Heat-gradient analytical technique for the simultaneous determination of some aromatic amines

A new sensitive analytical technique has been developed for the simultaneous determination of aromatic amines (aniline, p-nitroaniline, m-nitroaniline, o-nitroaniline, 1,3-phenylenediamine, and 1,4-phenylenediamine). It is based on the differential migration of colored derivatives formed by the reaction of diazotized amines with 8-hydroxy quinoline 5-sulphonic acid (FERRON) on a silica gel plate. Quantitative evaluation of amines is made by visual comparison of the intensities of color by spectrophotometry. The Beer’s law, molar absorptivity, and Sandell’s sensitivity have been determined. The effect of the analytical parameters on the migration and analysis have been evaluated. The method is highly reproducible and has been applied to the determination of amines in environmental samples. The text was submitted by the authors in English.     

Signals ratio method combined with wavelet transform: application to resolution of overlapped electrochemical signals

A signals ratio method combined with wavelet transform was proposed for the resolution of a weak voltammetric signal overlapped by other components. The signals ratio method usually suffers from interference from noise and baseline contained in the original signals because these factors cause distortion of the signals ratio. The multiresolution capability of the wavelet transform method was exploited here to simultaneously remove or reduce the noise and background. As a result, a deformation-free signals ratio with good signal-to-noise ratio (SNR) was obtained even for very noisy signals. The properties of the proposed method were compared to other resolution methods. It was demonstrated that the combined signals ratio wavelet transform method was particularly applicable to resolve a minor component in the presence of large amount of other components, suggesting that it can provide improved detection limits and quantified results for minor components. The method was employed for the voltammetric determination of residual chlorine in the presence of N,N-diethyl-p-phenylenediamine (DPD).     

Soft modelling for the resolution of highly overlapped voltammetric peaks: application to some Pb-phytochelatin systems

A differential pulse polarographic (DPP) study of the Pb²⁺/Cys-Gly, Pb²⁺/γ-Glu-Cys, Pb²⁺/PC₂ and Pb²⁺/PC₃ systems is performed, being PC₂ and PC₃ the phytochelatins of general structure (γ-Glu-Cys)_n-Gly, with n = 2 and 3, respectively. Analysis of DPP data is assisted by multivariate curve resolution with alternating least squares (MCR-ALS) method in order to establish the complexes formation sequence and their final stoichiometries. DPP signals of these systems present, besides overlapping of peaks due to free metal ion and metal complexes, interference of mercury anodic signals. Despite these complications, MCR-ALS allows us to propose a model of complexation for each system, and some tentative structures for the complexes.     

一种基于光谱分析的二元不完全重叠色谱峰的分离解析方法

基于二极管阵列检测器获得的色谱-光谱数据,建立了一种二元不完全重叠液相色谱峰的解析方法: 色谱数据经过去噪、归一化处理后,计算各时间点的光谱差异并进行系统聚类分析,提取特征光谱后,利用非负最小二乘法对色谱-光谱矩阵进行解析,得到基于特征光谱的流出曲线,进而得到分离后的色谱峰。将解析结果和纯标样的色谱峰进行比较,解析后的光谱图和纯标样的光谱图无显著差异,保留时间相差小于0.01 min。实验结果表明,该方法在二元不完全重叠液相色谱峰的解析方面能取得良好的效果。     

Application of a new method for simultaneous phase and baseline correction of NMR signals (SINC)

Recently, we presented a new approach for simultaneous phase and baseline correction of nuclear magnetic resonance (NMR) signals (SINC) that is based on multiobjective optimization. The algorithm can automatically correct large sets of NMR spectra, which are commonly acquired when reactions and processes are monitored with NMR spectroscopy. The aim of the algorithm is to provide spectra that can be evaluated quantitatively, for example, to calculate the composition of a mixture or the extent of reaction. In this work, the SINC algorithm is tested in three different studies. In an in-house comparison study, spectra of different mixtures were corrected both with the SINC method and manually by different experienced users. The study shows that the results of the different users vary significantly and that their average uncertainty of the composition measurement is larger than the uncertainty obtained when the spectra are corrected with the SINC method. By means of a dilution study, we demonstrate that the SINC method is also applicable for the correction of spectra with low signal-to-noise ratio. Furthermore, a large set of NMR spectra that was acquired to follow a reaction was corrected with the SINC method. Even in this system, where the areas of the peaks and their chemical shifts changed during the course of reaction, the SINC method corrected the spectra robustly. The results show that this method is especially suited to correct large sets of NMR spectra and it is thus an important contribution for the automation of the evaluation of NMR spectra.     

