Chemiluminometric determination of carvedilol in a multi-pumping flow system

In this work a simple, fast, sensitive and selective flow-based procedure for the chemiluminometric determination of carvedilol, a recent non-cardioselective β-blocker with noteworthy antioxidant activity, is proposed. The developed methodology takes advantage of the antioxidant capacity of carvedilol to inhibit the chemiluminescence response resulting from the oxidation of luminol by hypochlorite, by acting as a hypochlorite scavenger. The analytical process was implemented in a multi-pumping flow system that employs multiple solenoid actuated micro-pumps as the only active components. These acted as solution insertion, propelling and commuting units assuring an easily controlled, low cost, compact and reliable analytical system.A linear working range for carvedilol concentrations ranging from 1.2 × 10⁻⁷ to 3.0 × 10⁻⁶ mol l⁻¹ (r > 0.999, n = 6), was obtained, with a detection limit of 8.7 × 10⁻⁹ mol l⁻¹. The system handles about 65 samples per hour yielding precise results (R.S.D. < 1.3%, n = 10). Recoveries within 95 and 104% were obtained.     

Linear and cyclic N-acetyl-α-aryl-glycines: Synthesis and chemiluminescence studies

Summary A series of N-acetyl--arylglycines (IIa,IIb) was prepared by acid-induced electrophilic -amidoalkylation reactions; compounds of typeIIb were transformed into the corresponding 3-acetylaminobenzo[b]furan-2(3H)ones (III) by treatment with acetic anhydride. It was found that most of these new compounds (lactones as well as open chain derivatives) undergo base induced oxidation in the presence of oxygen with the emission of visible light. Preliminary structure-activity relationships for these novel chemiluminescence class are proposed.

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Lineare und cyclische N-Acetyl--aryl-glycine: Synthese und Chemilumineszenz-Untersuchungen

Zusammenfassung Eine Reihe von N-Acetyl--arylglycinen (IIa,IIb) konnte durch sauer induzierte elektrophile -Amidoalkylierung hergestellt werden; die Behandlung von Verbindungen des TypsIIb mit Acetanhydrid führte zu den entsprechenden 3-Acetylaminobenzo[b]furan-2(3H)onen (III). Es zeigt sich, daß die Mehrzahl dieser neuen Verbindungen (sowohl Lactone als auch offenkettige Derivate) bei basisch induzierter Oxidation mit (Luft-)Sauerstoff sichtbares Licht emittieren. Erste Struktur-Aktivitäts-Beziehungen für diese neue chemilumineszenzierende Klasse werden vorgeschlagen.

     

Effect of nicotine on the chemiluminescence of lucigenin in model membrane structures

The chemiluminescence of the classical lucigenin light reaction is adversely affected by nicotine in didodecyldimethylammonium bromide bilayer lamelar aggregates. The ratio of chemiluminescence quantum yields in the oriented medium, with and without nicotine, is equal to e^{–0.571[Nicotine]} whereas in the homogenous medium, the same ratio is equal to e^{–0.214[Nicotine]}. Furthermore, the appearance of the primary emitter's (N-methylacridone) emission in the chemiluminescence spectrum, already observed in oriented systems, is strongly supressed by nicotine.

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Der Effekt von Nikotin auf die Chemilumineszenz von Lucigenin in Modellmembranen

Zusammenfassung Die Chemilumineszenz der klassischen Lucigenin-Lichtreaktion wird von Nikotin in Didodecyldimethylammoniumbromid-Lamellaraggregaten geschwächt. Das Verhältnis der Chemilumineszenzquantenausbeuten ist in orientiertem Medium — mit oder ohne Nikotin — e^{–0,571[Nikotin]}, in homogenem Medium jedoch e^{–0,214[Nikotin]}. Außerdem wird die Emission des Primäremitters (N-Methylacridon) im Chemilumineszenzspektrum von Nikotin stark unterdrückt.

