Flow-injection determination of iron(II), iron(III) and total iron with chemiluminescence detection

Iron(II) (1.0 × 10^?9–1.0 × 10^?6 M) is determined by the production of chemiluminescence in a luminol system in the absence of added oxidant. Iron(III) (2.0 × 10.8^?8–2.0 × 10^?6 M) is determined after reduction to iron(II) in a silver reductor mini-column in the flow system. Cobalt, chromium, copper and manganese interfere.     

A chemiluminescence photometer for trace chromium(III) determinations

The design of a simple chemiluminescence photometer is described. The sample is injected into a spectrophotometric cell containing the reagents, and the resultant chemiluminescence peak is recorded along with the peak height and peak area. The instrument includes a temperature-controlled cell holder with stirring capabilities. The determination of p.p.b. levels of chromium(III) is described. Chromium(III) enhances the chemiluminescence reaction of luminol and hydrogen peroxide in basic solutions. Useful calibration curves are obtained from 4 · 10^-9 to 10^-4 M Cr(III); 5 · 10^-10 M is the detection limit. Chromium(III) is determined in natural water samples and NBS Orchard leaves.     

Determination of tetracycline by flow injection with chemiluminescence detection

Tetracycline hydrochloride (4 × 10^?5?1 × 10^?3M) in a 40-μl aqueous sample is determined in a flow system by measurement of the chemiluminescence emitted on reaction with bromine (9.3 × 10^?3 M) at pH 10.4 (carbonate buffer). The limit of detection is 1.6 nmol per 40-μl injection.     

Electrogenerated Chemiluminescence Determination of Dopamine and Epinephrine in the Presence of Ascorbic Acid at Carbon Nanotube/Nafion‐Ru(bpy)$\rm{ {_{3}^{2+}}}$ Composite Film Modified Glassy Carbon Electrode

Based on the inhibition effect of dopamine and epinephrine on Ru(bpy) ‐tripropylamine electrogenerated chemiluminescence system, the excellent properties of carbon nanotube, and the cation permselectivity of Nafion film, an electrogenerated chemiluminescence inhibition method for determination of dopamine and epinephrine in the presence of ascorbic acid at carbon nanotube/Nafion‐Ru(bpy) composite film modified glassy carbon electrode was described. The results showed that the proposed method was sensitive and selective for the determination of dopamine and epinephine. The linear calibration range was from 1.6×10^?9 M to 3.2×10^?5 M and 5×10^?8 M to 6×10^?5 M for dopamine and epinephrine, respectively. 200‐fold excess of ascorbic acid did not interfere with the determination of 1 μM dopamine and epinephrine.     

Screening of chemiluminescent systems for the determination of some biologically important organic compounds

Screening tests are described for the development of chemiluminescence systems (oxidizing systems) capable of detecting biological organic compounds. The light emission depends strongly on the oxidizing systems employed. Acidic permanganate system gives rise to light emission for many compounds, including catechols, catecholamines, triphenols and indoles. The following oxidizing systems led specifically to chemiluminescence for hydroquinone, adrenaline or phenylpyruvic acid: 10^?1 M thiosulphate with 10^?1 M sodium hydroxide and 10^?4 M Ag (I), 0.3 % hydrogen peroxide with 10^?3 M sodium hydroxide/50% acetonitrile and 10^?4 M Fe (II), and 0.3% hydrogen peroxide with 10^?2 M sodium hydroxide/10^?2 M didodecyldimethylammonium bromide and 10^?4 M Co(II), respectively.     

Liquid—liquid extraction and determination of uranium(IV) with 2,6-diacetylpyridine bis(benzoylhydrazone)

2,6-Diacetylpyridine bis(benzoylhydrazone) (H₂DPBH) is proposed as a ligand for the extraction of uranium(VI). Complete extraction from aqueous solutions into dichloromethane is achieved with a ligand/metal mole ratio of < for 10^?5?10^?4 M uranyl ion. Potentiometric measurements indicate that the extracted species is UO₂ (DPBH). Uranium can be determined in the extract by spectrophotometric measurements at 420 nm and by differentail pulse polarography (E_p = ?0.67 V) with tetraethylammonium bromide as supporting electrolyte. For both methods, the detection limit is about 2 × 10^?6 M in the extract.     

