Flow injection spectrofluorimetric study of the supramolecular interaction between beta-cyclodextrin and dequalinium chloride and its analytical application

The supramolecular interaction of dequalinium chloride (DQC) and beta-cyclodextrin has been studied by flow injection spectrofluorimetry. The results showed that beta-CD reacted with DQC to form a 1:1 host:guest complex with an apparent association constant of 4.99 x 10(2) L mol(-1). Based on the enhancement of the fluorescence intensity of DQC, a flow injection spectrofluorometric method for the determination of DQC in bulk aqueous solution in the presence of beta-CD was developed. The linear range was 0.0412-30.00 microg mL(-1). The detection limit was 12.3 ng mL(-1) with a sampling rate of 80 h(-1). There was no interference from the excipients normally used in tablets and serum compositions. The proposed method was successfully applied to the determination of DQC in tablets and serum.     

Study on the supramolecular system of 5-(p-hydroxyphenyl)-10,15,20-tris-(4-chlorophenyl)porphyrin with cyclodextrins and its analytical characteristics

The supramolecular systems of 5-(p-hydroxyphenyl)-10,15,20-tris-(4-chlorophenyl)porphyrin (p-HTClPP) with beta-cyclodextrin (beta-CD), heptakis(2,3,6-tri-O-methyl)-beta-CD (TM-beta-CD), carboxymethyl-beta-cyclodextrin (CM-beta-CD) and sulfurbutylether-beta-CD (SBE-beta-CD) have been investigated by means of absorption, fluorescence and (1)H NMR spectroscopy. The formation of inclusion complexes has been confirmed on the base of changes of spectroscopy properties. "The double reciprocal method" has been used to determine the stoichiometry and the inclusion constants of p-HTClPP with the four cyclodextrins (CDs). The results show that p-HTClPP can form 1:1 inclusion complexes with the four CDs. Compared with parent native beta-CD, the inclusion abilities of modified beta-CDs with p-HTClPP are stronger. It indicates that the hydrophobic effect plays an important role in the inclusion procedure. The mechanism of inclusion interaction was examined by (1)H NMR technique. During the study of p-HTClPP-TM-beta-CD supramolecular complex, an efficient enhancement of fluorescence intensity was observed. Based on this phenomenon, fluorometric method for the determination of p-HTClPP was developed. The relationship between fluorescence intensity and the concentration of p-HTClPP is linear from 1.0 x 10(-9) to 7.0 x 10(-6)mol L(-1). The limit of detection is 8.3 x 10(-10)mol L(-1) and the relative standard deviation (R.S.D.) is 1.3% (n=8). This research will provide useful information for further application of p-HTClPP.     

Spectrofluorimetric study of the beta-cyclodextrin-ibuprofen complex and determination of ibuprofen in pharmaceutical preparations and serum

The inclusion complexation of ibuprofen in beta-cyclodextrin (beta-CD) has been examined by means of spectrofluorimetry at both acid and alkaline pH. The results suggest that stable 1:1 complexes are formed in both media. The analysis of the pK(a) values for ibuprofen in both the absence and presence of beta-CD (4.12 and 4.66, respectively) suggests that in the inclusion complex the carboxylic group is located outside the cyclodextrin (CD) but interacting with it. Further structural characterization of the complex was carried out by means of am1 semiempiral calculations. Based on the obtained results, a spectrofluorimetric method for the determination of ibuprofen in the presence of beta-CD at 10 degrees C was developed in the range of 4.7-58 mug ml(-1). Better limits of detection (1.6 mug ml(-1)) and quantification (4.7 mug ml(-1)) were obtained in this latter case with respect to those obtained in the absence of beta-CD. The method was satisfactorily applied to the quantification of ibuprofen in pharmaceutical preparations. A novel spectrofluorimetric determination of ibuprofen in the presence of beta-CD was also developed for serum samples at concentration levels between 5 and 70 mug ml(-1). It uses second-order fluorescence excitation-emission matrices coupled to an algorithm based on self-weighted alternating trilinear decomposition (SWATLD), and avoids resorting to separative instrumental analyses.     

