NEW Comprehensive Behavioral Catalog

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Just Published: Journal of Chromatography A

A new issue of this journal has just been published. To see abstracts of the papers it contains (with links through to the full papers) click here:

Journal of Chromatography A

http://rss.sciencedirect.com/publication/science/5248

Selected papers from the latest issue:

Detection of ketamine and its metabolites in human hair using an integrated nanoflow liquid chromatography column and electrospray emitter fritted with a single porous 10μm bead

28 January 2013, 02:18:42

15 February 2013
Publication year: 2013
Source:Journal of Chromatography A, Volume 1277

Targeting metabolites incorporated into hair following drug administration is useful for evidential purposes as this approach can aid in differentiating between administration and passive exposure. Greater analytical sensitivity is required than for targeting the parent drug alone. A 20μm i.d. fused silica capillary column with an integrated electrospray emitter fritted with a single porous 10μm polymeric bead has been successfully fabricated to facilitate this purpose. The sensitivity gains through the use of these integrated single fritted columns coupled to a nanoelectrospray source (nanoflow–LC nanoESI) over conventional liquid chromatography–tandem mass spectrometry (LC–MS/MS) columns was explored by their application to the detection of ketamine and its phase I metabolites in human hair. Hair was collected from 4 volunteers following the administration of a small oral dose of ketamine (50mg) and subsequently analysed by the capillary–LC nanoESI approach. The drug and its metabolites were extracted from hair using solid phase extraction following a methanolic wash, pulverisation with a ball mill and acid digestion. From a 50μL extract, 1μL was injected and the method provided a limit of detection estimated to be 5fg on column for ketamine and norketamine and 10fg for dehydronorketamine. The single porous frit minimises extra column band broadening and offers an alternative fritting approach which reduces the blocking of the electrospray emitter, in comparison with other approaches such as sintering and polymerisation.

Highlights

► A 20μm i.d. capillary column with was fritted with a single 10μm porous bead. ► The column consisted of an integrated electrospray emitter. ► Dehydronorketamine was detected in hair samples for the first time.

Effects of injection volume on chromatographic features and resolution in the process of counter-current chromatography

28 January 2013, 02:18:42

15 February 2013
Publication year: 2013
Source:Journal of Chromatography A, Volume 1277

Counter-current chromatography is a high efficiency separation and purification technique. As a preparative separation technique, the final goal that we are concerned about is acquisition of maximum yields of the separated compounds under specific conditions. In this paper, the theory of counter current extraction table (TCCET), a numerical model for counter-current chromatography, was employed firstly to investigate the effects of injection volume on chromatographic features (retention time, peak height and peak width) and resolution between the separated compounds from theoretical point of view. Moreover, a series of experiments were performed to evaluate the effectiveness of the TCCET model when used for analysis of the influences of the injection volume on a counter-current chromatography separation process. Both the theoretical analysis and experiments show that: (1) the retention time or retention volume increases with the injection volume linearly; (2) the peak height increases with increase of the injection volume, and when the injection volume is smaller than ten percent of V m (volume occupied by mobile phase in a CCC column), the relationship between the peak height and the injection volume is a kind of linear relationship; and (3) the peak width also increases with increase of the injection volume, and obvious linear relationship between the peak width and the injection volume can be observed when the injection volume is smaller than a certain volume. In contrast, the resolution between the separated compounds decreases with increase of the injection volume.

Highlights

► TCCET model was used to investigate the effects of injection volume on CCC separation. ► The relationship between chromatographic features and injection volume was studied. ► Retention time, peak height and width change with the variation of injection volume. ► The resolution of separated compounds decreases with increase of injection volume. ► The injection volume has significant effects on chromatographic features.

An improved approach to hydrophilic interaction chromatography of peptides: Salt gradients in the presence of high isocratic acetonitrile concentrations

28 January 2013, 02:18:42

15 February 2013
Publication year: 2013
Source:Journal of Chromatography A, Volume 1277

Hydrophilic interaction chromatography (HILIC) for separations of peptides has been employed infrequently, particularly considering that this technique was introduced over 20years ago. The present manuscript describes a radical departure from the traditional HILIC elution approach, where separations are achieved via increasing salt (sodium perchlorate) gradients in the presence of high isocratic concentrations (>80%) of acetonitrile, denoted HILIC/SALT. This initial study compared to reversed-phase chromatography (RPC), HILIC and HILIC/SALT for the separation of mixtures of synthetic peptide standards varying in structure (amphipathic α-helix, random coil), length (10–26 residues), number of positively charged residues (+1 to +11) and hydrophilicity/hydrophobicity. Results showed a marked superiority of the HILIC/SALT approach compared to traditional HILIC and excellent complementarity to RPC for peptide separations. We believe these initial results offer a new dimension to HILIC, enabling it to transform from an occasional HPLC approach for peptide separations to a more generally applicable method.

Highlights

► We describe a radical departure from traditional HILIC of peptides. ► Elution is by a salt gradient in the presence of a high acetonitrile concentration. ► This HILIC/SALT method is superior to HILIC and complements RPC for peptides. ► Our results offer a new dimension to HILIC as a mainstream peptide analytical tool.