New analytical technique for the simultaneous determination of aromatic amines

Summary A new and sensitive analytical technique has been developed for the simultaneous determination of six aromatic amines. It is based on the differential migration of coloured derivatives formed by the reaction of the diazotized amines with 6-amino-1-naphthalene-3-sulphonic acid on a silica gel plate. The concentration is evaluated by colour comparison or by spectrophotometry under the influence of a temperature gradient. The method is highly reproducible and has been applied to the determination of amines in environmental samples. Standard deviations are 4.6–7.3%.     

A comparison of two algorithms for warping of analytical signals

The alignment of analytical signals is an important preprocessing step when further analysis (e.g. PCA) requires the same lengths of all of them. Two techniques for alignment of profiles, namely dynamic time warping (DTW) and correlation optimized warping (COW) were tested and compared. The attention was focused on chromatographic and spectroscopic profiles. Simulated and two sets of real data were studied in this study.     

Independent component analysis (ICA) algorithms for improved spectral deconvolution of overlapped signals in 1H NMR analysis: application to foods and related products

The major challenge facing NMR spectroscopic mixture analysis is the overlapping of signals and the arising impossibility to easily recover the structures for identification of the individual components and to integrate separated signals for quantification. In this paper, various independent component analysis (ICA) algorithms [mutual information least dependent component analysis (MILCA); stochastic non‐negative ICA (SNICA); joint approximate diagonalization of eigenmatrices (JADE); and robust, accurate, direct ICA algorithm (RADICAL)] as well as deconvolution methods [simple‐to‐use‐interactive self‐modeling mixture analysis (SIMPLISMA) and multivariate curve resolution‐alternating least squares (MCR‐ALS)] are applied for simultaneous ¹H NMR spectroscopic determination of organic substances in complex mixtures. Among others, we studied constituents of the following matrices: honey, soft drinks, and liquids used in electronic cigarettes. Good quality spectral resolution of up to eight‐component mixtures was achieved (correlation coefficients between resolved and experimental spectra were not less than 0.90). In general, the relative errors in the recovered concentrations were below 12%. SIMPLISMA and MILCA algorithms were found to be preferable for NMR spectra deconvolution and showed similar performance. The proposed method was used for analysis of authentic samples. The resolved ICA concentrations match well with the results of reference gas chromatography–mass spectrometry as well as the MCR‐ALS algorithm used for comparison. ICA deconvolution considerably improves the application range of direct NMR spectroscopy for analysis of complex mixtures. Copyright © 2014 John Wiley & Sons, Ltd.     

A novel stability‐indicating analytical method development for simultaneous determination of carboplatin and decitabine from nanoparticles

Drug resistance is one of the main problems of cancer treatment. For this reason, combination therapy is commonly used for years. The combination of a chemotherapeutic, carboplatin, and the epigenetic drug decitabine is a new approach to modulate drug resistance. Nanoparticulate systems can overcome the drawbacks associated with the drug combinations. An analytical method that can detect and quantify carboplatin and decitabine which is encapsulated into the nanoparticles is necessary for nanoparticle development. In the literature, there is no analytical method in which carboplatin and decitabine are determined simultaneously. The primary purpose of this study is to develop and validate a novel, and stability‐indicating high‐performance liquid chromatography method for simultaneous determination of carboplatin and decitabine in pharmaceutical preparations in addition to developing the first nanoformulation for this drug combination. Therefore, various experimental parameters were optimized. The chromatographic separation was achieved using an XSelect^® CSH C18 (250 × 4.6 mm I.D., 5 µm) column and a mobile phase consisting of methanol:water (containing 0.1% phosphoric acid) (3:97, v/v). The mobile phase pH was adjusted to 7.0 with 5 M NaOH. The developed method was successfully applied for the simultaneous determination and quantification of carboplatin and decitabine co‐encapsulated in nanoparticles and released into in vitro dissolution medium.     

