Chemometric Resolution Research Articles

Anthocyanins as markers for the classification of Argentinean wines according to botanical and geographical origin. Chemometric modeling of liquid chromatography–mass spectrometry data

A study of Argentinean red wines was performed by direct injection of untreated wine samples into a liquid chromatography–mass spectrometry system, processing the collected data with two chemometric algorithms: multivariate curve resolution with alternating least-squares and discriminant unfolded partial least-squares (D-UPLS). The objectives were: (1) the chemometric resolution of profiles in the modes represented by elution time and m/z ratio, (2) the discrimination of samples according to varietal and/or geographical origin, and (3) the identification of key compounds helping to perform sample discrimination. The results indicate that all wine varietals can be adequately discriminated, and also three wine producing regions (located in the east, south and north of the Cuyo region) were differentiated from the remaining regions. The applied chemometric models allowed the tentative identification of anthocyanin compounds as responsible for both type of discriminations, in the case of D-UPLS by employing the concept of variables importance in the projection.

Performance assessment of chemometric resolution methods utilized for extraction of pure components from overlapped signals in gas chromatography–mass spectrometry

Multivariate resolution technique is a set of mathematical tools that uncovers the underlying profiles from a set of measurements of time evolving chemical systems. This technique was proposed for resolving the overlapping GC–MS peaks into pure chromatogram and mass spectra. In this paper, several common resolution chemometric techniques in GC–MS resolution such as mean field-independent component analysis (MF-ICA), multivariate curve resolution-alternating least squares (MCR-ALS), and multivariate curve resolution-objective function minimization (MCR-FMIN) were investigated. The obtained solutions using chemometric methods are assessed by lack of fit (LOF) and R2. Results show that all solutions by fulfilling the same constraints have same performance in resolving high overlapping peaks. Also, the differences obtained in each case should be related to the unresolved rotational ambiguity.Among the different ambiguities such as intensity, permutation and rotation in resolution methods, rotational ambiguity is the most difficult and critical one. Because of rotational ambiguity, there is a set of feasible MCR solutions, which explain equally well the observed experimental data, and fulfill sufficiently the imposed constraints of the system. So in these methods, a range of feasible solutions exist. The rotational ambiguities of the profiles are a challenging fact which complicates the development of stable and universal self-modeling curve resolution (SMCR) algorithms. The relative component contribution (RCC) function values for the component profiles obtained by the different methods are calculated by MCR-BANDS. The values of RCC for these three methods are equivalent. Rotational ambiguities of the solutions of SMCR methods can be reduced by applying suitable constraints. The obtained results show, using data sets, which are arranged in a single augmented data matrix could be the best solution for reducing or removing of rotational ambiguity.

Fast determination of ginsenosides in ginseng by high-performance liquid chromatography with chemometric resolution

Ginseng is a well-known traditional Chinese medicinal herb, and ginsenosides are its major active components. A method for the fast determination of ginsenosides in ginseng samples by high-performance liquid chromatography was developed and used for the quantitative analysis of four ginsenosides in three different ginseng samples. In this method, instead of time-consuming gradient elution, isocratic elution was used to speed up the analysis. Under strong isocratic elution, all the ginsenosides are eluted in 2.3 min. Although the measured signal is composed of overlapped peaks with the interferences and background, the signal of ginsenosides can be extracted by chemometric resolution. A non-negative immune algorithm was employed to obtain the chromatographic information of the target components from the data. Compared with conventional chemometric approaches, the method can perform the extraction for one-dimensional overlapping signals. The method was validated by the determination of four ginsenosides in three different ginseng samples. The recoveries of the spiked samples were in the range of 94.08-107.3%.

Rapid determination of amino acids in ginseng by high performance liquid chromatography and chemometric resolution

Ginseng is one of the most important traditional Chinese medicines and functional foods. A method for the fast determination of amino acids in ginseng samples using high performance liquid chromatography(HPLC) was developed, in which strong isocratic elution was employed for simplifying the separation and speeding up the analysis. All amino acids were eluted within 3 min with the chromatogram composed of overlapped peaks from the interferences. Then, non-negative immune algorithm(NNIA) was adopted to resolve the chromatographic signals of the components from the chromatogram measured. The results show that the signals of the amino acids can be correctly extracted by NNIA and the signal extracted can be used for the quantitative analysis. The method was validated via determining six amino acids of four different samples of ginseng. The recoveries of the spiked samples are in a range of 96.6%–106.3%.

