A chitosan–polypyrrole magnetic nanocomposite as μ-sorbent for isolation of naproxen

An extracting medium based on chitosan–polypyrrole (CS–PPy) magnetic nanocomposite was synthesized by chemical polymerization of pyrrole at the presence of chitosan magnetic nanoparticles (CS-MNPs) for micro-solid phase extraction. In this work, magnetic nanoparticles, the modified CS-MNPs and different types of CS–PPy magnetic nanocomposites were synthesized. Extraction efficiency of the CS–PPy magnetic nanocomposite was compared with the CS-MNPs and Fe₃O₄ nanoparticles for the determination of naproxen in aqueous samples, via quantification by spectrofluorimetry. The scanning electron microscopy images obtained from all the prepared nanocomposites revealed that the CS–PPy magnetic nanocomposite possess more porous structure. Among different synthesized magnetic nanocomposites, CS–PPy magnetic nanocomposite showed a prominent efficiency. Influencing parameters on the morphology of CS–PPy magnetic nanocomposite such as weight ratio of components was also assayed. In addition, effects of different parameters influencing the extraction efficiency of naproxen including desorption solvent, desorption time, amount of sorbent, ionic strength, sample pH and extraction time were investigated and optimized. Under the optimum condition, a linear calibration curve in the range of 0.04–10 μg mL⁻¹ (R² = 0.9996) was obtained. The limits of detection (3S_b) and limits of quantification (10S_b) of the method were 0.015 and 0.04 μg mL⁻¹ (n = 3), respectively. The relative standard deviation for water sample spiked with 0.1 μg mL⁻¹ of naproxen was 3% (n = 5) and the absolute recovery was 92%. The applicability of method was extended to the determination of naproxen in tap water, human urine and plasma samples. The relative recovery percentages for these samples were in the range of 56–99%.     

Simultaneous spectrofluorimetric determination of levodopa and propranolol in urine using feed-forward neural networks assisted by principal component analysis

The simultaneous determination of levodopa (LD) and propranolol (PRO) using fluorescence spectrometric technique is described. The method involves measuring the natural fluorescence of these drugs in the micellar media of sodium dodecyl sulfate (SDS) using principal component analysis-feed-forward neural networks (PC-FFNNs). Experimental conditions such as effect of pH and SDS concentration were optimized. Under the optimum conditions, the linear determination ranges of LD and PRO are 2.0 × 10⁻⁸ to 1.0 × 10⁻⁵ mol L⁻¹ and 3.6 × 10⁻⁹ to 1.8 × 10⁻⁶ mol L⁻¹, respectively. A set of synthetic binary mixtures of LD and PRO was prepared and their concentrations were predicted by the proposed method. Satisfactory results were obtained by the combination of fluorescence technique with chemometrics methods. The method was successfully applied to the determination of LD and PRO in tap water and in urine samples.     

Rapid and sensitive spectrofluorimetric determination of enrofloxacin, levofloxacin and ofloxacin with 2,3,5,6-tetrachloro-p-benzoquinone

A highly sensitive spectrofluorimetric method was developed for the first time, for the analysis of three fluoroquinolones (FQ) antibacterials, namely enrofloxacin (ENR), levofloxacin (LEV) and ofloxacin (OFL) in pharmaceutical preparations through charge transfer (CT) complex formation with 2,3,5,6-tetrachloro-p-benzoquinone (chloranil,CLA). At the optimum reaction conditions, the FQ–CLA complexes showed excitation maxima ranging from 359 to 363 nm and emission maxima ranging from 442 to 488 nm.Rectilinear calibration graphs were obtained in the concentration range of 50–1000, 50–1000 and 25–500 ng mL⁻¹ for ENR, LEV and OFL, respectively.The detection limit was found to be 17 ng mL⁻¹ for ENR, 17 ng mL⁻¹ for LEV, 8 ng mL⁻¹ for OFL, respectively. Excipients used as additive in commercial formulations did not interfere in the analysis. The method was validated according to the ICH guidelines with respect to specificity, linearity, accuracy, precision and robustness. The proposed method was successfully applied to the analysis of pharmaceutical preparations. The results obtained were in good agreement with those obtained using the official method; no significant difference in the accuracy and precision as revealed by the accepted values of t- and F-tests, respectively.     

