Determination of Diammonium Glycyrrhizinate and Its Antioxidant Activity Using a Novel Chemiluminescence System

A novel chemiluminescence (CL) system was established for the determination of diammonium glycyrrhizinate (DG) in pharmaceutical preparations and its ability of scavenging hydroxyl radical. It was shown that a strong CL signal was observed when Eosin Y mixed with Fenton reagent. The CL intensity was decreased significantly when DG was added to the reaction system and partially scavenged the hydroxyl radicals in the solution. The extent of decrease in the CL intensity had a good stoichiometrical relationship with DG concentration. Based on this, we developed a new method for the determination of DG using a flow injection chemiluminescence (FI-CL) technique. Under the optimal conditions, the linear range of DG concentration was 6.0 × 10^?8–5.0 × 10^?6 mol/L (R = 0.9982) with a detection limit of 8.0 × 10^?9 mol/L (SN = 3), and the RSD was 3.8% for 2.0 × 10^?7 mol/L DG (n = 11). This method was successfully used in the determination of DG in tablets and the evaluation of hydroxyl radical scavenging capacity of DG. The possible reaction mechanism of the CL system is discussed.     

Reversed Flow Injection Chemiluminescence Determination of Pyridoxine Hydrochloride Based on the Cerium(IV)-Sodium Sulfite System

A rapid chemiluminescence (CL) reaction was observed when Ce(IV) was injected into the mixed solution of pyridoxine hydrochloride and sodium sulfite. A new flow-injection CL method for the determination of pyridoxine hydrochloride was established. The detection limit (3σ) was 0.5 mg/L pyridoxine hydrochloride and the relative standard deviation (RSD) was 3.3% (n = 11, γ = 5 mg/L). The CL intensity responded linearly to the concentration of pyridoxine hydrochloride in the ranges 1.0–10.0 mg/L and 10.0–100.0 mg/L with linear correlation coefficients of 0.9994 and 0.9991, respectively. The method had been applied to the determination of pyridoxine hydrochloride in tablets and injections successfully.     

Determination of Trenbolone Acetate in Cattle Feeds by a Flow Injection Chemiluminescence Method

A flow injection chemiluminescence (CL) method is described for the determination of trenbolone acetate based on the CL generated during its reaction with KMnO₄ in acidic medium. The CL intensity is greatly enhanced by alizarin yellow R. The CL intensity is linear with trenbolone acetate concentration in the range 0.1–100.0 mg L^?1 with a detection limit of 0.05 mg L^?1. The sample throughout is about 90 h^?1 and the relative standard deviation for 2.0 mg L^?1 trenbolone acetate solution is 1.5% (n = 11). The proposed method was applied to the determination of trenbolone acetate in cattle feeds.     

Determination of Total Chromium in Biological Samples by Automated Reagent Injection Chemiluminescence Analysis

A sensitive method for the determination of total chromium in real samples by flow injection–chemiluminescence (FI–CL) analysis was proposed. It was found that the CL intensity from luminol–lysozyme reaction could be markedly quenched, and the decrease of CL intensity was linear with the logarithm of Cr(III) concentrations over the range of 5.0 to 4000 pg mL^?1 with a detection limit of 2.0 pg mL^?1 (3σ) and relative standard deviations (RSDs) of 3.0, 2.6, and 2.0% for 10, 100, and 1000 pg mL^?1 Cr(III) (n = 7), respectively. At a flow rate of 2.0 mL min^?1, the whole process including sampling and washing could be accomplished within 36 s. The proposed CL method was successfully applied to the determination of total chromium in pharmaceutical capsules, a dietary supplement, and spiked human serum samples, with recoveries from 92.2 to 108.4% and RSDs of less than 4.0%. Using the homemade FI–CL model, the binding constant (K = 4.38 × 10⁶ L mol^?1) and the binding sites (n ≈ 1) of Cr(III) to lysozyme were given.     

