Sensors and Actuators B 114 (2006) 565–572

A reversible fluorescence sensor based on insoluble �-cyclodextrinpolymer for direct determination of bisphenol A (BPA)

Xu Wang, Hulie Zeng, Yanlin Wei, Jin-Ming Lin ∗

State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences,Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, China

Received 12 February 2005; received in revised form 14 June 2005; accepted 15 June 2005Available online 3 August 2005

Abstract

Based on the reversible recognizing reaction between insoluble �-cyclodextrin polymer (�-CDP) and bisphenol A (BPA), a bifurcatedoptical fiber chemical sensor has been proposed for continuous monitoring of BPA. When immobilized in a plasticized poly(vinyl chloride)membrane of 5 �m thickness, �-CDP extracts BPA from aqueous solutions into the bulk membrane phase and reacts with the analyte to forman inclusion complex with high fluorescence efficiency. Formation of the complex gives a significant enhancement of the intrinsic fluorescence(ssh©

K

1

rpspIiApts(rbm

0d

λex/λem = 286 nm/312 nm) of BPA which is suitable for signaling the occurrence of the host–guest recognizing interaction. The fluorescenceensor exhibits a dynamic detection range from 6.0 × 10−6 mol/L to 1.0 × 10−3 mol/Lwith a detection limit of 1.0 × 10−6 mol/L. The highelectivity of the sensor toward BPA depends on the synergistic shielding effect by �-CD units and an optimal space-matching between theost and the guest. The proposed sensor was successfully used for the determination of BPA in water samples.

2005 Elsevier B.V. All rights reserved.

eywords: Fluorescence sensor; Bisphenol A (BPA); Cyclodextrin polymer

. Introduction

The development of optical methods for highly selectiveecognition and detection of environmentally toxic com-ounds is an inspired and challenging work of contemporaryensor research, because it requires the specific recognition ofarticular element in the presence of closely related species.n recent years, the development of supramolecular transduc-ng systems has become interesting in a chemical sensor [1].

variety of receptor molecules, such as crown ethers [2], por-hyrin [3], cyclodextrin [4], and calixarenes [5], are used asypical host molecules to selectively detect or monitor organicpecies, metal ions, and proteins. Among them, cyclodextrinsCDs) are attractive for the construction of a supramolecularecognition system since they possess nanosize hydropho-ic cavities which enable them to incorporate various guestolecules in aqueous solution [6]. The formation of an

∗ Corresponding author. Tel.: +86 10 62841953; fax: +86 10 62841953.E-mail address: jmlin@mail.rcees.ac.cn (J.-M. Lin).

inclusion complex often can dramatically change the photo-physical and photochemical properties of the included guestmolecules [7]. Several weak intermolecular forces betweenhosts and guests, such as dipole–dipole, hydrophobic, Vander Waals, electrostatic, and hydrogen bonding interaction,cooperatively contribute to the molecular recognition process[8]. Cyclodextrin polymer (CDP) remains the basic structureof CD, thus the complex formation is available [9,10]. Thestability of CDP is also virtually increased in polymer matri-ces [11]. The porous three-dimensional network of the CDPstructure makes the CDP films be readily permeable to smallmolecules present in aqueous solutions. This structure offersmultiple exterior interaction sites for guest inclusions bring-ing about the recognition [12]. Moreover, the occurrence ofcooperative effects between a guest molecule and two CDunits (1:2 inclusion) of the same macromolecular chain wasreported [10,13,14].

In recent years, the ever-increasing number of organiccompounds being detected in surface waters has risen con-cern about the contamination of water resources [15,16].

925-4005/$ – see front matter © 2005 Elsevier B.V. All rights reserved.oi:10.1016/j.snb.2005.06.020

566 X. Wang et al. / Sensors and Actuators B 114 (2006) 565–572

Among the various pollutants, bisphenol A (BPA, a chemicalintermediate widely used in the synthesis of polycarbonateand epoxy resins, unsaturated polyester-styrene resins andflame-retardants [17]) was mainly released into the envi-ronment in wastewater from plastics-producing industrialplants and landfill sites. BPA was reported to show poten-tial detrimental reproductive effects on wildlife and humansthrough altering endocrine function and may disrupt growthand development by interfering with the production, release,transport, metabolism, binding, and regulation of develop-ment processes [18–23]. Because of its ubiquitous nature andits endocrine disrupting potential, BPA has been included inthe environmental water monitoring or determining study byseveral techniques [24–28]. But all these proposed methodssuffer from various disadvantages such as discontinuity, timeconsumption, analytes destruction, and high running cost.Consequentially, there is still a significant demand for thefabrication of a new optical fiber chemical sensor for BPAin waters, since the user-friendly optic-chemical sensors canoffer advantages in terms of size, cost, and signal transmis-sion.

