A host-guest optical sensor for aliphatic amines based on lipophilic cyclodextrin

A host-guest optical sensor for the determination of aliphatic amines as exemplified by octylamine is proposed. It is based on the reversible fluorescence enhancement of heptakis(2,6-di-O-isobutyl)-β-cyclodextrin(DOB-β-CD) hosting tetraphenylporphyrin (TPP) immobilized in poly(vinyl chloride) (PVC) membrane by aliphatic amine extracted from aqueous phase into membrane phase. The optimum membrane contained 1.15 wt % TPP, 6.15 wt % DOB-β-CD as sensing reagent and other membrane materials. The fluorescence enhancement of the membrane resulted from the formation of a stable three-component complex among DOB-β-CD, TPP, and aliphatic amines. With the optimum conditions described, the fluorescence response of the sensor to octylamine shows a good correlation with the theoretically derived equation in the range 1.0 × 10^–6 to 8.0 × 10^–4 mol/L. The response characteristics including reversibility, response time, reproducibility and lifetime and selectivity of this optical device are also discussed in detail. This sensor has also been applied for the determination of octylamine in water samples containing interferents with satisfactory recovery. Received: 21 November 1999 / Revised: 10 January 2000 / Accepted: 15 January 2000     

基于环糊精/卟啉包络物荧光猝灭的二氧化碳光学敏感膜的研究

全 -( 2 ,6-二 -O-异丁基 ) -β-环糊精 ( DOB-β-CD)对固定于增塑 PVC膜中的 meso-四 ( 4-甲氧基苯基 )卟啉( TMOPP)有明显的荧光增强效应 ,且该荧光可被溶液中的二氧化碳可逆猝灭 .本文据此研制了一种可用于测定水溶液中二氧化碳含量 ,即 [H2 CO3]浓度的荧光敏感膜 .研究了最佳膜的组成 .经过组成优化的敏感膜测定 [H2 CO3]浓度的范围为 4 .75× 1 0 - 7～ 3.9× 1 0 - 5 mol/L.该传感器响应迅速、重现性好 ,常见的离子无明显干扰 .     

Optical sensor for berberine utilizing its intrinsic fluorescence enhanced by the formation of inclusion complex with butylated-β-cyclodextrin

An optical sensor for berberine, the basic ingredient of the widely used traditional Chinese medicine Coptis Chinensis, based on its intrinsic fluorescence enhanced by butylated-β-cyclodextrin (HDB-β-CD) immobilized in plasticized poly(vinyl chloride) (PVC) membrane has been developed. The drastic enhancement of fluorescence intensity of berberine was attributed to the formation of an inclusion complex between HDB-β-CD and berberine, which has been utilized as the basis of the fabrication of a berberine-sensitive fluorescence sensor. The proposed sensor was quite distinct from those fluorescent sensors for berberine reported so far which relied upon quenching the fluorescence of the sensing reagent immobilized on membrane by berberine. The response mechanism of optode membrane was discussed in detail from the view of molecular dynamics and the optimum steric configuration of the inclusion complex was presented by molecular dynamics simulation. The analytical performance characteristics of the proposed berberine-sensitive sensor were investigated. The sensor can be applied to the quantification of berberine with a linear range covering from 4.0×10⁻⁷ to 2.0×10⁻⁵ mol l⁻¹ with a detection limit of 8.0×10⁻⁸ mol l⁻¹. The sensor exhibits excellent reproducibility, reversibility and selectivity. The recommended method was successfully used for the determination of berberine in pharmaceutical preparations.     

A fluorescent sensing membrane for iodine based on intramolecular excitation energy transfer of anthryl appended porphyrin

A single anthryl appended meso-tetraphenylporphyrin (TPP) dyad has been synthesized and applied in fluorescence sensing of iodine based on the intramolecular excitation energy transfer. The molecular recognition of the sensor is based on the interaction of iodine with inner anthracene moiety of the dyad, while the signal reporter for the recognition process is the TPP fluorescence quenching. Because the emission spectrum of anthracene is largely overlapped with the Soret band absorption of TPP, intramolecular excitation energy transfer interaction occurs between the donor, anthracene and acceptor, TPP. This energy transfer leads to TPP fluorescence emission by excitation of anthracene. The sensor was constructed by immobilizing the dyad in a plasticized poly(vinyl chloride) (PVC) membrane. The sensing membrane shows higher sensitivity compared to the sensors by using anthracene, TPP, or a mixture of anthracene and TPP as sensing materials. Under the optimum conditions, iodine in a sample solution can be determined from 2.04 to 23.6 mmol·L⁻¹ with a detection limit of 33 nmol·L⁻¹. The sensing membrane shows satisfactory response characteristics including good reproducibility, reversibility and stability, as well as the short response time of less than 60 s. Except for Cr₂O₇²⁻ and MnO₄⁻, other common metal ions and anions in foodstuff do not interfere with iodine determination. The proposed method was applied in the determination of iodine in table salt samples. The results agree well with those obtained by other methods. Supported by the National Outstanding Youth Science Foundation of China (Grant No. 20525518), the National Natural Science Foundation of China (Grant No. 20775005), and the National Natural Science Foundation of Hunan province (Grant No. JJ076021)     