Optimized chromatographic conditions for separation of halogenated acetic acids by ultra-performance liquid chromatography–electrospray ionization-mass spectrometry

28 January 2013, 02:18:42

15 February 2013
Publication year: 2013
Source:Journal of Chromatography A, Volume 1277

Emerging halogenated acetic acids (HAAs), especially mixed halogenated acids such as chlorobromo-, chloroiodo- and bromoiodo-acetic acids, are unregulated disinfection by-products in drinking water. Because these compounds are hydrophilic and strongly acidic, they are difficult to detect at trace levels using approved analytical methods. In the present study, 13 HAAs were effectively separated on three ultra-performance liquid chromatography columns. The effects of changing in the aqueous mobile phase, acidic solutions and cationic volatile ion pair reagents were investigated. The samples were pretreated by filtration, and extraction, while derivatization and concentration procedures were not required. The limits of quantitation for regulated HAAs were between 0.5μg/L and 1.7μg/L and for unregulated HAAs were 1.2 and 5.8μg/L, especially for the iodinated acetic acids were 1.5 and 2.1μg/L. The method was applied to two finished water samples collected in China (Shanghai and Xuzhou) from water treatment plants that use chlorine for disinfection. Multiple unregulated HAAs were found in the two samples, but iodoacids were only detected in the water sample from Shanghai, which could be attributed to the characteristics of the source water. The presence of unregulated HAAs, especially mixed bromo- and iodoacetic acids, in the finished water samples could affect human health, and this warrants further investigation.

Highlights

► Parameters for the separation of emerging halogenated acetic acids are optimized. ► Separation depends on the acid and volatile ion pair reagent in the mobile phase. ► Tandem mass spectrometry has good sensitivity for unregulated halogenated acids. ► Unregulated bromo- and iodoacetic acids are present in drinking water.

Development of isotope dilution-liquid chromatography tandem mass spectrometry for the accurate determination of fluoroquinolones in animal meat products: Optimization of chromatographic separation for eliminating matrix effects on isotope ratio measurements

28 January 2013, 02:18:42

15 February 2013
Publication year: 2013
Source:Journal of Chromatography A, Volume 1277

Isotope dilution-liquid chromatography/tandem mass spectrometry (ID-LC–MS/MS) has been established as a candidate reference method for the accurate determination of three representative fluoroquinolone antibiotics (enrofloxacin, ciprofloxacin, and norfloxacin) in meat products. Enrofloxacin-d 5, ciprofloxacin-¹³C3 ¹⁵N, and norfloxacin-d 5 were used as internal standards. After extraction and SPE clean-up, samples were analyzed by using LC–MS/MS in positive ion mode. We observed that the deuterium-labeled internal standards have slightly different LC retention time from their native analogues, which reduces the benefits of using isotope dilution techniques as ion suppression/enhancement effects caused by co-eluting matrix interferences are not completely compensated. In this study, LC conditions were optimized to minimize matrix effects causing different ionization efficiency between the target analytes and their isotope analogues by separating them from significant matrix interferences. The analytical method was validated by measuring samples (chicken breast, bovine muscle, and porcine muscle) gravimetrically fortified in various levels with the target analytes. The method provided accurate analytical results of the target analytes in the range of 5–50μg/kg with the relative expanded uncertainty of 1–5%.

Highlights

► Development of ID-LC/MS/MS method for the analysis of fluoroquinolones in meat. ► Slight separation of deuterated internal standards from their target analytes by LC. ► The R.T. difference causes bias in isotope ratio measurement due to matrix effects. ► LC conditions were optimized to get rid of biases from matrix effects in ID-LC/MS/MS. ► Method was validated for samples of bovine and porcine muscles, and chicken breast.

Evaluation of a liquid chromatography method for quality control of methylated cyclodextrins

28 January 2013, 02:18:42

15 February 2013
Publication year: 2013
Source:Journal of Chromatography A, Volume 1277

Halo C18 column (fused core particles) and Chromolith RP18 column (monolith) were evaluated in liquid chromatography in order to analyze methylated-β-cyclodextrins (Me-β-CD) with various degrees of substitution, DS such as the number of methyl groups per cyclodextrin ring. Chromolith RP18 enables a performing analysis of Me-β-CD with low DS but is not suitable for dimethyl-β-cyclodextrins (DM-β-CD). On the other hand, Halo C18 column allows an improved fingerprint of CDs having a DS from 4.9 up to a value major than 14 and avoiding the use of various chromatographic systems. Thus, liquid chromatography performed with this column and an evaporative light scattering detector can be used as a generic system for methylated CD analysis. Moreover, fused core particles of Halo C18 column enables a rapid analysis and liquid chromatography coupled with electrospray-mass spectrometry appears as a powerful tool to determine co-elution and to characterize various isomers of complex methylated-β-cyclodextrin mixtures.

Highlights

► Halo C18 and Chromolith RP18 columns were evaluated to analyze methylated CDs by LC. ► Halo C18 column is suitable for rapid LC analysis of various CDs. ► LC-ELSD with this column was proposed as a generic system for CD analysis.

Improving performance of a tandem simulated moving bed process for sugar separation by making a difference in the adsorbents and the column lengths of the two subordinate simulated moving bed units

28 January 2013, 02:18:42

15 February 2013
Publication year: 2013
Source:Journal of Chromatography A, Volume 1277

A tandem simulated moving bed (SMB) process for removal of sulfuric acid and acetic acid from sugars has been developed previously. This process consisted of two four-zone SMB units (Ring I and Ring II), in which the same adsorbent (Dowex99 resin) and the same column length were used. To improve the performance of such a tandem SMB process for sugar separation, it is worth adopting the strategy of making a difference between the column lengths of Ring I and Ring II. The results showed that such strategy could allow the adsorbent beds of both Ring I and Ring II to be fully utilized at the same time, which was impracticable in the previous tandem SMB mode. As a result, the tandem SMB based on such strategy could achieve higher productivity than the previous tandem SMB mode. In addition, the use of different adsorbents (Amberchrom-CG161C in Ring I and Dowex99 in Ring II) was proposed as the second strategy, which was confirmed to be highly effective in improving the productivity of the tandem SMB for sugar separation. Finally, a third strategy was proposed by combing the first and the second strategies. It was found that compared to the previous tandem SMB mode, the third strategy led to more than eleven times the productivity under the constraint of pressure drop ≤100psi. This was mostly because the third strategy had a remarkable advantage over the previous tandem SMB mode in the aspects of bed utilization and selectivities, which stemmed from the use of different column lengths and the use of different adsorbents respectively.