Sensitive and rapid analytical method for the quantification of glucosamine in human plasma by ultra high performance liquid chromatography with tandem mass spectrometry

A highly sensitive and rapid ultra high performance liquid chromatography with tandem mass spectrometry method has been developed and validated for the determination of glucosamine in human plasma using miglitol as the internal standard. Special attention was paid to achieve the high throughput and sensitivity of the established method, and the absence of a matrix effect on the analytes. The sample preparation procedure involved a simple deproteinization step. The chromatographic separation was achieved on a Waters ACQUITY HSS Cyano column using a mixture of acetonitrile/2 mM ammonium acetate solution containing 0.03% formic acid (80:20, v/v) as the mobile phase with a very short run time of 1.5 min. This method was validated over the concentration range of 10–3000 ng/mL for glucosamine. The intra‐ and inter‐batch precision was <13.9% for the low, medium, and high quality control samples. The established method is highly sensitive with a lower limit of quantification of 10 ng/mL, low enough to determine the circadian rhythm on endogenous glucosamine level in human plasma, which has not been reported in detail until now. The method was successfully applied to characterize the pharmacokinetic profile of glucosamine in healthy volunteers following a single oral administration of 750 or 1500 mg glucosamine hydrochloride.     

Fast method for routine simultaneous analysis of methylmercury and butyltins in seafood

A simple, fast, and accurate method for the simultaneous determination of methylmercury (MeHg(+)), monobutyltin (MBT), dibutyltin (DBT) and tributyltin (TBT) in seafood is proposed. The method makes use of relatively cheap instrumentation and allows simultaneous analysis of those four species in a routine basis. The sample is treated with methanolic potassium hydroxide in an ultrasound bath, derivatised with sodium tetraethylborate (NaBEt(4)), preconcentrated into n-hexane and analysed by gas chromatography with atomic emission detection (GC-MIP/AES). The soft extraction conditions provided by ultrasound energy prevent chemical decomposition of the analytes and allow fast and efficient recovery of the species considered. Both the extraction and the derivatisation/preconcentration steps were optimised. Detection limits of 34, 3, 6 and 8 ng g(-1) (dry mass) were obtained for MeHg(+), MBT, DBT and TBT, respectively, using the best experimental conditions found. The uncertainty of the analysis ranged from 11% (MeHg(+)) to 15% (MBT). The accuracy of the method was checked by the analysis of several certified reference materials, e.g., BCR 477 (mussel tissue, MBT, DBT and TBT), DOLT-2 (dogfish liver, MeHg(+)), BCR 463 (tuna fish, MeHg(+)) and NIST 2976 (mussel tissue, MeHg(+)) with satisfactory results. Several oyster samples collected in the estuary of the Oka River (Urdaibai, Unesco Reserve of the Biosphere, Basque Country) during four sampling campaigns in 2003-2004 were processed following the proposed procedure. Concentrations ranging from 65 to 149 ng g(-1) (MeHg(+)), 相似文献   

Application of the H-point standard additions method by using absorbance increment values as analytical signals

This paper demonstrates how the absorbance increment (DeltaA) between two wavelengths selected according to the fundamental criteria for application of the H-Point standard additions method (HPSAM) are only related to the analyte concentration. A procedure for calculation of the unknown analyte concentration with no bias error by applying HPSAM to DeltaA values in much the same way as the method of standard additions (MOSA), is reported. The method was also applied to a calibration with a single standard. The results obtained on 6 samples with maximal separations between 65 and 0 nm are reported. Finally, the proposed method was applied to the resolution of different phenol-o-cresol mixtures.     

