Dispersive Micro-Solid-Phase Extraction Using Mesoporous Hybrid

Article pubs.acs.org/JAFC

Dispersive Micro-Solid-Phase Extraction Using Mesoporous Hybrid Materials for Simultaneous Determination of Semivolatile Compounds from Plant Tea by Ultra-High-Performance Liquid Chromatography Coupled with Quadrupole Time-of-Flight Tandem Mass Spectrometry Wan Cao,†,§ Shuai-Shuai Hu,†,§ Li-Hong Ye,‡,§ and Jun Cao*,† †

College of Material Chemistry and Chemical Engineering, Hangzhou Normal University, 16, Xuelin Street, Xiasha High Education Zone, Hangzhou 310036, China ‡ Integrated Chinese and Western Medicine Hospital of Zhejiang Province, Hangzhou 310003, China ABSTRACT: This report described the use of mesoporous hybrid materials (MHM) in a dispersive micro-solid-phase extraction procedure to extract semivolatile compounds from plant tea that were then analyzed by ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry. Dihydrotanshinone I, tanshinone I, cryptotanshinone, and tanshinone IIA were selected as the model compounds, and the extraction parameters, including mesoporous concentration, extraction time, sample agitation and desorption solvents, were optimized. The interaction with the analytes and the large surface area of the MHM facilitated the adsorption of analytes. The method showed good linearity, with correlation coefficients >0.9980 in the range 0.25−100 ng/mL, and low limits of detection (0.012−0.046 pg). Finally, the recovery values were 91−103% for Danshen tea, 89−102% for Danshen, and 88−96% for tanshinone capsules. The results showed that the proposed method was suitable for the extraction and determination of tanshinones in complex samples. KEYWORDS: Danshen tea, dispersive micro-solid-phase extraction, mesoporous hybrid materials, quadrupole time-of-flight tandem mass spectrometry, ultra-high-performance liquid chromatography

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INTRODUCTION Ordered mesoporous materials are an important class of molecular sieves that are composed of extensively ordered arrays with pore sizes of 2−50 nm and surface areas up to 1000 m2/g. Since their discovery in the early 1990s, ordered mesoporous materials have aroused much attention from researchers due to their ability to interact with atoms, ions, molecules, and nanoparticles. Mesoporous materials have been widely used in chemical sensing, adsorption, molecular separation, photonics, drug delivery, catalysis, and nanodevices, especially for dealing with biomolecules, because of their high surface areas, tunable pore sizes and shapes, a multitude of compositions, and high hydrothermal and mechanical stability.1 Miniaturization has become an important issue in the development of sample preparation techniques, which can provide benefits not only to the environment but also to the economy. In recent years, a diversity of microextraction methods, including solid phase microextraction (SPME),2,3 hollow fiber liquid phase microextraction (HF-LPME),4,5 single drop microextraction6,7 (SDME), stir-bar sorptive extraction (SBSE), 8 , 9 dispersive liquid−liquid microextraction (DLLME),10,11 and gas purge microsyringe extraction (GPMSE),12 have been developed for sample preparation. Very recently, a new mode of microextraction, which was termed dispersive micro-solid-phase extraction (D-μ-SPE), was developed for the analysis of organophosphate pesticides,13 polycyclic aromatic hydrocarbons,14 triazines,15 ortho-phosphate ions,16 N-nitrosamines,17 and metal ions18 to improve the © 2014 American Chemical Society

preconcentration of the analytes using only a few microliters of extractant. In this technique, the use of nanomaterials, such as single-walled carbon nanohorns,14,15 magnetite nanoparticles,16 and multiwalled carbon nanotubes,18 produced a synergistic effect to achieve high extraction efficiency in the sample preparations. However, it is not suitable for extracting complex plant compounds because of the limited interface between the extractants and the aqueous samples. Therefore, expansion of the D-μ-SPE technique to further exploit highly efficient extractant media would be interesting and beneficial, especially if accompanied by mesoporous hybrid materials (MHM). Natural plant teas (NPTs) have a long therapeutic history over thousands of years in China and other countries. Today, NPTs are widely used as complementary and alternative medicines in the United States. Many NPTs consist of a mixture of complex constituents. Sample preparation is currently a bottleneck for the analysis of NPTs due to the very complex nature of the sample matrices.19 Although most sample preparation methods involve conventional techniques, such as solid−liquid extraction, liquid−liquid extraction, and solid-phase extraction (SPE), these methods have the disadvantages of using large amounts of organic solvents, involving time-consuming cleanup procedures, and being Received: Revised: Accepted: Published: 9683

