Determination of vitamin B<Subscript>12</Subscript> using a chemiluminescence flow system

A method to determine vitamin B₁₂ by measuring the chemiluminescence (CL) intensities using a flow injection (FI) system has been proposed. It is based on the catalytic effect of cobalt(II) in vitamin B₁₂ on the CL reaction between luminol and hydrogen peroxide in a basic medium. The increment of the CL intensity is proportional to the concentration of vitamin B₁₂ in the range 8.68–86.9 ng/mL (r ² = 0.9984) with a detection limit (3σ) of 0.89 ng/mL. The CL response is obtained in 10 s at a flow rate of 3.0 mL/min with a relative standard deviation (RSD) of less than 2.5% (n = 6). The method has been successfully applied to the determination of vitamin B₁₂ in pharmaceutical injections. The text was submitted by the authors in English.     

Determination of cefetamet pivoxil in human urine and serum using flow injection chemiluminescence procedure

A sensitive chemiluminescence method based on enhancing the effect of cefetamet pivoxil on the chemiluminescent reaction between luminol and dissolved oxygen in a flow injection system was proposed for the determination of cefetamet pivoxil. The increment of the chemiluminescence intensity was proportional to the concentration of cefetamet pivoxil, which yields a calibration graph that is linear over the concentration from 0.4 to 100.0 ng/mL (r ² = 0.991) with the detection limit of 0.1 ng/mL (3σ). At a flow rate of 2.0 mL/min complete determination of cefetamet pivoxil, including sampling and washing, could be accomplished in 40 s with the RSD of less than 0.03 (n = 5). The proposed method was applied successfully to the determination of cefetamet pivoxil in human urine and human serum. The text was submitted by the authors in English.     

Quantitative Monitoring of Rutin in Human Urine by Flow Injection‐Chemiluminescence Analysis

In this paper, a rapid and sensitive flow injection‐chemiluminescence (FI‐CL ) method is proposed for the quantitative determination of rutin based on the inhibitory effect of rutin on the chemiluminescence intensity from the luminol–chymotrypsin (CT ) system. The decrease of CL intensity was found to be proportional to the logarithm of rutin concentration in the range 0.1–30.0 ng/mL . A method for the quantification of rutin is proposed, with the limit of detection (LOD ) of 0.03 ng/mL (3σ). A complete analytical process including sampling and washing for rutin determination, which was conducted at a flow rate of 2.0 mL /min, could be performed completely within 30 s, yielding a sample efficiency of 120 h⁻¹. The proposed procedure was successfully applied for the determination of rutin in human urine after oral intake, with recoveries varying from 93.9 to 108.1% and relative standard derivation <4.0% (n = 5). Results showed that urine reached the maximum concentration at ~2.5 h, and the total excretion ratios were (83.5 ± 0.6) and (86.8 ± 0.7)%, respectively, for two volunteers in 8 h. The pharmacokinetic parameters, including the half‐life (1.05 ± 0.02 h), absorption rate constant (1.18 ± 0.01 h⁻¹), and elimination rate constant (0.70 ± 0.01 h⁻¹), were obtained. The possible CL mechanism of the luminol–CT –rutin reaction is discussed by FI‐CL , fluorescence, and molecular docking methods.     

Quantification of urapidil, α-1-adrenoreceptor antagonist, in plasma by LC-MS/MS: validation and application to pharmacokinetic studies

A sensitive high‐performance liquid chromatography–positive ion electrospray tandem mass spectrometry method was developed and validated for the quantification of urapidil in plasma. Following liquid–liquid extraction, the analyte was separated using an isocratic mobile phase on a reverse‐phase column and analyzed by MS/MS in the multiple reaction monitoring mode using the respective [M + H]⁺ ions, m/z 388 to 205 for urapidil and m/z 452 to 344 for the internal standard. The assay exhibited a linear dynamic range of 0.1–500 ng/mL for urapidil in plasma. Acceptable precision (<7%) and accuracy (100 ± 8%) were obtained for concentrations over the standard curve range. The method was successfully applied to quantify urapidil concentrations in a preclinical pharmacokinetic study after a single oral administration of urapidil at 3 mg/kg to rats. Following oral administration the maximum mean concentration in plasma (C_max; 616 ± 73 ng/mL) was achieved at 0.5 h (T_max) and area under curve (AUC_0–24) was 1841 ± 308 ng h/mL. The half‐life (t_1/2) and clearance (Cl) were 2.47 ± 0.4 h and 1660 ± 276 mL/h/kg, respectively. Moreover, it is plausible that the assay method in rat plasma would facilitate the adaptability of urapidil quantification in human plasma for clinical trials. Copyright © 2011 John Wiley & Sons, Ltd.     

