Multivariate analysis of HT/GC-(IT)MS chromatographic profiles of triacylglycerol for classification of olive oil varieties

The ability of multivariate analysis methods such as hierarchical cluster analysis, principal component analysis and partial least squares-discriminant analysis (PLS-DA) to achieve olive oil classification based on the olive fruit varieties from their triacylglycerols profile, have been investigated. The variations in the raw chromatographic data sets of 56 olive oil samples were studied by high-temperature gas chromatography with (ion trap) mass spectrometry detection. The olive oil samples were of four different categories (“extra-virgin olive oil”, “virgin olive oil”, “olive oil” and “olive-pomace” oil), and for the “extra-virgin” category, six different well-identified olive oil varieties (“hojiblanca”, “manzanilla”, “picual”, “cornicabra”, “arbequina” and “frantoio”) and some blends of unidentified varieties. Moreover, by pre-processing methods of chemometric (to linearise the response of the variables) such as peak-shifting, baseline (weighted least squares) and mean centering, it was possible to improve the model and grouping between different varieties of olive oils. By using the first three principal components, it was possible to account for 79.50% of the information on the original data. The fitted PLS-DA model succeeded in classifying the samples. Correct classification rates were assessed by cross-validation.     

Molecular diagnostics using analytical immuno high performance liquid affinity chromatography

Analytical immuno high performance liquid affinity chromatography (analytical immuno HPLAC) was evaluated as a molecular diagnostic tool. Antibodies raised in rabbits against bovine neurophysin II were immobilized through Protein A crosslinking onto coated silica. Interaction of immobilized antibody with mobile antigen was characterized by zonal and frontal elutions of¹⁴C-labeled bovine neurophysin II under isocratic, nondenaturing conditions. The Chromatographic behavior shows that analytical immuno HPLAC with immobilized antibodies can be used to detect the number and functional nature of matrix-interacting antigens in mixtures, thus providing a quantitative Chromatographic technology for “antigen mapping”.     

Danube River Water Data Modelling by Multivariate Data Analysis

 A data set (48×19) consisting of Danube river water analytical data collected at Galati site, Romania, during a four-year period has been treated by principal components analysis (PCA). The PCA indicated that seven latent factors (“hardness”, “biochemical”, “waste inlets”, “turbidity”, “acidity”, “soil extracts” and “organic wastes”) are responsible for the data structure and explain over 80 % of the total variance of the system. Its complexity is further proved by the application of multiple linear regression analysis on the absolute principal components scores (APCS) where the contribution of each natural or anthropogenic sources in the factor formation is shown. The apportioning makes clear that each variable participates to a different extent to each source and, in this way, no pure natural or pure anthropogenic influence could be determined. No specific seasonality for the variables in consideration is found. Received January 24, 2001. Revision July 6, 2001.     

Evaluation of high-performance liquid chromatography for determination of phenolic compounds in pear horticultural cultivars

Summary An analytical evaluation of an HPLC method with diode array detection to separate and quantify polyphenolic compounds from pears has been made. The method was applied to the quantitative analysis of phenolics from five pear horticultural cultivars (“Agua”, “Blanquilla”, “Conference”, “Pasagrana” and “Decana”) in both peel and pulp matrices and evaluated for precision and accuracy. Precision was taken as the reproducibility in peak area of the polyphenols of interest as well as in the slope of calibration graphs. Values ranged 2–5%. Accuracy was evaluated by recovery of all polyphenolic compounds from both peel and pulp in all pears investigated. Accuracy values ranged 92–102%, and were independent of the polyphenolic structure, horticultural cultivar and matrix. Identification was by comparing retention times and UV spectra with those of standards when commercially available. When not available commercially, provisional identification was according to spectral characteristics as well as from isolation and hydrolysis data. Application of the method revealed differences between peel and pulp in all cases studied; the higher levels of phenolics were found in the peels. “Decana” and “Pasagrana” cultivars showed the highest phenolic content compounds whereas “Conference” showed the lowest.     