     

Determination of As(III) and As(V) ions by chemiluminescence method

A new chemiluminescence (CL) method for the selective determination of As(III) and As(V) ions in aqueous solution has been studied using a FIA system. The method is based on the increased CL intensity with the addition of As(V) ion into a solution of lucigenin and hydrogen peroxide. The addition of As(III) ion into the solution did not change the CL intensity. Total concentration of As ions was determined after pre-oxidation of As(III) to As(V) with hydrogen peroxide in basic solution. The As(III) content was estimated by subtracting the content of As(V) ion from total As concentration. The effects of concentrations of KOH and H₂O₂, and flow rates of reagents on CL intensity have been investigated. The calibration curve for As(V) ion was linear over the range from 1.0×10^-2 to 10 μg/g, the coefficient of correlation was 0.997 and the detection limit was 5.0×10^-3 μg/g under the optimal experimental conditions.     

Chemiluminometric determination of the pesticide 3-indolyl acetic acid by a flow injection analysis assembly

A new method is proposed for the chemiluminescent determination of the pesticide 3-indolyl acetic acid by means of an flow injection analysis system. The chemiluminescence emission is obtained by oxidation of the analyte with Ce (IV) in nitric acid and presence of β-cyclodextrine.The continuous-flow method allows the determination of 159 samples h⁻¹ of 3-indolyl acetic acid in an interval of concentrations over the range 0.5-15.0 mg l⁻¹. The limit of detection was 0.1 μg l⁻¹ and the R.S.D. (n, 17) at 2.0 mg l⁻¹ of the pesticide level was 2.7%. The method was applied to water samples.     

In vivo lifetimes of the three color-sectors in bioluminescence emissions of the firefly Luciola praeusta at different temperatures

Bioluminescence emissions from fireflies have been well-studied for over a century. From the apparent features of the emitted light, conclusions have been drawn and hypotheses put forward on the characteristics of the highly efficient light emitting system. The basic emitter oxyluciferin, being chemically unstable, is difficult to study in isolation and, therefore, its analogs have been prepared and analyzed. In this letter, the lifetimes of the excited-state emitter oxyluciferin are measured, and an inference is drawn on the chemiluminescence reaction in vivo. The light from the Indian species of firefly Luciola praeusta contains three color-sectors: green, yellow, and red, and hence three optical filters are used to study time-resolved emissions from these sectors at different temperatures. All the three color-sectors are observed to be temperature sensitive in the time domain. An exponential variation of lifetime with temperature is observed for the emissions in these three regions.     

Flow Injection Chemiluminescence Method for Nalbuphine Hydrochloride in Pharmaceutical Formulations Using Tris(2,2'-bipyridyl)ruthenium(II) Chloride-diperiodatocuprate(III) Reaction

Asensitive and selective method employing chemiluminescence(CL) coupled with flow injection(FI) is reported for nalbuphine hydrochloride(NAL) assay in pharmaceutical formulations. The enhancement effect of NAL on the CL reaction between tris(2,2'-bipyridyl)ruthenium(II) chloride-diperiodatocuprate(III) {Ru[(bpy)₃]²⁺-Cu(III) complex} in acidic medium is used as analytical measurement. The optimal conditions of the CL reaction were sulfuric acid 1.0×10^-3 mol/L, Ru[(bpy)₃]²⁺ 7.5×10^-5 mol/L, Cu(III)/Ag(III) complexes 4.0×10^-4/5.0×10^-4 mol/L, sample loop volume of 120 μL and flow rate of 2.5 mL/min. The sensitivities of the method in terms of detection(S/N=3) and quantification(S/N=10) limits are 5×10^-4 and 0.001 ppm(1 ppm=1 mg/L), respectively. The linear response of the instrument in the form of CL intensity with respect to NAL concentration is over the range 0.001-15.0 ppm(R²=0.9999) with relative standard deviation from 0.8% to 3.2% and injection throughput of 120 injection/h. The applications of the method include the quantitative analysis of NAL in pharmaceutical injection samples. Variations and the average results of the proposed method are not signi-ficantly different from the results of a reported method by applying F- and paired student t-test. The most likely CL reaction mechanism is written in accordance with spectrophotometric and CL studies.     