A simple flow-injection chemiluminescence method for the determination of trace pentavalent vanadium in water samples

A simple method for rapid determination of trace pentavalent vanadium in natural water was presented by flow-injection chemiluminescence (CL). Through water injection, luminol and potassium permanganate were eluted from the anion exchange column to generate the CL, which was enhanced in the presence of V(V). Under the optimum conditions, the increased CL intensity was linear with V(V) concentration in the range from 0.1 to 100?ng?mL^?1. The limit of detection was 50?pg?mL^?1 (3σ) and the relative standard deviation (RSD) was 2.24% (n?=?5) for a 1.0?ng?mL^?1?V(V). At a flow rate of 2.0?mL?min^?1, one cycle of analysis could be performed in 0.5?min with a RSD of less than 3.0%. The proposed method was successfully applied to the determination of vanadium in natural water.     

Rapid determination of levofloxacin in pharmaceuticals and biological fluids using a new chemiluminescence system

A novel chemiluminescence method for the determination of levofloxacin is presented, which is based on the inhibitory effect of levofloxacin on the chemiluminescence reaction between luminol and myoglobin in a flow-injection system. The decrement of chemiluminescence intensity is linear with the logarithm of levofloxacin concentration over the range from 0.07 to 100.0 ng/mL (r ² = 0.9994), with the detection limit of 0.02 ng/mL (3σ). At a flow rate of 2.0 mL/min, a complete analytical process could be performed within 0.5 min, including sampling and washing, with a relative standard deviation of less than 3.0% (n = 5). The proposed procedure was applied successfully to the determination of levofloxacin in pharmaceutical preparations, human urine and serum without any pretreatment procedure.     

Determination of norfloxacin in pharmaceuticals,human serum,and urine using a luminol—dissolved oxygen chemiluminescence system

A sensitive chemiluminescence method, based on the enhancive effect of norfloxacin on the reaction between luminol and dissolved oxygen in a flow injection system, was proposed for the determination of norfloxacin. The increment of the chemiluminiscence intensity was proportional to the concentration of norfloxacin, giving a calibration graph linear over the concentration from 0.4 ng mL⁻¹ to 400.0 ng mL⁻¹ (r ² = 0.9988) with the detection limit of 0.1 ng mL⁻¹ (3 × σ _noise). At the flow rate of 2.0 mL min⁻¹, a complete determination of norfloxacin, including sampling and washing, could be accomplished in 30 s with the relative standard deviation lower than 3.0 %. The proposed method was applied successfully to determine norfloxacin in pharmaceuticals, human urine, and serum. Possible mechanism of the reaction was also discussed.     

Flow Injection Chemiluminescence Determination of Isoniazid Using On-Line Electrogenerated Manganese(III) as Oxidant

A novel flow injection chemiluminescence (CL) system for the determination of isoniazid has been proposed. It is based on the direct CL reaction of isoniazid and Mn(III) in sulfuric acid medium. The unstable Mn(III) was on-line electrogenerated by constant current electrolysis. The CL emission intensity was linear with isoniazid concentration in the range 0.1–10 μg/mL; the detection limit was 3.2 × 10⁻² μg/mL. The whole process could be completed in 1 min with a relative standard deviation of less than 5%. The proposed method is suitable for automatic and continuous analysis and has been applied successfully to the analysis of isoniazid in pharmaceutical preparation.     