BPA manifests very weak fluorescence property in aque-ous solutions because of its low fluorescent efficiency. In thesearch of an appropriate environment suitable for the intenseenhancement of fluorescence intensity of BPA, we observedthat the addition of �-CD could remarkably enhance the flu-omrttpc�ti(BtsTcbia

fssssbinfb

2. Experimental

2.1. Apparatus

Infra-red spectra were obtained from a NEXUS 670-FTIR(Nicolet, USA) spectrophotometer with KBr disk. Elemen-tary analysis was performed on a Flash EA 1112 elementaryanalyzer (Thermoquest, Italy). A Dektak 8 surface profiler(Digital Instruments, USA) was used to determine the filmthickness by scanning the edge of a small scratch that wasapplied to the sensing membrane coated on a circular quartzplate. All fluorescence measurements were carried out on aHitachi F-2500 fluorescence spectrometer (Hitachi, Tokyo,Japan) with excitation and emission slits set at 5 nm and10 nm, respectively. A homemade PTFE flow cell and abifurcated optical fiber (50 + 50 quartz fibers, diameter 6 mmand length 1.2 m) were used for the sensing measurements(Fig. 1). The quartz plate with a sensing membrane on itwas mounted in the flow cell. The membrane side is facingthe cell chamber with a circulating sample solution sweep-ing over the membrane driven by a peristaltic pump (LangeInstruments, Baoding, China). The opposite side of the quartzplate tightly matching the common end of the optical fiber.The excitation light was carried to the cell through one armof the bifurcated optical fiber and the emission light collectedthrough the other. A spin-on device [30] was used to preparet

2

icKtBcoRt

F(ql

rescence intensity of BPA in aqueous solutions because of aore protective hydrophobic microenvironment BPA expe-

ienced when it is included in the cavity of �-CD. Sincehe determination with an optical sensor can be performedhrough immobilizing a sensing material on a solid-state sup-ort to form a chemically recognized membrane which isonnected with a transducer device, the water-solubility of-CD precludes its use as a sensing compound. So, we syn-

hesized insoluble �-cyclodextrin polymer (�-CDP) and usedt as a sensing element in a membrane of poly(vinyl chloride)PVC) matrix. It exhibited that the fluorescence intensity ofPA was drastically enhanced upon extraction of BPA into

he membrane, which was associated with the formation of aupramolecular inclusion complex between �-CDP and BPA.his can be used to fabricate a BPA-sensitive optical fiberhemical sensor. The reason for the choice of PVC as a mem-rane matrix is due to not only its high stability and flexibilityn detection, but its preconcentration effect in trace amountnalysis [29].

This paper describes the preparation and monitoring per-ormance characteristics of the proposed BPA-sensitive sen-or. Moreover, the response mechanism of the proposed sen-or was studied. It is shown that the high selectivity of theensor toward BPA mainly depends on the synergistic inclu-ion by adjacent �-CD units and an optimal space-matchingetween the host and the guest. An optimum interaction modes presented, which can facilitate understanding of the recog-ition mechanism. The proposed sensor is successfully usedor the determination of BPA in real water samples and cane used in environmental monitoring works.

he membrane.

.2. Chemicals

Analytical reagent grade chemicals were used unlessndicated otherwise. High molecular weight PVC was pur-hased from Sigma (St. Louis, USA). BPA was from Tokyoasei Kogyo Co. Ltd. (Tokyo, Japan) and its stock solu-

ions were prepared by dissolving an appropriate amount ofPA in ethanol. Working solutions were prepared by suc-essive dilution of the stock solutions with water. �-CD wasbtained from China Medicine (Group) Shanghai Chemicaleagent Corporation (Shanghai, China) and was purified by

wice recrystallization in water, followed by vacuum drying

ig. 1. Schematic diagram of the flow cell arrangement. (1) excitation light,2) signal light, (3) bifurcated optical fibre, (4) screw cap, (5) cell body, (6)uartz glass slide, (7) O silicon ring, (8) sensing membrane, (9) sample inet and (10) sample out let.

X. Wang et al. / Sensors and Actuators B 114 (2006) 565–572 567

at 60 ◦C for 12 h. Epichlorohydrin, tetrahydrofuran (THF),chloroform, di(2-ethylhexyl) sebacate (DOS), tributyl phos-phate (TBP), and dioctyl phthalate (DOP) were obtainedfrom Beijing Chemical Factory (Beijing, China). Ultra-puredeionized water used in the experiment was obtained from anEasypure water purification system with a 0.2 �m fiber filter(Barnstead, USA).

