Determination of naproxen with flow injection chemiluminescence of Ru(bpy)32+–PbO2 system and its application for the binding study of naproxen to protein

Determination of pholcodine in syrups and human plasma using the chemiluminescence system of tris(1,10 phenanthroline)ruthenium(II) and acidic Ce(IV)

Pholcodine is an opiate derivative drug which is widely used in pediatric medicine. In this study, a chemiluminescence (CL) method is described that determines pholcodine in human plasma and syrup samples. This method is based on the fact that pholcodine can greatly enhance the weak CL emission of reaction between tris(1,10 phenanthroline)ruthenium(II), Ru(phen)₃²⁺ , and acidic Ce(IV). The CL mechanism is described in detail using UV-vis light, fluorescence and CL spectra. Effects of chemical variables were investigated and under optimum conditions, CL intensity was proportional to the pholcodine concentration over the range 4.0 × 10^-8 to 8.0 × 10^-6  mol  L^-1 . The limit of detection (LOD) (S/N = 3) was 2.5 × 10^-8  mol  L^-1 . Percent of relative standard deviations (%RSD) for 3.0 × 10^-7 and 3.0 × 10^-6  mol  L^-1 of pholcodine was 2.9 and 4.0%, respectively. Effects of common ingredients were investigated and the method was applied successfully to the determination of pholcodine in syrup samples and human plasma.

Flow injection chemiluminescence determination of loxoprofen and naproxen with the acidic permanganate-sulfite system

A novel flow injection chemiluminescence (CL) method for the determination of loxoprofen and naproxen was proposed based on the CL system of KMnO₄, and Na₂SO₃ in acid media. The CL intensity of KMnO₄-Na₂SO₃ was greatly enhaneed in the presence of loxoprofen and naproxen. The mechanism of the CL reaction was studied by the kinetic proecss and UV-vis absorption and the conditions were optimized. Under optimized conditions, the CL intensity was linear with loxoprofen and naproxen concentration in the range of 7.0 × 10⁻⁸ – 1.0 × 10⁻⁵ g/mL and 2.0 × 10⁻⁷ – 4.0 × 10⁻⁶ g/mL with the detection limit of 2.0 × 10⁻⁸ g/mL and 3.0 × 10⁻⁸ g/mL (S/N = 3), respectively. Thc relative standard deviations were 2.39% and 1.37% for 5.0 × 10⁻⁷ g/mL naproxen and 5.0 × 10⁻⁷ g/mL loxoprofen (n = 10), respectively. The proposed method was satisfactorily applied to thc determination of loxoprofen and naproxen in pharmaceutical preparations.

Recent applications of flow-injection and sequential-injection analysis techniques to chemiluminescence determination of pharmaceuticals

A review is presented on the state of the art of the chemiluminescence analysis of pharmaceuticals by the two most relevant automated controlled-flow methodologies--flow-injection analysis (FIA) and sequential-injection analysis (SIA). The current chemiluminometric applications of FIA and SIA in pharmaceutical analysis are discussed with special emphasis on the analytical figures of merit and sample matrix characteristics. The review involving 211 references and covering papers published between 2001 and 2006 is divided into several sections according to the fundamental types of chemiluminescence systems employed.

On-line chemical generation of tris(2,2′-bipyridyl)ruthenium(III) and its application in CE with chemiluminescence detection

A novel tris(2,2'-bipyridyl)ruthenium(III) [Ru(bipy)(3) (3+)]-based chemiluminescence (CL) detection in CE using an on-line chemical generation scheme has been demonstrated. Two continuous streams respectively containing solutions of Ru(bipy)(3) (2+) and acidic cerium(IV) used as a homogeneous chemical oxidant are employed to generate Ru(bipy)(3) (3+), which is delivered into the reaction capillary of a coaxial flow interface and then reacted with analytes at the end of the separation capillary to yield light. The important operational parameters for separation and detection are identified and optimized. Four alpha-ketocarboxylic acids used as models, outside of the amine-containing compounds, are successfully separated and detected to evaluate the feasibility of the approach. The excellent resolution and detection sensitivity was achieved by using 50 mmol/L phosphate running buffer (pH 9.5) with 0.7 mmol/L CTAB, and CL reagent solution streams containing 0.15 mmol/L Ru(bipy)(3) (2+) and 0.8 mmol/L cerium(IV) (0.25 mol/L H(2)SO(4)), respectively. The concentration detection limits for alpha-ketocarboxylic acids were below 3.7x10(-8) mol/L (S/N = 3). The proposed method was applied to the determination of alpha-ketocarboxylic acids in five different honey samples with satisfactory results.

