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Abstract: In recent years, total synchronous fluorescence (TSF) spectroscopy has become popular for the analysis of multifluorophoric systems. Application of PARAFAC, a popular deconvolution tool, requires trilinear structure in the three-way data array. The present work shows that TSF based three-way array data set of dimension sample×wavelength×Δλ does not have trilinear structure and hence it should not be subjected to PARAFAC analysis. This work also proposes that a TSF data set can be converted to an excitation–emission matrix fluorescence (EEMF) like data set which has trilinear structure, so that PARAFAC analysis can be performed on it. This also enables the retrieval of PARAFAC-separated component TSF spectra. [Copyright &y& Elsevier]

Abstract: Many complex natural or synthetic products are analysed either by the GC–MS (gas chromatography–mass spectrometry) or HPLC–DAD (high performance liquid chromatography–diode-array detector) technique, each of which produces a one-dimensional fingerprint for a given sample. This may be used for classification of different batches of a product. GC–MS and HPLC–DAD analyses of complex, similar substances represented by the three common types of the TCM (traditional Chinese medicine), Rhizoma Curcumae were analysed in the form of one- and two-dimensional matrices firstly with the use of PCA (Principal component analysis), which showed a reasonable separation of the samples for each technique. However, the separation patterns were rather different for each analytical method, and PCA of the combined data matrix showed improved discrimination of the three types of object; close associations between the GC–MS and HPLC–DAD variables were observed. LDA (linear discriminant analysis), BP-ANN (back propagation-artificial neural networks) and LS-SVM (least squares-support vector machine) chemometrics methods were then applied to classify the training and prediction sets. For one-dimensional matrices, all training models indicated that several samples would be misclassified; the same was observed for each prediction set. However, by comparison, in the analysis of the combined matrix, all models gave 100% classification with the training set, and the LS-SVM calibration also produced a 100% result for prediction, with the BP-ANN calibration closely behind. This has important implications for comparing complex substances such as the TCMs because clearly the one-dimensional data matrices alone produce inferior results for training and prediction as compared to the combined data matrix models. Thus, product samples may be misclassified with the use of the one-dimensional data because of insufficient information. [Copyright &y& Elsevier]

Abstract: Chemical imaging is a rapidly emerging analytical method in pharmaceutical technology. Due to the numerous chemometric solutions available, characterization of pharmaceutical samples with unknown components present has also become possible. This study compares the performance of current state-of-the-art curve resolution methods (multivariate curve resolution-alternating least squares, positive matrix factorization, simplex identification via split augmented Lagrangian and self-modelling mixture analysis) in the estimation of pure component spectra from Raman maps of differently manufactured pharmaceutical tablets. The batches of different technologies differ in the homogeneity level of the active ingredient, thus, the curve resolution methods are tested under different conditions. An empirical approach is shown to determine the number of components present in a sample. The chemometric algorithms are compared regarding the number of detected components, the quality of the resolved spectra and the accuracy of scores (spectral concentrations) compared to those calculated with classical least squares, using the true pure component (reference) spectra. It is demonstrated that using appropriate multivariate methods, Raman chemical imaging can be a useful tool in the non-invasive characterization of unknown (e.g. illegal or counterfeit) pharmaceutical products. [Copyright &y& Elsevier]

Abstract: The objective of this study was to investigate the spectral behavior of the relationship between reflectance and chlorophyll content and to develop a technique for non-destructive chlorophyll estimation and distribution in leaves using hyperspectral imaging. The hyperspectral imaging data cube of cucumber (Cucumis sativus) leaves in the range of 450–850nm was investigated and preprocessed. Sixty optical signatures or indices as a function of the associated reflectance (R λ ) at the special wavelength (λ) nm which proposed in the literatures were used to predict the total chlorophyll content in cucumber leaves. Finally, R 710/R 760, (R 780 − R 710)/(R 780 − R 680), (R 750 − R 705)/(R 750 + R 705), (R 680 − R 430)/(R 680 + R 430), R 860/(R 550 × R 708), (R 695−705)−1 −(R 750−800)−1, and REP-LEM (a index based on red edge position and estimated with a linear extrapolation method) were identified as optimum indices. Red-edge waveband (680–780nm) appeared in all these optimum indices, indicating the importance of REP (red edge position) in chlorophyll estimation. When (R 695−705)−1 −(R 750−800)−1, the best index was applied to an independent validation set, chlorophyll content (r =0.8286) were reasonably well predicted, indicating model robustness. Depending on the sample, this technique enables to identify and characterize the relative content of various chlorophyll that distribution in the cucumber leaves. The map shows a relatively low level of chlorophyll at margins. Higher level can be noticed in the regions along the main veins and in some areas exhibiting dark green tissue. Our results indicate that hyperspectral imaging has considerable promise for predicting pigments in leaves and, the pigments can be detected in situ in living plant samples non-destructively. [Copyright &y& Elsevier]

Abstract: Fundamental research on non-spectroscopic interferences, also known as matrix effects, in inductively coupled plasma (ICP) mass spectrometry with sample introduction using nebulization is critically and exclusively examined in this review, starting with fundamental processes that may be a source of matrix effects during sample introduction, ion generation in the ICP, ion extraction through the interface, and ion transport through the ion optics to the detector. Various methods for attenuating matrix effects are then reviewed and illustrated with some examples. Instead of exhaustively reviewing the literature, representative references are used to comprehensively describe the main issues, several of which are also common to ICP optical emission spectrometry. [Copyright &y& Elsevier]

Abstract: The output of many instruments can be modeled as a convolution of an impulse response and a series of sharp spikes. Deconvolution considers the inverse problem: estimate the input spike train from an observed (noisy) output signal. We approach this task as a linear inverse problem, solved using penalized regression. We propose the use of an L 0 penalty and compare it with the more common L 2 and L 1 penalties. In all cases a simple and iterative weighted regression procedure can be used. The model is extended with a smooth component to handle drifting baselines. Application to three different data sets shows excellent results. [Copyright &y& Elsevier]