Liquid chromatography–tandem mass spectrometry method for simultaneous quantification of urapidil and aripiprazole in human plasma and its application to human pharmacokinetic study

A sensitive and selective liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed and validated for simultaneous determination of urapidil and aripiprazole in human plasma. A simple liquid–liquid extraction with ethyl acetate was used for the sample preparation. Chromatographic separation was achieved on a Phenomenex C₁₈ (4.6 × 50 mm, 5 µm) column with 0.1% formic acid–acetonitrile (10:90, v/v) as the mobile phase with flow rate of 0.6 mL/min. The quantitation of the target compounds was determined in a positive ion multiple reaction monitoring mode. Calibration plots were linear over the range of 2.0–2503.95 ng/mL for urapidil and 1.0–500.19 ng/mL for aripiprazole. The lower limit of quantitation for urapidil and aripiprazole was 2.0 and 1.0 ng/mL, respectively. Mean recovery was in the range of 69.94–75.62% for both analytes and internal standards. Intra‐day and inter‐day precisions of the assay at three concentrations were 2.56–5.89% with accuracy of 92.31–97.83% for urapidil, and 3.14–6.84% with accuracy of 91.38–94.42% for aripiprazole. The method was successfully applied to human pharmacokinetic study of urapidil and aripiprazole in healthy human male volunteers. Copyright © 2013 John Wiley & Sons, Ltd.     

流动注射-化学发光法测定乌拉地尔

乌拉地尔 (Urapidil)即 6 - { [3 - [4- (o-甲氧苯基 ) - 1 -哌嗪 ]-丙基 ]-氨基 } - 1 ,3 -二甲基脲嘧啶 ,又名乌Scheme 1　 The chemical structure of Urapidil拉尔碱或压宁定 ,为苯哌嗪取代的脲嘧啶衍生物 ,其结构见 Scheme 1 .乌拉地尔是一种高选择性的α受体阻滞剂 ,能使     

Modified analcime loaded with zincon as a useful material for the separation and preconcentration of trace palladium and its determination by third-derivative spectrophotometry

This work assesses the potential of natural analcime zeolite as a sorbent for the preconcentration of palladium. Palladium is quantitatively retained on modified analcime zeolite loaded with zincon using the column method in the pH range from 2.5 to 3.5 at a flow rate of 1 mL/min. The palladium complex was removed from the column with 5.0 mL of dimethylsulfoxide (DMSO) and determined by third-derivative spectrophotometry. The detection limit is 0.03 μg/mL (signal-to-noise ratio = 3) in the final solution. Since it is possible to retain 0.15 μg of palladium from 600 mL of solution passing through the column, elution with 5.0 mL of DMSO gives a detection limit of 0.25 ng/mL for palladium in the initial aqueous solution. The calibration curve is linear over the range 0.1 to 5.0 μg/mL of palladium(II) in the final solution with a correlation coefficient of 0.9996. Seven replicated determinations of 5.0 μg of palladium in 5.0 mL dimethylsulfoxide gave a mean d ³ A/dλ³ (peak-to-peak signal between λ₂ = 625 and λ₁ = 654 nm) of 0.64 with a relative standard deviation of 1.2%. The sensitivity of the method (d ³ A/dλ³) is 0.5843 mL/μg of palladium(II) from the slope of the calibration curve. The interference of a large number of anions and cations has been studied and the optimized conditions developed were utilized for the determination of trace palladium in various synthetic and water samples. The text was submitted by the authors in English.     

Catalytic kinetic spectrophotometric determination of iron with (dibromo-<Emphasis Type="Italic">p</Emphasis>-sulfonic acid arsenazo)-potassium bromate-ascorbic acid system

A new method for the determination of traces of iron was developed based on its catalytic effect on the oxidation reaction of dibromo-p-sulfonic acid-arsenazo (DBS-arsenazo, DBS-ASA) by potassium bromate in a 5.0 × 10⁻³ M sulfuric acid medium. The optimum experimental conditions for the determination of iron using iron(III)-dibromo-p-sulfonic acid-arsenazo, (DBS-ASA)-potassium bromate-ascorbic acid system and its kinetic spectrophotometric properties were studied. The absorbance difference (ΔA) is linearly related with the concentration of iron(III) over the range of 0.20–6.0 ng/mL at the maximum absorption wavelength of 520 nm and described by the equation: ΔA = 0.133c (ng/mL) — 0.0133 with a regression coefficient of 0.9966. The detection limit of the method is 0.17 ng/mL. The method has been successfully used in the determination of traces of iron in potato samples. The obtained results agree with those of atomic absorption spectrometry.     

