which was coupled to a gas chromatograph equipped with a flame ionization detector for analysis. By using polydimethylsiloxane (PDMS) as the extraction phase and polycyclic aromatic hydrocarbons (PAHs) as the model analytes, the performance of the ACIT-SPME cartridge was systematically investigated. The extraction time was 2 min for 350 mL of water sample, and detection limits were between 0.8 and 1.7 ng/L with deviation of 2.8–9.7% RSD. Relative recoveries of analytes for real water samples were between 65.0% and 116%. The extraction time can even be further shortened to 10 s for 250 mL sample by applying vacuum at the outlet of the cartridge, with detection limits of 2.2–5.3 ng/L and deviation of 4.0–12% RSD.Highlights► Array capillary in-tube solid-phase microextraction (ACIT-SPME) was developed. ► ACIT-SPME was suitable for fast extraction of organic pollutants in water. ► Extraction was completed in 2 min for 350 mL water sample under gravity. ► The method was applied successfully for PAHs in real samples.

A surface ionization detector for capillary gas chromatography

Co-reporter:Weiwei Li, Yafeng Guan, Zheng Shen and Dapeng Wu

Chemical Communications 2011 vol. 47(Issue 8) pp:2423-2425

Publication Date(Web):20 Dec 2010

DOI:10.1039/C0CC04528D

A novel surface ionization detector using a reducing quartz liner and a Mo emitter with a quartz enclosed internal heater for selective measurement of alkylamines by gas chromatography is designed and evaluated.

A cryogen-free refrigerating preconcentration device for the measurement of C2 to C4 hydrocarbons in ambient air

Co-reporter:Hong Peng, JianWei Wang, Zheng Shen, Dapeng Wu and Yafeng Guan

Analyst 2011 vol. 136(Issue 3) pp:586-590

Publication Date(Web):15 Nov 2010

DOI:10.1039/C0AN00563K

A cryogen-free refrigerating preconcentration device for the enrichment of trace amounts of highly volatile organic compounds in the atmosphere prior to analysis has been designed and evaluated. The device consists of a microtrap housed in an insulated box, which is cooled by a conventional refrigeration unit. Experimental parameters, including adsorbent mass, trapping temperature, and thermal desorption temperature, were optimized. The on-line coupling of the device to a GC allows sufficient enrichment and separation of C2 to C4 hydrocarbons in less than 40 min without a second cryotrap. The target compounds analysis showed good linearity (correlation coefficients >0.99) and repeatability (relative standard deviation <5%). Detection limits for the 10 volatile organic compounds ranged from 14 ppt to 52 ppt, under the conditions of a 500 mL sampling volume and −10 °C trapping temperature. Real air sample measurements were conducted at an urban site, and five VOCs including ethane, ethene, propane, propene and 1-butene were detected and quantified.

Colorimetric filtrations of metal chelate precipitations for the quantitative determination of nickel(II) and lead(II)

Co-reporter:Liang Feng, Yue Zhang, Liying Wen, Liang Chen, Zheng Shen and Yafeng Guan

Analyst 2011 vol. 136(Issue 20) pp:4197-4203

Publication Date(Web):22 Aug 2011

DOI:10.1039/C1AN15290D

A colorimetric filtration method has been developed for the highly selective and sensitive determination of Ni2+ and Pb2+ ions. Determinations of Ni2+ and Pb2+ follow the filtration using nioxime (1,2-cyclohexanedione dioxime) and rhodizonic acid disodium salt, respectively, as colorimetric reagents. Different from regular instrumentation techniques, the metal chelate precipitations are continuously pumped into a home-made flow cell at a constant flow rate, and filtered by a cellulose acetate/nitrate membrane. The color changes of the membrane are imaged using a conventional flatbed scanner, and digitized. The special selection of individual channels in the red, green, and blue channels of the images filters the influences of coexisting ions and provides a highly selective detection of Ni2+ and Pb2+ cations. The linear relationship between the colorimetric response of the chosen channel and Ni2+ or Pb2+ concentrations indicates a quantitative detection. The detection limit for Pb2+ is 3 μM (almost half of the Chinese wastewater discharge standard concentration), and is well below the nM level (94 nM) for Ni2+ (a quarter of the WHO drinking water safe-exposure standard for Ni2+). The determinations take five to ten minutes. No shelf life issue exists because the chelating indicators react with metal directly without any pre-immobilizations.