Rapid analysis of Origanum majorana L. fragrance using a nanofiber sheet, gas chromatography with mass spectrometry, and chemometrics

Headspace nanofiber sheet microextraction together with GC-MS and chemometrics resolution techniques were implemented to separate and identify the volatiles emitted by intact marjoram (Origanum majorana L.) and their relative concentrations. A novel polyaniline-nylon-6 nanofiber composite was applied for headspace microextraction. Characteristics such as high surface-to-volume ratio and π-π functional groups in polyaniline together with the NH and C=O functional groups in nylon-6 make the polyaniline-nylon-6 nanofiber composite a suitable candidate for the extraction of volatiles and semivolatiles. The extracted constituents were desorbed and injected into the GC-MS system under the optimum conditions. Chemometric resolution techniques were utilized to solve the baseline offset, asymmetric peaks, and overlapped peaks problems that arise from GC-MS analysis. By means of these techniques and resolving the overlapped peak clusters, the number of identified constituents was increased to 67 compounds. The major released constituents from the intact marjoram leaves are 4-terpineol, β-linalool, cis-sabinol, and trans-geraniol.

Chemometric Resolution Approaches in Characterisation of Volatile Constituents inPlantago ovataSeeds using Gas Chromatography-Mass Spectrometry: Methodology and Performance Assessment

Comprehensive chemical profiling of herbal medicines (HMs) is a major challenge in chemical characterisation of source materials. Many analytical platforms such as gas chromatography-mass spectrometry (GC-MS) have been applied to the characterisation. However, the great complexity of analytical results has been an obstacle. Chemometric resolution methods as a supplementary tool for data processing are proposed for solving this problem. To develop and demonstrate the ability of chemometric techniques in the characterisation of volatile components in herbal medicines. The volatile components of Plantago ovata were extracted using a solvent extraction method. GC-MS analysis were performed using an Agilent HP-6890 gas chromatograph equipped with a HP-5MS capillary, interfaced with an Agilent HP- 5973 mass selective detector. Resolved spectra were identified by matching against the standard mass spectral database of the National Institute of Standards and Technology (NIST). Results of this study show that the 71 constituents that are qualitatively recognised represent 94.53% of the total relative content of constituents from Plantago ovata oil, whereas without applying the chemometric methods only 51 constituents were recognised by direct searching utilising a mass database. In addition the presence of valuable components such as thymol, 2,4-decadienal, linoleic acid and oleic acid in Plantago ovata oil has been demonstrated. GC-MS combined with chemometric resolution methods, such as multivariate curve resolution-alternating least squares (MCR-ALS), will provide a reliable means for rapid and accurate analyses of unknown complicated practical systems.

Analysis of essential oil ofNardostachys chinensisBatal by GC-MS combined with chemometric techniques

The essential oil extracted from Nardostachys chinensis Batal (NCB) was analyzed by gas chromatography-mass spectrometry (GC-MS) combined with two chemometric resolution methods (CRM), heuristic evolving latent projections (HELP), and selective ion analysis (SIA). Qualitative analysis was performed by comparing the obtained pure mass spectra with those in National Institute of Standards and Technology (NIST) mass spectra database. Identification of some compounds was assisted by comparison of programmed temperature retention indices (PTRIs). The quantitative results were obtained by overall volume integration (OVI). A total of 69 compounds in the essential oil of N. chinensis Batal were identified, accounting for 93.98% of the total content. The major compounds were (−)-spathulenol, epiglobulol, trans-longipinocarveol, and patchouli alcohol which contribute to the antimicrobial and antioxidant activity. The results showed that the efficiency and reliability were greatly improved by use of chemometric tech...

Enhancing the sensitivity of potential step voltammetry using chemometric resolution

Enhancing the sensitivity of analytical methods by improving the signal quality is a universal goal in analytical chemistry. In analytical electrochemistry systems, the double layer charging current has been an obstacle to the accurate measurement of the faradaic current despite theoretical and experimental efforts. In this study, a method for sensitivity enhancement for potential step voltammetry is developed using chemometric resolution. Trilinear decomposition is used to extract the net faradaic current and double layer charging current directly from the data matrix of the decaying curves measured at different potentials. The feasibility of the method is proven using simulated data and further validated by two experimental datasets of diffusion and adsorption control reactions. Compared with the conventional approach that records the current data at a later pulse time, the voltammogram of the extracted net faradaic current is an ideal sigmoid curve with a horizontal baseline, even for the samples of very low concentration. More importantly, the analytical sensitivity can be greatly improved when the net faradaic current is used for quantitative determination.