Dioctadecyldimethylammonium Chloride Bilayer Membrane Vesicle-Enhanced and Manganese (II)-Catalyzed Chemiluminescence for Determination of Adrenaline by a Flow-Injection Method

Abstract

A new chemiluminescence system reinforced by use of a surfactant and a metal catalyst is demonstrated for selective determination of adrenaline by a flow-injection method. The weak light emission originating from an aerobic oxidation of adrenaline in an alkaline solution is dramatically enhanced by ordered surfactant molecular assemblies, dioctadecyldimethylammonium chloride bilayer membrane vesicles, with the largest enhancement factor of 1000 which has not ever been realized. The enhanced emission is further increased by a Mn(II) catalyst with an enhancement factor of ca. 40. The limit of determination(S/N=2) is 1×10^?8M (0.2 ng in 100-μ1 injection), the linear range is four ordrers of magnitude, the sample throughput is 100 h^?1. and the relative standard deviation(n=5) is 0.9 % for 5×10^?7M adrenaline. Of other substances including dopamine, noradrenaline, and related compounds, p-hydroxymandelenic acid chemiluminesces most strongly after adrenaline, the 1×10^?3M solution providing a signal 24% of that for 1×10^?6M adrenaline.     

Differential preconcentration of arsenic(III) and arsenic(V) with thionalide loaded on silica gel

2-Mercapto-N-2-naphtylacetamide (thionalide) on silica gel is used for differential preconcentration of μg l^?1 levels of arsenic(III) and arsenic(V) from aqueous solution. In batch experiments, arsenic(III) was quantitatively retained on the gel from solutions of pH 6.5–8.5, but arsenic(V) and organic arsenic compounds were not retained. The chelating capacity of the gel was 5.6 μmol g^?1 As(III) at pH 7.0. Arsenic retained on teh column was completely eluted with 25 ml of 0.01 M sodium borate in 0.01 M sodium hydroxide containing 10 mg l^?1 iodine (pH 10). The arsenic was determined by silver diethyldithiocarbamate spectrophotometry. Arsenic(V) was subsequently determined after reduction to arsenic(III) with sulphite and iodide. Arsenic(III) and arsenic(V) in sea water are shown to be < 0.12 and 1.6 μg l^?1, respectively.     

Chemiluminescence Sensor with Mn(III)-Tetrakis (4-sulfonatophenyl)-porphyrin Immobilized on Dioctadecyldimethylammonium Chloride Bilayer Membranes Incorporated Into PVC Film

Abstract

An indicator phase for a flow-through chemiluminescence (CL) sensor composed of ordered surfactant assemblies, a polymer and a catalyst was evaluated by measuring adrenaline. The method is based on use of Mn (III)-porphyrin immobilized on a bilayer membrane contained in a blended film, prepared by incorporating dioctadecyl-dimethylammonium chloride into polyvinyl chloride. The sensor consisted of a Pyrex glass tube (30 mm × 5 mm i.d.) packed with silica glass wool, on which the indicator phase was coated, and a photomultiplier tube. The blend film functioned as a favorable reaction medium for the adrenaline CL, and further enhanced CL was observed with the immobilized catalyst. This indicator phase permitted adrenaline to be detected down to 3 × 10^?6 M with a 20 μl injection into a 0.3 M NaOH carrier solution. The relative standard deviation (n = 10) was 1.0% for 5 × 10^?5 M adrenaline. For 80 successive injections of 5 × 10^?5 M adrenaline, the variation of the CL signal was within the relative standard deviation. Almost the same sensitivity and precision were observed with the indicator phase stored in water for at least 3 days. The sensor was successfully applied to determine adrenaline in drug samples.     

Absolute rate constants for the reaction of O(3P) aroms with n-butane and NO(M  Ar) over the temperature range 298–439 K

Absolute rate constants for the reaction of O(³P) atoms with n-butane (k₂) and NO(M  Ar)(k₃) have been determined over the temperature range 298–439 K using a flash photolysis-NO₂ chemiluminescence technique. The Arrhenius expressions obtained were k₂ = 2.5 × 10^?11exp[-(4170 ± 300)/RT] cm³ molecule^?1 s^?1, k₃ = 1.46 × 10^?32 exp[940 ± 200)/ RT] cm⁶ molecule^?2 s^?1, with rate constants at room temperature of k₂ = (2.2 ± 0.4) × 10^?14 cm³ molecule^?1 s^?1 and k₃ = (7.04 ± 0.70)×10^?32 cm⁶ molecule^?2 s^?1. These rate constants are compared and discussed with literature values.     