June 22, 2014 September 14, 2014 September 18, 2014 September 18, 2014 dx.doi.org/10.1021/jf5029625 | J. Agric. Food Chem. 2014, 62, 9683−9689

Journal of Agricultural and Food Chemistry

Article

relatively expensive. Therefore, the development of effective extraction methods is critical for the quality control of NPTs while minimizing the environmental impact. With the improvement of living conditions and economic development, the incidence of cardiovascular disease increases dramatically. There is therefore increased emphasis on prevention since the disease is the leading cause of death in many countries. Danshen (DS), also known as Salvia miltiorrhiza and derived from the dried root or rhizome of Salvia miltiorrhiza Bge, is one of the most popular traditional herbal medicines and has been widely used for the treatment of angina pectoris, myocardial infarction, dysmenorrhea, insomnia, and bacterial infections.20 Danshen tea (DST), refined from Salvia miltiorrhiza and green tea, is a new type of health care product for the prevention and treatment of coronary heart disease and hyperlipidemia. Tanshinone capsules (TC) made from the extracts of Salvia miltiorrhiza are one of the most widely used plant preparations and have antibiotic and antiinflammation functions. These DS products are now experiencing a particularly strong and rapid demand in China, Japan, the United States, and many European countries for treatment and prevention of cardiovascular and cerebrovascular system disorders. Numerous bioactive compounds, mainly including soluble phenolic acids and lipophilic tanshinones, have been isolated from Salvia miltiorrhiza. Among them, tanshinones, including dihydrotanshinone I, tanshinone I, cryptotanshinone, and tanshinone IIA, are gaining popularity because of their significant pharmacological activities such as dilating coronary artery, activating blood circulation, and preventing myocardial ischemia.21−23 Therefore, extraction and quantitative determination of tanshinones are important for physiological and pharmacological studies. In this study, a novel extraction technique, D-μ-SPE, involving the use of MHM as the sorbent was evaluated for the extraction of semivolatile compounds (dihydrotanshinone I, tanshinone I, cryptotanshinone, and tanshinone IIA). The parameters affecting the extraction, such as mesoporous concentration, extraction time, sample agitation, and desorption solvents, were systematically studied and evaluated. The optimized microextraction methodology combined with ultrahigh-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (UHPLC-QTOF/MS) was then successfully applied to the determination of tanshinones in complex NPTs.

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Figure 1. Chemical structures of the four tanshinones. an Agilent Zorbax SB-C18 column (1.8 μm, 2.1 mm i.d. × 50 mm) maintained at 30 °C. Mobile phases A and B were 0.1% formic acid in water and methanol, respectively, and were applied according to the following gradient: 0−1 min, 10−30% B; 1−2 min, 30−50% B; 2−6 min, 50−70% B; and 6−7 min, 70−100% B. The injection volume was 2 μL for the standards and sample extracts. The UHPLC system was connected to an accurate mass Q-TOF instrument (Agilent Technologies, Santa Clara, CA) equipped with a Dual ESI ion source. Accurate product ion scan (MS/MS) spectra were acquired in the range of m/z values from 100 to 1000 units, and compounds were ionized in positive ESI by applying a capillary voltage of 3500 V. The other experimental parameters were as follows: drying gas temperature, 350 °C; drying gas flow, 12 L/min; nebulizer, 45 psi; fragmentor, 175 V; skimmer voltage, 65 V; and octapole RFPeak, 750 V. Selective UHPLC−MS and UHPLC−MS/MS chromatograms were extracted with a mass window of 0.01 Da around the [M + H]+ and the most intense product ion of each tanshinone, respectively. The Mass Hunter Workstation software (version B 05.00) was used to control the system and process the obtained data. Preparation of Mesoporous Hybrid Materials. The MHM was obtained by following a previously optimized procedure.24 Briefly, 1.0 g of [3-(trimethoxysilyl)propyl]-octadecyldimethylammonium chloride was mixed with 28.0 g of deionized water, 4.10 g of tetraethyl orthosilicate, and 0.60 g of 1,3,5-trimethylbenzene under vigorous stirring at room temperature for 15 min. Then, 3.0 g of (2.0 M) NaOH solution was added to the translucent mixture. The mixture was stirred for 2 h at 25 °C, transferred into a hydrothermal bomb, and treated at 110 °C for 24 h. Finally, the obtained precipitate was filtered, washed with 200 mL of ethanol and 50 mL of acetone, and then vacuum-dried at 60 °C overnight to obtain a fine powder. Sample Preparation. A 0.3 g sample of the dried powder (DST, DS, or TC) was accurately weighed and extracted with 50 mL of hot water in an ultrasonic bath for 5 min. After cooling, the solution was centrifuged at 15 000 rpm for 5 min before being subjected to the D-μSPE process. Extraction Procedures. An accurately weighed 2 mg aliquot of pristine MHM, added in 10 mL of Milli-Q water, was ultrasonicated (100 W, 40 Hz) for 20 min. Subsequently, the mixture was agitated using a vortex for 2 min to facilitate the dispersion of the material. The experimental setup of the D-μ-SPE extraction is illustrated in Figure 2. Briefly, 10 mL of the aqueous samples containing four tanshinones at a concentration within the quantification linear range was first placed in a 25 mL glass vial. After that, 1 mL of MHM dispersion at a final concentration of 0.02 g/L was quickly added to the vial, and the mixture was agitated at 3200 rpm for 2 min using an orbital shaker. Then, the MHM concentrated with the analytes was recovered by filtration on a 0.45 μm disposable nylon filter, which was previously cleaned with 3 mL of methanol and 3 mL of ultrapure water to remove any possible contamination. Finally, the analytes were desorbed by