Sequential injection affinity chromatography utilizing an albumin immobilized monolithic column to study drug–protein interactions

In this study, sequential injection affinity chromatography was used for drug-protein interactions studies. The analytical system used consisted of a sequential injection analysis (SIA) manifold directly connected with convective interaction media (CIM) monolithic epoxy disks modified by ligand-immobilization of protein. A non-steroidal, anti-inflammatory drug, naproxen (NAP) and bovine serum albumin (BSA) were selected as model drug and protein, respectively. The SIA system was used for sampling, introduction and propulsion of drug towards to the monolithic column. Association equilibrium constants, binding capacity at various temperatures and thermodynamic parameters (free energy DeltaG, enthalpy DeltaH) of the binding reaction of naproxen are calculated by using frontal analysis mathematics. The variation of incubation time and its effect in on-line binding mode was also studied. The results indicated that naproxen had an association equilibrium constant of 2.90 x 10(6)M(-1) at pH 7.4 and 39 degrees C for a single binding site. The associated change in enthalpy (DeltaH) was -27.36 kcal mol(-1) and the change in entropy (DeltaS) was -73 cal mol(-1)K(-1) for a single type of binding sites. The location of the binding region was examined by competitive binding experiments using a biphosphonate drug, alendronate (ALD), as a competitor agent. It was found that the two drugs occupy the same class of binding sites on BSA. All measurements were performed with fluorescence (lambda(ext)=230 nm, lambda(em)=350 nm) and spectrophotometric detection (lambda=280 nm).

Use of Triplet Excited States for the Study of Drug Binding to Human and Bovine Serum Albumins

The triplet excited states of (S)- and (R)-flurbiprofen (FBP) have been used as reporters for the microenvironments experienced within the binding sites of human and bovine serum albumins. Regression analysis of triplet decay provides valuable information on the degree of protection that these excited states are afforded from attack by a second FBP molecule, oxygen, or other reagents. The multiexponential fitting of these decays can be satisfactorily correlated with the distribution of the drug among the two binding sites and its presence as the noncomplexed form in the bulk solution. This assignment has been confirmed by using (S)-ibuprofen or capric acid as selective site II replacement probes. Triplet lifetimes and site occupancy are sensitive to the type of serum albumin employed (human versus bovine). Finally, the binding behaviour of (S)- and (R)-FBP exhibits little stereoselectivity.

Flow injection chemiluminescence determination of naproxen based on KMnO4–Na2SO3 reaction in neutral aqueous medium

A simple, rapid and sensitive flow injection chemiluminescence (CL) method is described for the determination of naproxen. It was found that strong CL signal was generated when naproxen was mixed with KMnO4 and Na2SO3 in neutral aqueous medium. Under the optimum experimental conditions, the CL intensity was linearly related to the concentration of naproxen from 4.0 x 10(-9) to 1.0 x 10(-6)g mL(-1) (r=0.9993). The detection limit was 2 x 10(-9)g mL(-1) naproxen, the relative standard deviation for 1.0 x 10(-7) g mL(-1) naproxen solution was 1.5% (n=11) and the sampling frequency was 120 h(-1). The method was applied to the determination of naproxen in pharmaceutical preparation with satisfactory results. The mechanism of CL reaction was discussed briefly.

Tris(2,2'-bipyridyl)ruthenium(II) chemiluminescence

This paper critically reviews analytical applications of the chemiluminescence from tris(2,2'-bipyridyl)ruthenium(II) and related compounds published in the open literature between mid-1998 and October 2005. Following the introduction, which summarises the reaction chemistry and reagent generation, the review divides into three major sections that focus on: (i) the techniques that utilise this type of detection chemistry, (ii) the range of analytes that can be determined, and (iii) analogues and derivatives of tris(2,2'-bipyridyl)ruthenium(II).