Spectrofluorimetric study of host-guest complexation of ibuprofen with beta-cyclodextrin and its analytical application

The characteristics of host-guest complexation between beta-cyclodextrin (beta-CD) and two forms of ibuprofen (protonated and deprotonated) were investigated by fluorescence spectrometry. 1:1 stoichiometries for both complexes were established and their association constants at different temperatures were calculated by applying a non-linear regression method to the change in the fluorescence of ibuprofen that brought about by the presence of beta-CD. The thermodynamic parameters (deltaH, deltaS and deltaG) associated with the inclusion process were also determined. Based on the obtained results, a sensitive spectrofluorimetric method for the determination of ibuprofen was developed with a linear range of 0.1-2 microg ml(-1) and a detection limit of 0.03 microg ml(-1). The method was applied satisfactorily to the determination of ibuprofen in pharmaceutical preparations.     

Fluorescence determination of DNA with 1-pyrenebutyric acid nanoparticles coated with beta-cyclodextrin as a fluorescence probe

A novel ultrasonication method has been successfully developed for the preparation of 1-pyrenebutyric acid (PBAC)/beta-cyclodextrin(beta-CD) complex nanoparticles. The as-prepared nanoparticles are characterized by transmission electron microscopy (TEM), fluorescence excitation and emission spectroscopy. Complex nanoparticles prepared with ultrasonication are smaller and better dispersed than single PBAC nanoparticles. At pH 3.0, the relative fluorescence intensity of complex nanoparticles of PBAC/beta-CD can be quenched by the concentration of DNA. Based on this, a novel fluorimetric method has been developed for rapid determination of DNA. In comparison with single organic fluorophores, these nanoparticle probes are better water-solubility, more stable and do not suffer from blinking. Under optimum conditions, the calibration graphs are linear over the range 0.2-15 microg mL(-1) for calf thymus DNA (ct-DNA) and 0.3-12 microg mL(-1) for fish sperm DNA (fs-DNA). The corresponding detection limit is 0.01 microg mL(-1) for ct-DNA and 0.02 microg mL(-1) for fs-DNA. The relative standard deviation of seven replicate measurements is 1.2% for 2.0 microg mL(-1) ct-DNA and 1.4% for 2.0 microg mL(-1) fs-DNA, respectively. The method is simple and sensitive. The recovery and relative standard deviation are very satisfactory. A mechanism proposed to explain the process also has been studied.     

Direct fluorimetric determination of ascorbic acid by the supramolecular system of AA with beta-cyclodextrin derivative

We established a simple and selective fluorimetric method for the determination of ascorbic acid (AA) with the novel mono-[6-N(4-carboxy-phenyl)]-beta-cyclodextrin (ACD). The method is based on the fluorescence intensity of ACD decreases as the ACD-AA supramolecular complexes form. The fluorescence intensity is measured at excitation and emission wavelengths of 270 and 352 nm, respectively. Under optimum condition, a linear relationship is obtained between the fluorescence intensity and the concentration of AA in the range of 0.05-8.0 microgml(-1). The detection limit is 0.012 microgml(-1). The method has been applied to the direct analysis of AA in real samples with satisfactory results.     

Determination of heparin using ciprofloxacin-Tb3+ as a fluorescence probe.

A new spectrofluorometric method was developed for the determination of trace amounts of heparin (Hep). Using ciprofloxacin (CIP)-terbium (Tb3+) as a fluorescent probe, in a buffer solution of pH 7.20, Hep can remarkably enhance the fluorescence intensity of the CIP-Tb3+ complex at lambda = 545 nm; also, the enhanced fluorescence intensity the Tb3+ ion is proportional to the concentration of Hep. The optimum conditions for the determination of Hep were also investigated. The dynamic range for the determination of Hep is 0.1 - 1.2 microg ml(-1) with a detection limit of 6.89 ng ml(-1). This method is simple, practical and relatively free of interference from coexisting substances, and can be successfully applied to assess Hep in biological samples. By the Rosenthanl graphic method, the association constant and binding numbers of heparin with the probe are 2.44 x 10(5) l mol(-1) and 19.7. Moreover, the enhancement mechanisms of the fluorescence intensity in the CIP-Tb3+ system and the CIP-Tb3+-Hep system have also been considered.     