Discrimination of Trace Heavy-Metal Ions by Filtration on SolGel Membrane Arrays

Co-reporter:Dr. Liang Feng;Yue Zhang;Liying Wen;Liang Chen;Dr. Zheng Shen ;Dr. Yafeng Guan

Chemistry - A European Journal 2011 Volume 17( Issue 4) pp:1101-1104

Publication Date(Web):

DOI:10.1002/chem.201003133

Colorimetric determination of copper(II) ions by filtration on sol–gel membrane doped with diphenylcarbazide

Co-reporter:Liang Feng, Yue Zhang, Liying Wen, Zheng Shen, Yafeng Guan

Talanta 2011 Volume 84(Issue 3) pp:913-917

Publication Date(Web):15 May 2011

DOI:10.1016/j.talanta.2011.02.033

A simple and sensitive colorimetric method for the determination of trace copper(II) ions in aqueous solution has been developed using diphenylcarbazide (DPC) immobilized sol–gel matrices. To enhance the odds of chelating interactions between copper(II) ions and DPC, a peristaltic pump was utilized to drive copper(II) ions solution pass through the cellulose acetate/nitrate membrane, which was coated with DPC immobilized sol–gel matrices. The membrane was sandwiched in a home-made flow cell. The porous silica matrix serves as a preconcentrator, and enriches the trace copper(II) ions. Meanwhile, the filtration increases the chelating interaction probability between copper(II) ions and DPC, thereby improves the sensitivity significantly. After the formation of purple complex compound, the color changes of the DPC immobilized sol–gel membrane were recorded using a flatbed scanner. The images were digitized, and the red (R), green (G), and blue (B) values were investigated. The colorimetric method provides a rapid and reliable determination of trace copper(II) ions with a detection limit as low as 0.16 μM and a kinetic range up to 1.6 μM in neutral medium. Moreover, the method shows good selectivity, and the color changes of the DPC immobilized sol–gel membranes are remarkable for the copper(II) ions detection even in the presence of other metal ions.

Temperature-controlled headspace liquid-phase microextraction device using volatile solvents

Co-reporter:Shiheng Chen, Hong Peng, Dapeng Wu, Yafeng Guan

Journal of Chromatography A 2010 Volume 1217(Issue 38) pp:5883-5889

Publication Date(Web):17 September 2010

DOI:10.1016/j.chroma.2010.07.033

A novel temperature-controlled headspace liquid-phase microextraction (TC-HS-LPME) device was established in which volatile solvents could be used as extractant. In this device, a PTFE vial cap with a cylindrical cavity was used as the holder of the extraction solvent. Up to 40 μl of extraction solvent could be suspended in the cavity over the headspace of aqueous sample in the vial. A cooling system based on thermoelectric cooler (TEC) was used to lower the temperature of extractant in PTFE vial cap to reduce the loss of volatile solvent during extraction process and increase the extraction efficiency. The selection of solvents for HS-LPME was then extended to volatile solvents, such as dichloromethane, ethyl acetate and acetone. The use of volatile extraction solvents instead of semi-volatile solvent reduced the interference of the large solvent peak to the analytes peaks, and enhanced the compatibility of HS-LPME with gas chromatograph (GC). Moreover, the use of larger volume of extractant solvent increases the extraction capacity and the injection volume of GC after extraction, thus improving detection limits. Several critical parameters of this technique were investigated by using chlorobenzenes (CBs) as the model analytes. High enrichment factors (498–915), low limits of detection (0.004–0.008 μg/L) and precision (3.93–5.27%) were obtained by using TC-HS-LPME/GC-FID. Relative recoveries for real samples were more than 83%.

Core−Shell Nanoarchitectures: A Strategy To Improve the Efficiency of Luminescence Resonance Energy Transfer

Co-reporter:Cuihong Song, Zhiqiang Ye, Guilan Wang, Jingli Yuan, and Yafeng Guan

ACS Nano 2010 Volume 4(Issue 9) pp:5389

Publication Date(Web):August 3, 2010

DOI:10.1021/nn100820u

The development of core−shell nanoparticles has shown a wide range of new applications in the fields of chemistry, bioscience, and materials science because of their improved physical and chemical properties over their single-component counterparts. In the present work, we took the core−shell nanoarchitectures as an example to research the luminescence resonance energy transfer (LRET) process between a luminescent Tb3+ chelate, N,N,N1,N1-[4′-phenyl-2,2′:6′,2′-terpyridine-6,6′-diyl]bis(methylenenitrilo)tetrakis(acetate)-Tb3+ (PTTA-Tb3+), and an organic dye, 5-carboxytetramethylrhodamine (CTMR). PTTA-Tb3+ and CTMR were chosen as the donor−acceptor pair of LRET in our model construction because of their effective spectral overlapping. The core−shell nanoparticles featuring a CTMR-SiO2 core surrounded by a concentric PTTA-Tb3+-SiO2 shell were prepared using a reverse microemulsion method. These nanoparticles are spherical, uniform in size, and highly photostable. The results of LRET experiments show that the sensitized emission lifetime of the acceptor in the nanoparticles is significantly prolonged (∼246 μs), which is attributed to the long emission lifetime of the Tb3+ chelate donor. According to the results of the steady-state and time-resolved luminescence spectroscopy, an energy transfer efficiency of ∼80% and a large Förster distance between the donor and the acceptor in the core−shell nanoparticles are calculated, respectively. The new core−shell nanoparticles with a high LRET efficiency and long Förster distance enable them to be promising optical probes for a variety of possible applications such as molecular imaging and multiplex signaling.Keywords: core−shell nanoparticle; luminescence resonance energy transfer; terbium chelate; tetramethylrhodamine