硫胺素-亚硝酸根体系的荧光性质研究及应用

研究了在碱性溶液中硫胺素（VB1）与亚硝酸根的荧光反应,建立了荧光光度法测定硫胺素的新方法。方法线性范围为1．28－324ng/mL,检出限0．52ng/mL,对15个浓度为100ng/mL的硫胺素溶液进行测定,相对标准偏差为1．4％。应用于药物中硫胺素的测定,回收率在96．5％－101．8％之间。     

荧光光谱法研究利血平的氧化作用及其分析应用

利血平自身有弱荧光,氧化后可形成较强荧光物质。本文系统地研究了稀ＨＮＯ３对利血平的氧化作用,提出了高灵敏度测定利血平含量的荧光光度分析新方法。结果表明,荧光强度和利血平的浓度在０．０２－０．４μｇ／ｍＬ范围内呈良好的线性关系,方法的检出限为０．００２μｇ／ｍＬ（６．７３＊１０＾－９ｍｏｌ／Ｌ）。该法简便,快速、灵敏度高,用于注射液中利血平含量的测定,结果令人满意。     

Evaluation of a sensitive HPLC method for the determination of Malondialdehyde, and application of the method to different biological materials

Summary Reactive oxygen species (ROS), important mediators of cell and tissue injury during inflammation, are produced by several types of inflammatory cells. The formation of ROS can be monitored by detection of lipid peroxidation products. The extremely broad spectrum of biological effects of aldehydic lipid peroxidation products has necessitated the development of a technique that enables the sensitive routine quantitation of aldehydes formed in biological materials. Malondialdehyde (MDA) is a by-product of enzymatic eicosanoid formation and an end-product of nonenzymatic peroxidation of polyunsaturated fatty acids with three or more bisallylic double bonds. The determination of the thiobarbituric acid derivative of MDA (TBA-MDA) is a widely used method for estimating overall lipid peroxidation. We describe a rapid, isocratic, simple, and sensitive high-performance liquid chromatographic (HPLC) method with spectrofluorimetric detection for measurement of MDA-TBA in human biological samples such as plasma, urine, wound secretions, amniotic fluid, sputum and tissue samples. By use of this method, picomole quantities of MDA can be readily and specifically detected in different biological materials. Coefficients of variation of repeated MDA-TBA assays were 4.4% within run and 6.9% from run to run. Reference values are given for a variety of human body fluids and for rat tissues.     

Spectrofluorimetric Determination of Trace Amounts of Gallium with Salicylaldehyde Benzoylhydrazone

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Two different strategies for the fluorimetric determination of piroxicam in serum

Two different spectrofluorimetric methods for the determination of piroxicam (PX) in serum are presented and discussed. One of them is based on the use of three-way fluorescence data and multivariate calibration performed with parallel factor analysis (PARAFAC) and self-weighted alternating trilinear decomposition (SWATLD). This methodology exploits the so-called second-order advantage of the three-way data, allowing to obtain the concentration of the studied analyte in the presence of any number of uncalibrated (serum) components. The method was developed following two different procedures: internal standard addition and external calibration with standard solutions, which were compared and discussed. The second approach investigated is based on the combination of solid-phase extraction (SPE) and room temperature fluorimetry. Both methods here presented yield satisfactory results. The concentration range in which PX could be determined in serum was 1–10 μg ml⁻¹. The limits of quantification for the experimental solutions using the chemometric approach were 0.09 μg ml⁻¹ for the standard addition mode and 0.12 μg ml⁻¹ using external calibration (both for PARAFAC and SWATLD algorithms). In the solid-surface fluorimetric method, the calibration graph was linear up to 0.22 μg ml⁻¹ and the limit of quantification was 0.02 μg ml⁻¹.     

偏最小二乘-同步荧光法测定人尿中黄蝶呤

建立了人尿中黄蝶呤含量测定的同步荧光分析方法。在pH 7.8 KH2PO4-NaOH缓冲溶液中,于Δλ为70 nm的条件下对黄蝶呤及其它蝶呤类化合物进行同步荧光扫描,所得的重叠波谱数据用主成分回归法(PCR)、偏最小二乘法(PLS)、经典最小二乘法(CLS)和径向基人工神经网络(RBF-ANN)等多元校正法进行处理,结果表明偏最小二乘法(PLS)的分析结果最好,其标准偏差为4.29%。该方法简便、快速、准确,避免了较繁琐的样品前处理过程,应用于人尿中黄蝶呤分析,结果令人满意。     

Highly sensitive spectrofluorimetric determination of trace amounts of lecithin

A new spectrofluorimetric method was developed for the determination of trace amounts of lecithin using the ciprofloxacin (CIP)–terbium (Tb³⁺) ion complex as a fluorescent probe. In a buffer solution at pH=5.60, lecithin can remarkably reduce the fluorescence intensity of the CIP–Tb³⁺ complex at λ=545 nm. The reduced fluorescence intensity of the Tb³⁺ ion is proportional to the concentration of lecithin. Optimum conditions for the determination of lecithin were also investigated. The linear range and detection limit for the determination of lecithin were 1.0×10⁻⁶–3.0×10⁻⁵ mol L⁻¹ and 3.44×10⁻⁷ mol L⁻¹, respectively. This method is simple, practical, and relatively free of interference from coexisting substances. Furthermore, it has been successfully applied to assess lecithin in serum samples.