Abstract: In this paper a new model based on frequency self deconvolution (FSD) is proposed for the quantitative analysis of a near infrared (NIR) spectrum. The model couples FSD and partial least square regression (PLS). The grid search optimization method is used to select the optimal values of the full width at half height (FWHH) and the truncation point of the apodization function. The proposed FSD–PLS provides a significant improvement in the prediction ability of the PLS model. Furthermore, a modification of the new FSD–PLS method is introduced to enable the removal of the baseline variations from the NIR spectra. The proposed models were validated using absorbance spectra of mixtures composed from glucose, urea and triacetin in a phosphate buffer solution where the concentrations of the components are selected to be within their physiological range in blood. The whole experiments were carried out in a non-controlled environment to show that the model can suppress effectively most of the experimental variations. The results show that the standard error of prediction (SEP) decreases from 35.58mgdL−1 using 8 factors for the PLS model to 15.53mgdL−1 by using 12 factors for the modified FSD–PLS model. The proposed models are also shown to yield a slightly improved performance than a newly developed second derivative-PLS model without incurring the shortcoming associated with the derivative approach in not providing interpretable results and in degrading the SNR of the spectra at a faster rate. [Copyright &y& Elsevier]

Abstract: Sign of two-dimensional (2D) correlation peaks provides information on sequence of spectral events. This information is related to molecular mechanism of changes in a given system. Recently, few papers addressing the problems with interpretation of the sign of 2D correlation peaks have been published. To overcome these problems, a modification of the generalized 2D correlation method has been proposed. This method compares variations in the dynamic spectrum with a linear change at a reference point. The rates of spectral responses at individual wavenumbers are proportional to magnitudes of the peaks in the slice of asynchronous spectrum at the reference point. This way, analysis of complex 2D contour plots is replaced by a simple examination of one-dimensional (1D) slice spectrum. In spite of reduced ability of the resolution enhancement, in special cases the proposed method provides information not accessible from the classical 2D correlation analysis. At first, the principles of this method are shown with the synthetic data. Next, the influence of spectral separation, band width and position changes on the slice spectrum is evaluated. Finally, the proposed approach is applied to the experimental spectra of two hydrogen-bonded systems. [Copyright &y& Elsevier]

Abstract: The use of single gold nanoparticle plasmon-based spectroscopy for the sensitive, anion-selective detection of arsenate is described. The method is based on the selective formation of electrostatic complexes between arsenate and poly(allylamine hydrochloride) (PAH) and changes in the single particle plasmon in Rayleigh scattering profiles. PAH, when modified with gold nanoparticles, binds arsenate via its amine-functionalities. The scattering properties of the resulting selectively formed complexes are altered, leading to significant changes in the surface plasmon resonance wavelength. The limit of detection of the method was determined to be 10nM, which is ca. 13 times more sensitive than U.S. EPA regulation levels. The response is essentially linear in the concentration range of 50–300nM. The method also shows good selectivity for arsenate in the presence of other environmentally relevant anions, including H2PO4 −, SO4 2−, NO3 −, and Cl−. [Copyright &y& Elsevier]

Abstract: In this article, the ability of a new and efficient hard–soft method, previously proposed by our research group, is reported for modeling of the complex formation equilibria in the presence of interferences. This method is based on the net analyte signal (NAS) concept, which is a part of total signal that is directly related to the concentration of the component of interest. It monitors the concentration changes of any chemical species involved in the evolutionary process without requiring any pure spectra or having previous knowledge about the presence of the interferences. The proposed hard–soft method based on net analyte signal (HS-NAS) only needs a chemical model for one of the species involved in the reaction under study. The reliability of the method was examined by applying it to the measured data and spectrum of the known real systems of Fe2+–azithromycin and Ca2+–tetracycline. [Copyright &y& Elsevier]

Abstract: The c-kit oncogene shows a cytosine-rich DNA region upstream of the transcription initiation site which forms an i-motif structure at slightly acidic pH values (Bucek et al. ). In the present study, the pH-induced formation of i-motif – forming sequences 5′-CCC CTC CCT CGC GCC CGC CCG-3′ (ckitC1, native), 5′-CCC TTC CCT TGT GCC CGC CCG-3′ (ckitC2) and 5′-CCCTT CCC TTTTT CCC T CCC T-3′ (ckitC3) was studied by spectroscopic techniques, such as UV molecular absorption and circular dichroism (CD), in tandem with two multivariate data analysis methods, the hard modelling-based matrix method and the soft modelling-based MCR-ALS approach. Use of the hard chemical modelling enabled us to propose the equilibrium model, which describes spectral changes as functions of solution acidity. Additionally, the intrinsic protonation constant, K in, and the cooperativity parameters, ω c, and ω a, were calculated from the fitting procedure of the coupled CD and molecular absorption spectra. In the case of ckitC2 and ckitC3, the hard model correctly reproduced the spectral variations observed experimentally. The results indicated that folding was accompanied by a cooperative process, i.e. the enhancement of protonated structure stability upon protonation. In contrast, unfolding was accompanied by an anticooperative process. Finally, folding of the native sequence, ckitC1, seemed to follow a more complex mechanism. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents an overview of the field of electrochemical stripping analysis in flow systems covering developments in the last 12 years (since 1998). The review discusses the flow schemes utilized in stripping analysis, techniques for on-line sample pre-treatment, the main pre-concentration and stripping/detection modes, the most important flow-through cell configurations used and the different types of working electrodes. Finally, applications in inorganic and organic analysis are discussed. Special emphasis is given to different novel approaches developed over the last few years that hold some promise for the future such as the use of the lab-on-a valve (LOV) configuration, microfluidic manifolds, flow-probes for remote sensing, environmentally friendly electrode materials and hyphenation with spectroscopic techniques. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, based on asymmetric least squares smoothing, a new algorithm for multiple spectra baseline correction is proposed. By means of the similarity among the multiple spectra, the algorithm estimates the baselines by penalizing the differences in the baseline corrected signals, which makes the algorithm possible to eliminate scatter effects on the spectra. In addition, a relaxation factor which measures the similarity of the baseline corrected spectra is incorporated into the optimization model and an alternate iteration strategy is used to solve the optimization problem. The proposed algorithm is fast and can output multiple baselines simultaneously. Experimental results on both simulated data and real data demonstrate the effectiveness and efficiency of the algorithm. [ABSTRACT FROM AUTHOR]