Spectrofluorimetric determination of piroxicam in the presence and absence of beta-cyclodextrin

The complexation between beta-cyclodextrin (beta-CD) and piroxicam (PX) was investigated by both fluorescence and absorption spectrometry. A 1:2 guest:host stoichiometry for the complex was established, and its association constant was calculated by applying a non-linear regression method to the changes brought about by the presence of beta-CD in both the fluorescence and absorbance spectra of PX. During the study of the influence of the pH on the fluorescence emission of the complex, an efficient enhancement of the signals at acidic pH was observed. This suggests that the protonated form of PX is included more effectively than the ionized form in the beta-CD cavity. Based on the results obtained, spectrofluorimetric methods for the determination of PX were developed. The best limits of detection and quantification were obtained using beta-CD at an acidic pH. The dynamic range in this latter case was 0.02-1 microgram ml-1. The method was applied satisfactorily to the determination of piroxicam in a pharmaceutical preparation.     

Spectroscopic study of orange G-beta-cyclodextrin complex and its analytical application

The mechanism of the inclusion of orange G and beta-cyclodextrin (beta-CD) has been studied by using both spectrophotometry and infrared spectroscopy. Effects of the pH, concentrations of beta-CD, and ionic strength on the inclusion complex of beta-CD and orange G were examined. The result showed that orange G reacts with beta-CD to form a 1:1 host-guest complex with an apparent formation constant of 3.03 x 10(3)mol(-1)l. The thermodynamic parameters of inclusion complex, DeltaG(0), DeltaH(0), and DeltaS(0) were obtained. Based on the enhancement of the absorbance of orange G produced through complex formation, a ratiometric method spectrophotometrically for the determination of orange G in bulk aqueous solution in the presence of beta-CD was developed, which overcome the effect of condition change on the determination of orange G. The linear relationship between the absorbance and orange G concentration was obtained in the range of 1.0 x 10(-5) to 4.0 x 10(-5)mol l(-1), with a correlation coefficient of 0.9998. The detection limit was 3.6 x 10(-6)mol l(-1). The principal advantage of the proposed method is high accuracy because ratiometry was used in measurement.     

Fluorimetric and mass spectrometric study of the interaction of beta-cyclodextrin and osthole

The inclusion complex of beta-cyclodextrin (beta-CD) and osthole was studied by the electrospray ionization mass spectrometry (ESI-MS) and fluorescence spectrometry. From the mass spectrum, the 1:1 stoichiometric inclusion complex of beta-CD and osthole was observed. The tandem mass spectrum was performed. The fluorescence intensity of osthole increased in the present of beta-CD. According to the 1:1 beta-CD-osthole mode, the dissociation constant (KD) was obtained by ESI-MS and fluorescence spectrometry. The KD of beta-CD-osthole inclusion complex is 6.96 x 10(-3) mol L(-1) obtained by mass spectrometry and that is 8.14 x10 (-3) mol L(-1) obtained by fluorescence spectrometry, which is consistent with each other.     

