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Quantification of endogenous hormones in plants is essential to understand their growth, development and response to biotic and abiotic stresses. However, it is challenging to develop high-throughput sample treatments from complex plant tissues containing low amounts of structurally unrelated and labile phytohormones while delivering clean and analyte-enriched extracts. In this paper we propose the use of supramolecular solvents (SUPRASs) made up or inverted hexagonal nanostructures of alkanols to address this challenge. The strategy was applied, as a proof of concept, to the quantification of stress-related phytohormones belonging to different categories (abscisic acid, salicylic acid, jasmonic acid, methyl jasmonate and 3-indoleacetic acid) in melon and pepper leaves. Sample treatment consisted in a single extraction-cleanup step involving the use of a low volume of SUPRAS (244 µL), the stirring (5 min) and centrifugation (15 min) of the sample at room temperature, and the direct analysis of the extract by liquid chromatography tandem mass spectrometry (LC-MS/MS). This high-throughput sample treatment method delivered excellent results for the target phytohormones regarding absolute recoveries (80-92%), method quantification limits (0.05-2 ng g-1), reproducibility (1-7%) and matrix effects (+13 to -31%), in both melon and pepper leaves, compared to reported methods based on repetitive solvent extraction, purification and solvent evaporation steps. The method was successfully applied to determine target hormones in melon and pepper plants for the evaluation of the effect of thermal stress. It was found that their concentration increased in the ranges 1.2-1.9 and 1.3-3.8 times in melon and pepper leaves, respectively, compared with control samples.

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RESUMO

Monohydroxylated polycyclic aromatic hydrocarbons (OH-PAHs), present in human urine at trace concentrations (viz. from ng L-1 to µg L-1), are considered the main biomarkers of human exposure to PAHs. In this work, we report a simple and high-throughput sample treatment platform to facilitate the biomonitoring of OH-PAHs by making it easier, greener and most cost-effective. This platform is based on the integration of analyte extraction and sample cleanup in a single step by the use of supramolecular solvents with restricted access properties (SUPRAS-RAM). The SUPRAS was spontaneously formed in situ in the urine by the addition of a colloidal suspension of decanoic acid in THF. Metabolites from naphthalene, fluorene, phenanthrene and pyrene were quantitatively extracted (absolute recoveries in the range 91-109%). Polysaccharides and proteins in the urine were excluded from extraction by physical and chemical mechanisms, which allowed the direct analysis of the SUPRAS extract by liquid chromatography tandem mass spectrometry. Absolute matrix effects for OH-PAHs were in the range 92-103%. Method quantification limits for OH-PAHs, without the need for evaporation of the SUPRAS extracts, were in the interval 1.0-6.7 ng L-1. The precision, evaluated in terms of repeatability and reproducibility, varied between 1.1 and 13.8%. The method was successfully applied to the analysis of urine from 16 smoking and non-smoking volunteers. Both analytical and operational features of this method make it suitable to evaluate human exposure to PAHs.

Assuntos

RESUMO

Halogen bonding (XB), a highly energetic and directional interaction, is here proposed as a new mechanism to increase solute solubilisation in solvent extractions. The approach is illustrated by the extraction of hexabromocyclododecane (HBCD) enantiomers in soils and sediments using supramolecular solvents (SUPRAS) containing XB donors in their structure. SUPRAS consisting of inverted hexagonal aggregates of decanoic acid, synthesized by water-induced coacervation of the amphiphile in tetrahydrofuran (THF), were explored for this purpose. Sample treatment involved the extraction of 400 mg of soil or sediment with 250 µL of SUPRAS for 5 min and then centrifugation for 10 min. SUPRAS extracts were directly analyzed by chiral liquid chromatography tandem mass spectrometry (LC-MS/MS) and quantification was carried out using isotopically labelled internal standards. Quantitative recoveries (93-102%) were obtained for the six HBCD enantiomers in both fresh and aged spiked samples. The mild experimental conditions required for extraction (room temperature and atmospheric pressure), the low SUPRAS volume/sample amount ratio needed (0.6 mL g─1), the short time required for sample treatment (15 min), and the simplicity of the procedure (use of conventional equipment and the possibility of treating several samples simultaneously), makes this method clearly superior to those previously reported. Method quantitation limits were in the intervals 0.58-2.23 ng g─1, and the relative standard deviations (n = 18, HBCD stereoisomer concentration = 50 ng g─1) obtained under repeatability and reproducibility conditions varied within the ranges 1.0-4% and 2.5-5%, respectively. The approach here described could be easily extended to the extraction of brominated flame retardants in different types of matrices.

RESUMO

The determination of organic and inorganic analytes from biological samples need efficient sample preparation procedures in order to capture the analyte in a media with many macromolecules, which can cause analytical errors and problems with the instruments. Thus, "intelligent" sorbents, called restricted access materials (RAMs), have been widely used with these samples, due to their ability to retain analytes and exclude macromolecules. These materials have been obtained by modifying the external surfaces of conventional sorbents (e.g. polymers, carbon nanotubes, active carbon, and silica-based materials) with hydrophilic groups (chemical barrier), as well as by the presence of small pores (physical barrier) accessible only to low molecular weight molecules. Supramolecular solvents (SUPRAs) have also been used as RAMs, due to their abilities to exclude proteins according to size or through precipitation with the solvents. Therefore, due to the relevance of these materials, this review presents an overview of the most recent advances in obtaining RAMs based on silica, polymers, carbon nanotubes, (activated) carbon, and solvents, as well as their applications in biological sample preparation.

Assuntos