Highlights

► Strategy of improving the tandem SMB performance for sugar separation was proposed. ► It was to make a difference in the adsorbents and column lengths of the 2 sub-SMBs. ► The Amberchrom-CG161C and Dowex99 adsorbents were used in the 1st and 2nd sub-SMBs. ► The strategy was highly effective in improving the productivity of the tandem SMB. ► The strategy had a clear advantage in term of bed utilization and selectivities.

Microcalorimetric study of the adsorption of native and mono-PEGylated bovine serum albumin on anion-exchangers

28 January 2013, 02:18:42

15 February 2013
Publication year: 2013
Source:Journal of Chromatography A, Volume 1277

The adsorption of native bovine serum albumin (BSA) and 12kDa-PEG-BSA on 12 different commercially available strong and weak anion-exchange resins is studied at 25°C and pH 7. The resins differ in their base matrix material, their functional groups and the type of polymer modification. A combination of equilibrium measurements and microcalorimetric experiments is used to determine the specific enthalpy of adsorption of the proteins. From these data, the entropic contributions to the specific Gibbs energy of adsorption are determined. The results strongly differ for different resins. They also depend on the loadings. The adsorption of BSA on strong (Q) anion-exchangers is exothermic and enthalpy-driven. The adsorption of BSA on weak (DEAE) anion-exchangers is endothermic and entropy-driven. The adsorption of PEG-BSA on strong (Q) anion-exchangers is exothermic or endothermic, depending on the resin, while the adsorption of PEG-BSA on weak (DEAE) anion-exchangers is exothermic for all studied resins. The present study provides a large body of new experimental data that contribute to the understanding of the nature of protein adsorption on ion exchange resins and the influence of the resin properties and polymer modification of the proteins on this process.

Highlights

► Adsorption equilibrium and thermodynamics of native BSA and PEGylated BSA on different anion-exchangers. ► Adsorption can be endo- or exothermic and driven by entropic contributions. ► Thermodynamics of adsorption highly depends on structure and properties of resin. ► Influence of PEG not predictable. Depends on resin properties.

Impurity analysis of pure aldrin using heart-cut multi-dimensional gas chromatography–mass spectrometry

28 January 2013, 02:18:42

15 February 2013
Publication year: 2013
Source:Journal of Chromatography A, Volume 1277

Identification and quantification of related-structure impurity is a research focus in the purity assessment of organic compounds. Determination of the purity value and uncertainty assessment are also important in the metrological research. A method for the determination of related-structure impurity in pure aldrin sample has been developed by using heart-cut multi-dimensional gas chromatography–mass spectrometry (MDGC/MS). Compared to the traditional one-dimensional (1-D) GC system, the two separated columns in the MDGC/MS system can effectively reduce co-elution, enhance separation capability, and thus improve detectability of the trace-level impurities. In addition, MDGC/MS system was simultaneously equipped with flame ionization detector (FID) or electron capture detector (ECD) in the first GC unit and mass spectrometry (MS) detector in the second GC unit. Therefore, accurate quantitative results of the trace-level impurities can be easily achieved by isolation of principal component to the second dimension column using “heart-cut” process. The mass fraction of related-structure impurities in aldrin samples obtained using MDGC/MS system ranged from 6.8×10⁻³ mgg⁻¹ to 26.47mgg⁻¹ with five orders of magnitude, which is hard to be realized by mean of the 1-D GC. Excellent linearity with correlation coefficients of above 0.999 was achieved for each impurity analysis over a wide range of concentrations. Limits of quantification (LOQ) varied from 250ngg⁻¹ to 330ngg⁻¹ for FID, and from 1.0ngg⁻¹ to 2.0ngg⁻¹ detected by ECD. The combined standard uncertainty (u c) was lower than 0.37mgg⁻¹ and 0.040mgg⁻¹ detected using FID and ECD, respectively. Therefore, performance characterization of MDGC/MS used in the study is fit for quantification analysis of trace-level impurity. These results demonstrate that the MDGC/MS is extremely suitable for the purity assessment of organic compounds with medium structural complexity and low polarity.

Highlights

► Application of heart-cut multi-dimensional gas chromatography-mass spectrometry. ► Method for determination of related-structure impurity in aldrin sample has been developed. ► Separation and qualitative analysis could be fulfilled in a simple cycle. ► Accurate quantitative results of trace-level impurities can be easily achieved. ► The method is fit for compounds with medium structural complexity and low polarity.

Prediction of retention times in temperature programmed gas chromatography using the retention equation derived from crystallization behavior of polymer

28 January 2013, 02:18:42

15 February 2013
Publication year: 2013
Source:Journal of Chromatography A, Volume 1277

Based on the enlightenment from the crystallization behavior of polymer, a novel retention equation constructed with only three pairs of isothermal retention data was proposed to predict retention times in temperature programmed gas chromatography (TPGC). The new retention equation worked beautifully in both the single- and the multiple-ramp temperature-programmed modes, yielding the average absolute relative errors of 0.65% for single-ramp TPGC across all the 18 analytes in 3 temperature programmed experiments and 0.30% for multiple-ramp TPGC across all the 8 analytes in 6 temperature programmed experiments tested in this work. Moreover, to compare with the new retention equation systematically and thoroughly, another 13 retention equations determined by two or three parameters were derived from a universal formula ln k = a 0 + a 1/T + a 2/T ² + a 3 ln T + a 4 T + a 5 T ² as a combination of the relationships between ln k and T with reference to four widely used retention equations in publications. Calculated by these 14 retention equations with the same experimental data, the absolute relative errors of prediction retention times for single-ramp TPGC mode were compared by means of statistical analysis. At a very high significance level of 1%, statistical evidences of paired t-test strictly implied that the new retention equation yielded the best prediction results among all of the 14 retention equations. In addition, remarkably, among the 13 retention equations, three seldom used in publications retention equations also worked nicely, yielding satisfactory average absolute relative errors of 0.78%, 0.81% and 0.84% for single-ramp TPGC.