A Lanthanide-Complex-Based Ratiometric Luminescent Probe Specific for Peroxynitrite

Co-reporter:Cuihong Song;Zhiqiang Ye Dr.;Guilan Wang ;Jingli Yuan ;Yafeng Guan

Chemistry - A European Journal 2010 Volume 16( Issue 22) pp:6464-6472

Publication Date(Web):

DOI:10.1002/chem.201000528

Abstract

A lanthanide-complex-based ratiometric luminescence probe specific for peroxynitrite (ONOO⁻), 4′-(2,4-dimethoxyphenyl)-2,2′:6′,2′′-terpyridine-6,6′′-diyl]bis(methylenenitrilo)tetrakis(acetate)-Eu³⁺/Tb³⁺ ([Eu³⁺/Tb³⁺(DTTA)]), has been designed and synthesized. Both [Eu³⁺(DTTA)] and [Tb³⁺(DTTA)] are highly water soluble with large stability constants at ≈10²⁰, and strongly luminescent with luminescence quantum yields of 10.0 and 9.9 %, respectively, and long luminescence lifetimes of 1.38 and 0.26 ms, respectively. It was found that the luminescence of [Tb³⁺(DTTA)] could be quenched by ONOO⁻ rapidly and specifically in aqueous buffers, while that of [Eu³⁺(DTTA)] did not respond to the addition of ONOO⁻. Thus, by simply mixing [Eu³⁺(DTTA)] and [Tb³⁺(DTTA)] in an aqueous buffer, a ratiometric luminescence probe specific for time-gated luminescence detection of ONOO⁻ was obtained. The performance of [Tb³⁺(DTTA)] and [Eu³⁺/Tb³⁺(DTTA)] as the probes for luminescence imaging detection of ONOO⁻ in living cells was investigated. The results demonstrated the efficacy and advantages of the new ratiometric luminescence probe for highly sensitive luminescence bioimaging application.

Visible-light-sensitized highly luminescent europium nanoparticles: preparation and application for time-gated luminescence bioimaging

Co-reporter:Jing Wu, Zhiqiang Ye, Guilan Wang, Dayong Jin, Jingli Yuan, Yafeng Guan and James Piper

Journal of Materials Chemistry A 2009 vol. 19(Issue 9) pp:1258-1264

Publication Date(Web):22 Jan 2009

DOI:10.1039/B815999H

Time-gated luminescence bioimaging based on microsecond-lifetime luminescent biolabels can provide complete background-free conditions for detecting target cells in an autofluorescence biosample matrix. However, a major drawback of the current lanthanide biolabels is the requirement for UV excitation (<370 nm), which leads to damage to many biological systems and greatly affects the improvement of time-gated luminescence instruments. Herein we describe luminescent europium nanoparticles that have an excitation peak around 406 nm with high quantum yield (∼66%) and fine monodispersity in aqueous solutions. The nanoparticles were prepared by copolymerization of a visible-light-sensitized Eu3+ complex 4,4′-bis(1″,1″,1″,2″,2″,3″,3″-heptafluoro-4″,6″-hexanedion-6″-yl)chlorosulfo-o-terphenyl-Eu3+-2-(N,N-diethylanilin-4-yl)-4,6-bis(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine conjugated with 3-aminopropyl(triethoxy)silane, free 3-aminopropyl(triethoxy)silane and tetraethyl orthosilicate in a water-in-oil reverse microemulsion. Characterization by transmission electron microscopy and luminescence spectroscopy indicates that the nanoparticles are monodisperse, spherical and uniform in size, <50 nm in diameter, and show strong visible-light-sensitized luminescence with a large quantum yield and a long luminescence lifetime. The new nanoparticles were successfully applied to distinguish an environmental pathogen, Giardia lamblia, within a concentrate of environmental water sample using a time-gated luminescence microscope with pulsed visible light excitation. The method resulted in highly specific and sensitive imaging for Giardia lamblia. These results suggest a broad range of potential bioimaging applications where both long time microscopy observation and high signal-to-background ratio are required for samples containing high concentrations of autofluorescence background.