Assessment of Water Quality for Human Consumption

 This study deals with the application of chemometric approaches (cluster analysis and principal components analysis) to a potable water monitoring demonstrated on a data set from the region of Kavala, Greece, being analysed according to the standard instructions and directives of the European Union. It is shown that the data classification by cluster analysis and data structure modeling by principal components analysis reveals similar results, namely four different patterns of water source sites are identified depending on the geographical site location (near to Nestos river, near to Strimon river, elevated sites and near-to-coast sites). Three latent factors, explaining over 85% of the total variance, are responsible for the data structure as follows: “water acidity (anthropogenic)”, “water hardness (natural)” and the “marine factor”. Their importance for the different sites is related to the site location. Finally, it is recommended to involve the environmetric data treatment as a substantial standard procedure in assessment of the quality of water intended for human consumption. Received October 18, 2001; accepted June 24, 2002     

Multivariate statistical assessment of polluted soils

This study deals with the application of several multivariate statistical methods (cluster analysis, principal components analysis, multiple regression on absolute principal components scores) for assessment of soil pollution by heavy metals. The sampling was performed in a heavily polluted region and the chemometric analysis revealed four latent factors, which describe 84.5 % of the total variance of the system, responsible for the data structure. These factors, whose identity was proved also by cluster analysis, were conditionally named “ore specific”, “metal industrial”, “cement industrial”, and “steel production” factors. Further, the contribution of each identified factor to the total pollution of the soil by each metal pollutant in consideration was determined.     

Synthesis and aromatizational rearrangements of new imino-, hydrazono-, and azino-2,5-cyclohexadienylidene systems as ligands for cascade type metallocomplexes

Three approaches to the synthesis ofN-substituted imino-, hydrazono-, and azino-2,5-cyclohexadienylidene systems based on reactions of 4-methyl-4-trichloromethylcyclohexa-2,5-dienone with aminophenols and hydrazones and condensation of hydrazones ofpara-semiquinoid ketones with carbonyl compounds, including that of the ferrocene series, were realized. The latter reaction, when applied to 3,6-dibromophenanthrene-9, 10-quinone, was accompanied by quantitative aromatizational molecular rearrangement with the elimination of the CCl₃ group. Using Rh¹ complexes as an example, it was shown that the heteroorganic ligands obtained can be used for the synthesis of mixed-ligand metallocomplexes with triple coordination of the metal atom including simultaneous metal-ligand interactions of the n-, π-, and σ-types. The principle of metal-ligand “cascade” appeared as a result of the generalization of two new phenomena of organometallic sereodynamics, which we have found recently^2,3 and have called oxidative and reductive redox-rotation. In the “cascade”, type1 (“metal-ligand-metal”) or type2 (“ligand-metal-ligand”) metallocomplexes, one or several coordinated metal ligand”) metallocomplexes, one or several coordinated metal atoms capable of concertedly and reversibly changing their valence in the course of intramolecular conformational transformation are in positions of mutual conjugation. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 363–367, February, 1997.     

High-resolution mass spectrometry for integrated qualitative and quantitative analysis of pharmaceuticals in biological matrices