Highlights

► A novel retention equation for TPGC retention times predicting is proposed. ► The new retention equation is derived from the crystallinity formula of polymer. ► The new retention equation characterized as a simple nonlinear curve. ► The new retention equation yield satisfactory prediction results in TPGC. ► Statistical evidences significantly verify this new retention equation as the best.

Now Make Rapid Viscosity Measurements with Precise Temperature Control

RheoSense, Inc. has proudly unveiled the newest member of the VROC family, microVISC TC, a precise temperature controller for the handheld microVISC viscometer.
Temperature dependence is one of the most important factors in determining viscosity so a minute variation can possibly lead to significantly erroneous results.

With the advent of microVISC TC, microVISC is now capable of offering accurate viscosity measurement which would eliminate any uncertainty and allow users to adhere to the most stringent requirements.

The Peltier-based microVISC TC has a temperature range between 15 ~ 50°C (60 ~ 122°F). A PID controller with advanced fuzzy logic allows faster and precise temperature control with an accuracy of 0.02^oC and stability of 0.07^oC.

An optional software program further allows remote temperature control as well as touch-pad operation of the microVISC.

Just Published: Chemometrics and Intelligent Laboratory Systems

A new issue of this journal has just been published. To see abstracts of the papers it contains (with links through to the full papers) click here:

Chemometrics and Intelligent Laboratory Systems
http://rss.sciencedirect.com/publication/science/5232

Selected papers from the latest issue:

Gravitational search algorithm: A new feature selection method for QSAR study of anticancer potency of imidazo[4,5-b]pyridine derivatives

25 January 2013, 09:19:36

15 March 2013
Publication year: 2013
Source:Chemometrics and Intelligent Laboratory Systems, Volume 122

Choosing the most suitable subset of descriptors among a large number of structural parameters is one of the most important and challenging steps in quantitative structure–activity relationship (QSAR) studies. So far, many feature selection algorithms have been applied in these studies, but none of them behave generally. In this study, a binary version of gravitational search algorithm (GSA) as a novel feature selection method is developed and coded for QSAR studies. The GSA is applied as a descriptor selection tool for anticancer potency modeling of a set of imidazo[4,5-b]pyridine derivatives consisting of 65 compounds. The GSA selected descriptors were subjected to Bayesian regularized artificial neural networks to model the anticancer potency. The generated model satisfactorily describes the experimental variation in the biological activity of the data set compounds. The results of external validation (R v ² =0.98) and internal cross-validation tests (Q LOO ² =0.94, R L4O ² =0.93, R L8O ² =0.92) in conjunction with Y-randomization confirm the predictive ability, robustness and effectiveness of the generated model. Also, comparison between GSA and genetic algorithm (GA) indicates that GSA has certain advantages over the GA.

Highlights

► Gravitational search algorithm (GSA) is developed and coded for QSAR studies. ► Anticancer potency of 65 imidazo[4,5-b]pyridine derivatives is investigated. ► The GSA is applied as descriptor selection tool for anticancer potency modeling. ► BR-ANN is used to model the anticancer potency using GSA selected descriptors. ► Comparison between GSA and GA indicates that GSA has certain merit over the GA.

Use of multivariate chemometric algorithms on 1H NMR data to assess a soluble fiber (Plantago ovata husk) nutritional intervention

25 January 2013, 09:19:36

15 February 2013
Publication year: 2013
Source:Chemometrics and Intelligent Laboratory Systems, Volume 121

The study of nutritional interventions in humans is difficult to assess because the induced metabolic changes are lower than the natural biological variability between subjects. Due to its holistic approach, ¹H NMR is one of the preferred technologies for this type of studies, even though it has a very low sensitivity. This work shows how the use of several chemometric algorithms on the measured data compensates for these drawbacks and allows the study of the effects of the nutritional intervention isolating them from the natural variability inherent to human studies. Mild to moderate hypercholesterolemic patients received either placebo or soluble fiber in a low saturated fat diet. Plasma samples were collected at week 0 and week 8. Spectra obtained with NMR equipment were processed with ANOVA simultaneous component analysis (ASCA). The application of clustering techniques revealed different responses based on the patient's basal state, which allowed the identification of responders from non-responders. Results showed a triglyceride level reduction of up to 15% (p=0.0032), with a higher reduction for those patients with a higher initial lipid profile. Moreover, line-shape fitting techniques applied to the NMR spectra allowed the conclusion that LDL (and VLDL) lipoprotein particles, and more noticeably triglycerides, moved to a profile configuration associated with lower cardiovascular risk. Results shed light on some of the metabolic modifications that husk fiber induces in humans which could not be seen with more conventional data analysis approaches. Our conclusion is that by using the right chemometric techniques it is possible to assess nutritional intervention effects in human NMR human studies despite the low sensitivity and selectivity that the technique offers today.

Highlights

► Mild to moderate hypercholesterolemic patients received either placebo or Po-husk. ► ASCA discerned induced metabolic changes from natural variability between subjects. ► Our study revealed different responses that depended on the patient's basal state. ► Spectral line shape fitting algorithms helped diagnose metabolic syndrome. ► Results showed a triglyceride level reduction of up to 15% (p=0.0032).