Determination of Homologue Imidazolium Ionic Liquid Cations by Ion Chromatography Using a Carboxyl Acid Cation-Exchange Column with Direct Conductivity Detection

An investigation into the determination of four imidazolium ionic liquid cations by ion chromatography using a carboxyl acid cation exchange column and direct conductivity detection was carried out. This research has developed a simple, selective, and accurate ion chromatographic method for separation of imidazolium ionic liquid cations. Detection limits (S/N = 3) for the cations were 3.2–24.3 mg/L. Relative standard deviations (RSD, n = 5) for peak areas were less than 1.6%. The method has been successfully applied to the determination of two ionic liquids synthesized by organic chemistry lab.     

A Novel Enhanced Chemiluminescence System with Ag(III) Complex for the Determination of Ofloxacin and Levofloxacin in Pharmaceutical Preparation and Biological Fluid

A novel chemiluminescence (CL) method is developed for determination of ofloxacin and levofloxacin with Ag(III) complex in H₂SO₄ solution medium. The CL intensity is proportional to drug concentration in a wider range with a correlation coefficient of 0.999. The limit of detection (s/n = 3) for ofloxacin and levofloxacin was 5.3 × 10^?9 g ml^?1 and 8.3 × 10^?9 g ml^?1, respectively, and their recoveries from urine and serum samples were in the range of 90.1–112% with the RSDs of 1.0–2.8%. The proposed method was applied for analysis of real samples with satisfactory result. The possible CL mechanism was discussed.     

Flow injection determination of cyromazine in natural water samples using diperiodatoargentate(III)–H2SO4–chemiluminescence system

A simple and sensitive chemiluminescence (CL) procedure is proposed for the determination of cyromazine (CYR) using flow injection technique. CYR has strong enhancing effect on the CL reaction of diperiodatoargentate-(III) complex (DPA) in H₂SO₄ medium. The CL intensity with solid phase extraction (SPE) technique and with and without using online ion exchange resin column (IERC; OH-form) was proportional to the concentration of CYR over the range 0.1–200, 10–1000 and 2–2500 µg L^–1 (R² = 0.9974, 0.9980 and 0.9990, n = 7 each), respectively. Under the conditions, the limits of detection (S/N = 3) 0.029, 2.5 and 0.5 µg L^–1, relative standard deviations (n = 3) 1.9–3.6%, 1.4–2.7% and 1.0–3.0% and sample throughputs were 120, 80 and 120 h^–1. The effect of reagents concentration, flow rate, sample loop volume, photomultiplier voltage and IERC length was optimised. The mean results for natural water samples analysed by the proposed method were not significantly different at 95% confidence limit with the previously reported HPLC method. Interference from chloride ions could be eliminated by using SPE procedure or incorporating an in-line IERC. The CL mechanism of DPA–H₂SO₄–CYR system was also discussed briefly.     

Efficient chemiluminescence by aptamer – reactant platform combination with activated Ag–Au alloy nanoparticles for cobalt detection

This article deals with the detection of Co(II) in real water sample using aptamer – reactant platform combination with activated Ag–Au alloy nanoparticles (NPs) by chemiluminescence (CL) method. CL is attributed to a catalytically enhanced decomposition of H₂O₂ by aptamer conjugated Ag–Au alloy NPs to produce reactive oxygen species. The Ag–Au alloy NPs were prepared by chemical method using double reducing agent (i.e. trisodium citrate and polyethylenimine) and used for detection of Co(II) from water by CL method. CL experiments were carried out with the variation of different parameters such as pH, concentration of luminol, concentration of H₂O₂ and Ag–Au alloy NPs. We found that Ag–Au alloy NPs have very good efficiency towards Co(II) detection. Analytical parameters and kinetics were studied in detail to know the nature and mechanism of CL in presence of aptamer conjugated Ag–Au alloy NPs. The linear range of the CL sensor of Co(II) is covered concentration from 0.01 to 10 µg/L with detection limit of 0.001 µg/L. The relative standard deviation for determination of Co(II) was 6.65 in 10 replicated measurements. CL method is first time applied to detect the Co(II) in real water samples at very low level using aptamer conjugated Ag–Au NPs as a catalyst.     

