Determination of nitrate and nitrite in freshwaters using flow‐injection with luminol chemiluminescence detection

A simple and sensitive flow‐injection (FI) method for the determination of nitrate and nitrite in natural waters, based on luminol chemiluminescence (CL) detection, is reported. Nitrate was reduced online to nitrite via a copperized cadmium (Cu–Cd) column and then reacted with acidic hydrogen peroxide to form peroxynitrous acid. CL emission was observed from the oxidation of luminol in an alkaline medium in the presence of the peroxynitrite anion. The limits of detection (S:N = 3) were 0.02 and 0.01 µg N/L, with sample throughputs of 40 and 90 /h for nitrate and nitrite, respectively. Calibration graphs were linear over the range 0.02–50 and 0.01–50 µg N/L [R² = 0.9984 (n = 8) and R² = 0.9965 (n = 7)] for nitrate and nitrite, respectively, with relative standard deviations (RSDs; n = 3) in the range 1.8–4.6%. The key chemical and physical variables (reagent concentrations, buffer pH, flow rates, sample volume, Cu–Cd reductor column length) were optimized and potential interferences investigated. The effect of cations [Ca(II), Mg(II), Co(II), Fe(II) and Cu(II)] was masked online with EDTA. Common anions (PO₄^3?, SO₄^2? and HCO₃^?) did not interfere at their maximum admissible concentrations in freshwaters. The effect of salinity on the luminol CL reaction with and without nitrate and nitrite (2 and 0.5 µg N/L, respectively) was also investigated. The method was successfully applied to freshwaters and the results obtained were in good agreement with those obtained by an automated segmented flow analyser reference method. Copyright © 2011 John Wiley & Sons, Ltd.     

Stopped‐flow chemiluminescence determination of the anticancer drug capecitabine: Application in pharmaceutical analysis and drug‐delivery systems

Capecitabine is a chemotherapeutic agent used for the treatment of patients with metastatic cancers. This study aimed at determining the drug capecitabine in a simple chemiluminescence (CL) system of acidic potassium permanganate using the stopped‐flow injection technique. Statistical methods were used to detect optimum conditions. The method showed two linear calibration ranges from 6.7 × 10^?6 to 6.7 × 10^?5 mol L^?1 and from 6.7 × 10^?5 to 2.7 × 10^?3 mol L^?1 with a detection limit of 1.5 × 10^?6 mol L^?1. Chitosan‐modified magnetic nanoparticles were studied in the drug‐delivery experiments. According to the pH sensitivity of chitosan and low pH values in tumour cells, the chitosan‐coated magnetic nanoparticles could provide a good targeting drug‐delivery system to tumour sites. To evaluate the applicability of the method, the capecitabine‐loaded magnetic chitosan nanoparticles were synthesized with two different cross‐linkers; loading and releasing rates of the drug were investigated using the proposed CL method and an ultraviolet–visible light spectrophotometric method (absorption at 305 nm). The results showed a good correlation between the two methods, and it was found that the synthesized chitosan‐modified magnetic nanoparticles could be used for pH‐dependent release of capecitabine in cancer cells. Moreover, determination of capecitabine in tablets and synthetic samples was performed.     

Flow injection–chemiluminescence determination of acyclovir

The chemiluminescence (CL) reaction of acyclovir (ACV)–potassium permanganate, with formaldehyde as an enhancer, was investigated by the flow‐injection system, and a new method is reported for the determination of ACV on the basis of the reaction. The method is rapid, effective and simple for the determination of acyclovir in the range 0.2–80 mg/L, with a limit of detection of 0.06 mg/L (3 S:N), a relative standard deviation (RSD) of 3.7% for the determination of 1.0 mg/L acyclovir solution in 11 repeated measurements. The method has been applied to the determination of acyclovir in pharmaceuticals, with satisfactory results. The possible reaction mechanism is also discussed briefly. Copyright © 2011 John Wiley & Sons, Ltd.     