An investigation on hydrogen bonding between 3-methylindole and ethanol using trilinear decomposition of fluorescence excitation–emission matrices

25 January 2013, 09:19:36

15 February 2013
Publication year: 2013
Source:Chemometrics and Intelligent Laboratory Systems, Volume 121

The multi-state fluorescence characteristics of 3-methylindole (MI) make its spectra rich in chemical information and the spectral interpretation rather challenging. The trilinear decomposition method could be appropriate for this task and provide a deeper insight into the hydrogen bonding to MI. Taking the excitation fluorescence spectra together with the emission counterparts to formulate a three-way data array and solving the data array using the Alternating Trilinear Decomposition (ATLD) algorithm is beneficial for studying hydrogen bonding to MI in several aspects. Firstly, making full use of the excitation spectra could guarantee that the experimentally collected data contain sufficient information necessary for investigating signals originated from the weak interactions buried in the strong interaction background. Secondly, the resolution of a three-way data array could theoretically guarantee the uniqueness of the resolved component spectra with actual physical meaning. Thirdly, the ATLD algorithm resolves spectra of complex mixture and determines the spectra of corresponding individual components of different states without disturbing the complex chemical equilibrium involved. The hydrogen bonding interaction of MI with other molecules has been studied using the ATLD algorithm. A detailed investigation has been undertaken for the ¹La and ¹Lb states as the lowest excited singlet states which dominate the fluorescence emission of MI depending on the effect of other molecules and the surrounding microenvironment. The hydrogen bonding between indole derivatives and other molecules has been examined and some association constants involving hydrogen bond formation have been estimated and compared with theoretical simulation results or experimental observations of previous researchers.

Highlights

► This paper implemented an in-situ interpretation of hydrogen bonding. ► Three types of hydrogen bond interaction were analyzed simultaneously. ► The hydrogen bond interactions were quantitatively detected for the first time. ► The trilinear decomposition method makes effective use of multi-state fluorescence.

Statistical process monitoring via generalized non-negative matrix projection

25 January 2013, 09:19:36

15 February 2013
Publication year: 2013
Source:Chemometrics and Intelligent Laboratory Systems, Volume 121

As a famous dimension reduction technique, non-negative matrix factorization (NMF) has been used in diverse scientific fields since its appearance. In this work, we aim to propose a new statistical monitoring method based on NMF framework. Considering that the projection method is standardly used in conventional methods such as principal component analysis (PCA), a new variant of NMF method based on positively constrained projections is presented here. This algorithm also relieves the non-negative restriction for original data. Hence it can be called generalized non-negative matrix projection (GNMP). Then, we use GNMP to extract the latent variables that drive a process and to combine them with process monitoring techniques for fault detection. Kernel density estimation (KDE) is adopted to calculate the confidence limits of defined statistical metrics. In addition, corresponding contribution plots are defined for fault isolation. Afterwards, the proposed method is applied to the Tennessee Eastman process to evaluate the monitoring performance. The experiment results clearly illustrate the feasibility of the proposed method.

Highlights

► Propose a new variant named generalized non-negative matrix projection (GNMP). ► Define the monitoring metrics and adopt KDE to calculate the confidence limits. ► Define the contribution plots for the monitoring indices, respectively. ► Apply TE process for evaluating the monitoring performance.

Nonlinear regression method with variable region selection and application to soft sensors

25 January 2013, 09:19:36

15 February 2013
Publication year: 2013
Source:Chemometrics and Intelligent Laboratory Systems, Volume 121

Regions of explanatory variables, X, are attempted to be selected in many fields such as spectral analysis and process control. A genetic algorithm-based wavelength selection (GAWLS) method is one of the methods used to select combinations of important variables from X-variables using regions as a unit of measurement. However, a partial least squares method is used as a regression method, and hence, a GAWLS method cannot handle nonlinear relationship between X and an objective variable, y. We therefore proposed a region selection method based on GAWLS and support vector regression (SVR), one of the nonlinear regression methods. The proposed method is named GAWLS–SVR. We applied GAWLS–SVR to simulation data and industrial polymer process data, and confirmed that predictive, easy-to-interpret, and appropriate models were constructed using the proposed method.

Highlights

► Regions of explanatory variables (X) are attempted to be selected in many fields. ► A traditional method cannot handle nonlinear relationship between variables. ► Our goal is to select appropriate X-variable regions and construct a nonlinear model. ► We proposed new variable region selection method with support vector regression. ► The performance of the proposed method was confirmed with a variety of data sets.

Product quality modelling and prediction based on wavelet relevance vector machines

25 January 2013, 09:19:36

15 February 2013
Publication year: 2013
Source:Chemometrics and Intelligent Laboratory Systems, Volume 121

In order to predict product quality and optimize production process, the product quality models need to be built. However, there are complex nonlinear relationship among the product quality parameters and the production process variables. The common methods cannot model the production process with high accuracy and the prediction intervals cannot be given by those methods. In contrast, the kernel methods can transform the original input data into a feature space via kernel function, and then the linear methods can be used to resolve the nonlinear problem accurately. Moreover, the relevance vector machine as a kernel method can give the prediction intervals, and wavelet kernel can inherit the ability of local analysis and feature extraction from the wavelet function. The product quality models based on wavelet relevance vector machine are proposed in this paper. A simulation data set, two chemistry data sets and a real field data set of zinc coating weights from strip hot-dip galvanizing are used to validate the model. The results demonstrate that the model based on wavelet relevance vector machines has a higher prediction precision than the common methods such as partial least squares(PLS), orthogonal signal correction-partial least squares(OSC-PLS), Quadratic-PLS, kernel partial least squares(KPLS), orthogonal signal correction-kernel partial least squares(OSC-PLS), least squares-support vector machines (LS-SVM) and ordinary relevance vector machines(RVM). The prediction intervals are also given by the presented model. Mexican, Morlet and Difference of Gaussian (DOG) wavelet relevance vector machines (WRVMs) for multi-group data show superior prediction performance compared to other methods mentioned above.

Highlights

► A product quality model based on wavelet relevance vector machine (WRVM) is proposed. ► Wavelet relevance vector machine model can give the exact prediction interval. ► Zinc coating weights from strip hot-dip galvanizing are predicted to validate the model. ► WRVM has a higher prediction precisions than PLS, Q-PLS KPLS, SVM and RVM.

