Modified graphene-silica as a sorbent for in-tube solid-phase microextraction coupled to liquid chromatography-tandem mass spectrometry. Determination of xanthines in coffee beverages

Metal organic framework derived composite as a new sorbent for micro-solid phase extraction of parabens from breast milk samples

In an attempt to enhance the adsorptive properties while addressing the limitations associated with powdered nature, zeolitic imidazolate framework (ZIF-67)-derived cobalt-doped nanoporous carbon (Co-NPC) was incorporated into chitosan and then shaped like hollow fiber by a simple casting method. Further modification with polyaniline (PANI) was also performed to improve extraction efficacy. The applicability of the modified hollow fibers was then investigated by packing them into a cartridge and utilizing them for conducting hollow fibers-packed in-cartridge micro solid-phase extraction (HF-IC µ-SPE) of parabens including methylparaben (MP), ethylparaben (EP), and propylparaben (PP) from human breast milk samples. Factors affecting extraction performance were studied using central composite design (CCD). Under the optimal conditions, good linearity was achieved within the range of 0.5-500 μg L-1 with the determination coefficient (R2) higher than 0.9901. All analytical parameters were obtained by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. In this regard, the limits of detection values (LODs) were 0.5 to 1.0 μg L-1. Intra- and inter-assay precision RSDs % were lower than 7.9 % and 8.4 %, respectively. Relative recoveries of breast milk samples were found in the range of 88.0-109.5 %. Accordingly, the novel nanocomposite sorbent based on PANI@Co-NPC/Chitosan hollow fiber was found to be an efficient, simple, and cost-effective packing material for HF-IC µ-SPE. It can also be offered as a promising alternative adsorbent to coated conventional hollow fiber.

Advances and Applications of Hybrid Graphene-Based Materials as Sorbents for Solid Phase Microextraction Techniques

The advancement of traditional sample preparation techniques has brought about miniaturization systems designed to scale down conventional methods and advocate for environmentally friendly analytical approaches. Although often referred to as green analytical strategies, the effectiveness of these methods is intricately linked to the properties of the sorbent utilized. Moreover, to fully embrace implementing these methods, it is crucial to innovate and develop new sorbent or solid phases that enhance the adaptability of miniaturized techniques across various matrices and analytes. Graphene-based materials exhibit remarkable versatility and modification potential, making them ideal sorbents for miniaturized strategies due to their high surface area and functional groups. Their notable adsorption capability and alignment with green synthesis approaches, such as bio-based graphene materials, enable the use of less sorbent and the creation of biodegradable materials, enhancing their eco-friendly aspects towards green analytical practices. Therefore, this study provides an overview of different types of hybrid graphene-based materials as well as their applications in crucial miniaturized techniques, focusing on offline methodologies such as stir bar sorptive extraction (SBSE), microextraction by packed sorbent (MEPS), pipette-tip solid-phase extraction (PT-SPE), disposable pipette extraction (DPX), dispersive micro-solid-phase extraction (d-µ-SPE), and magnetic solid-phase extraction (MSPE).

Synthesis, characterization and application of cross-linked functional terpolymer through epoxy group as sorbent for extraction of cadmium from waters and foods: Multivariate optimization

The purpose of this study was to develop a selective sorbent for cadmium ions (Cd(II)) enrichment in orbital shaker assisted solid phase microextraction (OS-SPME) from different aqueous and food samples. A maleic anhydride-styrene-glycidyl methacrylate (MA-St-GMA) terpolymer was synthesized and characterized in detail. Experimental variables of sample preparation step were optimized using a central composite design (CCD). The final determination step was performed using flame atomic absorption spectroscopy (FAAS). The MA-St-GMA sorbent exhibited a high adsorption capacity (195.9 mg g-1) for the Cd(II) ion. The developed method under optimal conditions provides satisfactory performance and a significant improvement compared to other protocols available in the literature. The linear range and detection limit of the method is 0.1-130 ng mL-1 and 0.03 ng mL-1, respectively. The robustness, intraday/interday precision, selectivity, and accuracy of the method were investigated. To further validate the method, a dedicated series of analysis was performed using certified reference materials (CRMs). This part of the study confirmed the applicability of the method for routine analysis. The OS-SPME-FAAS method was validated using water and food samples. Relative standard deviations and recovery for real-world samples were in ranges 1.7-2.2 % and 95.5-98.5 %, respectively. As a result, the MA-St-GMA sorbent showed that it could quantitatively extract Cd(II) ions from aqueous solution.