Multivariate curve resolution combined with on-line infrared spectroscopy for researching the synthesis mechanism of 3,4-bis(4′-aminofurazano-3′)furoxan

3,4-Bis(4′-aminofurazano-3′)furoxan(DATF), one of a new generation of high energy density materials, shows lots of interesting properties such as lower sensitivity, excellent thermal stability and superior detonation performance in chemistry and physics. In this paper, on-line infrared(IR) spectroscopy was used to monitor the synthesis process of DATF. The concentration profiles and IR spectra of the components were determined by analyzing the IR data via principal component analysis(PCA), evolving factor analysis(EFA) and multivariate curve resolution-alternating least squares(MCR-ALS). The geometric configurations of reactant, intermediates and product were optimized with the density functional theory(DFT) at B3LYP/6-31+G(d, p) level. Their vibrational frequencies and IR spectra were obtained on the basis of vibrational analysis. The result obtained by the chemometric resolution methods agreed well with that obtained by quantum chemical calculation method, which demonstrated the reliability of the proposed chemometric resolution methods. The unstable intermediate 3-amino-4-oxycyanofurazan(AOF) was confirmed via comparing the IR spectra resloved by chemometric resolution methods with those calculated by B3LYP/6-31+G(d,p) and analyzed by MCR-ALS. Finally, the possible synthesis mechanism of DATF was deduced by analyzing the above IR spectra.

Chemometric Resolution for Rapid Determination of Prometryn in Leek Samples Using GC–MS

Much effort has been made to analyze the pesticides in foods or vegetables due to the interferences in the sample matrix. In this work, taking the determination of prometryn in leek samples as an example, a simple method is proposed for fast analysis of the components in real samples using GC–MS and chemometric resolution. The purification step in preparing the samples was simplified, and a short capillary column and fast temperature program were employed in GC–MS measurement. Although the measured signal is composed of overlapped peaks with the interferences and background, the signal of prometryn can be extracted by chemometric resolution. Six leek samples from different markets were analyzed within an elution time of 6 min. Compared with the results by the standard method, the results by the proposed method were found to be reliable.

Fast Determination of Phenanthrene in Soil by Gas Chromatography‐Mass Spectrometry Using Chemometric Resolution and Standard Addition Method

AbstractA method for fast determination of the component in complex samples by using gas chromatography‐mass spectrometry (GC‐MS) was developed and used for quantitative analysis of phenanthrene in soils. In the method, window independent component analysis (WICA) was used for resolving the mass spectrum and non‐negative immune algorithm (NNIA) was employed for obtaining the chromatographic profile. Therefore, spectral and chromatographic information of a specific component can be obtained from the measured GC‐MS data of overlapping and high background. Six soil samples collected from different places were analyzed. The tedious pretreatments in preparing the samples and the elution in the separation were simplified for speeding up the analysis. Due to the complexity of the matrix, standard addition method was adopted for the final quantification. The applicability of the method was validated with a spiked sample and the results of the six samples are reasonable.

Chemometric resolution techniques combined with GC-MS to enhance determination of the volatile chemical constituents of bay leaves

The 71 constituents of essential oil (EO) of bay leaves were identified with gas chromatography-mass spectrometry (GC-MS) by applying a similarity search between the obtained mass spectra and database. This number was increased to 131 constituents with the help of different chemometric resolution techniques. Multivariate curve resolution-alternating least squares (MCR-ALS) is used to obtain pure chromatograms and mass spectra for the constituents present in each overlapping/embedded peaks cluster as well as their relative concentrations. Other chemometric methods such as simple to use interactive self-modeling mixture analysis (SIMPLISMA), morphological score (MS) and Fixed Size Moving Window Evolving Factor Analysis (FSMWEFA) were used to determine the number of constituents, pure variables, zero concentration and selective regions. The most important constituents of the Iranian bay leaves are linalool (12.31%), 1,8-cineole (11.38%), α-terpineol acetate (7.71%), eugenol methyl ether (6.87%) and α-phellandrene (4.30%). Despite previous studies, chemometric resolution techniques were implemented as a necessary step for the comprehensive analysis of the volatile constituents of bay leaves.