Abstract: Laser-induced breakdown spectroscopy (LIBS) has been used to identify the differences or similarities between crude oil and fuel residues. Firstly, a man portable LIBS analyzer was used for the on-site environmental control and analysis of the oil spill from The Prestige. An exhaustive analysis of crude oil and oil spill residues (collected during the field campaign in the Galician Coast) was performed in the laboratory. Characteristics elements in petroleum such as C, H, N, O, Mg, Na, Fe and V were detected. In addition, contributions from Ca, Si and Al in the composition of residues have been found. The use of intensity ratios of line and band emissions in the original fuel (crude oil) and in the aged residues allowed a better characterization of the samples than the simple use of peak intensities. The chemical composition between the crude oil and the fuel residues was found completely different. As well, a statistical method was employed in order to discriminate residues. Although significant differences were observed, no conclusions in terms of age and provenance could be reached due to the unknowledgment in the origin of the samples. [ABSTRACT FROM AUTHOR]

Abstract: A rapid, but sensitive and selective method for simultaneous screening and quantification of toxic pyrrolizidine alkaloids (PAs) by ultra performance liquid-chromatography (UPLC) coupled with tandem mass spectrometry (MS/MS) on a tandem quadrupole mass spectrometer (TQ-MS) is described. This was accomplished by incorporating the precursor ion scan (PIS) acquisition and multiple reaction monitoring (MRM) acquisition in the same UPLC–MS/MS run. Notably, the developed PIS approach for detecting two pairs of characteristic product ions at m/z 120/138 or 168/150, allowed specific identification of toxic retronecine and otonecine types PAs. This PIS method is highly sensitive with over 10-fold sensitivity improvement upon previously published LC–MS method. Moreover, this new approach is suitable for high sample throughput and was applied to the screening and quantifying toxic PAs in 22 samples collected from seven Parasenecio species and four Senecio species. In addition, coupling the MRM with PIS approach generated quantitative results equivalent to those obtained by conventional MRM-only approach. This coupled MRM with PIS approach could provide both qualitative and quantitative results without the need of repetitive analyses. [ABSTRACT FROM AUTHOR]

Abstract: A new, simple and highly sensitive method for spectrofluorimetric determination of amiloride (AMI) and furosemide (FUR) in pharmaceuticals is presented. The proposed method is based on the separation of AMI from FUR by solid-phase extraction using a nylon membrane, followed by spectrofluorimetric determination of both drugs, on the solid surface and the filtered aqueous solution, respectively. AMI shows low native fluorescence, but its separation-preconcentration by immobilization (solid-phase extraction) on nylon membrane surface provides a considerable enhancement in fluorescence intensity. The fluorescence determination is carried out at λ ex =237, λ em =415nm for FUR; and λ ex =365, λ em =406nm for AMI. The calibration graphs are linear in the range 3.20×10−4 to 0.8μgmL−1and 1.33×10−3 to 4.0μgmL−1, for AMI and FUR, respectively, with a detection limit of 9.62×10−5 and 4.01×10−4 μgmL−1 (S/N =3). The commonly found excipients in commercial pharmaceutical formulations do not interfere. The developed method is successfully applied to the determination of both drugs in pharmaceutical formulations. [Copyright &y& Elsevier]

Abstract: Ionic liquids (ILs) are composed entirely of ions and they possess fascinating properties, including low volatility, tunable viscosity and miscibility, and electrolytic conductivity, which make ILs unique and useful for many applications in chemical analysis. The dramatic increase in the number of publications on ILs is indicative of the tremendous interest in this field from analytical chemists. This review summarizes recent efforts in the major subdisciplines of analytical chemistry, including extractions, gas chromatography, liquid chromatography, capillary electrophoresis, mass spectrometry, electrochemistry, sensors, and spectroscopy. [Copyright &y& Elsevier]

Abstract: A method for the determination of uranium and radium isotopes in water samples is proposed. Liquid scintillation techniques were used for collecting alpha spectra, which were then analyzed by fitting the alpha peaks with overlapping Gaussians. The analysis can quantify the observed isotopes with accuracy depending on the activity of each isotope. In order to simulate the peaks with Gaussian normal distribution functions, the centroid of each peak as well as the full width at half maximum (FWHM) are required, as they depend on the quenching of the sample. For this purpose, samples with known activities of 226Ra and its decay products and also of the uranium isotopes 238U and 234U, at various quenching levels, were used to establish the correlation of the peaks’ shift with the quench effect. In addition, the correlation of the FWHM with the centroid of a peak was determined, using the same procedure. Following the above analysis technique, an average of 97±2% of detection efficiency and a lower limit of detection of 8.2mBqkg−1 for alpha isotopes were achieved. [Copyright &y& Elsevier]

Abstract: High-performance liquid chromatography (HPLC) fingerprint has been commonly used in the quality control and assessment of herbal medicines, and two-dimensional (2D) fingerprint obtained by means of HPLC-diode array detector (HPLC/DAD) can provide higher reliability. In this paper, an approach to the analysis of the 2D HPLC/DAD fingerprints, which was based on digital image recognition techniques, was developed for the first time. First, wavelet transform was employed to eliminate noise signal in the 2D fingerprint, and then the 2D fingerprint was converted into grayscale image. Second, several features of the image were calculated, and hierarchical clustering. This approach was applied to the qualitative analysis of the different samples of coptis chinensis, and the clustering result of samples was all highly consistent with the real situation. Based on the densities in grayscale image, three components in standard samples were quantitative analyzed, and the obtained correlation coefficients between concentration and grayscale density were more than 0.999. Our study indicated that the analysis of the 2D HPLC/DAD fingerprint was successful based on the idea and techniques of digital image recognition techniques, and this proposed approach provided a new pathway for the analysis of two-dimensional spectrums. [Copyright &y& Elsevier]