Selective determination of bisphenol A (BPA) in water by a reversible fluorescence sensor using pyrene/dimethyl β-cyclodextrin complex

A bifurcated optical fiber chemical sensor for continuous monitoring of bisphenol A (BPA) has been proposed based on the fluorescence quenching (λ_ex/λ_em = 286/390 nm) of pyrene/dimethyl β-cyclodextrin (HDM-β-CD) supramolecular complex immobilized in a plasticized poly(vinyl chloride) (PVC) membrane, in which pyrene served as a sensitive fluorescence indicator probe. The decrease of the fluorescence intensity of pyrene/HDM-β-CD complex upon the addition of BPA was attributed to the displacement of pyrene by BPA, which has been utilized as the basis of the fabrication of a BPA-sensitive fluorescence sensor. The response mechanism of the sensor was discussed in detail. The sensor exhibited a dynamic detection range from 7.90 × 10⁻⁸ to 1.66 × 10⁻⁵ mol L⁻¹ with a detection limit of 7.00 × 10⁻⁸ mol L⁻¹, and showed excellent reproducibility, reversibility, selectivity, and lifetime. The proposed sensor was successfully used for the determination of BPA in water samples and landfill leachate.     

Fabrication of an optical sensor based on the immobilization of Qsal on the plasticized PVC membrane for the determination of copper(II)

A novel optical sensor has been proposed for sensitive determination of Cu(II) ion in aqueous solutions. The copper sensing membrane was prepared by incorporating Qsal (2-(2-hydroxyphenyl)-3H-anthra[2,1-d]imidazole-6,11-dione) as ionophore in the plasticized PVC membrane containing tributyl phosphate (TBP) as plasticizer. The membrane responds to Cu(II) ion by changing color reversibly from yellow to dark red in acetate buffer solution at pH 4.0. The proposed sensor displays a linear range of 6.3 × 10^?7?1.00 × 10^?4 M with a limit of detection of 3.3 × 10^?7 M. The response time of the optical sensor was about 3?C5 min, depending on the concentration of Cu(II) ions. The selectivity of the optical sensor to Cu(II) ions in acetate buffer is good. The sensor can readily be regenerated by hydrochloric acid (0.1 M). The optical sensor is fully reversible. The proposed optical sensor was applied to the determination of Cu(II) in environmental water samples.     

Selective lanthanum ions optical sensor based on covalent immobilization of 4-hydroxysalophen on a hydrolyzed triacetylcellulose membrane

An optical sensor membrane is described for the determination of lanthanum(III) ions based on the immobilization of 4-hydroxysalophen on a hydrolyzed triacetylcellulose membrane. 4-Hydroxysalophen is covalently bonded to a transparent hydrolyzed triacetylcellulose film. The sensing membrane in contact with lanthanum ions at pH 4.0 changes color from white-yellow to orange (323 to 433 nm). Under the optimum conditions, the proposed membrane displayed a linear range from 1.0 × 10⁻⁶ to 1.0 × 10⁻² M La(III) with a limit of detection of 1 × 10⁻⁷ M. The response time of the membrane was within 5–6 min depending on the concentration of La(III) ions. The selectivity of the probe towards lanthanum ions was found to be excellent. The sensor was successfully applied to the determination of La(III) in water, industrial waste water, and in NIST-615 (glass matrix) and NIST-3127a (lanthanum solution) samples with satisfactory results.     