Quantitative and qualitative high-resolution (HR) dependent and independent acquisition schemes on a QqTOF MS (with resolving power 20,000–40,000) were investigated for the analysis of pharmaceutical compounds in biological fluids. High-resolution selected reaction monitoring (HR-SRM) was found to be linear over three orders of magnitude for quantitative analysis of paracetamol in human plasma, offering a real alternative to triple quadrupole LC–SRM/MS. Metabolic stability of talinolol in microsomes was characterized by use of three different acquisition schemes: (i) information-dependent acquisition (IDA) with a TOF MS experiment as survey scan and product-ion scan as dependent scan; (ii) MS^ALL by collecting TOF mass spectra with and without fragmentation by alternating the collision energy of the collision cell between a low (i.e., 10 eV) and high setting (i.e., 40 eV); and (iii) a novel independent acquisition mode referred to as “sequential window acquisition of all theoretical fragment-ion spectra” (SWATH) or “global precursor ions scan mode” (GPS) in which sequential precursor ions windows (typically 20 u) are used to collect the same spectrum precursor and fragment ions using a collision energy range. SWATH or GPS was found to be superior to IDA or MS^ALL in combination with UHPLC for qualitative analysis but requires a rapidly acquiring mass spectrometer. Finally, the GPS concept was used for QUAL/QUAN analysis (i.e. integration of qualitative and quantitative analysis) of bosentan and its metabolites in urine over a concentration range from 5 to 2,500 ng mL⁻¹.     

Evaluation of a new generation quadrupole-based ICP-MS for uranium isotopic measurements in environmental samples

We compare the analytical performance of a modern quadrupole-based ICP-MS (“X-Series”, Thermo-Electron, Winsford, UK) with a single-collector double-focusing sector-field ICP-MS (“Axiom”, VG Elemental, Winsford, UK) for uranium isotopic measurements in environmental samples. We focus on the precision and accuracy obtained with both instruments for the ²³⁵U/²³⁸U isotopic ratios and on the abundance sensitivity that is a key parameter for low ²³⁶U/²³⁸U isotopic ratios measurements. We observe that isotopic measurements are more precise accurate with the “X-Series” than with the “Axiom”. Besides, we demonstrate that the “Axiom’s” higher abundance sensitivity limits its capability to measure ²³⁶U/²³⁸U ratio below a few ppm.     

An advanced multivariate statistical approach to study coastal sediment data

The present paper deals with the application of classical and fuzzy principal components analysis to a large data set from coastal sediment analysis. Altogether 126 sampling sites from the Atlantic Coast of the USA are considered and at each site 16 chemical parameters are measured. It is found that four latent factors are responsible for the data structure (“natural”, “anthropogenic”, “bioorganic”, and “organic anthropogenic”). Additionally, estimating the scatter plots for factor scores revealed the similarity between the sampling sites. Geographical and urban factors are found to contribute to the sediment chemical composition. It is shown that the use of fuzzy PCA helps for better data interpretation especially in case of outliers.     

On the detection of rare,and moderately rare,nuclear events

Some of the more important developments in science and practical demands in commerce have been linked to attempts to detect rare events and rare contaminants, ranging from the early “counting” of solar neutrinos to the occurrence of dodder seeds in clover. For moderately rare events (≈5 to 50 counts) we consider limitations of the Poisson-normal approximation, together with the apparent problem of excessive false positives when a common expression is (mis-)used for detection decisions. For very rare events, rigorous approaches published more than half a century ago are applicable to such current problems as trace actinide contamination and nuclear treaty monitoring.     

Normalized Lempel-Ziv complexity and its application in bio-sequence analysis

In this article, we propose a new method to measure DNA similarity based on a normalized Lempel-Ziv complexity scheme. The new method can weaken the effect of sequence length on complexity measurement and save computation time. Firstly, a DNA sequence is transformed into three (0,1)-sequences based on a scheme, which considers “A” and “non-A” , “G” and “non-G”, “C” and “non-C” bases respectively. Then, the normalized Lempel-Ziv complexity of the three (0,1)-sequences constitute a 3D vector. Finally, by the 3D vector, one may characterize DNA sequences and compute similarity matrix for them. The examination of similarities of two sets of DNA sequences illustrates the utility of the method in local and global similarity analysis.     