Sensitive electrochemical immunosensor array for the simultaneous detection of multiple tumor markers

A novel electrochemical immunosensor array for the simultaneous detection of multiple tumor markers was developed by incorporating electrochemically addressing immobilization and one signal antibody strategy. As a proof-of-principle, an eight-electrode array including six carbon screen-printed working electrodes was used as a base array for the analysis of two important tumor markers, carcinoembryonic antigen (CEA) and α-fetoprotein (AFP) and a horseradish peroxidase-labeled antibody was employed as a signal antibody. The immunosensor in the array was fabricated in sequence by covalently coupling the capture antibody onto the surface of the desired working electrode, which was firstly electrochemically addressably grafted with an aminophenyl group by reduction of in situ generated aminophenyl diazonium cation generated from p-phenylenediamine, using glutaraldehyde as cross-linker. This allowed the selective immobilization of the capture antibody at the desired position on a single array via an electrochemical operation. The immunoassay in sandwich mode was performed by specifically binding the targets, second antibodies and one signal antibody to the immunosensor array. The result showed that the steady current density was directly proportional to the concentration of target CEA/AFP in the range from 0.10 to 50 ng mL(-1) with a detection limit of 0.03 ng mL(-1) for CEA and 0.05 ng mL(-1) for AFP (S/N = 3), respectively. This work demonstrates that the employment of an electrochemically addressing method for the fabrication of an immunosensor array and one signal antibody is a promising approach for the determination of multiple tumor markers in clinical samples.     

Classification of mathematical models of peak-shaped analytical signals

A classification has been proposed for empirical models of analytical peaks that systematizes known approximation models. Ways of developing new models with desired characteristics are proposed. Presented at the V All-Russian Conference with the Participation of CIS Countries on Electrochemical Methods of Analysis (EMA-99), Moscow, December 6–8, 1999.     

Optimization of an analytical method for determining organotin compounds in fish tissue by base-hydrolysis pretreatment and simultaneous ethylation-extraction procedures

To determine butyl- and phenyl-tins in fish muscle, a method including base digestion pretreatment, followed by a simultaneous ethylation-extraction procedure and gas chromatograph-flame photometric detector (GC-FPD) analysis is outlined. Key parameters that influence analyte recovery were investigated and optimized. A solution of 3% (w/v) potassium hydroxide (KOH) and 1 h digestion time at 60 °C were chosen in the base digestion step, to ensure complete solubilization of fish muscle and the decomposition of organotins was found to be insignificant. We found that the ratio of fish muscle/reaction solution should not exceed 0.2 g (dry weight) per 100 mL in order to avoid the matrix effect caused by the binding of hydrolyzed fish tissue with organotin ions. Ethylation of organotins were conducted at pH 6-7 with a 1% (w/v) sodium tetraethylborate (NaBEt₄) solution for 1 h. This simple and timesaving procedure should be able to be applied to the routine analysis of organotins in other bio-tissues.     

Sensitive fluorescence labelling for analysis of organotin compounds with morin

Summary Analytical procedures based on reversed-phase high-performance liquid chromatography combined with post-column derivatization with morin for the determination of organotin compounds in peanut oil, water samples or diet mixtures are described. A mixture of the isooctylesters of monooctyl tin and dioctyl tin thioglycolic acid (ZK 30 434), a mixture of the isooctylesters of monododecyl tin and didodecyl tin thioglycolic acid (ZK 32 283) or dibutyl tin difluoride (ZK 38 068) had to be analysed. The data obtained from validation and during routine analysis show that the post-column derivatization with morin is a powerful tool for the selective and sensitive detection of organotin compounds in complicated matrices. Interferences of peaks related to the organotins and the matrix constituents were not found. The values of the limit of detection were 10 g ZK 30 434 or ZK 32 283/ml peanut oil, 60 ng ZK 38 068/ml water and 2.5 mg ZK 30 434/kg rodent diet mixture. Regarding to the repeatability, the methods described are characterized by values of the relative standard deviation of mostly less than 5%. In case of the determination of ZK 30 434 dissolved in peanut oil atomic absorption spectrometry was used to investigate the accuracy of the HPLC method. A good correlation between the HPLC and AAS data was found. The limits of quantitation were 0.25 mg ZK 30 434/ml peanut oil, 0.22 mg ZK 32 283/ml peanut oil and 1.0 g ZK 38 068/ml water. The analytical procedures were applied within the framework of the analytical service for validation of toxicological studies according to the guidelines of good laboratory practices (G.L.P.). Both the correct preparation of the formulations and the homogeneity or stability could be checked.