Automatic image-based estimation of texture analysis as a monitoring tool for crystal growth

25 January 2013, 09:19:36

15 February 2013
Publication year: 2013
Source:Chemometrics and Intelligent Laboratory Systems, Volume 121

Online monitoring and feedback control are crucial elements in a commercial crystallization operation because they ensure that key production variables are closely regulated so as to achieve specified textural and physical properties of the end-product. Digital image texture analysis is a promising method in monitoring and control systems, and is becoming increasingly more attractive due to availability of high speed imaging devices and equally powerful computers. This paper investigates the use of texture analyses in the form of fractal dimension (FD) and energy signatures as characteristic parameters to track the crystal growth. This methodology deals with issues such as touching and overlapping problem in crystal images which limit available off-line and on-line imaging techniques. The algorithm uses a combination of thresholding and wavelet-texture analysis. The thresholding method is used to identify crystal clusters and remove empty backgrounds. Wavelet–fractal and energy signatures are performed afterwards to estimate texture on crystal clusters. A series of images obtained at different crystal growth stages during a NaCl–water–ethanol anti-solvent crystallization system is investigated and their texture characteristics as well as transform tendency during the crystallization process are evaluated.

Highlights

► Fractal dimension and energy signatures as parameters to track crystal growth. ► Uses combination of thresholding and wavelet-texture algorithms. ► Thresholding method identifies crystal clusters and removes empty backgrounds. ► Wavelet-fractal and energy signatures estimate texture on crystal clusters. ► Validated for anti-solvent crystallization.

Controlling Nucleation on Production Freeze Dryers

SP Scientific has announced that ControLyo™ Nucleation On-Demand Technology can now be retrofitted to a wide range of previously installed production freeze dryers.

The ControLyo™ technology, patented by Praxair Inc., was licensed exclusively by SP Scientific in 2010 for use on development freeze dryers with shelf surface areas < 1.0 sq.-m.  The technology was incorporated into the SP Scientific Lyostar 3 freeze dryer, the first commercial dryer to offer controlled nucleation capability.

Since that time, considerable research has been done at the development scale with controlled nucleation. ControLyo™ technology offers many benefits to freeze drying in the biotech and pharmaceutical industries including improved vial-to-vial uniformity, reduced cycle times, easier process scale-up, reduced protein aggregation and better conformance to the Food & Drug Administration's Process Analytical technology (PAT), and Quality by Design (QBD) Initiatives.

In order for the benefits demonstrated in development work to offer economic benefits to companies, the technology has to be scalable to production freeze dryers.  SP Scientific and Praxair have demonstrated that many commercial production dryers can be relatively quickly and easily retrofitted to benefit from the advantages offered by ControLyo™ technology.  It has also been demonstrated on production freeze dryers as large as 300 sq.-ft. (27 sq.-m), that controlled nucleation was achieved in nearly 9000 vials, ranging in size from 20ml to 100ml with fill volumes of ¼ and ½.  Economical retrofits and scalability of the technology open opportunities to significantly improve production cycles of lyophilized products, with concomitant reduction in costs.

Just Published: Microchemical Journal

A new issue of this journal has just been published. To see abstracts of the papers it contains (with links through to the full papers) click here:

Microchemical Journal
http://rss.sciencedirect.com/publication/science/6599

Selected papers from the latest issue:

Determination of total arsenic, total inorganic arsenic and inorganic arsenic species in rice and rice flour by electrothermal atomic absorption spectrometry

24 January 2013, 09:15:48

May 2013
Publication year: 2013
Source:Microchemical Journal, Volume 108

The determination of inorganic arsenic species in food has become very important during the last few years, since As(III) and As(V) are considered carcinogenic and found at high concentrations in food products, such as rice. The present work describes the development of three different methods for the determination of total arsenic, total inorganic arsenic, and As(III)–As(V) in rice and rice flour food products, purchased from the local market by electrothermal atomic absorption spectrometry (ETAAS). The methods were based on the use of different selective extraction procedures and the optimization of all crucial instrumental and methodological parameters. By these new preparation procedures for the determination of arsenic species, the loss and transformation of analytes during the extraction and digestion steps was prevented. For the validation of each method, precision, accuracy, and selectivity have been assessed, as performance criteria. All developed methods were accurate and precise. The calculated recoveries ranged between 92% and 105% and the (%) relative standard deviation values, under repeatability or reproducibility conditions, were lower than 15% for all different concentration levels tested. The validated methods were applied successfully for the determination of total arsenic and total inorganic arsenic in a proficiency test organized by the International Measurement Evaluation Program (IMEP-107). The methods were also applied in rice and rice flour samples purchased from the Greek market and the obtained results indicated that in almost all samples total arsenic and total inorganic arsenic were detected at ng/g levels.

Highlights

► Novel and simple procedures for inorganic As speciation in rice were developed ► Optimization and full validation of all methods were performed ► Proficiency test (IMEP-107) proved the accuracy of the proposed methods ► Application to rice and rice flour samples was performed ► Total inorganic As was equal to (64±19)% of total As in all samples.

Study of modern or ancient collagen and human fossil bones from an archaeological site of middle Nile by thermal analysis and chemometrics

24 January 2013, 09:15:48

May 2013
Publication year: 2013
Source:Microchemical Journal, Volume 108

Thermogravimetric (TG-DTG) curves were recorded for 23 different samples of human fossil bones from the El Geili necropolis. An accurate analysis of mass loss of the samples examined at different temperatures during a linear thermal scan between 25°C and 1000°C in dynamic air afforded a data set consisting of the thermal parameters of the decomposition processes of collagen and carbonate; this data set was then processed by standard chemometric techniques. The results obtained are discussed and attention is focused in particular on the old or modern collagen thermal breakdown and the possibility of formulating an “archaeometric” assessment that takes into account the often untied conclusions reported in the literature.