β-环糊精/萘丁美酮/直链醇体系的超分子作用机理及其分析应用的研究

利用稳态荧光法研究了β-环糊精（β-CD）与新型抗炎药物萘丁美酮（NAB） 间的超分子相互作用，探讨了直链醇（ROH）对该超分子体系的影响。研究表明无 论体系中是否含有直链醇，β-CD和萘丁美酮均形成1/1的超分子包合物其表观结合 常数K_(app)随醇碳链长度的增长而逐渐减小。将这一现象归因于醇对β-CD疏水性 空腔的竞争作用，而非β-CD/NAB/ROH三元包合物的形成所致。荧光猝灭实验表明 水相中β-CF增敏萘丁美酮荧光是源于其疏水性空腔对萘丁美酮激发单重态的屏蔽 效应。直链醇的加入抑制了该效应，从而进一步证实了醇对β-CD空腔的竞争作用 确实导致萘丁美酮被置换到水相中。利用β-CD对萘丁美酮的包结作用使其荧光显 著增大这一特性，建立了水相中高灵敏度测定萘丁美酮的荧光光度法，线性范围为 0～3.0μg·mL~(-1)，检测下限1.05 ng·mL~(-1)。常用药物赋形剂对测定不产生 干扰。应用本法测定片剂中萘丁美酮含量，结果令人满意。     

Spectrofluorimetric method for determination of aluminium with chromotropic acid and its application to water samples

A rapid and sensitive method for the trace level determination of aluminium based on the formation of a 1:1 complex with chromotropic acid (1,8-dihydroxynaphthlene-3,6-disulfonic acid) in an methanol medium is reported. The fluorescence intensity of the system was 50 times greater than that of the system without aluminium. This method is very sensitive and selective for the direct determination of aluminium ion. The fluorescence is excited at 346 nm and measured at 370 nm. The optimum conditions are a chromotropic acid concentration of 5.0 ml (1.0x10(-4) M) and pH 4.0+/-0.5 (acetic acid-sodium acetate buffer). The fluorescence intensity is a linear function of the concentration of Al(III) in the range 2-100 ng ml(-1) and the detection limit is 1.0 ng ml(-1). The method has been applied successfully to the determination of trace amount of Al(III) in tap, river and sea-water samples.     

Thermodynamic study on the effects of beta-cyclodextrin inclusion with berberine.

The fluorescence enhancement of berberine (Berb) as a result of complex with beta-cyclodextrin (beta-CD) is investigated. The association constants of alpha-CD and beta-CD with Berb are 60 and 137 M(-1) at 20 degrees C in pH 7.20 aqueous solution. Effects of temperature on the forming inclusion complexes of beta-CD with Berb have been examined through using fluorescence titration. Enthalpy and entropy values calculated from fluorescence data are -33.7 kJ mol(-1) and 74.3 J x mol(-1) K(-1) respectively. It was found that the dielectric constant of beta-CD cavity is about 24 in a rough analogy with absolute alcohol. These results suggest that the extrusion of 'high energy water' molecules from the cavity of beta-CD and hydrophobic interaction upon the inclusion complex formation are the main forces of the inclusion reaction. Effect of pH on the association of beta-CD with Berb was also studied. Mechanism of the inclusion of beta-CD with Berb is further studied by absorption and NMR measurements. Results show that beta-CD forms a 1:1 inclusion complex with Berb.     

Study on fluorescence property of carvedilol and determination of carvedilol by fluorimetry

The property of carvedilol in acid-alkaline medium was studied by spectrofluorimetry. Effects of organic solvents on carvedilol fluorescence spectra were examined and the reason was discussed. A simple, rapid and high sensitive fluorimetric method for the determination of carvedilol in medicine is developed. The measurement of relative fluorescence intensity was carried out at 356 nm with excitation at 254 nm. Effects of pH, standing time and foreign ions on the determination of carvedilol have been examined. A linear relationship was obtained between the relative fluorescence intensity and concentration of carvedilol in the range of 0.50-270 ng ml(-1). The linear regression equation of the calibration graph is C = 0.000543F - 0.002 (C is concentration (microg ml(-1)) and F is relative fluorescence intensity in the equation), with a correlation coefficient of linear regression of 0.9998 and relative standard deviation of 2.31%. The detection limit of this method is 0.19 ng ml(-1), and recovery is from 98.70 to 102.1%. This method can be used for determination of carvedilol in tablet. The results obtained by this method agreed with those by the official method.     

