Multivariate optimization of extraction and validation of phenolic acids in edible mushrooms by capillary electrophoresis.

A "green" analytical method is reported for the determination of phenolic acids in mushrooms. The sample preparation involves aqueous extraction based on acid hydrolysis, followed by analysis of extracts by capillary electrophoresis with diode array detector (CE-DAD). A central composite design was used to obtain the optimum conditions for the extraction of compounds from mushrooms, including the concentration of hydrochloric acid (2 mol·L-1), temperature (80 °C) and time (30 min). The proposed method avoids organic solvents such as methanol and acetonitrile commonly used as extraction solvent and/or mobile phase in studies on bioactive compounds in plant-based matrices by high-performance liquid chromatography, thus contributing to lower environmental impact. The validated CE-DAD method was applied to 42 samples of edible mushrooms, including the species Agaricus bisporus (white button mushroom and brown portobello), Lentinula edodes (shiitake), Pleurotus ostreatus (white oyster mushroom, hiratake and shimeji) and Pleurotus ostreatoroseus (pink oyster mushroom). The phenolic compounds homogentisic acid, cinnamic acid and p-coumaric acid were detected in the samples harvested in two seasons - summer and winter - with cinnamic acid reported as the major compound (levels between 53.88 and 440.42 mg·kg-1). Therefore, edible mushrooms have proved to be an alternative source of phenolic compounds.

Determination of parabens in shampoo using high performance liquid chromatography with amperometric detection on a boron-doped diamond electrode.

Methylparaben (MePa), ethylparaben (EtPa) and propylparaben (PrPa) have been widely used, among others, as chemical preservatives in cosmetics, drugs and foods. As these compounds are linked with allergies, dermatitis and estrogenic properties, it is necessary to control the concentration of these substances in different matrices. The aim of this paper are: to evaluate the electrochemical behavior of parabens on the boron-doped diamond (BDD) electrode and the development of a chromatographic method, with electrochemical detection (HPLC-ED), for determination of parabens in shampoo. A BDD (8000 ppm) electrode was adapted in a thin layer mode analytical cell consisting of a stainless steel and a platinum wire as reference and auxiliary electrodes, respectively. Chromatographic separations were obtained with a reversed phase C8 analytical column and a mobile phase of 0.025 molL(-1) disodium phosphate, pH 7.0, and acetonitrile (40:60, v/v), delivered at a flow rate of 1.0 mL min(-1). Sample preparation was performed by solid phase extraction using C18 cartridges and acetonitrile for elution. Benzylparaben was employed as internal standard. The HPLC-ED method developed, using the BDD electrode, was validated for the determination of parabens in shampoos and presented adequate linearity (>0.999), in the range of 0.0125-0.500% (w/w), detectability 0.01% (w/w), precision (RSD of 2.3-9.8%) and accuracy (93.1-104.4%) and could be applied for routine quality control of shampoos containing MePa, EtPa and PrPa.