Denaturation and intermediates study of two sturgeon hemoglobins by n-dodecyl trimethylammonium bromide

Varieties of hemoglobin (Hb) forms exist in fish, which are usually well adapted to the different ecological conditions or various habitats. In the current study, Hbs from two Sturgeon species of the Southern Caspian Sea Basin were purified and studied upon interaction with n-dodecyl trimethylammonium bromide (DTAB; as a cationic surfactant) by various methods including UV–visible absorption, dynamic light scattering (DLS), and ANS fluorescence spectrophotometry. The chemometric analysis of Hbs was investigated upon interaction with DTAB under titration, using UV–visible absorption spectra. The chemometric resolution techniques were used to determine the number of the components and mole fraction of the oxidized Hbs. These results provided the evidence for the existence of three different molecular components including native (N), intermediate (I) and denatured (D) in sturgeon Hbs. According to the distribution of intermediates, which were broadened in a range of DTAB concentration, the aggregation states, DLS experiments, and thermal stability (Tm obtained by differential scanning calorimetry (DSC)), the Acipenser stellatus Hb was more stable compared to Acipenser persicus Hb. These results demonstrate a significant relationship between the stability of fish Hbs and the habitat depth requirements.

Analysis of volatile components in herbal pair Semen Persicae‐Flos Carthami by GC‐MS and chemometric resolution

Analysis of volatile components in herbal pair (HP) Semen Persicae-Flos Carthami (SP-FC) was performed by GC-MS coupled with chemometric resolution method (CRM). Furthermore, temperature-programmed retention indices were used together with mass spectra for identification of the volatile components. With the help of CRM, the two-dimensional data obtained from GC-MS instruments were resolved into a pure chromatogram and a mass spectrum of each chemical compound. By use of these methods upon two-dimensional data, 26, 49, and 59 volatile chemical components in essential oils of single herb Semen Persicae, Flos Carthami, and HP SP-FC were determined qualitatively and quantitatively, accounting for 78.42, 81.08, and 82.48% total contents of essential oil of single herb Semen Persicae, Flos Carthami, and HP SP-FC, respectively. It is shown that the accuracy of qualitative and quantitative analysis can be enhanced greatly by means of CRM. It is further demonstrated that the numbers of volatile chemical components of HP SP-FC are almost the addition of those of two single herbs, but the main volatile chemical components of the former are completely different from those of single herb Semen Persicae or Flos Carthami because of chemical reactions and physical changes occurring in the process of decocting two single herbs. This means that chemical components especially pharmacologically active compounds in the recipe might be different from those of single herbs.

Analysis of the volatile chemical constituents in Mindium laevigatum by gas chromatography — Mass spectrometry and correlative chemometric resolution methods

The essential oil of Mindium laevigatum was extracted by applying simultaneous distillation extraction (SDE) method and studied with gas chromatography–mass spectrometry (GC–MS). The whole of 61 constituents was identified by applying similarity search between the obtained mass spectra and database. This number was expanded to 91 using multivariate curve resolution — alternation least square (MCR–ALS) method. Different chemometric methods such as simple-to use interactive self-modeling mixture analysis (SIMPLISMA), morphological score (MS) and Fixed Size Moving Window Evolving Factor Analysis (FSMWEFA) were used for determining the number of constituents, pure variables, zero concentration and selective regions. Self‐modeling curve resolution (SMCR) was suggested for resolving the co-eluted GC–MS peak into pure chromatograms and mass spectra. MCR–ALS prosperously applied for this aim. Pure variables from SIMPLISMA were applied as initial mixing matrix in iterative process. The resolved mass spectra were properly identified applying mass spectral search in NIST and Wiley library. The outcomes of this work proved that the combination of hyphenated chromatographic methods and resolution techniques provides a complementary method for the exact analysis of essential oils.

Synthetic Reaction Mechanism of Octogen by Chemometrics and Infrared Spectroscopy

Online IR spectrum was used for monitoring the reaction process of synthesizing octogen(HMX).The concentration profiles and IR spectra of reactants,intermediates and product were determined by analyzing the spectral data using multivariate curve resolution-alternating least squares(MCR-ALS) and heuristic evolving latent projection(HELP),and the reasonable mechanism was deduced.The stable geometry of intermediates was optimized at B3LYP/6-31G* theoretical level.Its vibrational frequencies and IR spectra were obtained on the basis of vibrational analysis.The results showed that the variation of intermediates could be obtained quickly with the aid of chemometric resolution and provided significant guidance to the choice of reaction.