MATERIALS AND METHODS

Reagents and Materials. HPLC grade hexane, ethanol, acetonitrile, acetone, and methanol were purchased from SigmaAldrich (St. Louis, MO). The dihydrotanshinone I, tanshinone I, cryptotanshinone, and tanshinone IIA standards were obtained from Winherb Medical Technology Co., Ltd. (Shanghai, China) (purity higher than 98%). The structures of these compounds are shown in Figure 1. Stock standard solutions for each of the analytes were prepared in methanol at a concentration of 0.5 μg/mL and were stored at 4 °C. The 0.45 μm disposable nylon filters were purchased from Anpel Scientific Instrument Co., Ltd. (Shanghai, China). Ultrapure water was produced using a Milli-Q (Millipore, Billerica, MA) water purification system. All tested samples, including DST, DS, and TC, were purchased from a local drugstore (Hangzhou, China). All other chemicals used were of analytical grade (Anpel Scientific Instrument Co., Ltd.) and were used as received without further purification. Apparatus. The UHPLC instrument was an Agilent 1290 Series (Agilent Technologies, Santa Clara, CA), consisting of a binary pump, an autosampler, and a thermostated column compartment. Chromatographic separation was performed at a flow rate of 400 μL/min using 9684

dx.doi.org/10.1021/jf5029625 | J. Agric. Food Chem. 2014, 62, 9683−9689


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account their higher surface areas.14 In this study, the usefulness of MHM for the extraction of semivolatile compounds, such as tanshinones, was evaluated. The addition of MHM was expected to enhance the extraction efficiency of D-μ-SPE because the material was different from that of the bulk counterparts due to the higher surface area and pore volume. Hence, the effect of adding MHM in microextraction, ranging from 0.01 to 0.04 (g/L) in the extraction phase, was studied. According to the obtained results (Figure 3), the peak areas of

Figure 2. Schematic procedure of MHM D-μ-SPE. For details, see text. passing 200 μL of methanol through the nylon filter, and 2 μL was injected into the UHPLC-Q-TOF/MS for identification and quantification of the tanshinones. Validation Procedure. The calibration samples were prepared using the described D-μ-SPE procedure in the range from 0.25 to 100 ng/mL. Five concentrations of the four analytes’ solution were extracted in triplicate, and then the calibration curves were constructed by plotting the mean peak areas versus the concentrations of target analytes. Intra- and interday variations, expressed by the relative standard deviations (RSD), were chosen to determine the precision of the proposed method. For intraday precision, the mixed standards solution was analyzed for six replicates on the same day, while, for interday precision, the solution was examined in duplicates for consecutive 3 days. The extraction solution containing 4 reference compounds was diluted to a series of appropriate concentrations, and an aliquot of the diluted solutions was injected into UHPLC-Q-TOF/ MS for analysis. The limits of detection (LODs) and quantification (LOQs) under the optimal chromatographic conditions were calculated on the basis of peak areas at a signal-to-noise of 3 and 10, respectively. Recovery test was used to evaluate the accuracy of Dμ-SPE method. The recoveries of four analytes were calculated by the following formula: recovery (%) = 100 × (amount found − original amount)/amount spiked. Table 1 shows the results of four analytes.