A Chemiluminescence Reaction Between Hydroxyl Radical and Rhodamine 6G and its Applications

Abstract

A novel chemiluminescence (CL) reaction between hydroxyl radical and ascorbic acid is described in this paper. Hydroxyl radical generated on line by the reaction between Fe³⁺ solution and H₂O₂ solution in HCl medium could oxidize rhodamine 6G to produce weak chemiluminescence. It was found that ascorbic acid could enhance the chemiluminescence and the excited rhodamine 6G was the emitter of the chemiluminescence reaction. The possible mechanism of the CL system was also discussed. Ascorbic acid can be determined in the range of 2.0×10^?6?8.0×10^?4 mg/ml with a detection limit of 1×10^?6 mg/ml (3σ). A complete analysis could be done in 1 minute with the relative standard deviation of 3.1% for 5.0×10^?5 mg/ml (n=11). In order to study the chemiluminescence reaction further, the application to the determination of ascorbic acid in food using the chemiluminescence reaction combined with flow injection is investigated.     

Absolute Rate Constants for the Addition of Cyanomethyl (·CH2CN) and (tert-Butoxy)carbonylmethyl (·CH2CO2C(CH3)3) radicals to alkenes in solution

Absolute rate constants and their temperature dependence were determined by time-resolved electron spin resonance for the addition of the radicals ·CH₂CN and ·CH₂CO₂C(CH₃)₃ to a variety of mono- and 1,1-disubstituted and to selected 1,2- and trisubstituted alkenes in acetonitrile solution. To alkenes CH₂?CXY, ·CH₂CN adds at the unsubstituted C-atom with rate constants ranging from 3.3·10³ M ^?1S ^?1 (ethene) to 2.4·10⁶ M ^?1S ^?1 (1,1-diphenylethene) at 278 K, and the frequency factors are in the narrow range of log (A/M ^?1S ^?1) = 8.7 ± 0.3. ·CH₂CO₂C(CH₃)₃ shows a very similar reactivity with rate constants at 296 K ranging from 1.1·10⁴ M ^?1S ^?1 (ethene) to 10⁷ M ^?1S ^?1 (1,1-diphenylethene) and frequency factors log (A/M ^?1S ^?1) = 8.4 ± 0.1. For both radicals, the rate constants and the activation energies for addition to CH₂?CXY correlate well with the overall reaction enthalpy. In contrast to the expectation of an electro- or ambiphilic behavior, polar alkene-substituent effects are not clearly expressed, but some deviations from the enthalpy correlations point to a weak electrophilicity of the radicals. The rate constants for the addition to 1,2- and to trisubstituted alkenes reveal additional steric substituent effects. Self-termination rate data for the title radicals and spectral properties of their adducts to the alkenes are also given.     

Flow constant-current stripping analysis for antimony(III) and antimony(V) with gold fibre working electrodes : Application to Natural Waters

Antimony(III) is determined by means of electrolysis at ?0.40 V vs. Ag/AgCl on a gold-coated gold fibre electrode for 0.5–10 min in a redox buffer containing 0.01 M iron(II) in 0.10 M hydrochloric acid, and subsequent stripping with a constant current of 0.50μA either in 2 M hydrochloric acid or in 4 M hydrochloric acid/4 M calcium chloride. Antimony(V) is determined by the same procedure in 4 M hydrochloric acid medium. Bismuth(III) is masked by the addition of iodide to the sample prior to electrolysis. Antimony(III) and antimony(V) are determined by standard addition methods; the whole procedure including digital and graphical evaluation of the results is fully automated. The antimony(V) concentrations in the river water reference sample SLRS-1 and the seawater reference sample NASS-1 were found to be 0.63 and 0.31 μg l^?1 with standard deviations of 0.046 and 0.051 μg l^?1, respectively (n=15). The certified value for SLRS- 1 is 0.63±0.05 μg l^?1; no certified value is available for NASS-1.     

Characterization of Anilinepentacyanoferrate (II) and (III)

The anilinepentacyanoferrate (II) complex has been characterized in aqueous solution. The complex exhibits a predominant ligand field transition at λ_max = 415 nm with ?_max = 494 M^?1 cm^?1. The corresponding Fe(III) complex displays a strong absorption at λ_max = 700nm(?_max = 1.61×10⁴ M^?1 sec^?1) which can be assigned as a ligand to metal charge transfer transition. The rate constants of formation and dissociation for the Fc(II) complex are (3.14±0.18)×10² M^?1W^?1 and 0.985±0.005 sec^?1, respectively, at μ = 0.10 M LiClO₄, pH = 8 and T = 25°C. The cyclic voltammetry of the complex shows that a reversible redox process is observed with E_1/2 value of 0.51±0.01 V vs. NHE at μ = 0.10 M LiClO₄, pH = 8 and T = 25°C. The kinetic study of the oxidation of the Fe(II) complex by ferricyanide ion yielded the rate constant of the reaction k_et = (1.43±0.04)x10 M sec^?1 at μ = 0.10 M LiClO₄, pH = 8 and T = 25°C.     