Highlights

► Characterization of ancient and modern collagen based on kinetic data. ► Systematization of incomplete information about thermal analysis of fossil bones. ► Characterization of the different kinds of carbonates from bone mineralization.

Classification of intact fresh plums according to sweetness using time-domain nuclear magnetic resonance and chemometrics

24 January 2013, 09:15:48

May 2013
Publication year: 2013
Source:Microchemical Journal, Volume 108

Time domain nuclear magnetic resonance (TD-NMR) and chemometric models were used to classify intact plums according to the total soluble solid content in percentage (% of SSC). The models were constructed using use Carr–Purcell–Meiboom–Gill (CPMG) decay (as independent variables) of intact plums. The reference values in % of SSC (as dependent variable) were obtained from the juice extracted from the same plums. The data sample was divided into two categories: class 1, up 9 to 12% of SSC and class 2, up 13 to 22% of SSC. The soft independent modeling of class analogy (SIMCA) of 171 plums correctly classified the class 1 plums approximately 89% of the total and the class 2 plums (sweeter) above 93% of the samples for both training and the validation data set, at 95% of confidence level. Therefore, the analysis of CPMG decay using SIMCA can be used to classify intact plums according to sweetness. This method is fast (seconds) and can easily be automated, allowing a better classification of each plum than the average SSC values of a lot.

Highlights

► Time domain nuclear magnetic resonance and Chemometrics models properly classify intact plums according to the sweetness. ► The model correctly classified the plums above 89% of the samples of low SSC and 93% of the samples of high SSC. ► This method is fast and can easily be automated.

Direct detection of aromatic amines and observation of intermediates of Schiff-base reactions by reactive desorption electrospray ionization mass spectrometry

24 January 2013, 09:15:48

May 2013
Publication year: 2013
Source:Microchemical Journal, Volume 108

The fast, sensitive detection for 6 aromatic amines and direct observation of intermediates of Schiff-base reactions were achieved through reactive desorption electrospray ionization mass spectrometry (reactive DESI-MS). Pure acetone was electrosprayed to impact the aromatic amines on the paper, allowing two reactions, a proton-transfer reaction and a Schiff-base reaction, to occur in these experiments. The former was used to detect the aromatic amines, and the protonated analytes generated were selected for the qualitative and quantitative analysis. The false-positive signals were excluded by tandem mass spectrometry. For the 6 analytes, linear signal responses were obtained, and each had a dynamic range of 5 orders of magnitude. The relative standard deviation (RSD) and limit of detection (LOD) for all the measurements were in 1.5–5.3% and 0.03–0.2pg/mm² range, respectively. The latter is a nucleophilic addition reaction that occurred between the aromatic amines and the acetone. The carbinolamine intermediates of these reactions were directly detected and identified by reactive DESI-MS. The data show that reactive DESI-MS is not only a reliable, sensitive tool for chemical analysis, but also a valid and promising method for studying organic reactions simultaneously, especially for heterogeneous reactions that occurred at a solution/solid interface.

Highlights

► 6 suspected carcinogenic aromatic amines were qualitatively and quantitatively analyzed without sample pretreatment. ► The intermediates of the heterogeneous Schiff-base reactions were directly observed and identified. ► Acetone was verified to be another choice of the spray solvent of DESI-MS.

Assay of high-purity sodium oxalate traceable to the international system of units by coulometric titration and gravimetric titration

24 January 2013, 09:15:48

May 2013
Publication year: 2013
Source:Microchemical Journal, Volume 108

Sodium oxalate is one of the key reference materials in volumetric analysis. This material and its solution are widely used as a reducing agent and as a standard to standardize oxidizing agents such as potassium permanganate; nevertheless, no certified reference material has been available until recently. The authors challenged purity assay of sodium oxalate basically with Ce(IV) which could accurately be standardized by coulometric titration. This paper describes the accurate determination of sodium oxalate through three different paths: gravimetric titration with Ce(IV) standardized by coulometric titration, gravimetric back titration using excess Ce(IV) and titrant thiosulfate both of which are standardized by coulometric titrations, and gravimetric back titration using excess Ce(IV) and titrant Fe(II) both of which are standardized by coulometric titration and gravimetric titration, respectively. Two kinds of back titrations of excess Ce(IV) mentioned above were carried out to completely proceed with the reaction between oxalate and Ce(IV). The comprehensive evaluation of the uncertainties for sodium oxalate assay was carried out, resulting in the significant improvement of accuracy of oxalate determination. Finally, sodium oxalate whose purity was traceable to the SI was developed as a certified reference material.

Highlights

► The purity of sodium oxalate was first determined with the linkage to the SI units. ► The determination methods were examined through three different paths. ► The determination methods with the highest accuracy were presented. ► High accuracy of each titration reaction was newly ascertained. ► The measurement methods presented enable analysts to obtain reliable results.

Simultaneous determination of quality parameters in biodiesel/diesel blends using synchronous fluorescence and multivariate analysis

24 January 2013, 09:15:48

May 2013
Publication year: 2013
Source:Microchemical Journal, Volume 108

An analytical method was developed to determine four quality parameters (Biodiesel percentage, Cetane Number, Heat of Combustion Gross and Color) in biodiesel/diesel blends through a simple synchronous fluorescence spectrum of the samples. For this purpose, chemometrics models based on fluorescence spectra and PetroSpect data obtained from mixtures of biodiesel/diesel were built. A variable selection by the successive projections algorithm (SPA) was used in order to obtain simple multiple linear regression (MLR) models based on a small subset of wavelengths. The SPA-MLR results were compared with a partial least squares (PLS) full spectrum regression. The best values found for the root mean square error of prediction using external validation were 0.37% (w/w) for the biodiesel in diesel, 0.5 for cetane number, 0.013MJ/kg for heat of combustion and 0.1 for color.