A selective sensing membrane for the determination of tetracycline with heptakis (2,6-di-O-isobutyl)-β-cyclodextrin as the substrate

When heptakis (2,6-di-O-isobutyl)-β-cyclodextrin(DOB-β-CD) is immobilized in a plasticized poly vinyl chloride (PVC) membrane, it extracts tetracycline (TC) from the sample solution into the organic membrane phase to form a complex of DOB-β-CD and TC. Since the complex formation results in an enhancement of fluorescence intensity of TC at 506 nm, the chemical recognition process can be directly translated into an optical signal. The maximum response of the sensitive membrane for TC was obtained in 0.2 mol/l KH₂PO₄–KOH buffer solution (pH 8.01). In the optimum conditions described, the proposed sensor responds linearly in the measuring range of 2.00×10⁻⁶ mol/l to 4.00×10⁻⁴ mol/l, and has a detection limit of 8.00×10⁻⁷ mol/l. The response time of the sensor is within 2.0 min. In addition to high reproducibility and reversibility, the sensor also exhibits good selectivity over some common pharmaceutical species and some common organic and inorganic compounds.     

An anthracene/porphyrin dimer fluorescence energy transfer sensing system for picric acid

The fluorescence energy transfer between anthracene (donor) and 5-p-[[4-(10′15′20′-triphenyl-5′-porphinato) phenyloxyl]-1-butyloxyl] phenyl-10,15,20-triphenyl-porphyrin (DTPP as acceptor) and an optical fiber sensor for the determination of picric acid based on this theory were studied. Because the emission spectrum of anthracene was largely overlapped with the absorption spectrum of the DTPP, the phenomenon of energy transfer occurred when anthracene and DTPP were immobilized in a PVC membrane. The membrane based on anthracene and DTPP contacting with picric acid showed much stronger fluorescence quenching comparing to membranes containing only anthracene or DTPP. The use of DTPP as acceptor was compared with 5,10,15,20-tetraphenylporphyrin (TPP). Both porphyrin compounds can be used as the acceptor, with DTPP clearly preferred. Under optimum conditions, picric acid in a sample solution can be determined from 3.0×10⁻⁷ to 2.0×10⁻³ mol l⁻¹ with a detection limit of 1.5×10⁻⁷ mol l⁻¹. The proposed optical fiber sensor shows satisfactory characteristics including good reproducibility, reversibility and selectivity as well as a short response time. The recovery tests of picric acid in industrial wastewaters were satisfactory.     

Complex Formation of Hematoporphyrin with Cyclodextrins and 1,1′-Diheptyl-4,4′-bipyridinium Dibromide in Aqueous Solutions

At around 5×10^-6?mol?dm^-3 of hematoporphyrin (HP), an HP dimer exists as well as an HP monomer. The equilibrium constant for the dimerization of HP in pH 10.0 buffer has been evaluated to be 1.70×10⁵?mol^-1?dm³ from the HP concentration dependence of the absorption spectrum. In aqueous solution, HP forms 1:1 inclusion complexes with β-cyclodextrin (β-CD), γ-cyclodextrin (γ-CD), and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (TM-β-CD). The fluorescence of HP is significantly enhanced by the addition of CDs. From simulations of the fluorescence intensity changes, the equilibrium constants for the formation of the CD–HP inclusion complexes have been estimated to be 200, 95.7, and 938?mol^-1?dm³ for β-CD, γ-CD, and TM-β-CD, respectively. HP forms a 1:1 complex with 1,1′-diheptyl-4,4′-bipyridinium dibromide (DHB) in aqueous solution. In contrast to the addition of CDs, the HP fluorescence is significantly quenched by the addition of DHB. The equilibrium constant for the formation of the HP–DHB complex has been evaluated to be 1.98×10⁵?mol^-1?dm³ from the fluorescence intensity change of HP. The addition of DHB to an HP solution containing β-CD induces a circular dichroism signal of negative sign, indicating the formation of a ternary inclusion complex involving β-CD, HP, and DHB. In contrast, there is no evidence for the formation of a ternary inclusion complex of HP with DHB and TM-β-CD.     

Design of an Optical Sensor for Determination of Bismuth

An optical chemical sensor (optode) for the determination of Bi(III) has been designed by immobilization of methyltrioctylammonium chloride on triacetylcellulose polymer. The exchange of chloride as counter ion with iodide in the membrane changes the colorless film to orange, when it is placed in acidic solution of Bi(III). The sensor can readily be regenerated by 0.1 mol L^‐1 sodium citrate solution in less than 15 s. Under optimum conditions, the proposed membrane is capable of determining Bi(III) over a dynamic range between 3.36 × 10^‐6 and 4.80 × 101^‐5 mol L^‐1 with a limit of detection 1.02 × 10^‐6 mol L^‐1. The relative standard deviation for seven replicate measurements of 9.60 × 10^‐6 and 3.84 × 10^‐5 mol L^‐1 of Bi(III) was 3.79 and 2.14%, respectively. The sensor was successfully applied to the determination of bismuth in tablet and water samples.     

