On-Line Flow-Injection Chemiluminescence Determination of Bovine Serum Albumin Using Surfactant-Enhanced Dichlorofluorescein-Hypochlorite System

A flow injection technique combined with a chemiluminescence method was established for the determination of bovine serum albumin (BSA). Strong chemiluminescence was observed when BSA-dichlorofluoresce (DCF) complex was oxidized by sodium hypochlorite (NaClO) in an alkaline medium and in the presence of cetyltrimethylammonium bromide (CTAB). The reaction conditions of the chemiluminescence were carefully optimized. Under the optimal conditions, the method had a linear range of 0.01–20.0 μg/mL, with a detection limit of 0.007 μg/mL for BSA (3σ). The relative standard deviation of 1.0 μg/mL BSA (n = 8) is 1.4%. The method was applied to determine BSA in milk samples and it worked well.     

Rapid Flow-Injection Method for the Determination of Colistin by Sensitized Chemiluminescence Using the Acidic Permanganate–Sulfite System

Abstract

A simple, rapid, and sensitive chemiluminescence method for the determination of colistin (Polymyxin E), a cyclic polypeptide with antibiotic effect produced by certain strains of Bacillus polymyxa, has been developed by combining a flow-injection technique and the bacteria's sensitizing effect on the chemiluminescence reaction between sulfite and acidic permanganate. The optimum conditions for chemiluminescence emission were established. The chemiluminescence was proportional to the log of concentration of colistin over the range 4–100 µg mL^?1 (3.5–87 µM). The detection limit was 1.2 µg mL^?1 (1.0 µM) of colistin. The method has been satisfactorily used for the determination of colistin in pharmaceuticals.     

Determination of Sugars by LC with On-Line Electrogenerated Cu(HIO6)2]5−–Luminol Chemiluminescence Detection

A novel method was developed for the determination of sugars such as glucose, fructose and lactose by column liquid chromatography coupled with chemiluminescence detection. The LC separation used a Kromasil NH₂ column (250 × 4.6 mm, i.d.: 5 μm, pore size, 100 Å) with a mobile phase consisting of acetonitrile and water. The chemiluminescence detection was based on the enhancement effect of the selected sugars on the chemiluminescence intensity between luminol and [Cu(HIO₆)₂]^5?, which was on-line electrogenerated by constant current electrolysis. The limits of detection for determination of glucose, fructose and lactose were 4, 3 and 20 μg mL^?1, respectively. The proposed method has been successfully applied to the determination of glucose and fructose in grape samples and lactose in milk samples.     

Selective determination of amino acids using flow injection analysis coupled with chemiluminescence detection

The determination of the amino acids proline, histidine, tyrosine, arginine, phenylalanine and tryptophan using flow injection analysis (FIA) with chemiluminescence detection is described. Proline was the only amino acid to exhibit chemiluminescence with the tris(2,2-bipyridyl)ruthenium(III) reaction at pH 10. While, histidine was found to selectively enhance the reaction of luminol with Mn(II) salts in a basic medium. Acidic potassium permanganate chemiluminescence was able to selectively determine tyrosine at pH 6.75. Low pressure separations using a C18 guard column allowed the simultaneous determination of tyrosine and tryptophan or phenylalanine and tryptophan with acidic potassium permanganate and copper(II)-amino acid-hydrogen peroxide chemiluminescence, respectively. Precision for each method was less than 3.9% (R.S.D.) for five replicates of a standard (1×10⁻⁵ M) and the detection limits ranged between 4×10⁻⁹ and 7×10⁻⁶ M. Preliminary investigations revealed that the methodology developed was able to selectively determine the individual amino acids in an equimolar mixture of the 20 naturally occurring amino acids.     

Chemiluminescence determination of indole derivatives in human body fluids and soil by flow injection analysis using potassium permanganate

A simple, sensitive and rapid flow-injection chemiluminescence (CL) method has been developed for the determination of indole derivatives including indole-2,3-dione (isatin) and indole-3-acetic acid (IAA), based on the increased CL reaction of potassium permanganate-formaldehyde system in acidic medium. Strong CL was observed when the indole derivatives were injected into the acidic potassium permanganate solution in a flow-cell. Under the optimum conditions, the linear range of the determination was 0.1–100.0 µM for isatin and 0.01–10.0 µM for IAA. The detection limit (3σ) was 10.0 nM for isatin and 1.0 nM for IAA. The method has been successfully applied to the determination of isatin in biological samples and of IAA in biological samples and soil extracts with satisfactory results.     