Determination of Cytochrome <Emphasis Type="Italic">c</Emphasis> in Human Serum and Pharmaceutical Injections Using Flow Injection Chemiluminescence

It was found that the complex of cytochrome c (Cyt c) and hydrogen peroxide could significantly catalyze the chemiluminescence (CL) reaction from luminol–hydrogen peroxide, and a sensitive, rapid, and simple CL procedure was proposed for the determination of Cyt c in a flow injection system for the first time. The increment of CL intensity was linear over the concentration of Cyt c ranging from 5 to 700 ng ml⁻¹, with a detection limit of 2 ng ml⁻¹ (3σ). At a flow rate of 2.0 ml min⁻¹, a complete analytical process could be performed in 30 s with a relative standard deviation of less than 4.0%. The proposed method was applied successfully for the assay of Cyt c in pharmaceutical injections and human serum, and the recoveries were from 98.0% to 108.8% and 92.5% to 109.0%. The possible mechanism of Cyt c enhanced CL reaction was also discussed.     

Direct analysis of clomipramine in human plasma by microbore high performance liquid chromatography with column-switching

Summary An automated microbore, liquid chromatographic method with column-switching was developed for the determination of clomipramine from human plasma samples. After direct injection of samples (60 μL), plasma proteins and clomipramine were separated in size-exclusion mode using 20% acetonitrile in 20 mM phosphate buffer (pH 7.0) on Capcell Pak MF Ph-1 precolumn (10×4 mm I.D.). By valve switching, a fraction containing clomipramine was directed to an intermediate column for subsequent main separation on a microbore C₁₈ column (250×1.5 mm I.D.) using 50% acetonitrile in 20 mM phosphate buffer (pH 2.5) at 0.1 mL min⁻¹. The method was advantageous for rapidity (total analysis time: 15 min), reproducibility (C.V.<4.8%), and increased sensitivity (1 ng mL⁻¹). The linearity of response was good (r ²≥0.999) over the concentration range 1–250 ng mL⁻¹.     

Analysis of Benzidine and Dichlorobenzidine at Trace Levels in Water by Silylation and Gas Chromatography–Mass Spectrometry

Conditions for silylation of benzidine (BZ) and 3,3′-dichlorobenzidine (DCBZ) have been optimized. Reactivity, repeatability, and derivative stability were compared for the silylating reagents N-Methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA) and N-Methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide (MTBDMSTFA) and the catalysts 3% trimethylsilylimidazole (TMS-I) and 0.3% NH₄-I–dithioerythritol. The results showed that derivatization with MTBDMSTFA/NH₄-I containing 0.1 mg dithioerythritol was superior to other methods. The silylation conditions selected were reaction with (MTBDMSTFA)–NH₄I, 1000:3, with catalysis by dithioerythritol, at 80 °C for 80 min. The TBDMS derivatives of BZ and DCBZ had very good chromatographic properties and very sensitive detection was achieved by gas chromatography with electron-impact ionization mass spectrometry (GC-EIMS). Simultaneous determination of BZ and DCBZ in water was developed on the basis of the TBDMS derivatives. Deuterated BZ (d8-BZ) was chosen as internal standard (IS) for analysis of water samples. BZ and DCBZ were extracted from water at pH 8.5 with dichloromethane and the extract was then dried and silylated. Recoveries of BZ and DCBZ were approximately 102 and 103% at a concentration of 2.0 ng mL⁻¹. The coefficients of variation for BZ and DCBZ were less than 9 and 4% at concentrations of 0.2 and 0.5 ng mL⁻¹, respectively. The method detection limits for 200 mL water were 0.004 ng mL⁻¹ for BZ and 0.02 ng mL⁻¹ for DCBZ.     

Selective Sorption–Spectrometric Determination of Nanogram Amounts of Vanadium(IV) and Vanadium(V)

Conditions of the selective sorption–spectrometric determination of vanadium(IV) and vanadium(V) using sulfonitrophenol M were found. The determination of vanadium (visual test (RSD = 30%) using a reference color scale or quantitative determination (RSD < 10%) by diffuse reflectance spectra is performed immediately after the dynamic-mode sorption of its colored complexes with sulfonitrophenol M at pH 3.5 (vanadium(IV)) or with sulfonitrophenol M and hydroxylamine at pH 1.5 (vanadium(V), 650 nm) at the surface of polyamide membrane disks (d= 1 cm, l= 0.1 mm, m= 2.7 mg). The flow rate is 10–20 mL/min. The detection limit is 5–7 ng of vanadium in the support zone or 0.2–0.5 ng/mL. The determination of 0.5–5 ng/mL vanadium(V) at pH 1.5 does not interfere with 20-fold amounts of V(IV) and 1000-fold amounts of Ni, Zn, Cd, Mg, Co, Cr(III), Mn, PO^3- ₄, and F^–.     