Optical fiber sensor for berberine based on fluorescence quenching of 2-(4-diphenylyl)-6-phenylbenzoxazole

A new optical fiber sensor was prepared for the determination of berberine in aqueous solution using a micrometer-sized flow-cell and a bifurcated optical fiber. The sensing is based on fluorescence quenching of 2-(4-diphenylyl)-6-phenylbenzoxazole (PBBO) in the PVC membrane. This process is accompanied by non-fluorescent ground-state complex formation. With this sensor, berberine can be determined in sample solutions from 2.42 × 10^–5 mol L^–1 to 6.04 × 10^–7 mol L^–1. Satisfactory reproducibility, reversibility, and short response times of less than 1 min are realized. The sensor also shows good selectivity over some common pharmaceutical species and alkali and alkali-earth metal salts, and can be used for the direct assay of berberine in commercial tablets. The results are in correspondence with those obtained by the pharmacopoeia method. Received: 4 April 1997 / Revised: 8 August 1997 / Accepted: 12 August 1997     

Optical fiber sensor for berberine based on fluorescence quenching of 2-(4-diphenylyl)-6-phenylbenzoxazole

A new optical fiber sensor was prepared for the determination of berberine in aqueous solution using a micrometer-sized flow-cell and a bifurcated optical fiber. The sensing is based on fluorescence quenching of 2-(4-diphenylyl)-6-phenylbenzoxazole (PBBO) in the PVC membrane. This process is accompanied by non-fluorescent ground-state complex formation. With this sensor, berberine can be determined in sample solutions from 2.42 × 10^–5 mol L^–1 to 6.04 × 10^–7 mol L^–1. Satisfactory reproducibility, reversibility, and short response times of less than 1 min are realized. The sensor also shows good selectivity over some common pharmaceutical species and alkali and alkali-earth metal salts, and can be used for the direct assay of berberine in commercial tablets. The results are in correspondence with those obtained by the pharmacopoeia method. Received: 4 April 1997 / Revised: 8 August 1997 / Accepted: 12 August 1997     

A simple optical sensor for cadmium ions assay in water samples using spectrophotometry

A new simple and inexpensive optical chemical sensor for cadmium(II) ions is presented. The cadmium sensing system was prepared by incorporating 2-amino-cyclopentene-1-dithiocarboxylic acid (ACDA) on a triacetylcellulose membrane. The absorption spectra of the optical sensor membrane in Cd(II) solution showed a maximum peak at 430 nm. The proportionality in intensity of the membrane color on the optode to varying amounts of Cd(II) suggests its potential applications for screening Cd(II) in aqueous samples by visual colorimetry. The sensor provided a wide concentration range of 3.0 × 10⁻⁶–3.4 × 10⁻⁴ M of Cd(II) ions with a detection limit of 1.0 × 10⁻⁶ M (0.2 μg/mL). The relative standard deviations for eight replicate measurements of 8.0 × 10⁻⁶ and 5.0 × 10⁻⁵ M Cd(II) were 2.7 and 2.3%, respectively. The response time of the optode was 6 min. The influence of interfering ions on the determination of 1.0 × 10⁻⁵ M Cd(II) was studied and the main interferences were removed by extraction method. The sensor was applied to the determination of Cd(II) in water samples.     

Electrochemical sensor for cinchonine based on a competitive host-guest complexation

An electrochemical sensor for cinchonine (CCN) using the β-cyclodextrin (β-CD) modified poly(N-acetylaniline) (PAA) electrode has been developed, in which 1,4-hydroquinone (HQ) was chosen as a probe. Complexation of HQ with β-CD modified on the glassy carbon electrode (GCE) was examined by cyclic voltammetry (CV). HQ was included in the cavity of β-CD and reversible voltammograms were observed. In the presence of CCN, a competitive inclusion equilibrium with β-CD was established between HQ and CCN, lowering the peak current of HQ. The decrease in the peak current of HQ is directly proportional to the amount of CCN. Linear calibration plot was obtained over the range from 4.0 × 10⁻⁶ to 8.0 × 10⁻⁵ M with a detection limit (S/N = 3) of 2.0 × 10⁻⁶ M. From the inhibitory effect of CCN on the inclusion of HQ by β-CD, the apparent formation constant of CCN with the immobilized β-CD was estimated. This electrochemical sensor showed excellent sensitivity, repeatability, stability and recovery for the determination of CCN. The response mechanism of the sensor was discussed in detail. The optimum steric configuration of inclusion complex was presented by molecular dynamics simulation.     