Microextraction by packed sorbent of N-nitrosamines from Losartan tablets using a high-throughput robot platform followed by liquid chromatography-tandem mass spectrometry

The development of a fast, cost-effective, and efficient microextraction by packed sorbent setup was achieved by combining affordable laboratory-repackable devices of microextraction with a high-throughput cartesian robot. This setup was evaluated for the development of an analytical method to determine N-nitrosamines in losartan tablets. N-nitrosamines pose a significant concern in the pharmaceutical market due to their carcinogenic risk, necessitating their control and quantification in pharmaceutical products. The parameters influencing the performance of this sample preparation for N-nitrosamines were investigated through both univariate and multivariate experiments. Microextractions were performed using just 5.0 mg of carboxylic acid-modified polystyrene divinylbenzene copolymer as the extraction phase. Under the optimized conditions, the automated setup enabled the simultaneous treatment of six samples in less than 20 min, providing reliable analytical confidence for the proposed application. The analytical performance of the automated high-throughput microextraction by the packed sorbent method was evaluated using a matrix-matching calibration. Quantification was performed using ultra-high-performance liquid chromatography-tandem mass spectrometry with chemical ionization at atmospheric pressure. The method exhibited limits of detection as low as 50 ng/g, good linearity, and satisfactory intra-day (1.38-18.76) and inter-day (2.66-20.08) precision. Additionally, the method showed accuracy ranging from 80% to 136% for these impurities in pharmaceutical formulations.

Modern automated microextraction procedures for bioanalytical, environmental, and food analyses

Sample preparation frequently is considered the most critical stage of the analytical workflow. It affects the analytical throughput and costs; moreover, it is the primary source of error and possible sample contamination. To increase efficiency, productivity, and reliability, while minimizing costs and environmental impacts, miniaturization and automation of sample preparation are necessary. Nowadays, several types of liquid-phase and solid-phase microextractions are available, as well as different automatization strategies. Thus, this review summarizes recent developments in automated microextractions coupled with liquid chromatography, from 2016 to 2022. Therefore, outstanding technologies and their main outcomes, as well as miniaturization and automation of sample preparation, are critically analyzed. Focus is given to main microextraction automation strategies, such as flow techniques, robotic systems, and column-switching approaches, reviewing their applications to the determination of small organic molecules in biological, environmental, and food/beverage samples.

Recent Trends in Graphene-Based Sorbents for LC Analysis of Food and Environmental Water Samples

This review provides an overview of recent advancements in applying graphene-based materials as sorbents for liquid chromatography (LC) analysis. Graphene-based materials are promising for analytical chemistry, including applications as sorbents in liquid chromatography. These sorbents can be functionalized to produce unique extraction or stationary phases. Additionally, graphene-based sorbents can be supported in various materials and have consequently been applied to produce various devices for sample preparation. Graphene-based sorbents are employed in diverse applications, including food and environmental LC analysis. This review summarizes the application of graphene-based materials in food and environmental water analysis in the last five years (2019 to 2023). Offline and online sample preparation methods, such as dispersive solid phase microextraction, stir bar sorptive extraction, pipette tip solid phase extraction, in-tube solid-phase microextraction, and others, are reviewed. The review also summarizes the application of the columns produced with graphene-based materials in separating food and water components and contaminants. Graphene-based materials have been reported as stationary phases for LC columns. Graphene-based stationary phases have been reported in packed, monolithic, and open tubular columns and have been used in LC and capillary electrochromatography modes.

Applicability and Limitations of a Capillary-LC Column-Switching System Using Hybrid Graphene-Based Stationary Phases

Graphene oxide sheets fixed over silica particles (SiGO) and their modification functionalized with C18 and endcapped (SiGO-C18ec) have been reported as sorbents for extraction and analytical columns in LC. In this study, a SiGO column was selected as the extraction column and a SiGO-C18ec as the analytical column to study the applicability and limitations of a column-switching system composed exclusively of columns packed with graphene-based sorbents. Pyriproxyfen and abamectin B1a were selected as the analytes, and orange-flavored carbonated soft drinks as the matrix. The proposed system could be successfully applied to the pyriproxyfen analysis in a concentration range between 0.5 to 25 µg/mL presenting a linearity of R² = 0.9931 and an intra-day and inter-day accuracy of 82.2-111.4% (RSD < 13.3%) and 95.5-99.8% (RSD < 12.7%), respectively. Furthermore, the matrix composition affected the area observed for the pyriproxyfen: the higher the concentration of orange juice in the soft drink, the higher the pyriproxyfen the signal observed. Additionally, the SiGO extraction column presented a life use of 120 injections for this matrix. In contrast, the proposed system could not apply to the analysis of abamectin B1a, and the SiGO-C18ec analytical column presented significant tailing compared to a similar approach with a C18 analytical column.