A Rapid and Sensitive LC–MS Method for Determination of Ezetimibe Concentration in Human Plasma: Application to a Bioequivalence Study

A selective and highly sensitive high performance liquid chromatography-electrospray ionization mass spectrometry method has been developed for determination of ezetimibe concentrations in human plasma. Ezetimibe was extracted from plasma with ethyl acetate followed by evaporation of the organic layer and, then, reconstitution of the residue in mobile phase before injection to chromatograph. The mobile phase consisted of acetonitrile-ammonium acetate (10 mM, pH 3.0), 75:25 (v/v). An aliquot of 10 μL was chromatographically analyzed on a prepacked Zorbax XDB-ODS C₁₈ column (2.1 × 100 mm, 3.5 micron). Detection of analytes was achieved by mass spectrometry with atmospheric pressure chemical ionization (APCI) interface in the negative ion mode operated under the multiple-reaction monitoring mode (m/z transition: ezetimibe 408–271). Standard curves were linear (r = 0.998) over the wide ezetimibe concentration range of 0.05–30.0 ng mL⁻¹ with acceptable accuracy and precision. The limit of detection was 0.02 ng mL⁻¹. The validated LC–APCI–MS method has been used successfully throughout a bioequivalence study on an ezetimibe generic product in 24 healthy male volunteers.

     

RP-LC and HPTLC Methods for the Determination of Olmesartan Medoxomil and Hydrochlorothiazide in Combined Tablet Dosage Forms

Two new, rapid, precise, accurate and specific chromatographic methods were described for the simultaneous determination of olmesartan medoxomil and hydrochlorothiazide in combined tablet dosage forms. The first method was based on reversed phase liquid chromatography using an Eurosphere 100 RP C18 column (250 × 4.6 mm ID, 5 μm). The mobile phase was methanol–0.05% o-phosphoric acid (60:40 v/v) at a flow rate of 1.0 mL min⁻¹. Commercially available tablets and laboratory mixtures containing both drugs were assayed and detected using a UV detector at 270 nm. The second method involved silica gel 60 F₂₅₄ high performance thin layer chromatography and densitometric detection at 254 nm using acetonitrile–ethyl acetate–glacial acid (7:3:0.4 v/v/v) as the mobile phase. Calibration curves ranged between 200–600 and 125–375 ng spot⁻¹ for olmesartan and hydrochlorothiazide, respectively.

     

ClO3--SO32--Rh6G-SDBS体系的化学发光及其用于亚硫酸根测定

Based on the micelle synergism mechanism, a chemiluminescence （CL） flow system for the determination of sulfite was described. The CL signal generated from the reaction of chlorate with sulfite in acidic solution was very weak, while the interfusion of sodium dodecylbenzenesulfonate （SDBS） resulted in a highly chemiluminescent intensity. The major goal of this work was to investigate and develop the SDBS rnicelle synergetic CL system. The mechanism was proposed and proved by spectrometry. The results indicated that the unique structure of SDBS micelles prorooted the aggregation of rhodamine 6G （Rh6G） and a much easier energy transfer, leading to a marked shift to red in the CL emission. This CL system was developed for the determination of sulfite and the concentration of sulfite was proportional to the CL intensity in the range of 5.0× 10^-8--1.0× 10^-5 mol/L with the detection limit of 1.7×10^-8 mol/L （S/N=3）. The relative standard deviation was 3.3% for 1.0×10^ 6 mol/L sulfite solution with eleven repeated measurements. This method was successfully applied to the determination of sulfite in powder sugar.     