Flow Injection Chemiluminescence Determination of Phenol in Neutral Medium

A new flow injection chemiluminescence method for the determination of phenol was proposed, based upon the chemiluminescence reaction of phenol, N-bromosuccinimide, and hydrogen peroxide in neutral aqueous medium in the presence of cetyltrimethylammonium bromide surfactant micelles. The chemiluminescence signal was proportional to the concentration of phenol in the range of 1.0 × 10^?7?8.0 × 10^?6 g/mL with a detection limit of 3 × 10^?8 g/mL. The relative standard deviation for 1.0 × 10^?6 g/mL phenol solution was 2.0% (n = 11). The proposed method was successfully applied to the determination of phenol in phenol ear drops. A possible CL reaction mechanism was also discussed briefly.     

Amperometric sensor based on carbon nanotubes and electropolymerized vanillic acid for simultaneous determination of ascorbic acid,dopamine, and uric acid

This paper describes the development of a simple and efficient nanostructured platform based on multi-walled carbon nanotubes (MWCNT) functionalized with an in situ generated vanillic acid (VA) polymer. It was used as an analytical sensor for the simultaneous determination of ascorbic acid (AA), dopamine (DA), and uric acid (UA). The electropolymerization process of VA, performed on MWCNT-modified glassy carbon electrode, produces three redox systems based on quinone/hydroquinone functionality, as observed by cyclic voltammetry. The amperometric sensor has as figures of merit for the simultaneous determination of AA, DA, and UA the following values: for AA, a linear range of 5–120 μM and detection limit of 3.5 μM; for DA, a linear range of 5–120 μM and detection limit of 4.5 μM; and for UA, a linear range of 5–120 μM and a detection limit of 1.5 μM. From the obtained performance, the development of the platform based on MWCNT/poly-VA is justified for the simultaneous determination of AA, DA, and UA.     

Flow Injection Chemiluminescence Determination of Difenidol Hydrochloride Using N-Chlorosuccinimide-Dichlorofluorescein Reaction

Abstract

A flow injection method combined with chemiluminescence detection was described for the determination of difenidol hydrochloride. Strong chemiluminescence was recorded when difenidol hydrochloride was added into the reaction mixture of N-chlorosuccinimide with dichlorofluorescein in alkaline medium. The experimental conditions that affected the chemiluminescence signal, including the concentrations of reactants, the reaction medium, and the instrumental parameters, were carefully optimized. Under the optimum experimental conditions, the enhanced chemiluminescence intensity was linear related to the concentration of difenidol hydrochloride in the range of 4.0 × 10^?9 to 4.0 × 10^?7 g/ml. The detection limit for difenidol hydrochloride was 7 × 10^?10 g/ml, and the sample throughput was 90/h. The relative standard deviation was 2.5% for 5.0 × 10^?8 g/ml difenidol hydrochloride solution (n = 11). The interference of common inorganic ions, excipients, and additives used in pharmaceutical preparation was studied, which showed the method has higher tolerance limit for these substances and has good selectivity. As a preliminary application, the method was applied to the determination of difenidol hydrochloride in tablets, and the satisfactory results were achieved.     

Influence of Zone Stacking Sequences on CL Intensity and Determination of Histidine in Sequential Injection Analysis

Abstract

A sequential injection method coupled to chemiluminescence detection was described for the determination of trace amount of histidine. The physical and chemical parameters depicting the system were studied to obtain optimum conditions. It was found that physical dispersion caused by the change of zone stacking sequence was significant factor influencing CL intensity for a rapid CL reaction. At optimized conditions, histidine can be determined in the linear range from 5.0 × 10^?7to 1.0 × 10^?3 M with a detection limit (3σ) of 2 × 10^?7 M for 60 µl sample. The relative standard deviation (RSD) for eleven repeated measurements of 4 × 10^?5 M histidine was 0.97%, and the sampling frequency was 80 h^?1, and the recoveries were varied from 90.0 to 103.3%. The proposed method has been successfully applied to the determination of histidine in beer samples.     

Silver nanoparticle-based chemiluminescence enhancement for the determination of norfloxacin

A chemiluminescence (CL) method is presented for the flow injection determination of norfloxacin (NFLX). It is based on the fact that the weak CL of the Ce(IV)-Na₂SO₃ redox system is strongly enhanced in the presence of silver nanoparticles. UV-visible and fluorescence spectroscopy was carried out and showed that the energy of the intermediate SO₂*, originating from the reaction of Ce(IV) with Na₂SO₃, was transferred to Tb³⁺ via NFLX, and that the silver nanoparticles (AgNPs) accelerate the process due to the electric activity of AgNPs. Norfloxacin was detected by measuring the CL intensity which increases linearly with the concentration of NFLX in the range from 10 nM to 50 μM. The detection limit is lowered to 2.0 nM. The method was successfully applied to the determination of NFLX in eyedrops.     