Figure 3. Effect of the MHM concentration (0.01−0.04 g/L) on the chromatographic peak areas of the selected tanshinones. Sample concentration: 25 ng/mL. Analytes: (1) dihydrotanshinone I, (2) tanshinone I, (3) cryptotanshinone, and (4) tanshinone IIA.

target analytes (25 ng/mL) were highest when 0.02 g/L MHM was used. The presence of MHM in sample solution resulted in an increase in the sensitivity of the analytes. This may be due to the increase in the interaction between the analytes and the sorbent surface following the addition of the appropriate sorbent material, thereby enhancing the mass transfer process. From the results shown in Figure 3, it is clear that the extraction efficiencies gradually decreased as the concentration of MHM increased from 0.02 to 0.04 (g/L). The possible reason for this observation was that the higher concentration of MHM increased the aggregation of the mesoporous material, which effectively reduced the surface available for analytes interaction. Finally, the proposed method permitted the use of a relatively small concentration of adsorbent (0.02 g/L) to ensure complete desorption of analytes from MHM by agitation, compared with other D-μ-SPE (0.2 g/L) in the

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RESULTS AND DISCUSSION Optimization of D-μ-SPE Process. The main parameters affecting the D-μ-SPE process, namely, the mesoporous concentration, extraction time, sample agitation, and desorption solvents, were optimized to obtain optimum performance of the mesoporous D-μ-SPE procedure. A 10 mL water sample containing 25 ng/mL of each tanshinone was used for the optimization experiments. Effect of the Mesoporous Concentration. Previous studies have demonstrated the applicability of nanometric sorbent materials in D-μ-SPE for the isolation and preconcentration of aromatic compounds from water samples, taking into

Table 1. Linearity, Precision, and Limits of Detection (LODs) and Quantification (LOQs) of the Developed D-μ-SPE Method precision (RSD) intraday (n = 6) analytes dihydrotanshinone I tanshinone I cryptotanshinone tanshinone IIA

regression eq y y y y

= = = =

20 061x + 9017 9423x + 2342 63 401x − 1911 39 097x − 8249

interday (3 days)

linear range (ng/ mL)

r2

time

areas

time

0.50−50.00 1.00−100.00 0.25−25.00 0.40−40.00

0.9990 0.9991 0.9980 0.9995

0.14 0.16 0.25 0.13

2.60 2.23 3.34 2.51

0.44 0.91 0.66 0.78

9685

LODs (pg)

LOQs (pg)

areas

ultrasonic method21

proposed method

proposed method

4.17 5.51 3.98 6.11

10 22 4 8

0.026 0.046 0.012 0.022

0.083 0.153 0.040 0.070



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literature.14,15 Therefore, MHM at a concentration of 0.02 g/L was chosen for the following experiments. Effect of the Extraction Time. Like SPME, D-μ-SPE involves dynamic partitioning of analytes to the sorbent. The extraction efficiency depends on the mass transfer between the MHM and the sample solution. Because mass transfer was a time-dependent process, the effect of the extraction time was investigated in the range 1−32 min. The sample solution was continuously agitated at room temperature with an orbital shaker to facilitate the mass transfer process, and the agitation speed was fixed at 3200 rpm. The results are shown in Figure 4.

Figure 5. Effect of the form of sample agitation on the chromatographic peak areas of the selected tanshinones. (A) magnetic stirring, (B) ultrasound, and (C) orbital shaker. Analytes: (1) dihydrotanshinone I, (2) tanshinone I, (3) cryptotanshinone, and (4) tanshinone IIA.

a vigorous stirring of the analytes and extractant, favoring interactions of the MHM and sample. Effect of Desorption Solvents. The tested tanshinones are relatively hydrophobic and are not easily eluted. Thus, a suitable organic solvent was needed for the desorption process to achieve optimum extraction performance.25 For this purpose, five solvents, including hexane, ethanol, acetonitrile, acetone, and methanol, were investigated for their suitability as desorption solvents, with the volume fixed at 200 μL in all instances. Figure 6 shows the influence of the desorption

Figure 4. Effect of the agitation time (1, 2, 4, 8, 16, and 32 min) on the chromatographic peak areas of the selected tanshinones. Analytes: (1) dihydrotanshinone I, (2) tanshinone I, (3) cryptotanshinone, and (4) tanshinone IIA.