Rapid determination of isoamyl nitrite in pharmaceutical preparations by flow injection analysis with on‐line UV irradiation and luminol chemiluminescence detection

Isoamyl nitrite is used as a therapeutic reagent for cardiac angina and as an antidote for cyanide poisoning, but it is abused because of its euphoric properties. Therefore, a method to determine isoamyl nitrite is required in many fields, including pharmaceutical and forensic studies. In this study, a simple, rapid and sensitive method for the determination of isoamyl nitrite was developed using a flow injection analysis system equipped with a chemiluminescence detector and on‐line photoreactor. This method is based on on‐line ultraviolet irradiation of isoamyl nitrite and subsequent luminol chemiluminescence detection without the addition of an oxidant. A linear standard curve was obtained up to 1.0 μM of isoamyl nitrite with a detection limit (blank + 3SD) of 0.03 μM. The method was successfully applied to determine isoamyl nitrite content in pharmaceutical preparations. Copyright © 2013 John Wiley & Sons, Ltd.     

Determination of clomipramine by flow‐injection analysis with acidic potassium permanganate–formic acid chemiluminescence detection

A sensitive and simple chemiluminescent (CL) method for the determination of clomipramine has been developed by combining the flow‐injection analysis (FIA) technique, which is based on the CL intensity generated from the redox reaction of potassium permanganate (KMnO₄)–formic acid in sulphuric acid (H₂SO₄) medium. Under the optimum conditions, the linear range for the determination of clomipramine was 0.04–4 µg/mL, with a correlation coefficient of 0.9988 (n = 10) and a detection limit of 0.008 µg/mL (3σ), and the relative standard deviation (RSD) for 2.0 µg/mL clomipramine (n = 11) is 1.26%. The proposed method has been successfully applied to the determination of the studied clomipramine in pharmaceutical preparations. The possible reaction mechanism is discussed. Copyright © 2011 John Wiley & Sons, Ltd.     

Determination of trace amounts of dopamine by flow‐injection analysis coupled with luminol–Ag(III) complex chemiluminescence detection

A novel flow injection analysis‐direct chemiluminescence (FI‐CL) method has been developed for determination of trace amounts of dopamine (DA) based on the enhancing effect of DA on the CL reaction of luminol with an Ag(III) complex in alkaline solution. Under optimum conditions, CL intensities are proportional to the concentration of DA in the range of 1.0 × 10^?10 to 4.0 × 10^?8 mol L^?1. The detection limit is 3.0 × 10^?11 mol L^?1 for DA (3s), with a relative standard deviation (n = 13) of 2.3% for 1.0 × 10^?8 mol L^?1 DA. This method has also been applied for the determination of DA in commercial pharmaceutical injection samples. On the basis of the CL spectra and the results of the free‐radical trapping experiment of this work, a reaction mechanism for this CL reaction is proposed and discussed. Copyright © 2010 John Wiley & Sons, Ltd.     

An ultrasensitive chemiluminescent method for the tanshinol borneol ester determination and its pharmacokinetic analysis

Tanshinol borneol ester (DBZ), a chemical combination of danshensu and borneol, is an experimental drug that exhibits efficacious anti‐ischemic activity in animal models. In this work, an ultrasensitive chemiluminescence (CL) method for the determination of DBZ was established based on the inhibitory effect of DBZ on the CL signal produced from the reaction between potassium permanganate and luminol in alkaline solution. The CL intensity responded linearly to the concentration of DBZ in the range 2.0 × 10^‐10 to 4.0 × 10^‐8 g/mL with a detection limit of 7 × 10^?11 g/mL. The relative standard deviation (RSD) was 3.8% for 4.0 × 10^?9 g DBZ (n = 11). The proposed method showed characteristics of high sensitivity, simple device and quick. In addition, this proposed method had been applied satisfactorily to the analysis of DBZ in blood. The pharmacokinetics of DBZ in rat has also been studied using the CL method. Copyright © 2013 John Wiley & Sons, Ltd.     

Post‐chemiluminescence determination of chloramphenicol based on luminol–potassium periodate system

A post‐chemiluminescence (PCL) phenomenon was observed when chloramphenicol was injected into a mixture of luminol and potassium periodate after the chemiluminescence (CL) reaction of luminol–potassium periodate had finished. The possible reaction mechanism was proposed based on studies of the CL kinetic characteristics, the CL spectra, the fluorescence spectra and the UV‐vis absorption spectra of the related substances. Based on the PCL reaction, a rapid and sensitive method for the determination of chloramphenicol was established. The linear response range was 6.0 × 10^?7–1.0 × 10^?5 mol/L, with a correlation coefficient of 0.9986. The relative standard deviation (RSD) for 5.0 × 10^?6 mol/L chloramphenicol was 2.3% (n = 11). The detection limit was 1.6 × 10^?7 mol/L. The method has been applied to the determination of chloramphenicol in pharmaceutical samples with satisfactory results. Copyright © 2011 John Wiley & Sons, Ltd.     