2.3. Synthesis of β-CDP

�-CDP was synthesized based on reference [31]. 12.0 g(10.6 mmol) of �-CD was completely dissolved in 150 mLwater and 40 mL of a 20 wt.% aqueous sodium hydroxidesolution, to which 11.8 g (0.13 mol) of epichlorohydrin wasadded dropwise at 60 ◦C over 45 min. After the reaction mix-ture was kept at 65 ◦C for 48 h with vigorous stirring, it wasneutralized with 2 mol/L HCl, dialyzed with distilled waterfor several days and freeze-dried. A total of 4.5 g of grayproduct was obtained.

2.4. Preparation of sensing membrane

The sensing membrane solution was prepared by dissolv-ing a mixture of 6.0 mg �-CDP, 60 mg PVC, and 100 mgDOS in 2 mL of THF-chloroform (80:20, v/v) mixed sol-vent. A circular quartz plate of 25 mm diameter was mountedo8wob

2

dtw2AtAui

3

3

wtstT

tary structure of free cyclodextrin. The absence of charac-teristic absorption bands of –(–CH–CH–)n– at 1250 cm−1

and of –CH2Cl at 735–720 cm−1 indicates no existenceof epichlorohydrin and free cyclodextrin derivative in thepolymer. The absorption derived from a C–O–C stretchingvibration (1070–1150 cm−1) was sharp for free cyclodextrin,while it was broad for the polymer because of the cross-linking. The subtle structure of the O–H bending mode at1140–1625 cm−1 disappeared in the polymer due to the poly-merization, which showed that some structural differenceappeared between the free CD and the polymer.

Because the type of binding between a guest and the CDpolymer depends partly on the ratio of linker units to CD unitsin the polymer, as well as on the nature of the guest [32], thephenol–sulfuric acid method [33] was used to determine the�-CD content in the synthesized insoluble �-CDP. The con-tent was 65%. The average molar degree of cross-linking ofthe �-CDP was calculated to be 4, according to its elemen-tal analysis with C% of 69.70% [34]. Based on this, �-CDPconcentration can be converted to �-CD concentration andthe inclusion mode between the host and the guest can beobtained.

3.2. The inclusion interaction between BPA and β-CDP

oflenscCtiwsa

n the spin-on device and then rotated at a frequency of00 rpm. Using a syringe, 0.2 mL of the membrane solutionas sprayed to the center of the plate. After a spinning timef 4 s, a membrane of 5 �m thickness, which was determinedy the surface profiler, was then coated on the quartz plate.

.5. Measurement procedure

Two arms of the bifurcated optical fiber were fixed in theetecting chamber of the spectrofluorimeter to carry the exci-ation and emission light. The fluorescence measurementsere carried out at the maximum excitation wavelength of86 nm and the maximum emission wavelength of 312 nm.sample solution was fed through the detecting chamber of

he flow cell by the peristaltic pump at a rate of 2.0 mL/min.fter each measurement, the flow cell was washed with waterntil the fluorescence intensity of the sensor reached the orig-nal blank value.

. Results and discussion

.1. Characterization of β-CDP

From the infrared spectra of �-CD and �-CDP (Fig. 2),e can find that the spectrum of �-CDP showed absorp-

ion bands at 3100–3500 and 2860–2880 cm−1 due to theymmetric and antisymmetric O–H stretching mode andhe stretching mode of CH2– of cyclodextrin, respectively.hese results indicates that �-CDP retains the elemen-

Fig. 3 shows the effect of the amount of �-CDP on flu-rescence emission of BPA in the sensing membrane. Theuorescence of BPA in a PVC membrane without �-CDP isssentially weak. In contrast, in the presence of �-CDP, sig-ificant fluorescence emissions appear, indicating the inclu-ion of BPA within the relatively non-polar cyclodextrinavity. More persuasive evidence for the formation of a �-DP/BPA inclusion complex can be provided by light scat-

ering measurement. As shown in Fig. 4, the light scatteringntensity of BPA in aqueous solution is relatively small, buthen BPA coexists with �-CDP, the light scattering spectrum

hows an obvious enhancement in light scattering intensitynd a blue shift at its maximum wavelength (from 306 to

Fig. 2. Infrared spectra of �-CD and �-CDP.

568 X. Wang et al. / Sensors and Actuators B 114 (2006) 565–572

Fig. 3. Effect of the amount of �-CDP on the fluorescence intensity of BPAin membranes (1) 0 mg; (2) 1.0 mg; (3) 2.0 mg; (4) 3.0 mg; (5) 4.0 mg; (6)5.0 mg; (7) 6.0 mg �-CDP in 2 mL of the membrane preparation solvent.The amount of BPA dissolved in it was 2.0 mg.