Spectrofluorimetric determination of aliphatic amines using a new fluorigenic reagent: 2,6-dimethylquinoline-4-(N-succinimidyl)-formate

A new amino fluorescence probe, 2,6-dimethylquinoline-4-(N-succinimidyl) formate (DMQF-OSu) has been synthesized. Based on the selective reaction of DMQF-OSu with primary and secondary aliphatic amines to yield strong fluorescence, a new spectrofluorimetric method for the determination of total aliphatic amines has been developed. At λ_ex/λ_em=324.4/416 nm, the linear calibration range was 6×10⁻⁸-6×10⁻⁶ mol l⁻¹ with the detection limit (3σ) of 1.94×10⁻¹⁰ mol l⁻¹ for the determination of aliphatic amines in weak basic media. The proposed method has been applied to the determination of aliphatic amines in tap water and lake water with the recoveries of 99-104%. Compared with the reported methods, the method presented here is rapid, simple, sensitive and feasible.     

An optical sensor for mercury ion based on the fluorescence quenching of tetra(p-dimethylaminophenyl)porphyrin

An optical sensor for mercury ion (Hg²⁺), based on quenching the fluorescence of the sensing reagent porphyrin immobilized in plasticized poly(vinyl chloride) (PVC) membrane, has been developed. The responses to mercury ion were compared for the sensors modified with three porphyrin compounds including 5,10,15,20-tetraphenylporphyrin (TPP), tetra(p-dimethylaminophenyl)porphyrin (TDMAPP) and tetra(N-phenylpyrazole) porphyrin (TPPP). Among them, TDMAPP showed the most remarkable response to Hg²⁺. The drastic decrease of the TDMAPP fluorescence intensity was attributed to the formation of a complex between TDMAPP and Hg²⁺, which has been utilized as the fabrication basis of a Hg²⁺-sensitive fluorescence sensor. The analytical performance characteristics of the TDMAPP modified sensor was investigated. The response mechanism, especially involving the response difference of three porphyrin compounds, was discussed in detail. The sensor can be applied to the quantification of Hg²⁺ with a linear range covering from 4.0 × 10⁻⁸ mol L⁻¹ to 4.0 × 10⁻⁶ mol L⁻¹. The limit of detection was 8.0 × 10⁻⁹ mol L⁻¹. The sensor exhibited excellent reproducibility, reversibility and selectivity. Also, the TDMAPP-based sensor was successfully used for the determination of Hg²⁺ in environmental water samples.     

Inclusion complexation of warfarin withβ-cyclodextrins and its influence on absorption kinetics of warfarin in rat

The inclusion complexes of warfarin withβ-cyclodextrin, 2-hydroxypropyl-β-CD and methyl-β-CD have been investigated in aqueous solution. The apparent binding constants of warfarin are found to be 542±19, 442±18 and 112±6M^?1 respectively, calculated from the increments in fluorescence emission of the drug. The influence of theβ-CDs on the absorption rate of the drug is investigated within situ experiments in a chronically isolated internal loop, in the small intestine of the rat. The first-order disappearance (absorption) rate constant decreases to 3.6×10^?4 min^?1 inβ-CD, to 5.0×10^?4 min^?1 in 2-hydroxypropyl-β-CD and to 1.4×10^?3 min^?1 in methyl-β-CD compared to 3.2×10^?3 min^?1 in isotonic phosphate buffer (pH=7.4) solution, all of them showing a good agreement with the percentage of free warfarin in their complexed solutions: 16%, 18% and 47% calculated, respectively.     

β-Cyclodextrin Derivatives as Fluorescence Enhancers of the Drug,Hesperidin

Abstract

The fluorescence behavior of the drug hesperidin in several cyclodextrins(CDS):β-cyclodextrin(β-CD), hydroxypropyl-β-CD (HP-β-CD) and methyl-β-CD(M-β-CD) was studied. The stoichiometry of the complexes and their apparent formation constants were estimated. The excitation wavelengths were at 335nm for hesperidin in β-CD, HP-β-CD and M-β-CD media. The emission wavelengths were at 444, 436 and 434 nm, respectively; The fluorescence enhancement of hesperidin was observed in different cyclodextrin media. The linear calibration plots between fluorescence intensity and hesperidin concentration were determined in the 10^?7 ～10^?5 M range. The mechanism for the enhanced fluorescence was attributed to protection of the excited state within the cyclodextrin cavity.