Rapid chemiluminometric determination of gabapentin in pharmaceutical formulations exploiting pulsed‐flow analysis

In this study, a straightforward and automated pulsed flow‐based procedure was developed for the chemiluminometric determination of gabapentin [1‐(aminomethyl)cyclo‐hexaneacetic acid], a new generation antiepileptic drug, in different formulated dosage forms. The software‐controlled time‐based injection method capitalizes on the decrease of the background chemiluminescence (CL) readout of the luminol–hypochlorite reaction in the presence of gabapentin. In short, gabapentin works as a hypochlorite scavenger. The analytical procedure was implemented in a multi‐pumping flow network furnished with a suite of microdispensing solenoid‐actuated pumps. The diaphragm‐type micropumps might be configured to operate as fluid propellers, commutation units and metering injectors. A dynamic linear working range for gabapentin concentrations in the range 60–350 µmol/L was obtained, with an estimated detection limit of 40 µmol/L. The flow analyser handles about 41 injections/h and yields precise results (RSD < 2%). The miniaturized flow analyser thus has potential to be exploited for in‐line monitoring of drug manufacturing within the quality assurance framework of modern pharmaceutical companies. Copyright © 2008 John Wiley & Sons, Ltd.     

Flow injection–chemiluminescence determination of amoxycillin using potassium permanganate and formaldehyde system

It was found that amoxycillin can react with potassium permanganate in an acidic medium to produce chemiluminescence, which is greatly enhanced by formaldehyde. The optimum conditions for this chemiluminescent reaction were studied in detail using a flow‐injection system. The experimental results indicate that, under optimum conditions, the chemiluminescence intensity is linearly related to the concentration of amoxycillin in the range 5.48 × 10^?8–2.74 × 10^?6 mol[sol ]L, with a detection limit (3σ) of 4.1 × 10^?8 mol[sol ]L. The relative standard deviation was 1.0% at 1.1 × 10^?6 mol[sol ]L amoxycillin (n = 11 measurements). This method has the advantages of high sensitivity, fast response and ease of operation. The method was successfully applied to the determination of amoxycillin in raw medicines and capsules. Copyright © 2005 John Wiley & Sons, Ltd.     

Trace analysis of N‐acetyl‐L‐cysteine using luminol–H2O2 chemiluminescence system catalyzed by silver nanoparticles

N‐Acetyl‐L‐cysteine (NAC) can inhibit the luminol–H₂O₂, reaction, which is catalyzed by silver nanoparticles. Based on this phenomenon a new method was developed for NAC determination. Under optimum conditions, a linear relationship between chemiluminescence intensity and NAC concentration was found in the range 0.034–0.98 µg/mL. The detection limit was 0.010 µg/mL (S/N =3), and the relative standard deviation (RSD) was <5% for 0.480 µg/mL NAC (n =5). This simple, sensitive and inexpensive method has been applied to measure the concentration of NAC in pharmaceutical tablets. Copyright © 2014 John Wiley & Sons, Ltd.     

CdS nanoparticles‐ enhanced chemiluminescence and determination of baicalin in pharmaceutical preparations

CdS nanoparticles (CdS NPs) of different sizes were synthesized by the citrate reduction method. It was found that CdS NPs could enhance the chemiluminescence (CL) of the luminol‐potassium ferricyanide system and baicalin could inhibit CdS NPs‐enhanced luminol‐potassium ferricyanide CL signals in alkaline solution. Based on this inhibition, a flow‐injection CL method was established for determination of baicalin in pharmaceutical preparations and human urine samples. Under optimized conditions, the linear range for determination of baicalin was 5.0 x 10^?6 to 1.0 x 10^?3 g/L. The detection limit at a signal‐to‐noise ratio of 3 was 1.7 x 10 ^?6 g/L. CL spectra, UV‐visible spectra and transmission electron microscopy (TEM) were used to investigate the CL mechanism. The method described is simple, selective and obviates the need of extensive sample pretreatment. Copyright © 2012 John Wiley & Sons, Ltd.     