Incorporation of graphene oxide–NiO nanocomposite and <Emphasis Type="Italic">n</Emphasis>-hexyl-3-methylimidazolium hexafluoro phosphate into carbon paste electrode: application as an electrochemical sensor for simultaneous determination of benserazide,levodopa and tryptophan

The benserazide (BZ) and levodopa (LD) are two important catechol drugs to inhibit dopamine production outside the brain. On the other hand, BZ is effective on tryptophan (Trp) metabolism as an inhibitor aromatic amino acid decarboxylase. A voltammetric sensor based on carbon paste electrodes modified with graphene oxide–NiO nanocomposite and n-hexyl-3-methylimidazolium hexafluoro phosphate (n-H-3MIHF) as a binder is proposed to detect and quantify of BZ, LD and Trp in drug and urine samples. In square-wave voltammetry technique, BZ, LD and Trp were given sensitive oxidation peaks at 156, 312 and 740 mV, respectively. At a best electrochemical conditions, the enhanced oxidation peak currents represented the excellent analytical performance of simultaneous detection of BZ, LD and Trp in the ranges of 0.1–600, 0.1–700 and 5.0–700 μM, with a low limit of detection of 0.05 μM for BZ, 0.05 for LD and 1.0 μM for Trp (S/N = 3), respectively. To further validate its possible application, the proposed sensor was successfully used for the determination of above compounds in tablet and urine with satisfactory results.     

Determination of tin in marine sediments by slurry sampling atomic absorption spectrometry with electrothermal atomization using a permanent modifier

A molecularly imprinted polymer (MIP) was synthesized by the precipitation polymerization method using triazophos (TAP) as the template. The MIP can selectively absorb TAP from sample solutions. The absorbed TAP strongly enhances the chemiluminescence (CL) of luminol-H₂O₂. This was applied to design a method for the on-line enrichment and detection of TAP. The change in CL intensity is linearly proportional to the concentration of TAP in the range from 1.0 μM to ~4.0 nM, and the detection limit is 2.5 nM (at an S/N of 3σ). This is about one order of magnitude lower than that of the conventional CL assay. The method was successfully applied to the determination of TAP in vegetable samples.     

Selective determination of L-dopa in the presence of ascorbic acid and uric acid using a 3D graphene foam

Three-dimensional interconnected network graphene foam (GF) was synthesized by chemical vapor deposition. The GF was transferred onto indium tin oxide glass, acting as an electrode for the selective determination of L-dopa in the presence of ascorbic and uric acid. Using differential pulse voltammetry (DPV) method, the oxidation peak current is well linear with L-dopa concentration in the range of 0.05–1 μM with a sensitivity of 2.64 μA μM^?1 and in the range of 1–40 μM with a sensitivity of 1.82 μA μM^?1. The detection limit of this electrode for L-dopa is about 20 nM. The proposed electrode can also effectively avoid the interference of ascorbic acid and uric acid, making the proposed sensor suitable for the accurate determination of L-dopa in human urine fluids. This electrode will have a wide range of potential application prospect in electrochemical detection.     

Flavin mononucleotide chemiluminescence in cationic micellar media for determination of chromium(III + VI) by flow injection

The flavin mononucleotide chemiluminescence system, originally developed for the determination of copper(II), is modified with cationic surfactant micelles for the determination of chromium(III + VI). In order for chromium to be detected predominantly, the copper-induced luminescent reaction is significantly suppressed by virtue of the cationic micellar effect. The limit of detection (signal-to-noise ratio = 2) is 5 × 10^?8 M chromium (50-μl sample injection).     

Improving continuous chemiluminescence determination method of formaldehyde in the atmosphere: reducing interference of acetaldehyde and others by using iodoform reaction

ABSTRACT

The continuous and selective determination method of formaldehyde (HCHO) in ambient air using chemiluminescence method has been developed. The counter current flow tube was used to collect gaseous formaldehyde. The major interferences of HCHO determination from acetaldehyde, ethanol, and ferrous ion were removed by applying iodoform reaction. Effect of acetaldehyde on chemiluminescence signal of formaldehyde at the same concentration was reduced from 19 to 0.3% by applying iodoform reaction. Subsequently, HCHO was online detected by measuring chemiluminescence produced from the reaction of HCHO, gallic acid, H₂O_2, and KOH. The limit of detection (S/N = 3) was 4.5 ppbv in air. The calibration graph was linear up to 6.25 ppmv. HCHO concentration measured by the present method showed good agreement with that obtained by the 2–4 DNPH-HPLC method.     