Chemical composition and antimicrobial activity of essential oils from Acantholippia deserticola,Artemisia proceriformis,Achillea micrantha and Libanotis buchtormensis against phytopathogenic bacteria and fungi

Essential oils from aerial parts of Acantholippia deserticola, Artemisia proceriformis, Achillea micrantha and Libanotis buchtormensis were analysed by GC–MS. The major compounds identified were β-thujone (66.5 ± 0.2%), and trans-sabinyl acetate (12.1 ± 0.2%) in A. deserticola; α-thujone (66.9 ± 0.4%) in A. proceriformis; 1,8-cineole (26.9 ± 0.5%), and camphor (17.7 ± 0.3%) in A. micrantha and cis-β-ocimene (23.3 ± 0.3%), and trans-β-ocimene (18.4 ± 0.2%) in L. buchtormensis. The oils showed a weak antimicrobial effect (MIC₁₀₀ > 1.5 mg/ml) on most phytopathogens tested. A moderate antimicrobial activity (MIC₁₀₀ between 0.5 and 1.5 mg/ml) was displayed by the oils of A. deserticola, A. micrantha and L. buchtormensis on Septoria tritici and by the oil of A. deserticola on Septoria glycine. The antimicrobial activity was associated to the contents of β-thujone, trans-sabinyl acetate and trans-sabinol. Our results indicate that the tested essential oils have little inhibitory potency not suitable for use as plant protection products against the phytopathogens assayed.     

Flow‐Injection Chemiluminescence Analysis of Cloperastione Hydrochloride

Abstract

A new chemiluminescence (CL) reaction was observed when cloperastine hydrochloride was injected into the reaction mixture after the CL reaction of Ce(IV) and sodium sulfite finished. A new flow injection CL method for the determination of cloperastine hydrochloride was established based on the CL reaction. The relative standard deviation (RSD) for the determination of cloperastine hydrochloride was 1.3% (n=11, c=1.0×10^?6 g/mL). The CL intensity responded linearly to the concentration of cloperastine hydrochloride in the range 2.0×10^?7～2.0×10^?5 g/mL (r=0.9962). The detection limit was 5×10^?8 g/mL cloperastine hydrochloride. The method had been applied to the determination of cloperastine hydrochloride in tablets with satisfactory results.     

Determination of Vitamin A in Infant Milk-Based Formulas and Pharmaceutical Formulations Using Flow Injection with Ce(IV)–Na2SO3 Chemiluminescence Detection

A rapid and simple flow injection (FI) method is reported for the determination of vitamin A (retinol) based on its strong enhancing effect on the Ce(IV)–Na₂SO₃ chemiluminescence (CL) reaction in an acidic solution. The effect of key chemical and physical parameters (i.e., reagent concentrations, flow rate, and sample volume) was optimized and potential interferences examined. Under the selected experimental conditions, a linear calibration was obtained between the CL intensity and vitamin A concentration in the range 0.1–8.0 µg mL^?1 (r ²  = 0.9986, n = 8). The limit of detection (3 s x blank) was 0.01 µg mL^?1 retinol (n = 6) and the relative standard deviation (RSD) for 0.25 µg mL^?1 retinol was 2.3% (n = 10) with a sampling rate of 180 h^?1. The method was successfully applied to infant milk-based formulas and pharmaceutical formulations and the results were not significantly different at 95% confidence interval with those obtained by using a spectrophotometric reference method. The possible CL mechanism is also discussed briefly supporting with UV-visible, fluorescence, and CL spectra.     

