Rapid simultaneous analysis of 1-naphthol and 2-naphthol in water samples by derivative variable-offset synchronous fluorescence spectroscopy

Derivative variable-offset synchronous fluorescence spectroscopy is developed to improve the spectral resolution and the selectivity of fluorescence measurements. 1-naphthol and 2-naphthol are employed to evaluate the proposed coupled technique and the various spectral comparisons are conducted. Second derivative variable-offset synchronous scanning permits the rapid simultaneous identification and quantitative determination of 1-naphthol and 2-naphthol in a mixture from a single spectrum. 6.7-2000 ng/ml 1-naphthol and 3.6-500 ng/ml 2-naphthol can be quantified with 1-naphthol and 2-naphthol ratios of 40: 1-1: 10. The determination of 1-naphthol and 2-naphthol in various spiked water samples gave a mean recovery of 100.7% with a relative standard deviation of 2.8% for 1-naphthol and mean recovery of 99.7% with a relative standard deviation (RSD of 2.6% for 2-naphthol, respectively.     

Second derivative synchronous fluorescence spectroscopy for the simultaneous determination of metoclopramide and pyridoxine in syrup and human plasma

A rapid, simple, and highly sensitive second derivative synchronous fluorometric method has been developed for the simultaneous determination of metoclopramide (MT) and pyridoxine (PY) in a binary mixture. The method is based on measurement of the native fluorescence of these drugs at delta lambda = 80 nm in methanol. The different experimental parameters affecting the native fluorescence of the drugs were carefully studied and optimized. The fluorescence-concentration plots were rectilinear over the ranges of 0.02-0.4 and 0.1-2 microg/mL for MT and PY, respectively. The limits of detection were 0.003 and 0.007 microg/mL and the limits of quantification were 0.008 and 0.02 microg/mL for MT and PY, respectively. The proposed method was successfully applied to the determination of MT and PY in synthetic mixtures and in commercial syrup. The results were in good agreement with those obtained with a reported method. The high sensitivity attained by the proposed method allowed the determination of MT in spiked and real human plasma samples. The mean percent recoveries of MT from spiked and real human plasma (n = 3) were 93.72 +/- 3.15 and 89.72 +/- 2.19 respectively.     

Chiral separation and determination of ofloxacin enantiomers by ionic liquid-assisted ligand-exchange chromatography

A simple and accurate method for the separation and determination of ofloxacin enantiomers was developed by ionic liquid-assisted ligand-exchange high performance liquid chromatography. Both achiral and chiral ionic liquids were tested for their efficiency of ofloxacin enantiomeric separation. The effects of ligands, concentration of metal ion, organic modifier, pH of the mobile phase, and temperature were also investigated and evaluated. Optimal conditions were obtained on a conventional C(18) column, where the mobile phase consisted of methanol/water (20 : 80, v/v) (containing 4.0 mmol L(-1) amino acid ionic liquid and 3.0 mmol L(-1) copper sulfate) at a flow rate of 0.5 mL min(-1). Under this condition, the ofloxacin enantiomers could be baseline separated within 14 minutes; the proposed method was used to analyze different commercial ofloxacin medicines.     

高效液相色谱法同时测定水体中氧氟沙星及其手性异构体

建立了一种简单快捷的手性配位交换高效液相色谱测定地表水中氧氟沙星及其手性异构体的方法,并研究了常见金属阳离子（Ca²⁺、Mg²⁺、Fe³⁺、Zn²⁺）和腐殖酸（HA）对二者分离的影响。采用C₁₈色谱柱（25 cm×0.46 cm,5 μm）,流动相为pH值4.5的20%（v/v）甲醇水溶液（含4 mmol/L异亮氨酸（配体）和3 mmol/L CuSO₄）,流速为1.0 mL/min,柱温为40℃,检测波长为293 nm。氧氟沙星及其手性异构体左氧氟沙星可在18 min内分离,分离度（R）为2.70。结果表明,不同金属阳离子和腐殖酸对手性分离未见明显影响,但会降低氧氟沙星及其手性异构体的峰面积,其中Fe³⁺和高浓度腐殖酸的影响最大。该法能够快速高效测定地表水中氧氟沙星及其手性异构体,但在测试中需考虑Fe³⁺和高浓度腐殖酸的影响。     

