Preconcentration of polar phenolic compounds from water samples and soil extract by liquid-phase microextraction and determination via liquid chromatography with ultraviolet detection.

This work proposes a liquid-phase microextraction (LPME) method to extract the highly polar compounds phenol (Ph), o-cresol (o-Cr), m-cresol (m-Cr), p-cresol (p-Cr), and 2,4-dimethylphenol (2,4-DMP) from aqueous matrices. The first extraction step of the LPME method employed a common volumetric flask and n-octanol, and the second extraction step used NaOH as the acceptor phase. The optimized extraction conditions were 900 µL of n-octanol as the extraction solvent, NaOH at 0.60 mol L(-1) as the acceptor phase, an extraction time of 5.0 min, HCl at 0.01 mol L(-1) and NaCl at 20.0% as the donor phase, and an extraction temperature of 20.0°C. The analysis of 50.0 mL of aqueous sample, pretreated under the optimized LPME conditions, afforded a limit of detection (LOD) between 0.3 and 3.5 µg L(-1), a limit of quantification (LOQ) between 1.2 and 11.6 µg L(-1), and a linear range from 2.50 to 50.0 µg L(-1) for Ph, o-Cr, m-Cr and p-Cr and from 12.5 to 250 µg L(-1) for 2,4-DMP. The proposed LPME method was a successful sample preparation strategy, and allowed for precise and accurate quantification of polar phenolic compounds in aqueous matrices such as tap water, river water, groundwater, and seawater, and also in a soil extract. The recovery values ranged from 72.5% to 126.0%, and the relative standard deviation was between 0.3 and 11.5%.

Interaction of phenol, o-cresol, and p-cresol with a clay-rich soil sample.

The present paper describes an interaction study of phenol, o-cresol, and p-cresol with a rich-clay soil sample (clay content of 62.3%). Experiments performed using long contact times, in concentrations of 50.0 mg L(-1) showed practically no signal of phenol, o-cresol, and p-cresol after 48, 72, and 120 h, respectively, suggesting a sorption process. Sorption experiments in the period of 24 h were carried out with the phenolic compounds in concentrations between 5.00 and 500.0 mg L(-1), and negligible interaction between the phenolic species and the soil was observed. Additional experiments were carried out using HgCl(2) or NaN(3) solution as biodegradation inhibitors. After 10 days of contact time in the presence of inhibitors, no alterations in the concentrations of the three compounds studied were observed, and the results suggest no sorption process, with the compounds being almost entirely biodegraded by the soil sample, or possibly the formation of nonextractable residues could occur.

Alelopatia intra-específica de extratos aquosos de folhas e raízes de alfafa na germinação e no crescimento inicial de plântulas de dois materiais de alfafa: crioulo e melhorado / Intra-specific allelopathy of leaves and roots aqueous extracts on germination and early seedling growth of two alfalfa materials: crioulo and improved

A alfafa é uma das culturas conhecidas que apresentam um tipo específico de alelopatia denominado autotoxicidade. Dessa forma, o objetivo deste trabalho foi avaliar os efeitos da concentração de extratos aquosos de partes (folhas e raízes) da planta de alfafa (material Crioulo) na germinação e no crescimento inicial de plântulas de dois materiais de alfafa (Crioulo e P5454). Placas de Petri contendo 50 sementes de cada variedade foram umedecidas com 10ml dos extratos em duas concentrações: 50 por cento e 100 por cento (extrato puro). Água deionizada foi usada como controle. O delineamento experimental foi inteiramente casualizado, com cinco repetições para cada variedade. Após seis dias da germinação, procedeu-se à contagem do número de sementes germinadas, bem como à medição do comprimento do hipocótilo e da radícula de cada plântula. Os extratos aquosos das folhas inibiram a germinação e o comprimento da radícula e do hipocótilo das duas variedades. No entanto, para o material Crioulo, a inibição na germinação e no desenvolvimento inicial só ocorreu com o uso do extrato puro das folhas, enquanto que na P5454 o extrato diluído a 50 por cento já reduziu tanto a germinação quanto o comprimento das plântulas. Os extratos aquosos das raízes não causaram inibição na germinação nem no comprimento das plântulas. Os resultados sugerem variações intra-específicas na tolerância aos compostos aleloquímicos e uma produção preferencial dos mesmos na parte aérea da planta de alfafa, material Crioulo.

Alfalfa is one of the known crops that present a specific type of allelopathy called autotoxicity. Hence, this research was aimed at evaluating the concentration effects of aqueous extracts of plant parts (leaves and roots) of alfalfa (var. Crioula) on germination and early development of seedlings of two alfalfa (Crioula and P5454) varieties. Fifty seed of each variety were placed in Petri dishes with moistened filter paper. Aliquots (ten ml) from each part extracts at two concentrations, 50 or 100 percent (pure extract), were added to petri dishes, and distilled water was used as a control. Treatments placed in Petri dishes were randomly arranged in a completely randomized design with five replicates. Measurements included: germination, and radicle and hypocotyl lengths taken six days after germination. The aqueous extracts of leaves inhibited germination and radicle and hypocotyl length of the two alfalfa varieties. However, on the var. Crioula germination and early development was inhibited only when it was used pure extracts of leaves, while in var. P5454 leaves extracts diluted to 50 percent already had some reduction on germination and seedlings length. The aqueous extracts of the alfalfa roots did not cause inhibition on germination and seedlings lengths. The results suggest intra-specific variations on tolerance to the allelochemicals and a preferential production of them in the aerial part of the alfalfa plant, var. Crioula.