Determination of Pentachlorophenol and 1-Naphthol by Peroxyoxalate Chemiluminescence

Abstract

Peroxyoxalate chemiluminescence is used for the determination of pentachlorophenol and 1-naphthol in soil. 1-Naphthol is brominated to make it amenable to the procedure. Calibration curves are linear over concentration ranges spanning four orders of magnitude and limits of detection are at the micromolar level. the processes can be carried out in the soil without prior extraction of the analytes.     

Detection and identification of the designer benzodiazepine flubromazepam and preliminary data on its metabolism and pharmacokinetics

The appearance of pyrazolam in Internet shops selling ‘research chemicals’ in 2012 marked the beginning of designer benzodiazepines being sold as recreational drugs or ‘self medication’. With recent changes in national narcotics laws in many countries, where two uncontrolled benzodiazepines (phenazepam and etizolam), which were marketed by pharmaceutical companies in some countries, were scheduled, clandestine laboratories seem to turn to poorly characterized research drug candidates as legal substitutes. Following the appearance of pyrazolam, it comes with no surprise that recently, flubromazepam (7‐bromo‐5‐(2‐fluorophenyl)‐1,3‐dihydro‐2H‐1,4‐benzodiazepin‐2‐one), a second designer benzodiazepine, was offered on the market. In this article, this new compound was characterized using nuclear magnetic resonance, gas chromatography‐mass spectrometry (GC–MS), liquid chromatography–mass spectrometry (LC–MS/MS) and liquid chromatography quadrupole time‐of‐flight MS (LC–Q–ToF–MS). Additionally, a study was carried out, in which one of the authors consumed 4 mg of flubromazepam to gain preliminary data on the pharmacokinetic properties and the metabolism of this compound. For this purpose, serum as well as urine samples were collected for up to 31 days post‐ingestion and analyzed applying LC–MS/MS and LC–Q‐ToF‐MS techniques. On the basis of this study, flubromazepam appears to have an extremely long elimination half‐life of more than 100 h. One monohydroxylated compound and the debrominated compound could be identified as the predominant metabolites, the first allowing a detection of a consumption for up to 28 days post‐ingestion when analyzing urine samples in our case. Additionally, various immunochemical assays were evaluated, showing that the cross‐reactivity of the used assay seems not to be sufficient for safe detection of the applied dose in urine samples, bearing the risk that it could be misused in drug‐withdrawal settings or in other circumstances requiring regular drug testing. Furthermore, it may be used in drug‐facilitated crimes without being detected. Copyright © 2013 John Wiley & Sons, Ltd.     

Automated,high performance,flow-through chemiluminescence microarray for the multiplexed detection of phycotoxins

A novel multiplexed immunoassay for the analysis of phycotoxins in shellfish samples has been developed. Therefore, a regenerable chemiluminescence (CL) microarray was established which is able to analyze automatically three different phycotoxins (domoic acid (DA), okadaic acid (OA) and saxitoxin (STX)) in parallel on the analysis platform MCR3. As a test format an indirect competitive immunoassay format was applied. These phycotoxins were directly immobilized on an epoxy-activated PEG chip surface. The parallel analysis was enabled by the simultaneous addition of all analytes and specific antibodies on one microarray chip. After the competitive reaction, the CL signal was recorded by a CCD camera. Due to the ability to regenerate the toxin microarray, internal calibrations of phycotoxins in parallel were performed using the same microarray chip, which was suitable for 25 consecutive measurements. For the three target phycotoxins multi-analyte calibration curves were generated. In extracted shellfish matrix, the determined LODs for DA, OA and STX with values of 0.5 ± 0.3 μg L⁻¹, 1.0 ± 0.6 μg L⁻¹, and 0.4 ± 0.2 μg L⁻¹ were slightly lower than in PBS buffer. For determination of toxin recoveries, the observed signal loss in the regeneration was corrected. After applying mathematical corrections spiked shellfish samples were quantified with recoveries for DA, OA, and STX of 86.2%, 102.5%, and 61.6%, respectively, in 20 min. This is the first demonstration of an antibody based phycotoxin microarray.