Determination of hexanal and heptanal in saliva samples by an adapted magnetic headspace adsorptive microextraction for diagnosis of lung cancer.

In this work, an analytical method for the determination of two endogenous aldehydes (hexanal and heptanal) as lung cancer biomarkers in saliva samples is presented for the first time. The method is based on a modification of magnetic headspace adsorptive microextraction (M-HS-AME) followed by gas chromatography coupled to mass spectrometry (GC-MS). For this purpose, an external magnetic field generated by a neodymium magnet is used to hold the magnetic sorbent (i.e., CoFe2O4 magnetic nanoparticles embedded into a reversed-phase polymer) in the headspace of a microtube to extract the volatilized aldehydes. Subsequently, the analytes are desorbed in the appropriate solvent and the extract is injected into the GC-MS system for separation and determination. Under the optimized conditions, the method was validated and showed good analytical features in terms of linearity (at least up to 50 ng mL-1), limits of detection (0.22 and 0.26 ng mL-1 for hexanal and heptanal, respectively), and repeatability (RSD ≤12%). This new approach was successfully applied to saliva samples from healthy volunteers and those with lung cancer, obtaining notably differences between both groups. These results reveal the prospect of the method as potential diagnostic tool for lung cancer by saliva analysis. This work contributes to the Analytical Chemistry field presenting a double novelty: on the one hand, the use of M-HS-AME in bioanalysis is unprecedentedly proposed, thus expanding the analytical potential of this technique, and, on the other hand, the determination of hexanal and heptanal is carried out in saliva samples for the first time.

Ultramicroextraction as a miniaturization of the already miniaturized. A step toward nanoextraction and beyond.

Miniaturization of the analytical process has been a widespread trend, and the sample preparation stage is not exempted from this downscaling. Since the introduction of microextraction techniques as miniaturization of classical extraction techniques, they have become one of the strengths in this field. However, some of the original approaches to these techniques did not fully cover all the current principles of Green Analytical Chemistry. For this reason, during the last years, much emphasis has been placed on reducing/eliminating toxic reagents, reducing the amount of the extraction phase, and searching for new greener, and more selective extractant materials. On the other hand, even though high accomplishments have been achieved, the same attention has not always been paid to reducing the amount of sample, which is essential when treating low-availability samples such as biological samples, or in developing portable devices. In this review, we intend to give the readership an overview of the advances toward further miniaturization of microextraction techniques. Finally, a brief reflection is made on the terminology used, or that should, in our opinion, be used to term these new generation of miniaturized microextraction approaches. To this regard, the term, 'ultramicroextraction' is proposed to refer to those approaches beyond microextraction.

New challenges in sample preparation: Miniaturized stir bar sorptive dispersive microextraction as a high-throughput and feasible approach for low-availability sample preparation.

The miniaturization of stir bar sorptive dispersive microextraction (mSBSDME) for the analysis of low-availability samples is presented. This new methodology is based on the principles of stir bar sorptive dispersive microextraction, but the amount of sorbent and, most importantly, the amount of sample are considerably reduced to a tiny amount and a few microliters, respectively. Thus, affordable 400-µL flat-base glass inserts and minute bar-shape neodymium magnets (3 mm length x 2 mm diameter) were used as extraction devices hold by a specifically designed multiextraction assembly, which comprises a high-rate stirring plate and a 3D-printed support to treat 15 samples simultaneously. This new approach allows a fast, affordable, portable, and high-throughput analysis of low-volume samples, expanding the potential of the technique. The same extraction device is used along the different stages, thus avoiding transfers, which reduces sample handling. Besides, the reduction in the sample, sorbent and organic solvent amounts allows a considerable decrease of the waste generation, and thus pursues a green sample preparation for bioanalysis. As a proof-of-concept of this new methodology, cortisone and cortisol were determined in human saliva using a composite material made of a reversed phase polymer (Strata™-X-RP) and CoFe2O4 magnetic nanoparticles. Liquid chromatography coupled to tandem mass spectrometry was used to measure both analytes obtaining good analytical features in terms of linearity (R2 > 0.997), method limits of detection and quantification (22.6 and 75.5 ng L-1 for cortisone, and 19.3 and 64.3 ng L-1 for cortisol, respectively), repeatability (RSD ≤11%) and relative recoveries (78-134%).