Preparation and time-gated luminescence bioimaging application of ruthenium complex covalently bound silica nanoparticles

Co-reporter:Cuihong Song, Zhiqiang Ye, Guilan Wang, Dayong Jin, Jingli Yuan, Yafeng Guan, James Piper

Talanta 2009 Volume 79(Issue 1) pp:103-108

Publication Date(Web):30 June 2009

DOI:10.1016/j.talanta.2009.03.018

Luminescent ruthenium(II) complex covalently bound silica nanoparticles have been prepared and used as a probe for time-gated luminescence bioimaging. The new nanoparticles were prepared by copolymerization of a luminescent Ru(II) complex tris(5-amino-1,10-phenanthroline)ruthenium(II) conjugated with 3-aminopropyl(triethoxy)silane (APS-Ru conjugate), free (3-aminopropyl)triethoxysilane (APS) and tetraethyl orthosilicate (TEOS) in a water-in-oil reverse microemulsion consisting of Triton X-100, n-octanol, cyclohexane and water in the presence of aqueous ammonia. Characterization by transmission electron microscopy indicates that the nanoparticles are monodisperse, spherical and uniform in size, 64 ± 4 nm in diameter. Compared with the dye-doping nanoparticles, dye leakage of the new nanoparticles was remarkably decreased. In addition, it was found that the Ru(II) complex luminescence could be effectively enhanced with a longer luminescence lifetime (∼2.3 μs) after forming the nanoparticles, which enables the nanoparticles to be suitable as a bioprobe for time-gated luminescence bioimaging applications. The nanoparticle-labeled streptavidin was prepared and successfully used for time-gated luminescence imaging detection of an environmental pathogen, Giardia lamblia, with high specificity and sensitivity.

Improved selection of LMW over HMW proteins from human plasma by mesoporous silica particles with external modification

Co-reporter:Yanxia Qi, Junying Wei, Hua Wang, Yangjun Zhang, Jing Xu, Xiaohong Qian, Yafeng Guan

Talanta 2009 Volume 80(Issue 2) pp:703-709

Publication Date(Web):15 December 2009

DOI:10.1016/j.talanta.2009.07.050

Selective extraction of low molecular weight (LMW) proteins and peptides from complex biological samples plays an important role in the discovery of useful biomarkers and signaling molecules. Various methods, such as solid-phase extraction (SPE), ultrafiltration, and size-exclusion chromatography have been developed for such extraction purpose. In this study, we present, to our knowledge, the first demonstration of alkyl-diol@SiO2 mesoporous material MCM-41 (alkyl-diol group on the external surface of mesoporous material) for selective extraction of LMW proteins and peptides from complex biological samples. The adsorption kinetics of LMW proteins, the influence of pH on adsorption and the desorption recovery by different elution solvents were investigated by using standard proteins as model samples. It was demonstrated that the modification of alkyl-diol group on the external surface could efficiently decrease the adsorption of HMW protein and increase the desorption recovery of LMW protein. Furthermore, the mesoporous materials were applied to selectively extract LMW proteins and peptides (<10 kDa) from crude human plasma. And the modified MCM-41 material had much better extraction selectivity and efficiency for LMW proteins and peptides than unmodified one.

Luminescent europium nanoparticles with a wide excitation range from UV to visible light for biolabeling and time-gated luminescence bioimaging

Co-reporter:Jing Wu, Guilan Wang, Dayong Jin, Jingli Yuan, Yafeng Guan and James Piper

Chemical Communications 2008 (Issue 3) pp:365-367

Publication Date(Web):12 Nov 2007

DOI:10.1039/B715054G

Silica-encapsulated highly luminescent europium nanoparticles with a wide excitation range from UV to visible light (200–450 nm) have been prepared and used for streptavidin labeling and time-gated luminescence imaging of an environmental pathogen, Giardia lamblia.

An improved Stöber method towards uniform and monodisperse Fe3O4@C nanospheres

Co-reporter:Xue-Bin Zhang, Hong-Wu Tong, Shao-Min Liu, Guo-Ping Yong and Ya-Feng Guan

Journal of Materials Chemistry A 2013 - vol. 1(Issue 25) pp:NaN7493-7493

Publication Date(Web):2013/04/11

DOI:10.1039/C3TA11249G

Further investigation of array capillary in-tube solid-phase microextraction of trace organic pollutants in water samples

Co-reporter:

Analytical Methods (2009-Present) 2014 - vol. 6(Issue 3) pp:NaN757-757

Publication Date(Web):2013/11/06

DOI:10.1039/C3AY41525B

A surface ionization detector for capillary gas chromatography

Co-reporter:Weiwei Li, Yafeng Guan, Zheng Shen and Dapeng Wu