Flow Injection Chemiluminescence Determination of Pipemidic Acid Using On-Line Electrogenerated Cobalt(III) as Oxidant

 A novel flow injection chemiluminescence (CL) system for the determinati on of pipemidic acid is described. It is based on the direct CL reaction of pipemidic acid and Co(III) in acid medium. The unstable Co(III) was on-line electrogenerated by constant current electrolysis. The CL intensity was linear with pipemidic acid concentration in the range of 0.01∼100 μg/ml, the determination limit was 3.3×10⁻⁹ g/mL. The whole process could be complete d in 1 min with a relative standard deviation of 3.2%. The proposed method is suitable for automatic and continuous analysis and has been applied successfully to the analysis of pipemidic acid in a pharmaceutical preparation. Received November 22, 1999. Revision March 24, 2000.     

Flow Injection Chemiluminescence Determination of Prednisone Acetate by Oxidation with N-Bromosuccinimide

A simple flow injection chemiluminescence (CL) method for the determination of prednisone acetate was developed. This method is based on the fact that the strong CL of N-bromosuccinimide (NBS) and calcein can be inhibited by prednisone acetate. The CL intensity correlated linearly with the concentration of prednisone acetate over the ranges of 0.02–0.4 mg/L and 0.4–10 mg/L. The CL mechanism was also proposed. The detection limit (3σ) of prednisone acetate was 13 ng/mL and the relative standard deviation was 1.3% at 0.1 mg/L prednisone acetate (n = 11 measurements). This method was applied to the determination of prednisone acetate in the tablets with good results.     

A Novel Enhancing Flow-Injection Chemiluminescence Method for the Determination of Glutathione Using the Reaction of Luminol with Hydrogen Peroxide

 A rapid flow-injection method with chemiluminescence (CL) detection is described for the determination of glutathione (GSH). The method is based on the CL reaction of luminol and hydrogen peroxide. GSH can greatly enhance the chemiluminescence intensity in 0.1 mol/L borax–sodium hydroxide buffer solution (pH = 9.7). The maximum CL intensity was directly proportional to the concentration of GSH in the range 3.0 × 10⁻⁷–2.0 × 10⁻⁵ mol/L, and the detection limit was 6.8 × 10⁻⁸ mol/L. The relative standard deviation was 3.4% for 5.0 × 10⁻⁶ mol/L of GSH (n = 11). Received October 23, 2001; accepted June 18, 2002     

Quantitative determination of Phakellistatin 13, a new cyclic heptapeptide,in rat plasma by liquid chromatography/tandem mass spectrometry: application to a pharmacokinetic study

A sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method, followed by a 96-well protein precipitation, has been developed and fully validated for the determination of Phakellistatin 13 (PK13), a new cyclic heptapeptide isolated from the sponge Phakellia fusca Thiele, in rat plasma. After protein precipitation of the plasma samples (50 μL) in a 96-well plate by methanol (200 μL) containing the internal standard Pseudostellarin B (20 ng/mL), the plate was vortex mixed for 3 min. Following filtration for 5 min, the filtrate was directly injected into the LC-MS/MS system. The analytes were separated on an XB-C18 analytical column (5 μm, 50 mm × 4.6 mm i.d.) using an eluent of methanol–water (85:15, v/v) and detected by electrospray ionization mass spectrometry in the negative multiple reaction monitoring mode with a chromatographic run time of 5.0 min. The method was sensitive with a lower limit of quantification (LLOQ) of 0.1 ng/mL, with good linearity (r > 0.999) over the quantitation range of 0.1–5 ng/mL. The validation results demonstrated that this method was significantly specific, accurate, precise, and was successfully applied in measuring levels of PK13 in rat plasma following intravenous administration of 20, 50, and 100 μg/kg of peptide in rats, respectively, which was suitable for the preclinical pharmacokinetic studies on PK13.