Chemometric resolution of coeluting peaks of eleven antihypertensives from multiple classes in high performance liquid chromatography: A comprehensive research in human serum, health product and Chinese patent medicine samples

A novel chemometric-assisted high performance liquid chromatography method coupled with diode array detector (HPLC-DAD) was presented for the simultaneous determination of eleven antihypertensives from multiple classes in most concerned matrix systems. With the aid of second-order calibration which enables specific information of analytes to be well extracted, the heavily overlapping profiles between analytes and the coeluting interferences can be successfully separated and thus accurately quantified. A great advantage of the novel strategy lies in the fact that the analysis could be carried out with the same isocratic mobile phase (methanol/KH2PO4: 58:42, v/v, pH 2.60) in a short time regardless of the changes of matrices, such as human serum, health product and Chinese patent medicine. Both qualitative and quantitative results indicate that the hybrid strategy that using HPLC-DAD coupled with second-order chemometric method would be a high performance approach for the purpose of simultaneously quantifying multiple classes of antihypertensives in complex systems. Additionally, the analytical strategy can potentially benefit drug monitoring in both therapeutic research and pharmaceutical quality control. Moreover, the accuracy and reliability of the proposed methodology has been evaluated using several statistical parameters such as root mean squared error of prediction (RMSEP), figures of merit (FOM) and reproducibility of inter-day analysis.

Bilinear Decomposition Based Alignment of Chromatographic Profiles

A novel alignment procedure for chromatographic signals with photodiode array detection is presented. At first, the complexity of the chromatographic signals is reduced by chemometric resolution of the pure constituents. For this, the application of multivariate curve resolution-alternating least squares leads to the decomposition of the multiway data block into a chemically meaningful bilinear model representing the chromatographic profiles and their spectral signatures. The flexible implementation of a spectral selectivity constraint allows the background to be differentiated from the constituent spectra. Hereby, the pure concentration profiles are obtained which are consequently individually aligned by correlation optimized warping. In its final step, the procedure reconstitutes the original data with the aligned chromatographic profiles and their corresponding spectra. The alignment is evaluated for two sets of chromatographic signals. The new procedure improves the original application of correlation optimized warping minimizing the risks of aligning noncorresponding chromatographic information.

Computational Analysis between two different hemoglobins from Caspian Sea sturgeons (Acipenser persicus and Acipenser stellatus) induced by n‐dodecyl trimethylammonium bromide

The multiplicity of the Hemoglobins (Hbs) of the and the A. stellatus, two species from the Caspian Sea, A.persicus was confirmed with the polyacrylamide gel electrophoresis (SDS‐PAGE), cellulose acetate electrophoresis, and isoelectric focusing (IEF) experiments. In the current study, the interaction of n‐dodecyl trimethylammonium bromide (DTAB) as a cationic surfactant under variable concentrations, with the purified dominant Hbs was investigated using UV‐visible absorption spectra and circular dichroism (CD). The chemometric resolution techniques were used to determining the number of the components and mole fraction of the oxidized Hbs. The analysis of the obtained spectral data using singular value decomposition (SVD), evolving factor analysis (EFA) and multivariate curve resolution‐alternative least square (MCR‐ALS) as well‐known chemometrical techniques, gave the evidence for the existence of four different molecular components including native (N), intermediate (I), intermediate (II) and denatured (D) in sturgeon Hbs. On the basis of the interpretation of chemometrical results, the formation of intermediate states of fish Hbs, plays an important role for regulation of the respiratory system of the fishes proportional to their habitat depths and environmental partial pressure of oxygen.

Combination of chromatographic and chemometric methods to study the interactions between DNA strands

This work describes the combination of size-exclusion chromatography and chemometric resolution methods to study the formation of complex DNA structures from individual strands. This combined procedure has been applied to two different experimental data. Firstly, the formation of an intermolecular Watson–Crick duplex structure formed by the individual unstructured strands. Secondly, the competition between the intermolecular Watson–Crick duplex and intramolecular quadruplex structures formed by two sequences found in the hTERT gene has been studied.The analysis of the recorded chromatograms at just one single wavelength may not always be enough to confirm the existence of a higher order structure. In these cases, recording the entire spectrum at each point of the chromatogram and applying appropriate chemometric resolution methods has shown to be a useful tool to resolve and quantify the contribution of all DNA structures to the analytical signal. In this work, the Multivariate Curve Resolution based on Alternating Least Squares (MCR-ALS) has been used to analyze the three-way data sets acquired along chromatographic runs.