Sol-Gel Microsphere Pelletisation Process for Fabrication of (U,Pu)O2, (U,Pu)C and (U,Pu)N Fuel Pellets for the Prototype Fast Breeder Reactor in India

A “dust-free” sol-gel microsphere pelletisation (SGMP) process has been developed for fabrication of (U,Pu)O₂, (U,Pu)C and (U,Pu)N fuel pellets containing around 15% plutonium for the forthcoming prototype fast breeder reactor (PFBR) in India. The objective was to produce homogeneous sintered pellets of ∼85% T.D. with a predominantly open-pore structure. Hydrated gel-microspheres of UO₃+PuO₂ and UO₃+PuO₂+C have been prepared from nitrate solutions of uranium and plutonium by the “ammonia internal gelation” process, using hexamethylene tetramine (HMTA) as an ammonia generator and silicone oil at 90±1°C as gelation bath. For oxide fuel pellets, the hydrated UO₃+PuO₂ gel-microspheres were calcined at around 700°C in Ar+8% H₂ atmosphere to produce “non-porous”, “free-flowing” and coarse (around 400 micron) microspheres which could be directly pelletised at 550 MPa to green pellets. The mixed oxide pellets were subjected either to low temperature (∼1100°C) oxidative sintering (LTS) in N₂+air containing ∼1500 ppm O₂ or to high temperature (1650°C) sintering, (HTS) in Ar+8% H₂. For monocarbide and mononitride pellets, hydrated gel-microspheres of UO₃+PuO₂+C were subjected to carbothermic synthesis in vacuum (∼1 Pa) and flowing nitrogen (flow rate: 1.2 m³/h) in the temperature range of 1450–1550°C respectively. The monocarbide and mononitride microspheres thus produced were relatively hard and required higher compaction pressure (∼1200 MPa) for making reen pellets which could be sintered to 85% T.D. in Ar+8% H₂ at 1700°C. The sintered oxide, monocarbide and mononitride pellets had a “blackberry” “open” pore microstructure with fine grain size. The microspheres retained their individual identity in the sintered pellets because during sintering densification took place mainly within and not between the microspheres.     

Multivariate statistical analysis of coastal sediment data

Multivariate statistical analysis of sediment data (information matrix 123 × 16) from the Gulf of Mexico, USA shows that the data structure is defined by four latent factors conditionally called “inorganic natural”, “inorganic anthropogenic”, “bioorganic” and “organic anthropogenic” explaining 39.24%, 23.17%, 10.77% and 10.67% of the total variance of the data system, respectively. The receptor model obtained by the application of the PCR approach makes it possible to apportion the contribution of each chemical component for the latent factor formation. A separation of the contribution of each chemical parameter is achieved within the frames of “natural” and “anthropogenic” origin of the respective heavy metal or organic matter to the sediment formation process. This is a new approach as compared to the traditional “one dimensional” search with a limited number of preliminary selected tracer components. The model suggested divides natural from anthropogenic influences and allows in this way each participant in the sediment formation process to be used as marker of either natural or anthropogenic effects. Received: 20 March 1999 / Revised: 1 June 1999 / Accepted: 3 June 1999     

Multivariate statistical analysis of coastal sediment data

Multivariate statistical analysis of sediment data (information matrix 123 × 16) from the Gulf of Mexico, USA shows that the data structure is defined by four latent factors conditionally called “inorganic natural”, “inorganic anthropogenic”, “bioorganic” and “organic anthropogenic” explaining 39.24%, 23.17%, 10.77% and 10.67% of the total variance of the data system, respectively. The receptor model obtained by the application of the PCR approach makes it possible to apportion the contribution of each chemical component for the latent factor formation. A separation of the contribution of each chemical parameter is achieved within the frames of “natural” and “anthropogenic” origin of the respective heavy metal or organic matter to the sediment formation process. This is a new approach as compared to the traditional “one dimensional” search with a limited number of preliminary selected tracer components. The model suggested divides natural from anthropogenic influences and allows in this way each participant in the sediment formation process to be used as marker of either natural or anthropogenic effects. Received: 20 March 1999 / Revised: 1 June 1999 / Accepted: 3 June 1999     