Abstract: A direct spectrophotometric method for the determination of three artificial colors – amaranth, sunset yellow FCF and tartrazine – in beverages samples is proposed. The spectra were recorded between 359 and 600nm. The spectra of the samples (just filtrated), pure dyes (concentrations ranged between 0.01 and 1.8mgL−1 for amaranth, 0.08 and 4.4mgL−1 for sunset yellow and 0.04 and 1.8mgL−1 for tartrazine) and synthetic mixtures were disposed in a column-wise augmented data matrix. This kind of data structure, analyzed by multivariate curve resolution-alternating least squares (MCR-ALS) makes it possible to exploit the so called ‘second order advantage’. MCR-ALS algorithm was applied to the experimental data under the non-negativity and equality constraints. As a result, the concentration of each dye in the samples and their corresponding pure spectra were obtained. The results were validated using internal reference materials and no significant differences were found (α =5%) between the reference values and the ones obtained with the proposed method. The second order advantage made it possible to obtain unbiased results even in the presence of interferences. [Copyright &y& Elsevier]

Abstract: A simple high performance liquid chromatographic method for the determination of process-related impurities in bulk drug of the central anticholinergic compound pridinol mesylate, has been developed and validated. Spectroscopically characterized synthetic impurities were used as standards. The chromatographic separation was optimized employing an experimental design strategy, and was achieved on a C18 column with a mobile phase containing 50mM potassium phosphate buffer (pH 6.4), MeOH and 2-propanol (20:69:11, v/v/v), delivered at a flow rate of 1.0mLmin−1. UV detection was performed at 245nm. The optimized method was thoroughly validated, demonstrating to be selective, when the chromatogram was recorded with a diode-array detector and peak purities were evaluated (>0.9995). The method is robust and linear (r 2 >0.99) over the range 0.05–2.5% (5–250% with regards to the 1% specification limit for both process-related impurities); it is also precise, regarding repeatability (RSD≤1.5% for all of the analytes) and intermediate precision aspects and LOQ values for the impurities are below 0.01%. Method accuracy, evidenced by low bias of the results and analyte recoveries in the range of 99.1–102.7%, was assessed at five analyte concentration levels. The usefulness of the determination was also demonstrated through the analysis of different lots of pridinol mesylate bulk substance. The results indicate that the method is suitable for the quality control of the bulk manufacturing of pridinol mesylate drug substance. [Copyright &y& Elsevier]

Abstract: The spectral distribution of chemiluminescence provides key evidence in the elucidation of the reaction mechanism and emitting species. We have collected chemiluminescence spectra for the oxidation of sodium sulphite and captopril in the presence of a range of fluorescent and non-fluorescent enhancers. This evidence was used to evaluate several previously proposed light-producing pathways, and revealed some new approaches to enhance the chemiluminescent oxidation of sulphite and thiol compounds. Chemiluminescence reactions between sulphite and permanganate produce two potential emitters: one derived from the oxidation of sulphite (in some cases via energy transfer to a more efficient luminophore) and another derived from the reduction of permanganate. This second light-producing pathway is rarely considered in discussions on the chemiluminescent oxidation of sulphite, but can make a significant contribution to the overall emission. Non-fluorescent enhancers of sulphite chemiluminescence result in several distinct spectral distributions and, contrary to previous postulation, these reactions are unlikely to lead to the same emitting species. Non-fluorescent enhancers of sulphite chemiluminescence can also significantly increase the weak emission from the oxidation of thiol compounds such as captopril. [Copyright &y& Elsevier]

Abstract: It has been proved to be a very useful method to distinguish similar samples by two-dimensional correlation spectroscopy when they are hardly distinguished by the conventional one-dimensional spectroscopy. To acquire the quantitative description of the differences between samples, the similarity of the series dynamic spectra, which reflects the similarity of the samples themselves if obtained under the same perturbation condition, is evaluated by the symmetry of hetero 2DCOS map. Two parameters, the Euclidian distance and correlation coefficient between the upper left and lower right triangular parts of a hetero 2DCOS map, are introduced for the quantitative measure of the symmetry, which in turn characterizes the similarity of the responses of samples to a given perturbation. The above method is used to discriminate one genus of Astragalus from the others to ensure the medicinal efficacy and safety of the herb. Hypothesis tests show that the inter-distances between samples from different genera are significantly larger than the intra-ones within the same genera, while the inter-correlation coefficients are smaller than the intra-ones. The excellent result of the identification for all samples carried out by a t-test based on the distances indicates that this method provides an efficient technique for the quantitative evaluation of similarity between samples. [Copyright &y& Elsevier]

Abstract: By employing the simple but effective principle ‘survival of the fittest’ on which Darwin''s Evolution Theory is based, a novel strategy for selecting an optimal combination of key wavelengths of multi-component spectral data, named competitive adaptive reweighted sampling (CARS), is developed. Key wavelengths are defined as the wavelengths with large absolute coefficients in a multivariate linear regression model, such as partial least squares (PLS). In the present work, the absolute values of regression coefficients of PLS model are used as an index for evaluating the importance of each wavelength. Then, based on the importance level of each wavelength, CARS sequentially selects N subsets of wavelengths from N Monte Carlo (MC) sampling runs in an iterative and competitive manner. In each sampling run, a fixed ratio (e.g. 80%) of samples is first randomly selected to establish a calibration model. Next, based on the regression coefficients, a two-step procedure including exponentially decreasing function (EDF) based enforced wavelength selection and adaptive reweighted sampling (ARS) based competitive wavelength selection is adopted to select the key wavelengths. Finally, cross validation (CV) is applied to choose the subset with the lowest root mean square error of CV (RMSECV). The performance of the proposed procedure is evaluated using one simulated dataset together with one near infrared dataset of two properties. The results reveal an outstanding characteristic of CARS that it can usually locate an optimal combination of some key wavelengths which are interpretable to the chemical property of interest. Additionally, our study shows that better prediction is obtained by CARS when compared to full spectrum PLS modeling, Monte Carlo uninformative variable elimination (MC-UVE) and moving window partial least squares regression (MWPLSR). [Copyright &y& Elsevier]

Abstract: In this paper, we employ two peroxidases (horseradish peroxidase, HRP and cytochrome c peroxidase, CcP) to demonstrate their ability to retain their redox and biological functions after their immobilisation on mesoporous TiO2 and SnO2 electrodes. We will also demonstrate the use of HRP immobilised on the metal oxide electrodes for the development of reagentless optical and electrochemical biosensors for the detection of hydrogen peroxide (H2O2) with low detection limit of 0.04 and 1μM, respectively. [Copyright &y& Elsevier]