Fig. 4. Effect of �-CDP on the light scattering spectra of BPA in aqueoussolution. BPA concentration, 2.5 mg/L; �-CDP concentration, 20 mg/L.

300 nm). The remarkable spectral changes observed upon �-CDP interaction clearly indicate the formation of a certaintype of molecular assembly in solution, formed by the spon-taneous association of a number of solute components [35].In a word, the variation of the light scattering spectra of BPAcould be attributed to the presence of organized entities of

Fig. 5. Fluorescence spectra of the sensing membrane in the presence of dif-ferent concentrations of BPA: (1) 5.0 × 10−5 mol/L; (2) 1.0 × 10−4 mol/L;(3) 2.5 ×10 −4 mol/L; (4) 6.0 × 10−4; (5) 1.0 × 10−3 mol/L (λex = 286 nm,λem = 312 nm).

a supramolecular nature, resulting from the formation of aninclusion complex between �-CDP and BPA in solution [36].

3.3. Optimization of membrane compositions

Since plasticization can increase the mobility of poly-mer segments to improve the rate of guest extraction intoand diffusion throughout the film [37] and to increase theworkability, flexibility and distensibility of the film, sev-eral membrane compositions were investigated by selectingappropriate plasticizers and varying the ratio of plasticizersto �-CDP. As shown in Table 1, sensing membranes wereprepared by employing different plasticizers such as TBP,DOS and DOP. Membranes containing DOS showed a rela-tively good response to BPA and the longest lifetime. Whenthe amount of �-CDP and PVC for immobilizing was 6.0 mgand 60 mg, respectively, the optimal amount of DOS wasfound to be 100 mg.

3.4. Response characteristics of the sensor

Fig. 5 shows the fluorescence spectra of the sensing mem-brane exposed to solutions containing different concentra-

Table 1Composition of the membrane cocktail and the response behavior of the sensor to BPAa

Membrane number Plasticizer (mg) Working range (mol

1 DOP (100) 2.3 × 10−5 to 2.1 ×2 TBP (100) 2.0 × 10−6 to 9.2 ×3 DOS (100) 6.0 × 10−6 to 1.0 ×4 DOS (200) 1.0 × 10−5 to 1.5 ×5 DOS (300) 4.0 × 10−6 to 1.0 ×

a Each membrane cocktail contains 6.0 mg �-CDP, 60 mg PVC, and the listed a(80:20, v/v) mixed solvent.

b The working range was defined as 0.05 < α < 0.95 and α was defined as a responc The detection limit was defined as α = 0.01.d The lifetime was defined as the usage times of the sensing membrane that produ

/L)b Detection limit (mol/L)c Lifetime (times)d

10−3 7.7 × 10−6 12010−4 8.7 × 10−7 10010−3 1.0 × 10−6 23010−3 3.3 × 10−6 18010−3 1.3 × 10−6 150

mount of plasticizer, which were dissolved in 2 mL of a THF-chloroform

se parameter [38].

ced fluorescence signal changes less than 5% [39].

X. Wang et al. / Sensors and Actuators B 114 (2006) 565–572 569

Fig. 6. The time dependent response of the sensor. The sensor is alter-natively exposed to (a) 5.0 × 10−4 mol/L, (b) 2.5 × 10−4 mol/L and (c)5.0 × 10−5 mol/L BPA solutions with (d) blank solution in between.

tions of BPA, which were recorded at λex = 286 nm andλem = 312 nm. Owing to extraction into the membrane andinclusion into the hydrophobic cavity of �-CD, BPA exhib-ited a strong fluorescence enhancement, whereas a weak onein bulk water solution. From Fig. 5, one can see that the flu-orescence intensity of the sensing membrane increase withincreasing the BPA concentration, which constitutes the basisfor determination of BPA with the optical fiber sensor pro-posed in this paper.

The response of the sensor toward BPA is associatedwith the analyte diffusion into the membrane entity and thereversible interaction between �-CDP and the analyte. Underthe optimum conditions, the sensor exhibited a dynamicdetection range from 6.0 × 10−6 mol/L to 1.0 × 10−3 mol/Land a detection limit of 1.0 × 10−6 mol/L. The dynamicresponse behavior of the sensor to BPA is shown in Fig. 6.As can be seen, the proposed sensor was quite reversible andno noticeable hysterically effect was observed. The responsetime of the sensor was also studied. The response time wasfound to depend on the mode of the BPA concentrationchange. The time required to reach an equilibrium increasedwhen increasing the BPA concentration. Namely the forwardresponse time (going from lower to higher BPA concentra-tion) was within 9 min (t90) whereas the time for the reverseresponse was around in the range of 2 min over the entireconcentration range.

ipbdrsoip

Fig. 7. Effect of pH on the fluorescence intensity of the sensing membranerecorded after contacting 6.0 × 10−4 mol/L BPA.

ple response already falls within the most sensitive responseregion.