Trace determination of tetrahydrocannabinol (THC) in cosmetic products by stir bar sorptive dispersive microextraction followed by liquid chromatography-tandem mass spectrometry.

An analytical method for the determination of tetrahydrocannabinol (THC) at trace level in cosmetics is presented. As psychoactive compound, the presence of THC in consumer products should be avoided. However, it might be unintentionally present in cannabidiol-rich or hemp-based products by contamination or isomerization of cannabidiol. Due to the low concentrations expected, a sensitive and selective method is necessary for the analytical control of these products. In this sense, the presented method is based on stir bar sorptive dispersive microextraction (SBSDME) followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). In this work, a magnetic composite made of CoFe2O4 magnetic nanoparticles embedded in a commercial reverse-phase polymer (Strata™-X-RP) was employed as magnetic sorbent material taking advantage of its affinity to the target analyte. Under the optimized conditions, the method was validated and showed good analytical features in terms of linearity (at least up to 10 ng mL-1), limits of detection and quantification (2.2 and 7.2 ng g-1, respectively) and repeatability (RSD <10%). Moreover, relative recoveries between 99 and 109% were obtained, showing matrix effects were negligible using deuterated THC (THC-D3) as surrogate. This new approach was successfully applied to ten commercially-available cosmetic samples of different matrices, thus showing it is suitable for the analytical control of THC in cosmetic products. The proposed methodology overcomes some of the drawbacks of the previous works with the same purpose, such as the higher limits of detection, time-consuming procedures, and consumption of large volumes of organic solvents.

Use of green alternative solvents in dispersive liquid-liquid microextraction: A review.

Dispersive liquid-liquid microextraction is one of the most widely used microextraction techniques currently in the analytical chemistry field, mainly due to its simplicity and rapidity. The operational mode of this approach has been constantly changing since its introduction, adapting to new trends and applications. Most of these changes are related to the nature of the solvent employed for the microextraction. From the classical halogenated solvents (e.g., chloroform or dichloromethane), different alternatives have been proposed in order to obtain safer and non-pollutants microextraction applications. In this sense, low-density solvents, such as alkanols, switchable hydrophobicity solvents, and ionic liquids were the first and most popular replacements for halogenated solvents, which provided similar or better results than these classical dispersive liquid-liquid microextraction solvents. However, despite the good performances obtained with low-density solvents and ionic liquids, researchers have continued investigating in order to obtain even greener solvents for dispersive liquid-liquid microextraction. For that reason, in this review, the evolution over the last five years of the three types of solvents already mentioned and two of the most promising solvent alternatives (i.e., deep eutectic solvents and supramolecular solvents), have been studied in detail with the purpose of discussing which one provides the greenest alternative.

Green, rapid and simultaneous determination of 'alternative preservatives' in cosmetic formulations by gas chromatography-mass spectrometry.

Some hydroxylated compounds commonly used in cosmetic formulations including short chain glycols, benzylic alcohols, and organic acids show antimicrobial activity, although they are not considered as preservatives according to the existing European legislation. These 'alternative preservatives' are not exempt of potential side-effects for cosmetics users. The aim of this work is to develop a simple and affordable analytical method useful for the simultaneous and green determination of fourteen compounds used as 'alternative preservatives' in cosmetic samples with different matrices. The proposed method allows a rapid sample preparation by simple dissolution or dispersion of the sample in ethanol using ultrasound-assisted leaching of the analytes from the cosmetic matrix. Gas chromatography coupled to mass spectrometry (GC-MS) is used for the analysis of the samples. Working conditions for the instrumental measure and the quantification of analytes were studied. The method was found to have high sensitivity and good precision (relative standard deviation below 13%) as well as low limits of detection (i.e., 0.01·10-3-2.14·10-3% w/w) and quantification (i.e., 0.04·10-3-7.14·10-3% w/w). The method was successfully applied to five commercial cosmetic samples of different composition. Recovery values near 100% were obtained. Each sample was found to contain at least three of the analytes of the study and their concentrations were determined with low standard deviations. The analytical features of the proposed method and the obtained results agree with the principles of Green Analytical Chemistry and make it a useful tool for controlling these alternative preservatives in the cosmetic industry in order to guarantee quality and safety of the products.