Abstract: In the traditional framework of multivariate spectroscopic calibration, the most popular method, partial least squares (PLS), shrinks the regression coefficients based on the information of training sample concentrations. Motivated by the concept of parallel calibration, the second direction for shrinkage of regression coefficients, the direction towards unknown sample spectra is investigated in this paper. A different multivariate calibration method, parallel calibration model based on partial least squares, PCPLS is proposed. With both theoretical support and analysis of some real data sets, it is demonstrated that the second shrinkage direction is at least as natural and necessary as the traditional one. An interesting difference of the proposed method from traditional methods is the involvement of unknown sample spectra and consideration of their error in the training process. Some new related problems and potential applications of this method are also briefly discussed. [Copyright &y& Elsevier]

Abstract: Multivariate deconvolution methods applied for resolution of overlapping chromatographic peaks require bilinearity. This implies that the shape of the spectrum of each analyte should not change during the elution of a compound. However, in chromatography, the concentration of a compound in the detector changes rapidly. For scanning instruments, like most mass spectrometers where the ions within a scan are not recorded simultaneously, these concentration differences introduce significant differences between spectra on the left and right side of the chromatographic peak. Because of this scan-effect, the assumption of bilinearity is not valid. Several methods, all having their limitations, have previously been applied to reduce this effect. In this paper a methodology for reduction of the scan-effect by a rank annihilation approach is described, and applications on both simulated and experimental data are shown. The rank annihilation approach is more efficient and has a broader range of applications than previously described methods. [Copyright &y& Elsevier]

Abstract: A spectral similarity measure was developed that can differentiate subtle differences between two spectra. The spectra are digitalized into a vector. The difference between the two spectra is defined by a difference vector, which is one spectrum minus the other. The spectral similarity measure is transformed into a hypothesis test of the similarities and differences between the two spectra. The scalar mean of the difference vector is used as the statistical variable for the hypothesis test. A threshold for the hypothesis that the spectra are different was proposed. The Bayesian prior odds ratio was estimated from multiple spectra of the same sample. The posterior odds ratio was used to quantity the spectral similarity measure of the two spectra. Diffuse reflectance near-infrared spectra of tobacco samples of two formulations were used to demonstrate this method. The results show that this new method can detect subtle differences between the spectra. [Copyright &y& Elsevier]

Abstract: Several techniques have been proposed for treatment of spectrophotometric data, with the objective of extracting a largest amount of analytical information from spectra composed of unresolved bands. Undoubtedly, a major success was achieved by derivative treatment of the absorbance curves-plotting of the first or a higher order mathematical derivative of absorbance against wavelength (dA/dλ). Derivative spectrophotometry has been applied to many chemical systems, such as pharmaceuticals, foods, cosmetics, and environmental samples. The instrumental development and analytical applications of derivative UV–vis regions absorption spectrophotometry produced in the last 5 years (since 2004) are reviewed. [Copyright &y& Elsevier]

Abstract: The solubility and molar absorptivity of trans- and cis-resveratrol isomers in aqueous solvents are poorly described. This study aimed to develop and describe a new simple method for the determination of trans- and cis-resveratrol concentrations in aqueous solutions. Up to 300μM trans-resveratrol was dissolved in water by sonication for 2h. Cis-resveratrol was obtained by exposing a 100-μM trans-resveratrol aqueous solution to sunlight for 8h, followed by HPLC separation and analysis by mass spectrometry (resveratrol oxidation products were absent). Accurate values for UV absorbance in water were , ɛ 286nm =23400M−1 cm−1 for trans-resveratrol and , ɛ 304nm =9515M−1 cm−1 for cis-resveratrol. These values allowed us to propose formulae to assess the trans-/cis-resveratrol ratio in water, using a simple and reliable UV–vis spectrophotometric method. Statistical analysis revealed no significant difference between our UV method and the commonly used HPLC method. All these data are transferable to 150mM NaCl and 10mM phosphate buffer solutions, which could be particularly useful for cell culture, ex vivo and in vivo studies. [Copyright &y& Elsevier]

Abstract: This paper presents a Bayesian approach to the development of spectroscopic calibration models. By formulating the linear regression in a probabilistic framework, a Bayesian linear regression model is derived, and a specific optimization method, i.e. Bayesian evidence approximation, is utilized to estimate the model “hyper-parameters”. The relation of the proposed approach to the calibration models in the literature is discussed, including ridge regression and Gaussian process model. The Bayesian model may be modified for the calibration of multivariate response variables. Furthermore, a variable selection strategy is implemented within the Bayesian framework, the motivation being that the predictive performance may be improved by selecting a subset of the most informative spectral variables. The Bayesian calibration models are applied to two spectroscopic data sets, and they demonstrate improved prediction results in comparison with the benchmark method of partial least squares. [Copyright &y& Elsevier]

Abstract: A wine fermentation has been monitored on a daily basis by 1H NMR spectroscopy. Following data pre-processing that includes synthesis of the spectra to ensure all peaks are of constant half-width, the series of spectra were examined using generalised two-dimensional correlation techniques. Synchronous and asynchronous data maps have been generated and employed to interpret the changes in the fermentation process as a function of time. The results illustrate the potential of high resolution NMR with multivariate data analysis as a tool for process monitoring and the manner in which two-dimensional correlation mapping can aid in data interpretation. [Copyright &y& Elsevier]

Abstract: Both near-infrared (NIR) and Raman spectroscopy have been studied for the quantitative measurement of components (H3PO4, HNO3, and CH3COOH) in an etchant solution and the corresponding prediction robustness has been evaluated. Both measurements were accomplished by illuminating radiation directly through a Teflon tube. Raman spectral features of each component were much clearer and more selective than those observed in the NIR spectrum. Especially, NIR spectral variation pertinent to H3PO4 and HNO3 were mostly based on the displacement and perturbation of water bands rather than due solely to NIR absorption. Therefore, the resulting spectral variations were not highly specific. When the validation set contained minor spectral variations resulting from a slight instrumental change, NIR prediction performance for all three components degraded substantially by showing obvious prediction bias. However, the accuracies of Raman predictions were maintained. Since partial least squares (PLS) models for each component were built using NIR spectra of poor specificity with broadly overlapping features, even minor spectral differences introduced by instrumental variations sensitively influenced the prediction performance of the NIR models. Overall, the selectivity (specificity) of a targeting spectroscopic method should be considered critically to secure prediction robustness for monitoring components in an etchant solution. [Copyright &y& Elsevier]