Environmetrical Treatment of Water Quality Survey Data from Yantra River, Bulgaria

 The environmetrical analysis carried out has indicated that the short-term water quality survey may give a very important information on the latent factors influencing the water quality of Yantra river basin. The principal components analysis carried out reveals that at least four principal components are necessary for multivariate statistical modeling of the water quality – combination of natural and anthropogenic influences (“mixed” factor) reflecting parameters such as water hardness, marine influence, organic pollution; typical anthropogenic influences (“anthropogenic” factor) explaining the metal contamination of the river water; everyday wastes, usually N-containing pollutants such as nitrates, nitrites or ammonia, form the “N-containing wastes” factor and a “temperature” factor formed by typical physical parameters such as water and air temperature. The formation of these special features of the river waters from Yantra basin is also confirmed by the results of cluster analysis (variable clustering) where the content of the significant clusters of the variables is the same as the content of the principal components modeling over 75% of the total variance of the system. Additionally, the cluster analysis of the objects has proved that the water quality during both sampling traverses is very stable and reproducible. Few exceptions are observed due to momentary local pollution in an industrial area along the river stream. Comparison with standard requirements for water quality has indicated that the Yantra river waters are of high quality and could be used after minor pretreatment as potable water sources. The environmetrical approaches applied reveal a specific information concerning the river water quality. In this way the ecological problem treated has not a local importance but suggests a strategy for estimation of similar ecosystems in global sense. Received July 30, 1998. Revision June 1, 1999.     

Vertex topological indices and tree expressions,generalizations of continued fractions

We expand on the work of Hosoya to describe a generalization of continued fractions called “tree expressions.” Each rooted tree will be shown to correspond to a unique tree expression which can be evaluated as a rational number (not necessarily in lowest terms) whose numerator is equal to the Hosoya index of the entire tree and whose denominator is equal to the tree with the root deleted. In the development, we use Z(G) to define a natural candidate ζ(G, v) for a “vertex topological index” which is a value applied to each vertex of a graph, rather than a value assigned to the graph overall. Finally, we generalize the notion of tree expression to “labeled tree expressions” that correspond to labeled trees and show that such expressions can be evaluated as quotients of determinants of matrices that resemble adjacency matrices.     

Fast LC analysis of the α-acid content of “fresh” and “aged” hops

Summary A quaternary mobile phase was optimized in conjunction with Fast LC techniques to separate α and β acids extracted from hops in less than 4 minutes. The method is proposed for automated analysis of large numbers of hop samples and its usefulness is demonstrated by comparing α-acid levels obtained by liquid chromatographic and conductometric techniques. Both assays provided similar values for “fresh” hops but in “aged” hops liquid chromatography showed a lower level of α-acids.     

Distribution of selected trace elements in samples of sediment,suspension and water taken along the Isar River,Bavaria

The three phases “dissolved solids”, “suspended solids” and “sediment” of four sampling sites along the river Isar were analysed by INAA. In these as well as in the different grain-size fractions between<2 and 63 μm 17 trace elements were determined. Compared with the values of other rivers in Middle Europe the river Isar is still below the levels of significant pollution.     

ko-measurements and related nuclear data compilation for (n, γ) reactor neutron activation analysis

k_o-factors of 35 isotopes used in reactor neutron activation analysis were measured with a high degree of accuracy (1–2%). To minimize systematic errors, measurements were carried out using different reactor types, irradiation conditions (18 < Φ_s/Φ_e), Ge(Li) detectors, sample detector geometry, etc. Analyst-oriented tabulations including all necessary nuclear data, “best values”, as well as recommended k_o-values are given to facilitate analytical work with the new method. Some practical aspects as well as limitations of the k_o-method are also outlined together with the applied neutron flux and cross-section conventions. Research associate of the National Fonds voor Wetenschappelijk Onderzoek, Belgium