The highest extraction was achieved at 2 min, and after more than 2 min, a considerable decrease in the peak area response was observed for all of the target analytes. The results indicated that, at the given conditions, initial partitioning was rapid, followed by a protracted uptake; eventually, a steady state was reached at 16 min, except for dihydrotanshinone I. For dihydrotanshinone I, when the extraction time was increased from 4 to 32 min, the extraction profile remained flat, implying that the adsorption of the analyte was very efficient. Therefore, in this work, 2 min was chosen as the optimum extraction time. Form of Sample Agitation. Sample agitation played an important role as an assisting factor in the D-μ-SPE process and affected the mass transfer rates of the tested solutes.15 Three alternatives for sample agitation (magnetic stirring, ultrasound and orbital shaking) were tested in the extraction step. Figure 5 compares the extraction performance of the three modes when samples spiked with 25 ng/mL tanshinones were extracted with 1 mL of mesoporous suspension with an extraction time of 2 min at room temperature (25 °C). The extraction efficiency of magnetic stirring was significantly lower than that of the other two methods, possibly because the MHM was lost as a result of its deposition on the magnetic bar, which reduced the extraction yield of the target analytes. Moreover, for the extraction yields of the four tanshinones, sonication was higher than magnetic stirring but lower than orbital shaking. The obtained results showed that the use of sonication significantly decreased the extraction affinity for the compounds of interest, leading to a low analytical response. Thus, the orbital shaker was chosen for the subsequent experiments because it provided

Figure 6. Effect of the desorption solvents on the chromatographic peak areas of the selected tanshinones: (A) hexane, (B) ethanol, (C) acetonitrile, (D) acetone, and (E) methanol. Analytes: (1) dihydrotanshinone I, (2) tanshinone I, (3) cryptotanshinone, and (4) tanshinone IIA.

capabilities of these solvents in D-μ-SPE. For all of the tanshinones, methanol offered the highest desorption efficiency, whereas acetone showed the smallest peak areas under the same extraction and elution conditions. The results also indicated that the greater solubility of target compounds in desorption solvents resulted in higher elution performance in 9686



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intraday and interday repeatabilities from four individual standards prepared at a concentration of 5 ng/mL. The results obtained are listed in Table 1 as the relative standard deviation (RSD); they ranged from 0.13% to 3.34% (n = 6) for intraday precision and were lower than 6.11% for interday precision in 3 consecutive days. The LODs and LOQs for the tanshinones ranged from 0.012 to 0.046 pg and from 0.040 to 0.153 pg. This resulted in a 334- to 478-fold improvement in the LODs relative to the conventional method, illustrating the better sensitivity achieved by the proposed procedure. Application to Real Samples. Under the indicated extraction and UHPLC-Q-TOF/MS conditions, the proposed D-μ-SPE method was applied to the identification and quantification of four tanshinones in real samples, such as DST, DS, and TC. The results are shown in Table 2. The target components in the samples were identified by matching their retention times and were confirmed by comparing the MS/MS spectra with those of the corresponding standards. Figure 8 shows the MS spectra of tanshinones in the positive ion mode. The accurate protonated molecule [M + H]+ was selected as the precursor ion for CID fragmentation to produce MS/MS product ion spectra. The results showed that all compounds could be detected in all samples (Table 2). However, the contents of these four major compounds varied among three samples. The contents of four active compounds in the DST were much lower than those in the DS and TC. All of the real samples were spiked with the four hydrophobic standard solutions at different concentration levels to evaluate the analyte recovery and matrix effects. The recovery values were 89−102% for DS, 88−96% for TC, and 91−103% for DST, which indicated that the present method was effective for the determination of tanshinones in plant samples. Additionally, the developed D-μ-SPE showed a reduction in extraction time (12 min) when compared to a traditional ultrasonic method (80 min).21 In conclusion, an MHM-based D-μ-SPE technique, in conjunction with UHPLC-Q-TOF/MS, was developed in this report. After optimization of the experimental conditions affecting the D-μ-SPE procedure, the sorbent capacity of MHM was tested in plant samples from different sources (DST, DS, TC), yielding satisfactory results for the recovery values and in terms of linearity, precision, and LODs. Most importantly, this newly developed microextraction technique was easy to prepare in-house at a reasonable cost, and it was more precise compared to the conventional method. In general, this study demonstrated that the extraction technique was a fast, simple, and effective method for the preparation of complex samples while preventing coextraction of extraneous materials.