Abstract: This article aims at designing a wavelet alternative to Fourier transform infrared spectra (FTIR). In order to select the most suitable wavelet parameters to perform, several decomposition levels and 53 wavelets were tested by trial and error approach, respectively. The result indicated that discrete meyer wavelet (dmey) associated with its third decomposition level was very efficient for this purpose. On the base of it, a novel library named as Fourier transform infrared wavelet coefficients library (FTIR-WC) has been constructed. Finally, two tools such as library search and structure elucidation were developed to evaluate the capability of the new library system. The results obtained were also compared with those from FTIR library by a variety of indices. The results suggested that the new library performed better but with less volume. This work is expected to propose a novel and practical strategy in infrared spectroscopic analysis. [Copyright &y& Elsevier]

Abstract: A new acetolactate synthase (ALS)-inhibiting herbicide, propyl 4-(2-(4,6-dimethoxypyrimidin-2-yloxy)benzylamino)benzoate (ZJ0273), was applied to oilseed rape (Brassica napus L.) leaves in different leaf positions. Visible/near-infrared (Vis/NIR) spectroscopy was investigated for fast and non-destructive determination of ALS activity and protein content in rapeseed leaves. Partial least squares (PLS) analysis was the calibration method with comparison of different spectral preprocessing by Savitzky–Golay (SG) smoothing, standard normal variate (SNV), first and second derivative. The best PLS models were obtained by first-derivative spectra for ALS, whereas original spectra for soluble, non-soluble and total protein contents. Simultaneously, certain latent variables (LVs) were used as the inputs of back-propagation neural network (BPNN) and least squares-support vector machine (LS-SVM) models. All LS-SVM models outperformed PLS models and BPNN models. The correlation coefficient (r), root mean square error of prediction (RMSEP) and bias in validation set by LS-SVM were 0.998, 0.715 and 0.079 for ALS, 0.999, 33.084 and 1.178 for soluble protein, 0.997, 42.773 and 6.244 for non-soluble protein, 0.999, 59.562 and 7.437 for total protein, respectively. The results indicated that Vis/NIR spectroscopy combined with LS-SVM could be successfully applied for the determination of ALS activity and protein content of rapeseed leaves. The results would be helpful for further on field analysis of using Vis/NIR spectroscopy to monitor the growing status and physiological properties of oilseed rape. [Copyright &y& Elsevier]

Abstract: In this work the ANOVA-PCA method is applied to a MIR spectroscopy dataset of carraghenan in order to evaluate which of the factors within its fixed effects experimental design are significant in relation to the residual error. The factors defined in the experimental design are concentration (1% and 2%), temperature (30, 40, 45, 50, and 60°C), day (1 and 2) and sample (20 samples, 3 repetitions). The two factors, concentration and temperature, were considered as significant and the main features related with its physico-chemical properties were identified. It is also of interest to acquire a better understanding of the interaction between concentration and temperature and its effect on the adhesion of gels onto the surface of contact. In fact, no significant interaction was found between the two factors, but it was shown that the factor temperature behaves in a non-linear way. As classification using the ANOVA-PCA procedure has not been developed until now, a new method is proposed for the classification of new samples in respect to the levels of each significant factor. [Copyright &y& Elsevier]

Abstract: In the present study the qualitative and quantitative determination of diterpenoids in commercial distilled gin was carried out. This widely consumed juniper-based spirit is aromatized using Juniper (Juniperus communis) berries. Although juniper reportedly contains several diterpenic compounds, no studies have addressed the diterpenic composition of juniper-based spirits or beverages. With this objective, here we followed a multilevel factorial experimental design to optimize a direct immersion-solid phase microextraction (DI-SPME) method coupled to gas chromatography/mass spectrometry and analyzed eight commercial brands of gin. With total concentrations ranging from 10 to 190μgL−1, manool, manoyl oxide and trans-totarol were the most abundant diterpenoids of the 10 identified or tentatively identified at variable but not negligible concentrations in the distilled gin samples. The diterpenic composition allowed the brands to be differentiated. This indicates that these compounds contribute to the sensory characteristics of the distinct commercial brands, thus guaranteeing the authenticity and consequently the quality of the product. [Copyright &y& Elsevier]

Abstract: A new type of carbon film electrode, composed of a thin layer of tightly packed carbon black (CB) nanoparticles deposited onto a gelatin-covered indium tin oxide/glass support using the surface-induced deposition (SID) approach, is presented. Some parameters of the novel SID method were optimized and the surface image and functionalization of the investigated carbon black film electrode (CBFE) was inspected by employing scanning electron microscopy and infrared spectroscopy. A cyclic voltammetry (CV) study was conducted in which the electron-transfer kinetics and CBFE interfacial characteristics were evaluated employing several selected reference redox systems, such as [Ru(NH3)6]3+/2+, [Fe(CN)6]3−/4− and Fe3+/2+ in aqueous, and ferrocene/ferrocenium in acetonitrile media. CV recordings were also performed in order to compare the electrochemical behavior of the CBFE with that of some well-known and established bare carbon-based electrodes. In order to confirm the validity of the CB film preparation method, the electroanalytical performance of the proposed CBFE was examined by carrying out linear sweep voltammetry of ascorbic acid (AA), anodic stripping square-wave voltammetry of Cu(II) in acidic medium, and amperometric measurements of hydrogen peroxide under flow injection conditions. The sensing characteristics of the novel carbon film electrode, demonstrated in this preliminary study, comprise: (i) a wide working potential window ranging from +1.0 to −1.3V (depending on the solution pH), (ii) a wide applicable pH range (at least from 2 to 12), (iii) low voltammetric background (<5μAcm−2), (iv) a satisfactory linear voltammetric and amperometric response (r 2 >0.99) to various analytes, (v) good reproducibility (for example, r.s.d. of 2% in amperometric detection of H2O2 and r.s.d. of 8.5% for electrode-to-electrode CV runs), and (vi) stable and fast current response (at least 100 CV runs with negligible change in CV response). The main advantages of the proposed CBFE originate from the unique CB film formation procedure that enables fast, simple, inexpensive and non-toxic CBFE preparation, which can find application in advanced electrochemical devices and is suitable for mass production. [Copyright &y& Elsevier]