Flow‐injection chemiluminescence method for the determination of chloramphenicol based on luminol–sodium periodate order‐transform second‐chemiluminescence reaction

A new chemiluminescence (CL) reaction was observed when chloramphenicol solution was injected into the mixture after the end of the reaction of alkaline luminol and sodium periodate or sodium periodate was injected into the reaction mixture of chloramphenicol and alkaline luminol. This reaction is described as an order‐transform second‐chemiluminescence (OTSCL) reaction. The OTSCL method combined with a flow‐injection technique was applied to the determination of chloramphenicol. The optimum conditions for the order‐transform second‐chemiluminescence emission were investigated. A mechanism for OTSCL has been proposed on the basis of the chemiluminescence kinetic characteristics, the UV‐visible spectra and the chemiluminescent spectra. Under optimal experimental conditions, the CL response is proportional to the concentration of chloramphenicol over the range 5.0 × 10^?7–5.0 × 10^?5 mol/L with a correlation coefficient of 0.9969 and a detection limit of 6.0 × 10^?8 mol/L (3σ). The relative standard deviation (RSD) for 11 repeated determinations of 5.0 × 10^?6 mol/L chloramphenicol is 1.7%. The method has been applied to the determination of chloramphenicol in pharmaceutical samples with satisfactory results. Copyright © 2011 John Wiley & Sons, Ltd.     

Capillary electrophoresis analysis of isoniazid using luminol-periodate potassium chemiluminescence system

A rapid and simple capillary electrophoresis method coupled with chemiluminescent (CL) detection was proposed for analysis of isoniazid (ISO) based on the enhancement effect of ISO to CL emission of luminol‐periodate potassium reaction. Under the optimal conditions, ISO can be assayed in the range of 7.0 × 10^?7 to 3.0 × 10^?5 g mL^?1 (R² = 0.9990) with a limit of detection of 3.0 × 10^?7 g mL^?1 (signal‐to‐noise ratio of 3). The whole analysis process can be completed within 2.5 min with a theoretical plate number of 6258. The relative standard deviations of the signal intensity and the migration time were 3.1 and 1.4% for a standard sample at 1.0 × 10^?5 g mL^?1 (n = 5), respectively. The presented novel strategy was successfully applied to the determination of ISO in commercial pharmaceutical preparations and spiked human serum samples. Copyright © 2010 John Wiley & Sons, Ltd.     

Selective determination of human immunoglobulin G by flow‐injection chemiluminescence

A novel flow‐injection chemiluminescence method was developed for the selective determination of human immunoglobulin G (IgG) in the presence of thiomersal by changing the flow rates of peristaltic pump. The study was based on the independence and additivity of the CL signals of human IgG and thiomersal in the galangin–potassium permanganate–polyphosphoric acid system. In meantime, two equations relating to the concentrations of mixing solutions of human IgG and thiomersal vs the CL intensity were established and solved, on the basis of which the content of thiomersal included in samples was simultaneously determined too. The enhanced CL intensity was in proportion to concerntrations in the range 8.0 × 10^?7 to 8.0 × 10^?5 g/mL for human IgG and 1.0 × 10^?7 to 2.0 × 10^?6 g/mL for thiomersal with the detection limits of 5.0 × 10^?7 g/mL for human IgG and 6.0 × 10^?8 g/mL for thiomersal, respectively. The relative standard deviation for 1.0 × 10^?5 g/mL human IgG was 0.8% and for 2.0 × 10^?7 g/mL thiomersal it was 2.0% (n = 10). The proposed method was applied to determine three synthetic samples with recoveries of 91.5–109.5%. In addition, the possible chemiluminescence mechanisms are discussed as well. Copyright © 2010 John Wiley & Sons, Ltd.     

Development of a sensitive flow‐injection–chemiluminescence detection method for the determination of laevodopa

A simple chemiluminometric method using flow injection has been developed for the determination of laevodopa, based on its sensitizing effect on the weak chemiluminescence (CL) reaction between Na₂SO₃ and acidic KMnO₄. Under optimum experimental conditions, the CL intensity was linearly related to the concentration of laevodopa from 3.4 × 10^–8 to 2.4 × 10^–5 mol/L and the detection limit was 1.1 × 10^–8 mol/L (s:n = 3). The relative standard deviation (RSD) of the proposed method calculated from 20 replicate injection of 3 × 10^–7 mol/L laevodopa was 3.3%. The correlation coefficient was 0.997. The method was successfully applied to the determination of laevodopa in commercial pharmaceutical formulations and spiked urine samples. Copyright © 2008 John Wiley & Sons, Ltd.     