Spectrofluorimetric study on the inclusion interaction between lomefloxacin and p-sulfonated calix[4]arene and its analytical application

The characteristics of host-guest complexation between p-sulfonated calix[4]arene (SC4A) and lomefloxacin (LMFX) were investigated by fluorescence spectrometry. A 1:1 stoichiometry for the complexation was established and an association constant of 6.48x10(4) l mol-1 at 25 degrees C was calculated by applying a deduced equation. The interaction mechanism of the inclusion complex was discussed and the various factors affecting the inclusion process were examined in detail. It was found that an appropriate amount of cationic surfactant cetyltrimethylammonium bromide (CTAB) can remarkably enhance the fluorescence intensity of the supramolecular complex system. Based on the obtained results, a novel sensitive spectrofluorimetric method for the determination of lomefloxacin based on supramolecular complex was developed with a linear range of 0.01-3.0 microg ml-1 and a detection limit of 0.008 microg ml-1, for the first time. The method was applied for the determination of lomefloxacin in pharmaceutical preparations successfully.     

Enhancement of fluorescence of terbium/trimesic acid/cyclodextrin system by zirconate and its application to the determination of terbium

A new approach of fluorescence enhancement for the determination of terbium based on the formation of a new fluorescence system of Tb-TMA-beta-CD (benzene-1,3,5-tricarboxylic acid (TMA), beta-cyclodextrin (beta-CD)) in an aqueous medium of pH 5.0 provided by a HAc-NaAc buffer in the presence of an oxy-acid of transition metal, zirconate acid, is reported. The maximum excitation and emission wavelengths are 301 nm and 545 nm for the terbium complex, respectively. Under the optimal conditions, the method allows the determination of terbium over the range of 0.508-521 ng ml(-1) with a S.D. of 0.392, and the recovery is in the range of 99.0-100.1%. The emulsion formed by Tb-TMA-beta-CD with zirconate acid makes the determinate system more stable than the system of Tb-TMA-beta-CD. The proposed method has been employed for the determination of some international standard reference or samples with a good precision (RSD < 1.7%, n = 5).     

Spectrofluorometric determination of verapamil hydrochloride in pharmaceutical preparations and human plasma using organized media: application to stability studies

A highly sensitive spectrofluorometric method was developed for the determination of verapamil hydrochloride (VP HCl) in pharmaceutical formulations and biological fluids. The proposed method is based on investigation of the fluorescence spectral behavior of VP HCl in micellar systems, such as sodium dodecyl sulfate (SDS) and beta-cyclodextrin (beta-CD). In aqueous solutions of borate buffer of pH 9 and 8.5, VP HCI was well incorporated into SDS and beta-CD, respectively, with enhancement of its native fluorescence. The fluorescence was measured at 318 nm after excitation at 231 nm. The fluorescence intensity enhancements were 183 and 107% in SDS and in beta-CD, respectively. The fluorescence-concentration plots were rectilinear over the range of 0.02-0.2 and 0.02-0.25 microg/mL, with lower detection limits of 5.58 x 10(-3) and 3.62 x 10(-3) microg/mL in SDS and beta-CD, respectively. The method was successfully applied to the analysis of commercial tablets and the results were in good agreement with those obtained with the official method. The method was further applied to the determination of VP HCl in real and spiked human plasma. The mean % recoveries in the case of spiked human plasma (n=4) was 92.59 +/- 3.11 and 88.35 +/- 2.55 using SDS and beta-CD, respectively, while that in real human plasma (n=3) was 90.17 +/- 6.93 and 89.17 +/- 6.50 using SDS and beta-CD, respectively. The application of the method was extended to the stability studies of VP HCl after exposure to ultraviolet radiation and upon oxidation with hydrogen peroxide.     