terms of chromatographic peak areas from the MHM after extraction. Hence, methanol was selected as the optimal desorption solvent. The suitable volume of methanol used for desorption was also determined to be between 100 and 400 μL. As seen from Figure 7, a small volume (100 μL) of desorption solvent gave

Figure 7. Effect of the volume of desorption solvent (100−400 μL) on the chromatographic peak areas of the selected tanshinones. Analytes: (1) dihydrotanshinone I, (2) tanshinone I, (3) cryptotanshinone, and (4) tanshinone IIA.

low peak areas with poor reproducibility. A volume of 200 μL of methanol was found to be sufficient to completely desorb the analytes from the filter containing functionalized mesoporous material. When the volume of methanol was increased from 200 to 400 μL, a considerable decrease in the peak areas for all of the analytes was observed. This phenomenon was due to the dilution of the analytes in the eluent with increasing volume of desorption solvent. To test the carryover effects, the extraction device was further eluted after the first desorption with the above conditions. No analytes remained on the filter in the second desorption using nylon filters with a 0.45 μm pore size. Consequently, 200 μL of methanol was chosen as the optimum volume. Analytical Figures of Merit. The D-μ-SPE method was evaluated by characterizing its analytical performance in terms of linearity, precision, and limits of detection (LODs) at the optimized working conditions determined earlier (i.e., extractant phase, MHM; sample volume, 11 mL; agitation time, 2 min; desorption solvent, methanol). The obtained results are listed in Table 1. The linearity of the method was tested over a range 0.5−50, 1−100, 0.25−25, or 0.4−40 ng/mL, depending on target analytes. The calibration plots of each analyte prepared at five concentration levels were linear, with correlation coefficients (r2) between 0.9980 and 0.9995. The precision of the method was evaluated by calculating the Table 2. MS/MS Data and Concentrations of Target Analytes

concentrations (mg/g) analytes

molecular formula

tR (min)

[M + H]+

collision energy (V)

MS/MS

DST

DS

TC

dihydrotanshinone I tanshinone I cryptotanshinone tanshinone IIA

C18H14O3 C18H12O3 C19H20O3 C19H18O3

3.778 4.694 4.778 5.912

279.1031 277.0878 297.1506 295.1352

20 20 20 25

179.0904;167.0855;223.0711 167.0857;179.0854;249.0873 239.1205;281.0580;283.0518 265.0828;268.5011;280.1182

0.06 0.02 0.11 0.26

1.02 1.43 1.69 3.61

1.97 4.67 5.68 9.61

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Figure 8. Total ion chromatograms (TICs) of standard solution (analytes concentrations of 25 ng/mL) (A) and DST sample solution (F). Extracted ion chromatograms (EICs) of dihydrotanshinone I (B), tanshinone I (C), cryptotanshinone (D), and tanshinone IIA (E) in standard solution; EICs of dihydrotanshinone I (G), tanshinone I (H), cryptotanshinone (I), and tanshinone IIA (J) in sample solution. Analytes: (1) dihydrotanshinone I, (2) tanshinone I, (3) cryptotanshinone, and (4) tanshinone IIA.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Phone: +86-571-28867909. Fax: +86-571-28867909. Author Contributions §

These authors contributed equally to this work.

Funding

This study was supported by General Program of National Natural Science Foundation of China (No.81274065), Research on Public Welfare Technology Application Projects of Zhejiang Province (No.2014C37069), Changjiang Scholars and Innovative Research Team in Chinese University (IRT 1231), Young and Middle-Aged Academic Leaders of Hangzhou (2013-45), Scientific Research Foundation of Hangzhou Normal University (2011QDL33), and the newshoot Talents Program of Zhejiang province (2013R421044, 2014R421019). Notes

The authors declare no competing financial interest.

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Dispersive Micro-Solid-Phase Extraction Using Mesoporous Hybrid

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