Simultaneous determination of sulpiride and its alkaline degradation product by second derivative synchronous fluorescence spectroscopy

Simple and sensitive synchronous fluorimetric, and second derivative synchronous fluorometric methods were developed for the validated and simultaneous determination of sulpiride (SLP) and its alkaline degradation product (DSLP). The method is based on measuring the synchronous fluorescence of both the drug and its degradation product in borate buffer of pH 8 at Δλ of 45 nm. The peak amplitude (²D) was measured at 295.5 and 342 nm for SLP and DSLP, respectively. The different experimental parameters affecting the synchronous fluorescence intensity of both compounds were studied and optimized. The fluorescence-concentration plots were rectilinear over the range of 0.05-1.0 and 2-10 μg mL⁻¹ for SLP and DSLP, respectively. The limits of detection (LOD) were 0.02 and 0.4 μg mL⁻¹ and quantification limits (LOQs) were 0.05 and 1.2 μg mL⁻¹ for SLP and DSLP, respectively. The proposed methods were successfully applied to commercial capsules and tablets. Statistical comparison of the results with those of the official method revealed good agreement and proved that there were no significant difference in the accuracy and precision between the two methods, respectively. The method was utilized to study the kinetics of the alkaline induced degradation of the drug. The application was further extended to include the in vivo and in vitro determination of sulpiride. The mean % recoveries (n = 3) were 100.22 ± 2.04 and 92.00 ± 3.00 for spiked and real human plasma, respectively.     

衍生荧光法测定盐酸西布曲明

通过衍生反应，建立了用荧光光度法测定盐酸西布曲明的新方法。并对衍生体系、反应条件、产物稳定性等进行了研究。实验确定丙二酸和乙酸酐混合试剂与盐酸西布曲明在75℃的水浴中加热15min，所得产物发射强荧光，最大激发波长λcx=456nm，最大发射波长λem=496nm。在上述波长下，荧光强度与盐酸西布曲明的质量浓度在0．11～9．5μg／mL范围内呈良好的线性关系，检出限为13．4ng／mL，标准加入回收率在95．4％～104．2％。用于曲美胶囊中盐酸西布曲明的测定。     

比值导数荧光光谱法同时测定色氨酸和5-羟基色氨酸

建立了比值导数荧光光谱法同时测定色氨酸和5-羟基色氨酸的方法。在比值导数荧光光谱法中,色氨酸浓度在4.0×10-6~2.0×10-5mol/L范围内比值导数荧光光谱峰高与其浓度成正比,线性相关系数为0.9901,检出限为1.3×10-7mol/L。5-羟基色氨酸浓度在4.0×10-8~2.0×10-5mol/L范围内比值导数光谱峰高与其浓度成正比,线性相关系数为0.9996,检出限为1.3×10-8mol/L。同时测定了实际样品中的色氨酸和5-羟基色氨酸,测定结果与高效液相色谱法有良好的一致性。     

The determination of lead by atomic fluorescence spectroscopy

The atomic fluorescence characteristics of lead are described in air-acetylene, nitrous oxide-hydrogen, and argon-oxygen-hydrogen flames. An electrodeless discharge tube is used as the source of excitation. A detection limit of 0.01 μg/ml of lead in aqueous solution is obtained by measurement of the direct-line fluorescence at 405.8 nm in the argon-oxygen-hydrogen flame. The effect of 100-fold excesses of 30 cations and anions is examined: only aluminium interfered significantly. Effects of multipass optics and signal collection mirrors are examined and their effect on signalnoise ratios is discussed.     

Chemometrics-assisted excitation-emission fluorescence spectroscopy for simultaneous determination of ethoxyquin and tert-butylhydroquinone in biological fluid samples

A novel method applying simple, rapid, effective and inexpensive excitation-emission matrix (EEM) fluorescence spectroscopy coupled with second-order calibration method for simultaneous determination of ethoxyquin (EQ) and tert-butylhydroquinone (TBHQ) contents in biological fluid samples was developed. After a simple data preprocessing that was to insert zeros below the first-order Rayleigh scattering, the second-order calibration method based on the alternating normalization-weighed error (ANWE) algorithm was used to deal with EEM data. Via the introduced "second-order advantage", the individual con- centrations of the analytes of interest could be obtained even in the presence of uncalibrated interferences. The experimental concentration ranges for the analytes were as follows: EQ, from 4.58 to 20.6 g mL 1 in plasma and from 6.87 to 20.6 g mL 1 in urine; TBHQ, from 4.49 to 20.2 g mL-1 in plasma and from 6.73 to 22.4 g mL-1 in urine. The recoveries from spiked biological fluid samples were in the ranges of 92.8%-106.2% for EQ and 94.6%-107.2% for TBHQ. These results demonstrate that the three-dimensional EEM fluorescence with second-order calibration method is a powerful tool for obtaining both EQ and TBHQ quantitative results in plasma and urine samples, and could be applied to more complex matrices.     

