Ion-pair Fluorescence Research Articles

Anthraquinone-1,8-Derived (Pseudo-) Crown and Lariat Ethers:Design and Applications as Fluorescent and Chromogenic Ion (Pair) Sensors.

Cyclic polyamine/ethers embedded with anthraquinone moieties and functional pendants, are structural analogues of crown ethers and (oxo-) cyclams, and could be utilized as sensitive and selective chemosensors towards metal cations. Those pseudo- (similar but geometrically distinct) crown and lariat ethers show various cation-binding patterns and stoichiometry, being modulated by donor type, cavity size and pendants' chelating ability. The luminescent and chromogenic properties also differ a lot along with the derivation of the parental macrocycle. Methodological designing including synthesis and post-functionalization through nucleophilic substitution, Mannich condensation etc., as well as the sensing performance of those pseudo-crown and lariat ethers are summarized in this review, basing on the spectroscopic, voltammetric and X-ray crystallographic determinations. Anion effect in sensing cations is evaluated according to the ion-pair recognition theory. Those results shed some light on exemplifying the anions' role in bioinorganic systems including metalloenzymes.

The pyranine-benzalkonium ion pair: A promising fluorescent system for the ratiometric detection of wound pH

Pyranine is a non-toxic fluorescent dye, with a broad range of applications in biomedicine where it allows precise ratiometric detection of pH within the physiological pH window. Hereby, the facile synthesis, potentially interesting for commercial applications, of a novel ion pair between pyranine and benzalkonium is described. Benzalkonium, a quaternary ammonium salt with potent antimicrobial properties, makes pyranine sufficiently hydrophobic to allow its incorporation in conventional membranes and commercial wound dressings while maintaining its pH sensing performance unaffected and conferring the resulting ion pair strong antimicrobial properties. In conclusion, this novel fluorescent ion pair could be extremely promising for the non-invasive monitoring of wound pH.

Fluorescent and cooperative ion pair receptor based on tolan for Na+ (or Li+) and HSO4-: logic AND gate.

A tolan derivative was synthesized as a fluorescent and cooperative ion pair receptor. As both Na+ and HSO4- ions were complexed to the receptor, only substantial fluorescence was quenched. Thus, it also acts as a logic AND gate.

Interaction of quinine sulfate with anionic micelles of sodium dodecylsulfate: A time-resolved fluorescence spectroscopy at different pH

Photophysical behavior and rotational relaxation dynamics of quinine sulfate (QS) in anionic surfactant, sodium dodecylsulfate (SDS) at different pH have been studied using steady state and time resolved fluorescence spectroscopy. It has been observed that the cationic form of quinine sulfate (at pH 2) forms a fluorescent ion pair complex with the surfactant molecules at lower concentrations of surfactant. However, for higher concentrations of SDS, the probe molecules bind strongly with the micelles and reside at the water–micelle interface. At pH 7, QS is singly protonated in bulk aqueous solution. At lower concentrations of SDS aggregation between probe and surfactant molecules has been observed. However, for higher concentrations of SDS, an additional fluorescence peak corresponding to dicationic form of QS appears and this has been attributed to double protonation of the QS molecule in micellar solution. At pH 7, in the presence of SDS micelles, the photophysical properties of QS showed substantial changes compared to that in the bulk water solution. At pH 12, an increase in fluorescence intensity and lifetime has been observed and this has been attributed to the increase in radiative rate due to the incorporation of QS at the micelle–water interface. The local pH at micellar surface has been found different from the pH of bulk solution.

A Simple but Effective Dual Redox and Fluorescent Ion Pair Receptor Based on a Ferrocene−Imidazopyrene Dyad

The ferrocene-imidazopyrene dyad, bearing the imidazole ring as the only receptor site, acts as a redox and optical molecular sensor for ion pairs, exhibiting an easily detectable signal change in the redox potential of the ferrocene/ferrocinium redox couple and in the emission spectrum. Perturbation of the emission spectrum follows the order Pb(2+) > Hg(2+) > Zn(2+) for cations and H(2)PO(4)(-) > AcO(-) for anions.

Optimization and validation of spectrofluorimetric method for the determination of clomipramine hydrochloride via ion-pair complexation with alizarin red S

A simple and sensitive spectrofluorimetric method has been developed and validated for the determination of the antidepressant clomipramine hydrochloride in its dosage forms. The method was based on the fluorescent ion-pair complex formation between clomipramine and alizarin red S at pH 1.99. The ion-pair complex showed maximum fluorescence intensity at 561 nm with excitation at 490 nm. Different variables affecting the reaction conditions such as the concentration of alizarin red S, pH, reaction time and the extracting solvents were carefully studied. Under the optimised conditions, the fluorescence intensity was found to be linearly related with clomipramine hydrochloride concentration in the range of 1.0–20 μg ml−1. The detection and quantitation limits were 0.32 and 0.97 μg ml−1, respectively. No interference was observed from the excipients commonly present in dosage forms. The proposed method was successfully applied to the determination of clomipramine in its pharmaceutical tablets with good accuracy and precision; the recovery values were 99.75–100.05%.

