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Background: The phenomenon known as the ''matrix-induced chromatographic response enhancement'' commonly affects the sensibility, precision, and accuracy in pesticide residue analysis. The presence of matrix effects can be given by adsorption and/or thermal decomposition of pesticides on the gas chromatograph injection port. Objective: To reduce the matrix-induced chromatographic response enhancement on pesticide residues analysis in food through the use of several operational modes of programmable temperature vaporizer inlet. Methods: The analyses were carried out in potato (Solanum tuberosum) extracts by gas chromatography with mass spectrometry detector. In this study, four programmable temperature vaporizer splitless modes were investigated: hot, pulsed, cold and solvent vent. Another topic developed in this study has to do with the influence of injection volume, assessed for the matrix effects. Results: The analysis of variance (ANOVA) (α = 0.05) indicates that when the hot splitless is used most compounds are subjected to matrix-induced chromatographic response enhancement. Furthermore, with the pulsed splitless, a decrease in the number of compounds with matrix-induced chromatographic response enhancement was found, approximately 20% compared to the classic hot splitless. Finally, a remarkable decrease in matrix-induced effects was found when cold splitless mode was used, since there was up to 55% reduction in the compounds, relative to traditional hot splitless, that showed statistical differences between responses in matrix-free standards and matrix-matched standards. Conclusions: It was found that the use of conventional hot splitless and pulsed splitless modes caused matrix-induced effects in more than 70% of the studied compounds. In addition, the results indicate that for most compounds there is an inverse relationship between matrix-induced chromatographic response enhancement and the volume of injection.

Saponins are glycosides regularly found in plants, and they are frequently analyzed by means of electrospray ion sources and tandem mass spectrometry (ESI/MSn), not only to obtain an overall molecular weight through the high sensitivity of mass spectrometry, but also to obtain their structural information. The use of modern analytic techniques (such as ESI/MSn) aids the discovery and quality control assessment of new molecules found in botanicals; however, some rearrangements have been described for oligosaccharides that produce an incorrect elucidation of the molecules. For the first time, evidence for an internal sugar loss on the protonated fragmentation of α-hederin has been reported. This phenomenon can be avoided by using alkali metal ion adducts, such as lithium and sodium cations, to confirm the real sugar sequence when a structural identification is performed. In this study, the structural characterization of α-hederin and hederacoside C is conducted by comparing positive and negative modes. Different fragmentation patterns occur, and such patterns are useful in the structural analysis of saponins when they are present on different matrixes.Las saponinas son glicósidos encontrados frecuentemente en plantas y son analizados habitualmente por espectrometría de masas en tándem y fuentes de ionización por electrospray (ESI/MSn), no solo por su alta sensibilidad sino además por la información estructural que es obtenida. Tanto el descubrimiento de nuevas entidades químicas como el control de calidad de productos naturales involucran el uso de técnicas analíticas modernas como ESI/MSn. Sin embargo, algunos re-arreglos de azúcares en los glicósidos pueden conducir a realizar falsas interpretaciones de las secuencias de los mismos. La pérdida de un azúcar interno de la porción oligosacárida de α-Hederina es evidenciada por primera vez. Este fenómeno puede ser evitado si se favorece la formación de aductos con iones metálicos como litio y sodio, con el fin de obtener la secuencia real de azúcares de un glicósido. La caracterización estructural de α-Hederina y hederacósido C es realizada comparando los espectros obtenidos tanto en modo de ionización positiva como negativa, evidenciando diferentes mecanismos de fragmentación los cuales proporcionan información útil en el análisis estructural.

El desarrollo de las investigaciones en bioprospección marina requiere el fortalecimiento de los inventarios de organismos marinos, lo que implica una clasificación taxonómica exhaustiva de los mismos. La clasificación de las esponjas marinas es compleja desde el punto de vista morfológico y se facilita con el uso de información quimiotaxonómica basada en la composición de sus esteroles. El presente estudio describe la composición de esteroles libres de la esponja Mycale laevis, recolectada en la Bahía de Cispatá (Córdoba, Colombia). A partir del extracto metanólico de la esponja M. laevis, se obtiene el subextracto de diclorometano, que se fracciona mediante cromatografía en columna sobre sílica gel, eluyendo con mezclas de hexano-acetato de etilo con aumento gradual de la polaridad. La obtención de la fracción mayoritaria (Rf = 0.77, sílica gel/ hexano-acetato de etilo 1:1) y su análisis por cromatografía de gases acoplada a espectrometría de masas (CG-EM), permite la identificación de 9 esteroles monohidroxilados con núcleos esteroidales Δ0, Δ5 y Δ7 . Los estanoles (núcleo Δ0) son los más abundantes en la fracción esterólica, con el 71.7 % del total de compuestos presentes. Estos resultados contribuyen a los estudios quimiotaxonómicos de esponjas marinas pertenecientes a la familia Mycalidae.The development of marine bioprospection research requires to fortify of marine organisms inventories, which also implies their exhaustive taxonomic classification. From the morphological point of view, the classification of marine sponges is a complex procedure and it is facilitated with the use of chemotaxonomic information based on the composition of its sterols. This study describes the free sterols composition of the Mycale laevis sponge, collected in the Cispatá Bay (Córdoba, Colombia). The subextract of dichloromethane is obtained from the methanol extract of the sponge; this subextract is fractionated through chromatography in column on silica gel, using hexane-ethyl acetate mixtures with a gradual increase of the polarity as a mobile phase. The obtention of the majoritary fraction (Rf = 0.77, silica gel /hexane: ethyl acetate 1:1) and its analysis by means of gas chromatography coupled to mass spectrometry (GC-MS), allows the identification of 9 monohydroxylated sterols with nuclei steroidal Δ0,Δ5 and Δ7 sterols. Stanols (nucleus Δ0) are the most abundant in the sterolic fraction with 71.7% of the total of the present compounds. These results contribute to chemotaxonomics studies marine sponges in the Mycalidae family.