The sensor repeatability and reproducibility were calcu-lated according to the definition by Alabbas et al. [41]. Theresults showed that the repeatability of the membrane wasbetter than the reproducibility. The R.S.D. (relative standarddeviation) for repeatability of the sensor for the measurementof 2.5 × 10−4 mol/L and 6.0 × 10−4 mol/L BPA was calcu-lated to be 0.74% and 0.62%, respectively. On the other hand,the R.S.D. for reproducibility was 1.67% and 1.96% for BPAconcentrations of 2.5 × 10−4 mol/L and 6.0 × 10−4 mol/L,respectively.

3.5. Selectivity of the sensor

One of the most important features of a sensor is itsresponse to a specific species among other species presentin a sample solution. Some ions and species commonlyexisting in water were chosen for the selectivity test of theBPA sensor. A foreign specie was considered not to inter-fere with measurement if a relative error caused by it wasless than 5% in the determination of 8.0 × 10−6 mol/L BPA.The experimental results revealed that no significant inter-ference was observed for 1000-fold of Na+, K+, NH4

+,Cl−, NO3

−, Br− CO32− or Zn2+, 800-fold of F−, NO2

−,Mg2+, Ca2+, Ni2+, Fe2+ or Fe3+, 600-fold of Co2+, Zn2+,M4cnc2hcie

The effect of solution pH on the sensor performance wasnvestigated in a wide pH range from 2.0 to 12.0 in theresence of 6.0 × 10−4 mol/L BPA. As shown in Fig. 7,ecause the pKa of BPA is approximately 9.28 [40], theissociation of BPA was inhibited at pH < 9.50 and the fluo-escence intensity of the inclusion complex remained con-tant. In contrast, at relatively higher pH, BPA in aque-us solution inclines to dissociate, which in turn reducests supramolecular inclusion with �-CDP. This means thatH adjustment of a sample is unnecessary since the sam-

n2+ or Cr3+, 500-fold of SO42−, SiO3

2−, SO32− or Al3+,

20-fold of MnO4−or HCOO−, 150-fold of o-cresol, m-

resol, p-cresol or 2,6-xylenol, 80-fold of o-nitrophenol, m-itrophenol, p-nitrophenol or 2,4-dinitrophenol, 50-fold of p-hlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol or,4,6-trinitrophenol, 30-fold of pyrocatechol, resorcinol orydroquinone, 10-fold of 1-naphthol or phenol. This indi-ates that the proposed sensor has a high selectivity in mon-toring BPA in water, which was resulted from the shieldingffect of �-CDP against other coexistent species.

570 X. Wang et al. / Sensors and Actuators B 114 (2006) 565–572

Table 2Recovery study of spiked BPA in tap water and Qinghe River water (n = 5)

Samples BPA determined (mol/L) BPA spiked (mol/L) BPA recovered (mol/L) Recovery (%)

Tap water 0 8.0 × 10−6 (8.48 ± 0.13) × 10−6 106Qinghe River water 1 0 5.0 × 10−5 (4.75 ± 0.17) × 10−5 95.0Qinghe River water 2 0 1.0 × 10−5 (0.95 ± 0.10) × 10−5 95.0

3.6. The response mechanism of the sensor

The significant enhancement of the intrinsic fluorescence(λex/λem = 286 nm/312 nm) of BPA was ascribed to its forma-tion of an inclusion complex with �-CDP when BPA enteredthe sensing membrane. �-CDP possesses the hydropho-bic cavity identical with that of �-CD. Besides, as �-CDPwas obtained by cross-linking of �-CD monomers throughhydroxyl groups in parent �-CD to form a three-dimensionalnetwork, the non-polarity and hydrophobicity of the exteriorshell surrounding the interior cavities of CD was substan-tially increased. Thus, a much more hydrophobic and pro-tective microenvironment for BPA was formulated shieldingthe excited state of BPA from quenching by water and dis-solved oxygen molecules. An additional factor favorable forthe fluorescence enhancement is that the rigidity of the �-CDP network decreases the degree of freedom in the motionof the BPA molecules entrapped in it. Based on the effect ofthe amount of �-CDP on the fluorescence emission of BPA inthe sensing membrane (Fig. 3), the Benesi–Hildbrand equa-tion [42] was used to obtain the complex ratio between thehost and the guest. A good linear relationship was obtainedwhen 1/(F − F0) was plotted against 1/[�-CD]2, support-ing the formation of a 2:1 (host:guest) complex (r = 0.9972,Fig. 8). This interaction mode results from a synergisticshielding effect by the �-CD units and an optimal spacegtbA

Fig. 9. The complex mode between �-CDP and BPA.

calculated to be 4, the complex mode shown in Fig. 9 can bededuced.

