Chemometric techniques have been used to group samples with similar features as well as to discriminate among experimental data on edible oils. The objective of this study was to provide a simple method for differentiating vegetable oil types and to classify unknown samples using analytical techniques commonly used in the edible oil industry. We used principal component analysis to study the relationship between FA composition, tocopherol levels, CIF (Commission Internationale de l'Eclairage) parameters, and a photometric color index. The total variance in the original data matrix was established mainly by three principal components. Data processing allowed the oil samples to be identified and created a 2‐D map as a fingerprint of the oil types. This analysis can be used successfully to differentiate vegetable oil types and classify them as crude or refined oils.

The relationship between the herbicidal activity of a number of novel 1,2,5-oxadiazole N-oxides and some physicochemical properties potentially related with this bioactivity, such as polarity, molecular volume, proton acceptor ability, lipophilicity, and reduction potential were studied. The semiempirical molecular orbital method AM1 was used to calculate theoretical descriptors such as dipolar moment, molecular volume, Mulliken´s charge and the octanol/water partition coefficients (log Po/w). The values of the reduction potentials (Er) were obtained by cyclic voltammetry. In addition, the retention factors (log k’w) on a reversed-phase high-performance liquid chromatography (RP-HPLC) column in pure aqueous mobile phases were measured for several N-oxide derivatives. The log k’w values show good correlation with the calculated values of log Po/w, showing that the chromatographic parameter can be used as lipophilicity descriptor for these compounds. The multiple regression analysis between the descriptors for the N-oxide derivatives and the herbicide activity indicate that the variance in the biological activity can be explained by changes in the lipophilicity and in the reduction potential.

The chronic intake of an excessive amount of alcohol is currently ascertained by determining the concentration of direct alcohol metabolites in the hair samples of the alleged abusers, including ethyl glucuronide (EtG) and, less frequently, fatty acid ethyl esters (FAEEs). Indirect blood biomarkers of alcohol abuse are still determined to support hair EtG results and diagnose a consequent liver impairment. In the present study, the supporting role of hair FAEEs is compared with indirect blood biomarkers with respect to the contexts in which hair EtG interpretation is uncertain. Receiver Operating Characteristics (ROC) curves and multivariate Principal Component Analysis (PCA) demonstrated much stronger correlation of EtG results with FAEEs than with any single indirect biomarker or their combinations. Partial Least Squares Discriminant Analysis (PLS-DA) models based on hair EtG and FAEEs were developed to maximize the biomarkers information content on a multivariate background. The final PLS-DA model yielded 100% correct classification on a training/evaluation dataset of 155 subjects, including both chronic alcohol abusers and social drinkers. Then, the PLS-DA model was validated on an external dataset of 81 individual providing optimal discrimination ability between chronic alcohol abusers and social drinkers, in terms of specificity and sensitivity. The PLS-DA scores obtained for each subject, with respect to the PLS-DA model threshold that separates the probabilistic distributions for the two classes, furnished a likelihood ratio value, which in turn conveys the strength of the experimental data support to the classification decision, within a Bayesian logic. Typical boundary real cases from daily work are discussed, too.

No abstract

Solvent effects on the absorption spectra of N-@-nitrophenyl)dimethylenediamine (la), N-(p-nitropheny1)trimethylenediamine (Ib), N-@-nitrophenyl)tetramethylenediamine(Ic), N-methyl-N-@-nitropheny1)tetramethylenediamine (111, N-butyl-p-nitroaniline (111) and N-(o-nitropheny1)trimethylenediamine (IV) were studied at different temperatures. Whereas 11, Ill and 1V do not show any variation in their spectra characteristics with changes in temperature, I shows a hypsochromic shift with a hypochromic effect when the temperature is increased. The Kamlet and Taft solvatochromic comparison method was applied. A strong effect of the fl parameter on I and 111 was interpreted as being due to the hydrogen bond donor ability of the H atom in the aromatic amino groups. In I, the fl inEuence increases with increase in temperature. These facts are explained by proposing the formation of intramolecular hydrogen bonds between amine groups in all compounds I, besides the intermolecular interactions between compounds I and the solvent. On the other hand, the values of vor s and b for Ib are smaller than the corresponding values for Ia and Ic. Since in Ib a six-membered ring may be formed, a more stable bond is expected.Comparative 'H N M R of the aniline hydrogen for I and IV (in non-hydrogen bond acceptor solvents) shows a particular downfield chemical shift for I which suggests hydrogen bond formation. Since this effect is independent of concentration, the hydrogen bond is assumed to be intramolecular, in agreement with solvatochromic and thermochromic studies. These conclusions were corroborated by IR spectroscopy in the solid state and in chloroform solutions.