Abstract: A new method using microwave digestion combined with inductively coupled plasma-mass spectrometry (ICP-MS) was studied to analyze the elemental composition of a variety of komatiites samples. Microwave digestion consisted in two-stage heating and pressurizing acid treatments for maximum dissolution of the samples. We report here different quality control measurements (external and internal calibration, monitoring of reference materials) which involve standard deviation calculations and recovery examinations in order to test the precision and accuracy of the analytical procedure. Data for 17 elements (Na, P, K, T, V Cr, Mn, Co, Ni, Cu, Zn, Zr, Pb, Al, F, Ca and Mg) in eight komatiite samples and two USGS basalt reference samples (BCR-2 and BHVO-2) are presented. We evaluate our new digestion and instrumental procedure. The element concentration obtained for BCR-2 and BHVO-2 agreed well with the certified values, the relative standard deviations were lower than 5% and recoveries were good. Our analytical results demonstrate that it reproduces accurately the concentrations of minor and trace elements in komatiites. The ease of digestion of the samples and the speed (less than 12h) to digest the komatiite material makes this technique an efficient method to be used easily and routinely for preparing and analyzing komatiites samples for multiple elements determination. [Copyright &y& Elsevier]

Abstract: Dielectric spectroscopy (DS) is one of the most powerful and prevailing structural analysis techniques for dielectric materials. Engine lubricating oil is a typical dielectric material. But DS for qualitative or quantitative analysis of engine lubricating oil has received little attention. In this paper, DS in association with support vector machines (SVM) classification technique was employed to classify 20 samples of engine lubricating oils from Mobil, Shell and Esso by Society of Automotive Engineers (SAE) viscosity grade and source (manufacturer). Both distinguishing the multi-grade from the single-grade according to SAE grade and classification according to manufacturer were done perfectly, which proved that DS can provide useful compositional and structural information on engine lubricating oil. The work in this article has laid the foundation for further quantitative determination of properties of engine lubricating oil and will be a good start to application of DS to petroleum analysis and testing. [Copyright &y& Elsevier]

Abstract: The optimum performance of an optical oxygen sensor based on polysulfone (PSF)/[Ru(II)-Tris(4,7-diphenyl-1,10-phenanthroline)] octylsulfonate (Ru(dpp)OS) was checked by carefully tuning the parameters affecting the membrane preparation. In particular, membranes having thickness ranging between 0.2 and 8.0μm with various luminophore concentrations were prepared by dip-coating and tested. The membrane thickness was controlled by tuning the solution viscosity, and was measured both by secondary ion mass spectrometry (SIMS) and by visible spectroscopy (Vis). Luminescence-quenching-based calibration was a single value of the Stern–Volmer constant () for membranes containing up to 20mmolRu(dpp)g−1 PSF (1.35μm average thickness). The value decreased for larger concentration. The highest sensitivity was obtained with membrane thickness around 1.6μm, having a response time close to 1s. Thicker membranes exhibited an emission saturation effect and were characterized by longer response time. The behavior was interpreted on the basis of a mathematical approach accounting for the contribution of luminescence lifetime (τ 0), oxygen diffusion coefficient () and oxygen solubility inside the membrane () establishing the role of all of them and allowing their experimental determination. Moreover, a simple experimental way to estimate without needing calibration was proposed. It was based either on the light emission asymmetry or on the percent variation of light emission on passing from pure nitrogen to pure oxygen. [Copyright &y& Elsevier]

Abstract: Meso-tetramesitylporphyrin (MTMP) deposited glass plate (solid state sensor) was used to sense hydrogen chloride (HCl) gas based on optochemical method. Exposure of the solid state sensor to HCl vapor results in the formation of protonated meso-tetramesitylporphyrin (PMTMP). UV–vis and fluorescence spectral techniques were used to study the protonation of MTMP in dichloromethane–methanol mixture. The optical spectra of MTMP show an intense Soret band at 418nm with a 14nm red shift upon protonation by HCl. Ab-initio calculations were carried out to visualize the effect of protonation on planarity and stability of the porphyrin ring. The solid state sensor was characterized by UV–vis spectral technique. The sensor exhibits characteristic Soret and Q bands for the deposited MTMP with slight red shift when compared to MTMP in dichloromethane. The concentration of gaseous HCl was monitored from the changes in the absorbance of Soret band of PMTMP at 452nm. The detection limit of the solid state sensor towards gaseous HCl was found to be 0.03ppm. The present solid state sensor was highly stable for several months. [Copyright &y& Elsevier]

Abstract: A simple, rapid, and sensitive method for the determination of traces of thirteen sulfonamide antibacterials in milk and eggs is presented. This method is based on the combination of polymer monolith microextraction (PMME) technique with hydrophilic interaction chromatography/mass spectrometry (HILIC/MS). The extraction was performed with a poly(methacrylic acid-ethylene glycol dimethacrylate) monolithic capillary column while the subsequent separation was carried out on a Luna NH2 column by HILIC. To obtain optimum results, several parameters relating to HILIC and PMME were investigated. After optimization, acetonitrile (contain 0.05% formic acid, v/v) was used as the elution solution, which was well compatible with the mobile phase in HILIC. Good linearities were obtained for thirteen SAs with the correlation coefficients (R 2) above 0.997. The limits of detection (S/N=3) of the method were found to be 0.4–5.7ngmL−1 of SAs in whole milk and 0.9–9.8ngg−1 of SAs in eggs. The recoveries of thirteen SAs in two matrices ranged from 80.4 to 119.8%, with relative standard deviations less than 11.8%. [Copyright &y& Elsevier]

Abstract: The paper describes the application of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for the isotopic analysis of individual uranium-oxide particles. The procedure developed is suitable for the accurate measurement of 234U, 235U, 236U and 238U isotopes in single actinide particles with lateral dimensions down to 10μm. The 235U/238U isotope ratios can be obtained with a precision of a few percent relative standard deviation using a single collector ICP-MS instrument. The precision could be improved by the use of slow ablation and by taking several LA-ICP-MS replicate spectra on the same particle investigated. For the minor isotopes use of higher mass resolution (R =4000) was necessary in some cases to avoid spectral interferences. The technique developed offers a rapid and accurate possibility for the isotopic composition determination of uranium-containing individual particles in environmental and safeguards samples. [Copyright &y& Elsevier]