Highlights

► Chemometric models are useful to determine parameters with a simple synchronous fluorescence spectrum of the fuel sample. ► The proposed method is rapid and inexpensive compared to official methods. ► The quality parameters are fatty acid methyl esters (FAME), cetane number, gross heat of combustion and color.

Extraction and detection of organoarsenic feed additives and common arsenic species in environmental matrices by HPLC–ICP-MS

24 January 2013, 09:15:48

May 2013
Publication year: 2013
Source:Microchemical Journal, Volume 108

Organoarsenic compounds, such as roxarsone (3-nitro-4-hydroxyphenylarsonic acid, ROX) and p-arsanilic acid (ASA), are widely used as animal feed additives, while animal wastes bearing these compounds are often used to fertilize agricultural land, which can cause arsenic pollution of soil, surface water, and groundwater. Determination of a number of inorganic and organic arsenic species in a variety of environmental matrices is necessary to study the environmental fate of organoarsenic feed additives and to assess their risk. A robust analytical method was developed in this work for precise and accurate quantification of ROX, ASA, dimethyl arsenic acid (DMA), monomethyl arsenic acid (MMA), arsenate [As(V)], and arsenite [As(III)] by HPLC–ICP-MS with gradient elution. Extraction conditions for recovering the inorganic and organic arsenic species from soils and sediments were also optimized, and the best results were obtained with 0.5mol·L⁻¹ H3PO4 under constant shaking for 16h. This method was applied in determining the levels of inorganic and organic arsenic species in sediments, soils, and surface water surrounding several swine farms in the Pearl River Delta in southern China and the results showed that the environmental media were already impacted by organoarsenic feed additives.

Highlights

► Organoarsenic compounds are widely used as feed additives to animals. ► Unmetabolized organoarsenic feed additives are released into the environment. ► A method was developed to measure these additives and environmental arsenic species. ► Conditions for extracting these As compounds from soils and sediments were optimized. ► The method can help study the environmental distribution and fate of these additives.

Optimization and application of headspace liquid-phase microextraction coupled with gas chromatography–mass spectrometry for determination of furanic compounds in coffee using response surface methodology

24 January 2013, 09:15:48

May 2013
Publication year: 2013
Source:Microchemical Journal, Volume 108

A simple and accurate method for determination of furanic compounds in coffee samples using headspace liquid-phase microextraction (HS-LPME) combined with gas chromatography–mass spectrometry (GC/MS) was developed and validated. In addition to furan, other furanic compounds such as 2-methylfuran, 2,5-dimethylfuran, 2-vinyl furan, 2-(methoxymethyl) furan and furfural were also determined. The effective parameters in HS-LPME process, including ionic strength, stirring rate, temperature and time of extraction process were optimized using response surface methodology (RSM) based on central composite design. The results of optimization study showed that stirring rate, temperature and time of extraction parameters have positive effect on the efficiency of microextraction process but the effect of salt addition on response was negative. The optimal extraction conditions using a quadratic model were: stirring rate 700rpm, extraction temperature 43°C, extraction time 15min and without salt addition. The calibration curves showed good linearity (R² >0.99) for all the furanic compounds in the range of 0.2–400ngml⁻¹. Repeatability varied from 4.2% to 9.5%. The method accuracy was acceptable with recoveries ranging from 79.6% to 102%. Good enrichment factors were obtained e.g. 1270 for furan. The limits of detection (LOD) and limits of quantification (LOQ) ranged from 0.02 to 10ngg⁻¹ and 0.06 to 39ngg⁻¹, respectively. The comparison of validated method with two other methods for furan analysis showed comparable merit figures and proved the applicability of HS-LPME followed by GC/MS for extraction and determination of furanic compounds in coffee samples.

Highlights

► A simple method was proposed to determine of furanic compounds from coffee. ► The method is based on HS-SPME combined with GC–MS. ► The effective parameters in HS-LPME were optimized using RSM based on CCD. ► The absence of matrix effect using the HS-LPME has been demonstrated. ► The figures of merit for furans in coffee using the proposed method were perfect.

Evaluation of drying conditions of fish tissues for inorganic mercury and methylmercury speciation analysis

24 January 2013, 09:15:48

May 2013
Publication year: 2013
Source:Microchemical Journal, Volume 108

The influence of drying conditions on the behavior of Hg species (Hg²⁺ and CH3Hg⁺) present in fish tissues was evaluated. Drying conditions were evaluated for six fish species using air circulation drying oven in different temperatures (50 to 175°C) and lyophilization (0.25mm Hg, −2°C). Evaluation of drying step was based on losses and conversions of original Hg species after each drying condition. The extraction efficiency was determined by comparing the concentration of total Hg in digested samples (wet digestion in closed system using HNO3) with extracted Hg using l-cysteine solution. Chemical vapor generation-inductively coupled plasma mass spectrometry (CVG-ICP-MS) and liquid chromatography-chemical vapor generation-inductively coupled plasma mass spectrometry (LC-CVG-ICP-MS) were used for the determination of total Hg and Hg species, respectively. The accuracy was evaluated using certified reference materials and an agreement better than 97% with certified values was obtained for CH3Hg⁺ and total Hg. The relative standard deviation of the proposed method was below 5.5%. Limit of detection of 1.7 and 2.3ngg⁻¹ as Hg was obtained for Hg²⁺ and CH3Hg⁺, respectively. Results showed that with drying temperatures above 100°C losses and conversions of CH3Hg⁺ to Hg²⁺ can occur for some fish species.

Highlights

► Critical evaluation of drying conditions for mercury speciation analysis in fish. ► Dependence of temperature for losses or conversion of mercury species in fish. ► Feasibility of selected drying conditions for further LC-CVG-ICP-MS determination of Hg species.