Pablo L. Pisano

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.

Thymine based copolymers: feasible sensors for the detection of persistent organic pollutants in water

Polycyclic Aromatic Hydrocarbons (PAHs) are among the main persistent organic pollutants in water, because they can cause serious diseases in living organisms. The PAHs trace levels in environmental samples makes their detection particularly difficult. The development of new fluorescence spectroscopic sensors is a realistic alternative for the quantification of PAHs at very low concentrations. Bio-inspired copolymers based on thymine and charged groups showed high affinity for benzo[a]pyrene, the nastiest contaminant of the PAHs group, and can be used to enhance their native luminescence. In the present work we rationalized the observed experimental evidence using a theoretical model that studies the plausible non-covalent interactions (polar hydrogen–π, π–π “stacking”, etc.) between these compounds, in order to make a realistic design of new thymine-based copolymers sensors.

α-Hydroxyacids accelerate the Diels–Alder reaction of dibutyl vinylboronate with cyclopentadiene: experimental results and mechanistic insights

We have found that α-hydroxyacids accelerate the Diels–Alder reaction of dibutyl vinylboronate with cyclopentadiene. When stoichiometric quantities are used, excellent yields are obtained, while catalytic activities are moderate. DFT calculations suggested that the activation of the dienophile occurs by ligand exchange with both functionalities of the α-hydroxyacid.

Discrimination of Annona muricata and Rollinia mucosa Extracts by Using Multivariate Curve Resolution and Partial Least-Squares Regression of Liquid Chromatography-Diode Array Data

Species of the Annonaceae family are used in traditional medicine, and several antitumor acetogenins have been isolated from the leaves of Annona muricata and Rollinia mucosa. Leaves samples (self-shaded and sun-exposed) of these species were collected during winter and summer seasons. Extraction media were prepared from mixtures of five solvents according to a simplex centroid design. Plant extracts were analysed by injection into a high-performance liquid chromatography with diode array detection (HPLC-DAD) and evaluated after applying by multivariate curve resolution-alternating least-squares (MCR-ALS) and discriminant-unfolded partial least-squares (D-UPLS). The objective was to check whether the chemometric resolution of chromatographic profiles could help in the discrimination of samples according to taxonomic classification, sun exposition and/or harvest season. The results indicate that extraction media containing ethanol as main solvent achieved discrimination of self-shaded versus sun-exposed plants and harvest season of Annona muricata. Also, D-UPLS analysis allowed taxonomic discrimination between Annona muricata and Rollinia mucosa extract samples.

Alkylhalovinylboranes: a new class of Diels–Alder dienophiles

The Diels–Alder reactions of alkylhalovinylboranes have been investigated theoretically and experimentally. Alkylhalovinylboranes presented higher reactivity than the corresponding dialkylvinylboranes. Although endo/exo selectivities were high for the reactions with cyclopentadiene, facial selectivities for the chiral analogues were low. Our results demonstrate that the replacement of an alkyl group on the boron atom by a halogen increases the dienophilicity considerably.

Chapter 21 – Data analysis

In this chapter, the analysis of chromatographic data generated by the current instrumentation is addressed. The evolution and advances achieved when going from zeroth-order (univariate) to third-order data are discussed, taking into account the advantages and limitations when using each type of data, specifically focused on liquid chromatography. Emphasis is directed to the quantification of target analytes when overlapping among chromatographic peaks occurs, and correction of unintended effects such as baseline artifacts, peak shifts, and so on are required in complex samples. The different topics are discussed based on recent literature examples concerning the analysis of biological, food, and environmental samples.