Abstract: The development of a faradic impedimetric immunosensor based on electropolymerized polytyramine (Ptyr) films for the detection of S. typhimurium in milk is described for the first time. Polyclonal anti-Salmonella was cross-linked, in the presence of glutaraldehyde vapors, on Ptyr-modified gold electrodes. The dielectric behaviour of Ptyr films was evaluated with capacitance measurements, while their stability in neutral aqueous solutions was examined with impedimetric measurements. The effect of the concentration of tyramine in the forming solution on both the sensitivity and the dynamic range of the resulted immunosensors was also investigated. The alteration of the interfacial features of the electrodes due to different modification or recognition steps, was measured by faradic electrochemical impedance spectroscopy in the presence of a hexacyanoferrate(II)/(III) redox couple. At samples containing a low initial concentration of 10cfumL−1 S. typhimurium, that actually defines the LOD of the immunosensors, signal changes of 33% and 88% were achieved after 3 and 10h incubation, respectively. To achieve the working simplicity expected by a biosensor, immunoreaction was performed directly in cultures. This resulted in the elimination of various centrifugation and washing steps, which are used for the isolation of bacteria cells from the culture, thus making the proposed immunosensors promising candidates for on-site applications. Finally, the proposed immunosensors were successfully used for the detection of S. typhimurium in experimentally inoculated milk samples. [Copyright &y& Elsevier]

Abstract: In this work, it has been extended to methanol:water mobile phases, the use of a background correction method for on-line LC–FTIR measurements named Univariate background correction based on the use of a reference spectra matrix (UBC-RSM) and absorbance ratios. It permits to overcome the problem related to spectral changes occurring during the gradient elution, which in the past limited the on-line coupling of LC and FTIR to isocratic elutions. The combined use of the aforementioned background correction technique in on-line isocratic and gradient LC–FTIR, and partial least squares (PLS) has been applied for the search of the critical conditions for polymers. Polyethylenglycol (PEG) has been used as a model example and results found fitted well with previously published ones. [Copyright &y& Elsevier]

Abstract: Metabonomic profiling using proton nuclear magnetic resonance (1H NMR) spectroscopy and multivariate data analysis of human serum samples was used to characterize metabolic profiles in renal cell carcinoma (RCC). We found distinct, easily detectable differences between (a) RCC patients and healthy humans, (b) RCC patients with metastases and without metastases, and (c) RCC patients before and after nephrectomy. Compared to healthy human serum, RCC serum had higher levels of lipid (mainly very low-density lipoproteins), isoleucine, leucine, lactate, alanine, N-acetylglycoproteins, pyruvate, glycerol, and unsaturated lipid, together with lower levels of acetoacetate, glutamine, phosphatidylcholine/choline, trimethylamine-N-oxide, and glucose. This pattern was somewhat reversed after nephrectomy. Altered metabolite concentrations are most likely the result of the cells switching to glycolysis to maintain energy homeostasis following the loss of ATP caused by impaired TCA cycle in RCC. Serum NMR spectra combined with principal component analysis techniques offer an efficient, convenient way of depicting tumour biochemistry and stratifying tumours under different pathophysiological conditions. It may be able to assist early diagnosis and postoperative surveillance of human malignant diseases using single blood samples. [Copyright &y& Elsevier]

Abstract: It has been developed a partial least squares near infrared (PLS-NIR) method for the determination of estuarine sediment physicochemical parameters. The method was based on the chemometric treatment of first order derivative reflectance spectra obtained from samples previously lyophilized and sieved through a lower than 63μm grid. Spectra were scanned from 833 to 2976nm, averaging 36 scans per spectrum at a resolution of 8cm−1, using chromatographic glass vials of 9.5mm internal diameter as measurement cells. Models were built using reference data of 31 samples selected through the use of a hierarchical cluster analysis of NIR spectra of sediments obtained from the Ria de Arousa estuary and prediction parameters were established from a validation set of 50 samples of the same area. pH, redox potential (Eh), carbon (C), nitrogen (N) and hydrogen (H) content together with Sn, Pb, Cd, As, Sb and total Cr and also acid soluble, reducible and oxidable Cr fractions were employed as characteristic parameters of the studied sediments. Standard error of prediction values for C and N content were of the order of 4 and 1.3mgg−1 for H. Prediction errors for pH and Eh were 0.15 units and 37mV, respectively, thus indicating the good prediction capabilities of the method. Regarding trace metal concentrations PLS-NIR provided prediction error levels for unknown samples around 20% for Sn, Pb, As and Sb and root mean square errors of prediction around 40% for concentration levels of 400ngg−1 Cd and 100μgg−1 Cr. For the different extractable fractions of Cr the residual prediction deviation varied from 1.3 to 1.7 but relative errors found for samples of the validation set were only useful for screening purposes. [Copyright &y& Elsevier]

Abstract: The aim of this paper focuses on the determination of nine coal properties related to combustion power plants (moisture (%), ash (%), volatile matter (%), fixed carbon (%), heating value (kcalkg−1), carbon (%), hydrogen (%), nitrogen (%) and sulphur (%)) by mid-infrared spectroscopy. For that, a wide and diverse coal sample set has been clustered into new homogeneous coal subgroups by the use of hierarchical clustering analysis. This process was performed including property values and spectral data (scores of principal component analysis, PCA) as independent variables. Once the clusters were defined, the corresponding property calibration models were performed by partial least squares regression. Several mathematical pre-treatments were applied to the original spectral data in order to cope with some non-linearities. The accuracy and precision levels for each property were studied. The results revealed that coal properties related to organic components presented relative error values around 2% for some clusters, comparable to those provided by commercial online analysers. Finally, the discrimination level between those groups of samples was evaluated by linear discriminant analysis (LDA). The sensitivity of the system was studied accomplishing percentages close to 100% when the samples were classified attending only to their mid-infrared spectra. [Copyright &y& Elsevier]