Isolation and Purification of Highly Polar Antioxidants from Chirita longgangensis by Combination of Macroporous Resin and HSCCC

An efficient and simple method to isolate and purify highly polar antioxidants from the antioxidant active site of Chirita longgangensishas been established. Firstly, the antioxidant active site was enriched with D101 macroporous resin, and then high-speed counter-current chromatography (HSCCC) was used with the two-phase solvent system ethyl acetate–n-butanol–methanol–water (5:0.1:0.5:4.5, v/v) to obtain four antioxidants in one step. They were identified as plantainoside D (28.4 mg), plantainoside B (9.5 mg), calcedarioside B (18.1 mg) and calcedarioside A (16.7 mg) by analysis of electrospray ionization mass spectrometry (ESI-MS) and nuclear magnetic resonance (NMR) spectra. The purities were all above 97 % as determined by HPLC. The inhibiting effects of the crude extracts, enriched fraction and the obtained compounds on superoxide anion radical, hydroxyl radical and hydrogen peroxide were determined by different chemiluminescence (CL) systems. The result shows that all of them have good antioxidant activity. However, the sequence of antioxidant abilities among compounds I–IV was different when assayed by different CL systems (superoxide anion radical, hydroxyl radical, and hydrogen peroxide). This is the first report on preparative isolation and purification of antioxidants from C. longgangensis by HSCCC combined with macroporous resin and their inhibition of free radical-induced luminol chemiluminescence.     

Determination of Melamine in Fresh Milk with Hollow Fiber Liquid Phase Microextraction Based on Ion-Pair Mechanism Combined with High Performance Liquid Chromatography

In this work, a novel analytical method based on hollow fiber liquid phase microextraction (HF-LPME) and high performance liquid chromatography (HPLC) was developed for the analysis of melamine in fresh milk. The conditions of the HF-LPME were investigated and optimized. As a result, a supported liquid membrane containing 6-undecanone and di-2-ethylhexyl phosphoric acid (D2EHPA) was selected. The extractions were made from 25 mL aqueous donor phase (prepared from milk) with pH 5.0 to a more acidic acceptor phase (36 µL 1 M HCl) and the mass transfer was driven by the proton gradient between these phases. Other optimum conditions of the HF-LPME were 60 min extraction time at 360 rpm stirring rate and an extraction factor of 21 times (extraction efficiency 3%) was obtained. The C8 column was operated at 1 mL/min at room temperature and the UV detection wavelength was 240 nm for HPLC. The mobile phase was 10 mM sodium n-octanesulfonate (pH 3.0) mixed with acetonitrile (85:15, v/v). The relative recovery of melamine for milk samples spiked with 0.5–25 mg/kg was in the range of 89.1–120.6% with the RSDs (n = 4) of 4.0–8.5%. It was found that the proposed method provided a linear range from 0.1 to 50 mg/kg (r ²  = 0.9993), method detection limit (MDL) of 0.003 mg/kg and method quantification limit (MQL) of 0.01 mg/kg. The obtained results demonstrated that HF-LPME combined with HPLC is a simple and cheap method for the determination of melamine in fresh milk.     

LC–MS–MS Simultaneous Determination of Paracetamol, Pseudoephedrine and Chlorpheniramine in Human Plasma: Application to a Pharmacokinetic Study

A liquid chromatography–tandem mass spectrometry (LC–MS–MS) method was developed for the simultaneous determination of paracetamol, pseudoephedrine and chlorpheniramine in human plasma. Diphenhydramine was used as the internal standard. Analytes were extracted from alkalized human plasma by liquid–liquid extraction (LLE) using ethyl acetate. After electrospray ionization positive ion fragments were detected in the selected reaction monitoring (SRM) mode with a triple quadrupole tandem mass spectrometer. The method was linear in the concentration range of 20.0–10000.0 ng mL^?1 for paracetamol, 1.0–500.0 ng mL^?1 for pseudoephedrine and 0.1–50.0 ng mL^?1 for chlorpheniramine. The intra- and inter-day precisions were below 14.5% and the bias was between ?7.3 and +2.8% for all analytes. The validated LC–MS–MS method was applied to a pharmacokinetic study in which each healthy Chinese volunteer received a tablet containing 300 mg benorylate, 30 mg pseudoephedrine hydrochloride and 2 mg chlorpheniramine maleate. This is the first assay method described for the simultaneous determination of paracetamol, pseudoephedrine and chlorpheniramine in human plasma samples.     