3.7. Preliminary analytical application

Recovery of spiked BPA in Beijing Qinghe River watersand tap water was studied with the proposed optical fibersensor. Qinghe River water samples were filtered through a0.45-�m filter membrane before analysis. The tap water wasanalysed without any pretreatment. However, the proposedsensor showed that no BPA was present in the samples. Sothey were spiked with standard BPA solutions and then ana-lyzed. The results are shown in Table 2. We can see that therecovery of the proposed sensor is satisfactory. The presentsensor may be useful for the determination of BPA in realsamples.

4. Conclusions

A bifurcated optical fiber chemical sensor for continuousmonitoring of bisphenol A (BPA) has been proposed basedon the reversible recognizing reaction between insoluble �-cyclodextrin polymer (�-CDP) and the analytes. The varia-tion in fluorescence signal was fairly reversible and was pro-portional to the BPA concentration. The experimental resultsprovided a better understanding of the host–guest chemistryaasibit

eometry of the multiple attachment between the host andhe guest. The apparent formation constant was determined toe 1.25 × 106 mol−2 L2 through the non-linear regression fit.s the average molar degree of cross-linking of �-CDP was

Fig. 8. Benesi–Hildbrand plot for the complex ratio determination.

nd showed that the supramolecular assembly could be useds a powerful tool for developing a high-quality chemical sen-or. Although these preliminary experiments were performedn a laboratory, the fabricated sensor was virtually promisingecause it can be easily adaptable to field use through improv-ng the mechanical flexibility of the optical fiber and reducinghe physical size of the sensor system.

X. Wang et al. / Sensors and Actuators B 114 (2006) 565–572 571

Acknowledgments

The authors gratefully acknowledge financial support ofthe National Science Fund for Distinguished Young Scholarsof China (no. 20125514), National Natural Science Founda-tion of China (no. 20437020, 50273046) and Major ResearchProgram of Chinese Academy of Sciences (KZCX3-SW-432).

References

[1] C.M. Rudzinski, A.M. Young, D.G. Nocera, A supramolecularmicrofluidic optical chemosensor, J. Am. Chem. Soc. 24 (2002)1723–1727.

[2] A. Yamauchi, T. Hayashita, A. Kato, S. Nishizawa, M. Watanabe, N.Teramae, Selective potassium ion recognition by benzo-15-crown-5 fluoroionophore/�-cyclodextrin complex sensors in water, Anal.Chem. 72 (2000) 5841–5846.

[3] X.B. Zhang, C.C. Guo, Z.Z. Li, G.L. Shen, R.Q. Yu, An opticalfiber chemical sensor for mercury ions based on a porphyrin dimer,Anal. Chem. 74 (2002) 821–825.

[4] T. Tanabe, K. Touma, K. Hamasaki, A. Ueno, Immobilized fluores-cent cyclodextrin on a cellulose membrane as a chemosensor formolecule detection, Anal. Chem. 73 (2001) 3126–3130.

[5] C. Lynam, K. Jennings, K. Nolan, P. Kane, M.A. McKervey, D.Diamond, Tuning and enhancing enantioselective quenching of cal-ixarene hosts by chiral guest amines, Anal. Chem. 74 (2002) 59–66.

[

[

[

[

[

[[

[

[

Louisiana, USA and Ontario, Canada, Sci. Total Environ. 311 (2003)135–149.

[19] T. Colborn, F.S. Saal, A.M. Soto, Environmental health issues, Env-iron. Health Perspect. 101 (1993) 378–384.

[20] L.A. Jone, R.A. Hajek, Effects of estrogenic chemicals on develop-ment, Environ. Health Perspect. 103 (Suppl. 7) (1995) 63–67.

[21] Y. Takai, O. Tsutsumi, Y. Ikezuki, Y. Kamei, Y. Osuga, T. Yano, Y.Taketan, Preimplantation exposure to bisphenol A advances postnataldevelopment, Reprod. Toxicol. 15 (2001) 71–74.

[22] D. Zalko, A.M. Soto, L. Dolo, C. Dorio, E. Rathahao, L. Debrauwer,R. Faure, J.-P. Cravedi, Biotransformations of bisphenol A in aMammalian model: answers and new questions raised by low-dosemetabolic fate studies in pregnant CD1 mice, Environ. Health Per-spect. 111 (2003) 309–319.

