Tunable Polarity Carbon Fibers, a Holistic Approach to Environmental Protection

Wooden-based materials: Eco-friendly materials for direct mass spectrometric analysis and microextraction

Lignocellulosic materials have arisen as a sustainable alternative in microextraction techniques during the last 10 years. As they are natural materials, their use fits into some of the principles of Green Analytical Chemistry. Their inherent porosity, narrow shape, and rigidity permit their use in ambient ionization mass spectrometry techniques. In particular, the combination of wooden-based materials and direct analysis gives birth to the so-called wooden-tip electrospray ionization mass spectrometry technique. This approach has been used for the direct analysis of complex samples, and as a streamlined tool for fingerprint quality analysis. Also, wooden-based materials can be superficially modified to boost the interaction with target compounds, allowing their isolation from complex samples. This review describes the potential and applicability of direct analysis using lignocellulosic materials, as well as other alternatives related to their use in microextraction.

Carbon fibers as green and sustainable sorbent for the extraction of isoflavones from environmental waters

Isoflavones are a group of phytoestrogens of important environmental concern due to their endocrine disrupting effects. This article presents a rapid, green, and sustainable method for determining four isoflavones (daidzein, genistein, formononetin, and biochanin A) in environmental waters complying with current trends in Analytical Chemistry. The method consists of in-syringe dispersive solid-phase extraction (DSPE) as the extraction approach, using carbon fibers as extraction material. The synthesis of carbon fibers is simple and sustainable, since it only requires a natural product such as raw cotton as precursor, which is thermally treated (600 °C for 30 min) in an inert (Ar) atmosphere to convert it into carbon fibers. After extraction, the final eluate is analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The proposed methodology allows the determination of the four isoflavones in water samples at the ng L^-1 range, with limits of detection in the range from 17 to 25 ng L^-1, relative standard deviations (RSD) from 2.8 to 10.1%, and good batch-to-batch repeatability (RSD < 13%). The method was finally applied to six environmental water samples from different sources and two swimming pool waters, and concentrations of all analytes up to 490 ng L^-1 were found. The highest concentrations were found in those samples close to crop fields. Relative recovery values (80-121%) showed that the aqueous matrices considered in this work did not significantly affect the extraction process. This method overcomes the drawbacks of the previous works with the same purpose, such as consuming large volumes of organic solvents or prolonged extraction times. Moreover, this procedure would allow the extraction stage to be carried out in situ, since only the sorbent material (previously synthesized in the laboratory) and disposable syringes are required.

Returning to Nature for the Design of Sorptive Phases in Solid-Phase Microextraction

Green analytical chemistry principles aim to minimize the negative impact of analytical procedures in the environment, which can be considered both at close (to ensure the safety of the analysts) and global (to conserve our natural resources) levels. These principles suggest, among other guidelines, the reduction/minimization of the sample treatment and the use of renewable sources when possible. The first aspect is largely fulfilled by microextraction, which is considered to be among the greenest sample treatment techniques. The second consideration is attainable if natural products are used as raw materials for the preparation of new extraction phases. This strategy is in line with the change in our production system, which is being gradually moved from a linear model (take–make–dispose) to a circular one (including reusing and recycling as key terms). This article reviews the potential of natural products as sorbents in extraction and microextraction techniques from the synergic perspectives of two research groups working on the topic. The article covers the use of unmodified natural materials and the modified ones (although the latter has a less green character) to draw a general picture of the usefulness of the materials.