A Chemiluminescence Microarray Based on Catalysis by CeO2 Nanoparticles and Its Application to Determine the Rate of Removal of Hydrogen Peroxide by Human Erythrocytes

In this work, cerium oxide nanoparticles are capable of strongly enhancing the chemiluminescence (CL) of the luminol–hydrogen peroxide (H₂O₂) system. Based on this, a microarray CL method for the determination of the removal rate constant of H₂O₂ by human erythrocytes has been developed. It is providing direct evidence for a H₂O₂-removing enzyme in human erythrocytes that acts as the predominant catalyst. A reaction mechanism is discussed. The proposed microarray CL method is sensitive, selective, simple and time-saving, and has good reproducibility and high throughput. Relative CL intensity is linearly related to the concentration of H₂O₂ in the range from 0.01 to 50 μM. The limit of detection is as low as 6.5?×?10^?11 M (3σ), and the relative standard deviation is 2. 1 % at 1 μM levels of H₂O₂ (for n?=?11).     

Electrochemiluminescence detection system for microchip capillary electrophoresis and its application to pharmaceutical analysis

We describe an efficient and easily fabricated electrochemiluminescence detection system for microchip capillary electrophoresis. A 300-μm-diameter platinum disc working electrode was embedded in a titanium tube which provides an adequate holding for working electrode and acts as counter electrode. We also have designed a simplified detection cell with a guide channel for the electrode. The integrated working-counter electrode can be easily aligned to the outlet of the separation channel through the guide channel. The functionality of the system was demonstrated by separation and detection of proline and tripropylamine. The response to proline is linear in the range from 5 μM to 5,000 μM, and the detection limit is 1.0 μM (S/N?=?3). The system was further applied to the determination of chlorpromazine hydrochloride in pharmaceutical formulations. The system is believed to have potential applications in pharmaceutical analysis.

Platinum nanoparticles–decorated graphene-modified glassy carbon electrode toward the electrochemical determination of ascorbic acid,dopamine, and paracetamol

In the present study, we report the synthesis and characterization of platinum nanoparticles decorated graphene (GPtNPs) nanocomposite toward the electrochemical determination of ascorbic acid (AA), dopamine (DA), and paracetamol (PCT). GPtNPs demonstrated synergistic catalytic activity with enhanced currents in all of the measurements when compared with graphene-modified glassy carbon electrode (G-GCE) and bare GCE. The nanocomposite exhibited low overpotential for AA oxidation and good peak-to-peak separation of 218.0, 218.0, and 436.0 mV for AA–DA, DA–PCT, and AA–PCT, respectively. Cyclic voltammetry (CV) and chronoamperometry (CA) determination of AA, DA, and PCT showed wide linearity ranges. CV determination of AA exhibited linearity range from 300 μM to 20.89 mM and from 22.02 to 39.87 mM. DA determination using CV exhibited linearity range from 5 to 104 μM and from 114 to 684 μM, whereas CA determination of PCT showed a linearity range from 20 μM to 6.43 mM. Differential pulse voltammetry determinations of AA, DA, and PCT exhibited low detection limits of 300, 5, and 5 μM, respectively.     

Zeolite-Modified Carbon-Paste Electrode as a Selective Voltammetric Sensor for Detection of Tryptophan in Pharmaceutical Preparations

Abstract

Several synthetic zeolites such as mazzite, mordenite, zeolite L, zeolite beta, and MCM-41 were tested as electrode modifiers in voltammetric determination of tryptophan. It was found that addition of zeolite beta to the carbon paste would generate the peak current of Trp because of its catalytic effect. The anodic peak currents were proportional to Trp concentrations in the range of 5.0 × 10^?7 to 5.0 × 10^?3 M. The detection limit was 1.0 × 10^?7 M. The influence of several species, especially other amino acids, were tested. The proposed method was applied successfully to the determination of tryptophan in pharmaceutical formulations.     

Amperometric Determination of Cholesterol-Reducing Drug,Ezetimibe, Using Glassy Carbon Electrode Modified with Multiwalled Carbon Nanotubes and Sodium Dodecylsulfate

A simple and sensitive electrochemical method is described for the determination of the cholesterol-reducing drug ezetimibe in aqueous solution. A glassy carbon electrode, modified with multiwalled carbon nanotubes and sodium dodecylsulphate was used as the working electrode. Ezetimibe yields a well-defined anodic peak at the surface of the electrode in an aqueous solution of pH 13. A linear amperometric calibration curve was obtained in the range of 1.2–78 μM (0.5–32.0 μg/mL) of ezetimibe, with a sensitivity of 88.6 nA/μM and a detection limit of 300 nM (0.12 μg/mL). The sensor was applied successfully to the determination of ezetimibe in pharmaceutical preparations.