[23] A.V. Krishnam, P. Starhis, S.F. Permush, L. Tokes, D. Ferd-man, Bisphenol-A: an estrogenic substance is released from poly-carbonate flasks during autoclaving, Endocrinology 132 (1993)2279.

[24] S. Rodriguez-Mozaz, M.J.L. Alda, D. Barcelo, Monitoring ofestrogens, pesticides and bisphenol A in natural waters anddrinking water treatment plants by solid-phase extraction–liquidchromatography–mass spectrometry, J. Chromatogr. A 1045 (2004)85–92.

[25] X. Jin, G. Jiang, G. Huang, J. Liu, Q. Zhou, Determination of 4-tert-octylphenol, 4-nonylphenol and bisphenol A in surface watersfrom the Haihe River in Tianjin by gas chromatography–mass spec-trometry with selected ion monitoring, Chemosphere 56 (2004)1113–1119.

[26] Y. Watabe, T. Kondo, H. Imai, M. Morita, N. Tanaka, K. Hosoya,Reducing bisphenol A contamination from analytical procedures todetermine ultralow levels in environmental samples using automated

[

[

[

[

[

[

[

[

[

[

[

[6] J. Szejtli, T. Osa (Eds.), Comprehensive Supramolecular Chemistry,vol. 3, Pargamon/Elsevier, Oxford, 1996.

[7] K.A. Connors, The stability of cyclodextrin complexes in solution,Chem. Rev. 97 (1997) 1325–1358.

[8] M.V. Rekharsky, Y. Inoue, Complexation thermodynamics ofcyclodextrins, Chem. Rev. 98 (1998) 875–1918.

[9] M. Komiyama, H. Hirai, Preparation of immobilized �-cyclodextrinsby use of alkanediol diglycidyl ethers as crosslinking agents and theirguest binding abilities, Polym. J. 19 (1987) 773–775.

10] W. Xu, A. Jain, B.A. Betts, J.N. Demas, B.A. DeGraff, Single andmultiple binding of �-cyclodextrins and polymeric �-cyclodextrinsto luminescent ruthenium(II) �–diimine complexes, J. Phys. Chem.A 106 (2002) 251–257.

11] F. D’Souza, Y.-Y. Hsieh, H. Wickman, W. Kutner, New sensor fordissolved dioxygen: a gold electrode modified with a condensationpolymer film of �-cyclodextrin hosting cobalt tetraphenylporphyrin,Chem. Commun. (1997) 1191–1192.

12] N. Thuaud, B. Sebille, E. Renard, Insight into the chiral recognitionof warfarin enantiomers by epichlorhydrin/�-cyclodextrin polymer-based supports: determination of stoichiometry and stability ofwarfarin/�-cyclodextrin polymer complexes, J. Biochem. Biophys.Methods 54 (2002) 327–337.

13] A. Harada, M. Furue, S. Nozakura, Inclusion of aromatic compoundsby a �-cyclodextrin epichlorohydrin polymer, Polym. J. 13 (1981)777–781.

14] T.C. Werner, K. Colwell, R.A. Agbaria, I.M. Warner, Bindingof pyrene to cyclodextrin polymers, Appl. Spectrosc. 50 (1996)511–516.

15] S.D. Richardson, Water analysis, Anal. Chem. 73 (2001) 2719–2734.16] S.D. Richardson, Water analysis: emerging contaminants and current

issues, Anal. Chem. 75 (2003) 2831–2857.17] C.A. Staples, P.B. Dorn, G.M. Klecka, S.T. Block, L.R. Harris, A

review of the environmental fate, effects, and exposures of bisphenolA, Chemosphere 36 (1998) 2149–2173.

18] G.R. Boyd, H. Reemtsma, D.A. Grimm, S. Mitra, Pharmaceuticalsand personal care products (PPCPs) in surface and treated waters of

HPLC microanalysis, Anal. Chem. 76 (2004) 105–109.27] H.M. Kuch, K. Ballschmiter, Determination of endocrine-disrupting

phenolic compounds and estrogens in surface and drinking waterby HRGC-(NCI)-MS in the picogram per liter range, Environ. Sci.Technol. 35 (2000) 3201–3206.

28] D. Li, J. Park, J.-R. Oh, Silyl derivatization of alkylphenols,chlorophenols, and bisphenol A for simultaneous GC/MS determi-nation, Anal. Chem. 73 (2001) 3089–3095.

29] P.E. Koulouridakis, N.G. Kallithrakas-Kontos, Selective mercurydetermination after membrane complexation and total reflection X-ray fluorescence analysis, Anal. Chem. 76 (2004) 4315–4319.