Chemiluminescence Determination of Gossypol by Oxidation with N‐Bromosuccinimide

A chemiluminescence (CL) phenomenon was observed when gossypol was injected into a reaction mixture of N‐bromosuccinimide (NBS) and alkaline dichlorofluorescein (DCF). Based on this phenomenon, a rapid and sensitive method for the determination of gossypol was established. Under the optimum conditions, the linear range was from 1.0 × 10^?9 to 1.0 × 10^?6 M. The detection limit was 1.0 × 10^?10 M. The method has been applied to the determination of gossypol in cottonseed, cottonseed oil, pharmaceutical and biological fluids with satisfactory results. The possible CL reaction mechanism was discussed briefly.     

Peroxyoxalate chemiluminescence of 1,4-dihydroxy-3-methyl-thioxanthone and quenching effect of β-cyclodextrin

The chemiluminescence generated from the reaction of bis(2,4,6-trichlorophenyl) oxalate (TCPO), hydrogen peroxide and 1,4-dihydroxy-3-methyl-thioxanthone (DMT) was investigated. Effects of reacting components, solvent and concentrations of TCPO, sodium salicylate, hydrogen peroxide and DMT were studied and their optimal values were determined. In addition, the influences of β-Cyclodextrin (β-CD) on the peroxyoxalate chemiluminescence (PO-CL) system of DMT were examined at optimized condition. The results showed that the presence of β-CD causes both enhancing and quenching effects on PO-CL system of DMT based upon its concentration. The Stern–Volmer quenching constant (K _q) was evaluated as 2.32?×?10⁴?M^?1 (R ^2?= 0.991) by creating a linear regression plot on experimentally obtained data. This study resulted in satisfactorily determination of β-CD in the range 5.0?×?10^?6 to 1.0?×?10^?4?M.     

Indirect Pyrophosphate Determination by Atomic Absorption Using Copper(II) Ions and A Liquid Ion Exchanger

Abstract

Pyrophosphate (5 × 10^?6 M to 5 × 10^?6 M in the final aqueous solution) may be determined in the presence of similar concentrations of phosphate, other condensed phosphates, or some other anions, by measurement of its inhibitory effect on the extraction of copper(II) by Amberlite LA-1 into MIBK or ethyl acetate. The copper extracted is determined by atomic absorption spectrophotometry.     

Peroxide optrode based on micellar-mediated chemiluminescence reaction of luminol

Cetyltrimethylammonium bromide (CTAB) was used to overcome the pH mismatch of the luminol (5-amino-2,3-dihydrophthalazine-1,4-dione ) chemiluminescence reaction when coupled to the glucose/glucose oxidase reaction at neutral pH. The results demonstrate the feasibility of conducting both reactions simultaneously and efficiently at pH 7.5–8.5. The incorporation of the CTAB micellar system in the coupled luminol/enzymatic reaction allows quantification of glucose in the 3 × 10^?7?3 × 10^?4 M range. The relative standard deviation (RSD) for 5 replicates of 5 × 10^?5 M glucose was 3.8%. Also, hydrogen peroxide was quantified in the 1.2 × 10^?4?2.4 × 10^?8 M range with RSD 2.6%. The micellar-mediated luminol reaction was applied successfully to the determination of glucose in blood serum. Excellent agreement with reported results by standard assays was obtained.     

Determination of trace amounts of chromium (VI) by flow injection analysis with chemiluminescence detection

A new sensitive chemiluminescence (CL) method combined with continuous flow injection analysis is described for the determination of Cr(VI). Strong CL signals were generated by Cr(VI)-catalysed oxidation of gallic acid in the presence of potassium permanganate and hydrogen peroxide. Effects of reagent concentrations, temperature, pH, flow rates, mixing coil length and mixing flow sequences on the chemiluminescence intensity were studied. Under the optimised experimental conditions, the relationship between the logarithm of concentration (log?C) of Cr(VI) and the logarithm of intensity (log?I) is linear over the range of 2?×?10^?11 – 5?×?10^?4?mol?L^?1, with the detection limit (3σ) of 4?×?10^?12?mol?L^?1. Relative standard deviation of ten measurements of 1?×?10^?9?mol?L^?1 Cr(VI) is 1.7%. This flow injection analysis (FIA) system proved to be able to analyse up to 40 samples h^?1. Effects of various interferences possibly present in the water samples were investigated. Most cations and anions, as well as organic compounds, did not interfere with the determination of Cr(VI) in water samples. The experimental results obtained for chromium in reference materials were also in good agreement with the certified values.     

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.