Investigation of Chemiluminescence Behavior of Flavonoids with Cerium (IV)‐Rhodamine B System

Abstract

The chemiluminescence (CL) behavior of five major flavonoid types in cerium (IV)‐rhodamine B system was investigated by flow‐injection. Strong CL was observed when cerium (IV) reacted with rhodamine B in sulfuric acid medium in the presence of flavonoids. This reaction system has been established as a simple, rapid, and highly sensitive flow injection CL analysis for quercetin and kaempferol, and their detection limit (3σ) was 2.7 and 0.22 nmol/L, respectively. The relative standard deviation (n=8) was 1.2% for 1.0 µmol/L quercetin and 1.9% for 0.5 µmol/L kaempferol. This method was successfully applied to the determination of quercetin in the hydrolysate of rutin and compared well with the high performance liquid chromatography (HPLC) method. From a comparison of several related flavonoids, it was concluded that only flavonoids that contain a free 3‐hydroxyl and 2, 3‐double bond in conjugation with 4‐oxo function could produce a relatively strong CL emission.     

Flow-assisted automated solid-phase microextraction for the determination of chloroethers in aqueous matrices

In this study a method of flow-assisted automated solid-phase microextraction (FA-SPME) was developed for the determination of organic pollutants in aqueous samples. A CTC Combi-PAL autosampler coupled with gas chromatography–mass spectrometry (GC–MS) was used to automate the entire extraction process. In this method, the SPME fibre was exposed to 100 mL of sample in a direct immersion mode for 10 min. After exposure, the fibre was desorbed at the injection port of GC–MS. To demonstrate the applicability of FA-SPME, chloroethers were selected as model compounds. Good linear correlation was found over a concentration range of 0.5–100 µg/L. The detection limits of the method were determined between 0.02 and 0.05 µg/L with the coefficients of determination (R²) from 0.9980 to 0.9996. The relative standard deviations (RSDs) of the FA-SPME for three sequential FA-SPME analyses were determined to be in the range between 1.2% and 6.2% (n = 3). The applicability of the method was assessed by means of recovery studies and satisfactory values for all compounds were obtained. This optimised method was used in the analysis of water and human urine samples to show the matrix effect on FA-SPME. This FA-SPME/GC–MS is substantially faster and suitable for the routine continuous flow-mode environmental monitoring applications.     

Determination of Three Nonsteroidal Anti-Inflammatory Drugs in Human Plasma by LC Coupled with Chemiluminescence Detection

A simple and sensitive method was developed for the determination of three nonsteroidal anti-inflammatory drugs (NSAIDs)—ibuprofen, naproxen and fenbufen in human plasma. The method involved in column liquid chromatographic separation and chemilumenescence (CL) detection based on the CL reaction of NSAIDs, potassium permanganate (KMnO₄) and sodium sulfite (Na₂SO₃) in sulfuric acid (H₂SO₄) medium. The chromatographic separation was carried out using a reversed-phase C₁₈ column, which allowed the selective determination of the three medicines in the complicated samples. The special features of the CL detector provided lower LOD for determination than that of existing chromatographic alternatives. The results indicated that the linear ranges were 0.01–10.0 μg mL⁻¹ for ibuprofen, 0.001–1.0 μg mL⁻¹ for naproxen, and 0.01–10.0 μg mL⁻¹ for fenbufen. The limits of detection were 0.5 ng mL⁻¹ for ibuprofen, 0.05 ng mL⁻¹ for naproxen and 0.5 ng mL⁻¹ for fenbufen (S/N = 3). All average recoveries were in the range of 90.0–102.3%. Finally, the method had been satisfactorily applied for the determination of ibuprofen, naproxen and fenbufen in human plasma samples.