Spectrofluorimetric Method for the Determination of Doxepin Hydrochloride in Commercial Dosage Forms

A novel spectrofluorimetric method has been developed for the determination of doxepin hydrochloride in commercial dosage forms. The method is based on the fluorescent ion pair complex formation of the drug with eosin Y in the presence of sodium acetate-acetic acid buffer solution of pH 4.52 which is extractable in dichloromethane. The extracted complex showed fluorescence intensity at lambdaem=567 nm after excitation at 464 nm. The calibration curve was linear over the working range of 0.1-0.8 microg ml(-1). Under the optimized experimental conditions, present method is validated as per International Conference on Harmonization guidelines. The limit of detection for the developed method is 2.95 ng ml(-1). The method has been successfully applied to the determination of doxepin hydrochloride in commercial dosage forms. The results are compared with the reference spectrofluorimetric method.

A high performance liquid chromatographic post‐column fluorescent ion pair extraction system: Application to physostigmine and its metabolite eseroline in human serum

A high performance liquid chromatographic post-column fluorescent ion pair extraction system was developed for the analysis of quaternary ammonium and amine drugs in serum. A new fluorescent ion pair reagent, sodium alpha-(3,4-dimethoxyphenyl) cinnamonitrile-2'-sulfonate (DPS), was synthesized and characterized. The post-column extraction system consisted of a three-dimensional knitted teflon mixing coil and a membrane phase separator which was modified from an original literature design. Physostigmine and its metabolite eseroline were used as model cations. A solid phase extraction procedure using octadecylsilane columns was developed to extract the compounds and neostigmine bromide (internal standard) from human serum. The compounds were chromatographed on a diol column using a 80:20 aqueous phosphate buffer pH 4 absolute methanol mobile phase at a flow rate of 1 mL/min. Methylene chloride was used as the on-line extraction solvent for the DPS ion pairs formed. Fluorescence of the extracted ion pairs was measured using an excitation of 243 nm and an emission cut-off filter at 418 nm. Linearity was in the 2-100 ng/mL and 5-100 ng/mL ranges for physostigmine and eseroline, respectively. Detection limits based on a signal-to-noise ratio of 2, were 2 and 5 ng/mL, respectively. Precision of the method was found to be in the 1.5-3% range and percentage error in the 1.5-7% range for both compounds.

HPLC Post-Column Ion-Pair Extraction of Acidic Drugs Using a Substituted α-Phenylcinnamonitrile Quaternary Ammonium Salt as a New Fluorescent Ion-Pair Reagent

Abstract A reversed-phase HPLC post-column ion-pair extraction system was developed for the analysis of carboxylic acid drugs and their salts using α-(3,4-dimethoxyphenyl)-4′ -trimethylammonium-methylcinnamonitrile methosulfate (DTM) as a new fluorescent ion-pair reagent. The on-line post-column extraction system was optimized with respect to the reagent concentration, extraction coil length and internal diameter, ionic strength of mobile phase, extraction solvent, and the membrane phase separator. Sodium salicylate, ketoprofen, ibuprofen, probenecid, and valproic acid were used as model compounds to evaluate the ion-pair extraction system. The method was applied to pharmaceutical dosage forms containing ketoprofen and valproic acid. Other acidic compounds evaluated using the ion-pair reagent showed that lipophilic acids produced more extractable ion-pairs and higher sensitivities than hydrophilic acids.

Sodium Coumarin 6-Sulfonate, A Fluorometric Ion-Pairing Reagent for Tertiary Amines. Application to the Determination of Chlorpheniramine Maleate

Abstract A study of sodium coumarin 6-sulfonate as a fluorescent ionpair reagent indicated that it could be useful in the analysis of tertiary amines such as chlorpheniramine maleate. The physical properties of the coumarin sulfonate that make it suitable as a fluorescent ion-pair reagent for basic drugs are its high relative quantum yield (0.76) and its acidity (pKa of −7.66). Methylene chloride containing 5% n−pentanol was used to extract the coumarinchlorpheniramine ion-pair from aqueous solution. It was found that a 10−2 M coumarin concentration yielded a 92% recovery of chlorpheniramine at pH 5. Following phase separation, the coumarin species was completely ionized by the addition of tetrabuty1 ammonium hydroxide to the organic phase. After irradiation for 30 min using long wavelength ultraviolet light (365 nm), the fluorescence intensity of the sample was measured using excitation and emission wavelengths of 400 and 540 nm, respectively. Comparison of fluorescence data of spiked aqueous samples to that of a chlorpheniramine maleate standard curve performed concurrently gave drug concentration in the samples. The calibration curve was linear in the 50–1000 ng/ml range (0.13 − 2.6 × 10 −6 M). The procedure allowed the determination of chlorpheniramine maleate with an accuracy of 4–6% and a precision of 2–6% RSD (relative standard deviation). The minimum detectable concentration of drug (S/N = 2) that can be assayed by this method is 50 ng/ml of the maleate salt (35.3 ng/ml of chlorpheniramine free base).

Fluorimetric determination of propantheline in human blood plasma by an ion-pair extraction method

Propantheline bromide, an anticholinergic quaternary ammonium compound, was determined in human blood plasma by an ion-pair extraction method. The extraction and dissociation constants of the ion pairs involved were determined. In the method, the drug is extracted as the perchlorate ion pair to methylene chloride, the extract is purified and the propantheline is quantitatively converted to a fluorescent ion pair with the highly fluorescent anion 9,10-dimethoxyanthracene-2-sulphonate; 10–15 ng of propantheline per ml can be determined with a standard deviation of 0.6 ng ml -1.