Second-derivative synchronous fluorescence spectroscopy for the simultaneous determination of cinnarizine and nicergoline in pharmaceutical preparations

A rapid, simple, and highly sensitive second-derivative synchronous fluorometric method has been developed for the simultaneous analysis of binary mixtures of cinnarizine (CN) and nicergoline (NIC). The method is based upon measurement of the native fluorescence of these drugs at constant wavelength difference (Deltalambda) = 80 nm in aqueous methanol (50%, v/v). The different experimental parameters affecting the native fluorescence of the studied drugs were carefully studied and optimized. The fluorescence-concentration plots were rectilinear over the range of 0.025-1.5 and 0.25-5.5 microg/mL for CN and NIC, respectively, with lower detection limits of 0.58 and 0.82 ng/mL and quantitation limits of 1.93 and 2.73 ng/mL for CN and NIC, respectively. The proposed method was successfully applied for the determination of the studied compounds in synthetic mixtures and in commercial tablets. The results obtained were in good agreement with those obtained with reference methods. The high sensitivity attained by the proposed method allowed the determination of CN in real and spiked human plasma. The mean recovery in the case of spiked human plasma [number of trials (n) = 3] was 102.82 +/- 2.17%, while that in real human plasma (n = 3) was 105.25 +/- 2.05.     

Separation of ofloxacin enantiomers by capillary electrophoresis with fluorescence detection using deoxyribonucleic acid oligonucleotides as chiral selectors

This study used capillary electrophoresis with fluorescence detection- and a partial-filling mode-based method for chiral separation of ofloxacin. The deoxyribonucleic acid oligonucleotides with different base sequences were studied as potential chiral selectors including deoxyribonucleic acid tetrahedron, G-quadruplex, and G-riched double-strand deoxyribonucleic acid. Under the optimized conditions, all the deoxyribonucleic acid chiral selectors exhibited excellent chiral separation capabilities with a resolution higher than 1.5. The electrophoretic behavior of the ofloxacin enantiomer might result from the intermediate conjugate with different stabilities between chiral selectors and analytes by a combination of the hydrogen bond and spatial recognition structure. Moreover, satisfactory repeatability regarding run-to-run and interday repeatability was obtained, and all the relative standard deviation values of migration times and resolutions were below 4% (n = 6). Conclusively, both spatial structure and arrangement of the G bases potentiated the chiral separation capability of deoxyribonucleic acid for ofloxacin enantiomer. This work offered a stepping stone for enantioseparation using deoxyribonucleic acid as chiral selectors.     

Simultaneous determination of warfarin and bromadiolone by derivative synchronous fluorescence spectrometry

By using second derivative synchronous fluorescence spectrometry the simple resolution of mixtures of the anticoagulant rodenticides warfarin and bromadiolone in the presence of beta-cyclodextrin is accomplished which causes a differential effect on the fluorescence intensity of these compounds. The determination method developed is simple, fast and inexpensive; in addition, measurements are performed in a single scan. Mixtures of warfarin and bromadiolone in ratios between 4:1 and 1:10 were satisfactorily resolved.     

Chiral separation of ofloxacin enantiomers by ligand exchange chromatography

Abstract  

The enantioseparation conditions of ligand exchange chromatography were examined using ofloxacin enantiomers. A C₁₈ column was used with the mobile phase consisting of a methanol–water solution (containing different concentrations of l-isoleucine and copper sulfate) at flow rate of 0.5 cm³ min⁻¹. The effect of different kinds and concentrations of ligands, bivalent ligand ions, and organic modifier, and temperature on enantioseparation were evaluated; the results showed that enantioselectivity was strongly affected by the ligand concentration of the mobile phase. Under the optimum conditions (methanol/water 20:80 v/v, containing 2.5 mmol dm⁻³ l-isoleucine and 0.6 mmol dm⁻³ Cu²⁺, room temperature), baseline separation of the two enantiomers was obtained with resolution of 1.32 in less than 30 min. The separation method was used to analyze the ofloxacin enantiomers in different commercial medicines.     