Spectrophotometric study of the inclusion complex between beta-cyclodextrin and dibenzoyl peroxide and its analytical application

The noncovalent interaction of dibenzoyl peroxide and beta-cyclodextin (beta-CD) has been studied by spectrophotometry. The mechanism of the inclusion was studied. The results showed that beta-CD reacts with dibenzoyl peroxide to form a 2:1 host-guest complex with an apparent formation constant of 2.5 x 10(4)mol(-2)L(2). The beta-CD reacts with benzoic acid to form a 1:1 host-guest complex with an apparent formation constant of 6.9 x 10(2)mol(-1)L after the dibenzoyl peroxide was reduced by hydroxyl ammonium. Based on the enhancement of the absorbance of dibenzoyl peroxide produced through complex formation, a spectrophotometric method for determination of dibenzoyl peroxide in bulk aqueous solution in the presence of beta-CD was developed. A linear relationship between the absorbance and dibenzoyl peroxide concentration was obtained in the range of 0.300-50.0 microg mL(-1). Linear regression equation of the calibration graph C=0.02926+53.25 A, with a correlation coefficient of 0.9984 and a relative standard deviation (R.S.D.) of 3.4%. The detection limit was 0.200 microg mL(-1), and the recovery was from 98.00 to 105.0%. The proposed method was used to determine the dibenzoyl peroxide in the flour with satisfactory results. The principal advantage of the proposed method is its excellent selectivity based on molecule recognition of beta-CD.     

Fluorometric study of the inclusion interaction of beta-cyclodextrin derivatives with tetraphenylporphyrin and its analytical application

The effects of native beta-cyclodextrin (beta-CD) and four kinds of alkylated beta-cyclodextrin (beta-CDs), i.e. heptakis (2,6-di-O-isobutyl-beta-cyclodextrin) (I), heptakis (2,6-di-O-octyl-beta-cyclodextrin) (II), heptakis (2,6-di-O-dodecyl-beta-cyclodextrin) (III), and heptakis (2,6-di-O-hexadecyl-beta-cyclodextrin) (IV), on the fluorescence behaviors of tetraphenylporphyrin (TPP) are investigated. An obvious fluorescence enhancement is observed from TPP by using alkylated derivatives compared to that obtained in beta-CD aqueous or in water. A 114-N fluorescence emission intensity enhancement is found for the complex with 2,6-di-O-octyl-beta-cyclodextrin relative to the free analyte. The exact stoichiometric ratios and the formation constants of the inclusion complexes have been examined by application of curve fitting method. The linear calibration plots between fluorescence intensity and TPP concentration are determined in the 1.14 x 10(-8)-5.06 x 10(-6) mol l(-1) range.     

Study on the supramolecular multirecognition mechanism of beta-naphthol/beta-cyclodextrin/anionic surfactant in a tolnaftate hydrolysis system

Based on the fact that tolnaftate degrade to beta-naphthol sodium (RONa) at 5.00 mol/L NaOH solution and RO(-) was protonated to ROH after being acidified and adjusted to the pH 4.50 by acetic acid-sodium acetate buffer solution, we studied and discussed the mechanism of the supramolecular multirecognition interaction among the anionic surfactants sodium lauryl sulfate (SLS), beta-cyclodextrin (beta-CD), and beta-naphthol (ROH) by means of fluorescence spectrum, surface tension of the solution, infrared spectrograms, and (1)HNMR spectroscopy. The apparent formation constant of the ternary inclusion complex was determined to be (5.48 +/- 0.13) x 10(3) L(2)/mol(2). The thermodynamic parameters (DeltaG degrees, DeltaH degrees, DeltaS degrees ) for the formation of the inclusion complexes were obtained from the van't Hoff equation. It was indicated that the multiple and synergistic protection effect of SLS and beta-CD on the excited singlet state ROH played very important roles in the enhancement of the fluorescence of ROH. Results showed that, at room temperature, the naphthalene ring of ROH and the hydrophobic hydrocarbon chain of SLS were included into the cavity of beta-CD to form a ROH/SLS/beta-CD ternary inclusion complex with stoichiometry of 1:1:1, which provided effective protection for the excited state of ROH and increased the fluorescent intensity of ROH obviously.