30] H.H. Zeng, K.M. Wang, C.L. Liu, R.Q. Yu, A reversible optodemembrane for picric acid based on the fluorescence quenching ofpyrene, Talanta 40 (1993) 1569–1573.

31] J.-M. Yi, K.-W. Tang, Insoluble �-cyclodextrin polymer for capil-lary gas chromatographic separation of enantiomers and isomers, J.Chromatogr. A 883 (2000) 137–142.

32] W. Xu, J.N. Demas, B.A. DeGraff, M. Whaley, Interactions of pyrenewith cyclodextrins and polymeric cyclodextrins, J. Phys. Chem. 97(1993) 6546–6554.

33] M. Dubois, K.A. Gilles, J.K. Hamilton, P.A. Rebers, F. Smith, Col-orimetric method for determination of sugars and related substances,Anal. Chem. 28 (1956) 350–356.

34] I. Sugiura, M. Komiyama, N. Toshima, H. Hirai, Immobilized �-cyclodextrin. Preparation with various crosslinking reagents andthe guesting binding properties, Bull. Chem. Soc. Jpn. 62 (1989)1643–1651.

35] R. Yang, K. Li, K. Wang, F. Zhao, N. Li, F. Liu, Porphyrin assemblyon �-cyclodextrin for selective sensing and detection of a zinc ionbased on the dual emission fluorescence ratio, Anal. Chem. 75 (2003)612–621.

36] R.F. Pasternack, E.J. Gibbs, D. Bruzewicz, D. Stewart, K.S.Engstrom, Kinetics of disassembly of a DNA-bound porphyrinsupramolecular array, J. Am. Chem. Soc. 124 (2002) 3533–3539.

37] J. Crank, G.S. Park (Eds.), Diffusion in Polymers, Academic Press,London, 1968, p. 21.

572 X. Wang et al. / Sensors and Actuators B 114 (2006) 565–572

[38] M.M.F. Choi, X.J. Wu, Y.R. Li, Optode membrane for determinationof nicotine via generation of its bromoethane derivative, Anal. Chem.71 (1999) 1342–1349.

[39] R.H. Yang, K.A. Li, F. Liu, N. Li, F.L. Zhao, W.H. Chan, 3,3′,5,5′-Tetramethyl-N-(9-anthrylmethyl)benzidine: a dual-signaling fluores-cent reagent for optical sensing of aliphatic aldehydes, Anal. Chem.75 (2003) 3908–3914.

[40] H. Yamamoto, H.M. Lilestrand, Partitioning of selected estrogeniccompounds between synthetic membrane vesicles and water: effectsof lipid components, Environ. Sci. Technol. 38 (2004) 1139–1147.

[41] S.H. Alabbas, D.C. Ashworth, R. Narayanaswamy, Design and per-formance features of an optical-fibre reflectance pH sensor, Anal.Proc. 26 (1989) 373–375.

[42] S. Hamai, Room-temperature phosphorescence from 1:1:1 inclusioncompounds of beta-cyclodextrin with brominated alcohols and ace-naphthene, J. Am. Chem. Soc. 111 (1989) 3954–3957.

Biographies

Xu Wang received his MSc degree from Shandong Normal Universityin 2003. Now he is a PhD student in State Key Laboratory of Envi-ronmental Chemistry and Ecological Toxicology, Research Center for

Eco-Environmental Sciences, Chinese Academy of Sciences. His currentresearch is focused on optical sensors based on host–guest chemistry andsupramolecular chemistry and its application in environmental analysis.

Hulie Zeng is currently a PhD student in Sate Key Laboratory of Envi-ronmental Chemistry and Ecological Toxicology, Research Center forEco-Environmental Sciences, Chinese Academy of Sciences. Her researchactivities concern microchip with fluorescence detection, chiral separationand bioassay methods in microdevices.

Yanlin Wei received his PhD degree in analytical chemistry at OkayamaUniversity, Japan. Now he is associate professor of environmental ana-lytical chemistry, State Key Laboratory of Environmental Chemistry andEcological Toxicology, Research Center for Eco-Environmental Sciences,Chinese Academy of Sciences. His research interests cover environmentalchemistry and analytical chemistry.

Jin-Ming Lin received a PhD degree in analytical chemistry at TokyoMetropolitan University. He had studied and worked in this universitynear 10 years. He is currently a professor of Research Center for Eco-Environmental Sciences, the deputy director of State Key Laboratory ofEnvironmental Chemistry and Ecotoxicology. He received several awardsfor his contributions in luminescence and chromatography. He is theauthor and co-author of 98 original research papers published in inter-national journals, 10 reviews, one book and chapter contributions of theedited books and 11 patents.