The determination of glutamine with flow‐injection chemiluminescence detection and mechanism study

The main purpose of this study was to develop an inexpensive, simple, rapid and sensitive chemiluminescence (CL) method for the determination of glutamine (Gln) using a flow‐injection (FI) system. Gln was found to strongly inhibit the CL signal of the luminol–H₂O₂–CuSO₄ system in Na₂B₄O₇ solution. A new FI‐CL method was developed for the determination of Gln. Parameters affecting the reproducibility and CL detection were optimized systematically. Under the optimized conditions, the corresponding linear regression equation was established over the range of 5.0 × 10^?7 to 2.5 × 10^?6 mol/L with the detection limit of 1.8 × 10^?8 mol/L. The relative standard deviation was found to be 1.8% for 11 replicate determinations of 1.5 × 10^?6 mol/L Gln. The proposed method has been satisfactorily applied for the determination of Gln in real samples (Marzulene‐s granules) with recoveries in the range of 98.7–108.6%. The minimum sampling rate was about 100 samples/h. The possible mechanism of this inhibitory CL was studied by fluorescence spectrophotometer and UV–vis spectrophotometer. Copyright © 2009 John Wiley & Sons, Ltd.     

A validated silver‐nanoparticle‐enhanced chemiluminescence method for the determination of citalopram in pharmaceutical preparations and human plasma

A simple and sensitive chemiluminescence (CL) method was developed for the determination of citalopram in pharmaceutical preparations and human plasma. The method is based on the enhancement of the weak CL signal of the luminol–H₂O₂ system. It was found that the CL signal arising from the reaction between alkaline luminol and H₂O₂ was greatly increased by the addition of silver nanoparticles in the presence of citalopram. Prepared silver nanoparticles (AgNPs) were characterized by UV–visible spectroscopy and transmission electron microscopy (TEM). Various experimental parameters affecting CL intensity were studied and optimized for the determination of citalopram. Under optimized experimental conditions, CL intensity was found to be proportional to the concentration of citalopram in the range 40–2500 ng/mL, with a correlation coefficient of 0.9997. The limit of detection (LOD) and limit of quantification (LOQ) of the devised method were 3.78 and 12.62 ng/mL, respectively. Furthermore, the developed method was found to have excellent reproducibility with a relative standard deviation (RSD) of 3.65% (n = 7). Potential interference by common excipients was also studied. The method was validated statistically using recovery studies and was successfully applied to the determination of citalopram in the pure form, in pharmaceutical preparations and in spiked human plasma samples. Percentage recoveries were found to range from 97.71 to 101.99% for the pure form, from 97.84 to 102.78% for pharmaceutical preparations and from 95.65 to 100.35% for spiked human plasma. Copyright © 2013 John Wiley & Sons, Ltd.     

Determination of ethanol using permanganate–CdS quantum dot chemiluminescence system

A novel and highly sensitive chemiluminescence (CL) method for the determination of ethanol was developed based on the CdS quantum dots (QDs)–permanganate system. It was found that KMnO₄ could directly oxidize CdS QDs in acidic media resulting in relatively high CL emission. A possible mechanism was proposed for this reaction based on UV/Vis absorption, fluorescence and the generated CL emission spectra. However, it was observed that ethanol had a remarkable inhibition effect on this system. This effect was exploited in the determination of ethanol within the concentration range 12–300 µg/L, with detection at 4.3 µg/L. In order to evaluate the capability of presented method, it was satisfactorily utilized in the determination of alcohol in real samples. Copyright © 2014 John Wiley & Sons, Ltd.     

Determination of iodide using flow injection with acidic potassium permanganate chemiluminescence detection.

A simple and rapid flow-injection method is described for the determination of iodide, based on potassium permanganate chemiluminescence detection via oxidation of formaldehyde in aqueous hydrochloric acid. The calibration graph was linear over the range 1.0-12 x 10(-6) mol/L (r2 = 0.9955) with relative standard deviations (n = 4) in the range 1.0-3.5%. The detection limit (3sigma) was 1.0 x 10(-7) mol/L, with sample throughput of 120/h. The effect of interfering cations [Ca(II), Mg(II), Ni(II), Fe(II), Fe(III) and Pb(II)] and anions (Cl-, SO4(2-), PO4(3-), NO3-, NO2-, F- and SO3(2-)) were studied. The method was applied to iodized salt samples and the results obtained in the range 0.03 +/- 0.005 - 0.10 +/- 0.006 mg I/g were in reasonable agreement with the amount labelled. The method was statistically compared with the results obtained by titration; no significant disagreement at 95% confidence was observed.