Time-resolved fluorescence spectroscopy of hematoporphyrin derivative in micelles

Time-resolved fluorescence spectroscopy was performed on hematoporphyrin derivative in buffer at different concentrations of surfactants. New molecular species were detected, with fluorescence decay time constants of ≈0.7 and ≈2.7 ns and emission peaks at 630 and 675 nm, respectively. Deaggregation effects were observed, mainly in the presence of cationic micelles.     

Determination of ofloxacin enantiomers in sewage using two-step solid-phase extraction and liquid chromatography with fluorescence detection

A robust analytical method has been developed and validated for the trace analysis of ofloxacin enantiomers in sewage using two-step solid-phase extraction purification and liquid chromatography with fluorescence detection (LC-FL). Ofloxacin enantiomers were separated on an Aglient TC-C-18 column using MeOH-water containing 4mmol/L CuSO4 and 5mmol/L l-isoleucine as mobile phase. The ofloxacin enantiomers were first extracted by a weak cation-exchange resin (WCX) and eluted with acidified MeOH (0.5% formic acid), then further purified by mixed mode of anion-exchange resin (MAX), resulting in ofloxacin recoveries generally above 95%. The limit of quantification was 0.08microg/L for each enantiomer. No significant matrix effect was found during the analytical procedure and standard solution calibration curves could be used for quantification. Total concentrations of both enantiomers in real sewage samples based on LC-FL method were consistent with those obtained upon liquid chromatography using tandem mass spectrometry (LC-MS/MS) method.     

二阶导数-同步荧光法同时测定微量维生素B_1,B_2和烟酰胺

建立了二阶导数-同步荧光法同时测定微量维生素B1,B2和烟酰胺含量的方法.在最佳实验条件下,维生素B1,B2和烟酰胺的检测限分别为2.1,2.6,和2.8 ng/mL,相对标准偏差为1.5%～4.9%,加标回收率为92%～105%.该方法可用于样品中微量维生素的测定.     

Pharmacokinetic study of ofloxacin enantiomers in Pagrosomus major by chiral HPLC

(S)‐(?)‐Ofloxacin and (R)‐(+)‐ofloxacin concentrations in the plasma of Pagrosomus major after drug treatment were detected by chiral high‐performance liquid chromatography, and various pharmacokinetic parameters were calculated from these data. The elimination half‐life of (S)‐(?)‐ofloxacin was significantly shorter than that of the (R)‐(+) enantiomer. (S)‐(?)‐Ofloxacin also had a significantly lower maximum plasma concentration, area under the concentration–time curve from zero to infinity, and mean residence time than (R)‐(+)‐ofloxacin. However, the apparent volume of distribution and total body clearance of (S)‐(?)‐ofloxacin were greater than those of (R)‐(+)‐ofloxacin. The ratio of the (S)‐(?)‐ to (R)‐(+)‐ofloxacin plasma concentration was always <1.0. Together, these data suggest that (S)‐(?)‐ofloxacin was preferentially excreted and (R)‐(+)‐ofloxacin was preferentially absorbed. Although the difference in pharmacokinetic parameters was small, the metabolic behavior of the ofloxacin enantiomers in P. major was enantioselective. Copyright © 2015 John Wiley & Sons, Ltd.     

Highly sensitive determination of chlorpheniramine as fluorescence derivative by high-performance liquid chromatography

A new method has been developed for the quantitative analysis of chlorpheniramine in human blood using high-performance liquid chromatography with a fluorescence detector. Benzyl chloroformate was found to be suitable as a fluorometric derivatizing reagent. A linear calibration curve ranging from 0 to 40 ng was obtained for chlorpheniramine, and the minimum detectable concentration was 0.1 ng/ml (whole blood) at a signal-to-noise ratio of 2. It was confirmed that chlorpheniramine levels in the blood of healthy adult volunteers could be precisely determined up to 96 h after a single oral administration of a tablet containing 4 mg of chlorpheniramine.