MIL-101(Cr) molecular cage anchored on 2D Ti3C2TX MXene nanosheets as high-performance electrochemical sensing platform for detection of xanthine

A new electrochemical sensing material based on the MIL-101(Cr) molecular cage anchored on 2D Ti₃C₂T_X-MXene nanosheets was prepared by using the in situ growth molecular engineering strategy. The sensing material was characterized by using different methods such as SEM, XRD, and XPS. The electrochemical sensing performance of MIL-101(Cr)/Ti₃C₂T_x-MXene was studied by DPV, CV, EIS, and other techniques. The electrochemical tests showed that the linear range of the modified electrode for xanthine (XA) detection was 1.5-73.0 μM and 73.0-133.0 μM, the detection limit was 0.45 μM (working potential of + 0.71 V vs. Ag/AgCl), and the performance is superior compared with the reported enzyme-free modified electrodes for detecting XA. The fabricated sensor has high selectivity and stability. It has good practicability in serum analysis with recoveries of 96.58-103.27% and a relative standard deviation (RSD) of 3.58-4.32%.

Application of an in-house packed octadecylsilica-functionalized graphene oxide column for capillary liquid chromatography analysis of hormones in urine samples

Graphene oxide-based LC stationary phases were developed and applied for separating hormones from urine using capillaryLC-MS/MS. Using two analytical approaches - direct injection and column-switching arrangement - it was possible to evaluate the chromatographic parameters and perform tests on the raw biological fluid. Two stationary phases (SPs) were produced, varying the amino silica support particle diameter (Si, 5, and 10 μm). Graphene oxide was covalently bonded to the surface of Si particles, and this material was functionalized by the insertion of octadecylsilica groups, generating the SiGO-C18. Infra-red spectroscopy assays revealed that both steps were successful - supporting GO onto Si and further C18 customization. Scanning electron microscopy showed spherical geometries with minor irregularities and narrow particle size distribution for the produced SPs. The GO-coating rate was higher on the Si particles of 10 μm. As a result, the 10 μm produced column reported better resolution, efficiency, and peak capacity. Therefore, this SiGO-C18 capillary column (100 mm × 0.32 mm i.d., 10 μm dp) was applied successfully in a column-switching method to separate hormones in urine. Linearity (R2 above 0.99), quantification limits (between 1.0 and 5 μg/L), and other figures of merit of the method were determined. It is worth mentioning that the SiGO-C18 capillaryLC column performed adequately, separating the target compounds in less than 6 min. We hope this work could significantly contribute to shedding some light on graphene-based materials as a promising class of stationary phase for miniaturized liquid chromatography.

Online Extraction Followed by LC-MS/MS Analysis of Lipids in Natural Samples: A Proof-of-Concept Profiling Lecithin in Seeds

Sample preparation is usually a complex and time-consuming procedure, which can directly affect the quality of the analysis. Recent efforts have been made to establish analytical methods involving minimal sample preparation, automatized and performed online with the analytical techniques. Online Extraction coupled with Liquid Chromatography-Mass Spectrometry (OLE-LC-MS) allows a fully connected extraction, separation, and analysis system. In this work, the lecithin profile was investigated in commercial sunflower, almonds, peanuts, and pistachio seeds to demonstrate that the concept of extraction, followed by the online analysis of the extract, could be applied to analyze this class of analytes in such complex solid matrices without a prior off-line solvent extraction step. The extraction phase gradient method was optimized. Two different analytical columns were explored, one being a conventional C18 (50 × 2.1 mm, 1.7 µm SPP) and the other a novel self-packed SIGO-C18ec (100 × 0.5, 5 µm FPP), which resulted in better separation. The analysis repeatability was investigated, and suggestions to improve it were pointed out. A characteristic ion with a m/z of 184, related to lysophosphatidylcholine structure, was used to identify the lecithin compounds. The temperature effect on the chromatograms was also explored. In short, it was found that the OLE-LC-MS approach is suitable for the analysis of lecithin compounds in seeds, being a promising alternative for lipidomics approaches in the near future.

Determination of selected herbicides in sugarcane-derived foods by graphene-oxide based disposable pipette extraction followed by liquid chromatography-tandem mass spectrometry

Sugarcane is widely cultivated in Brazil. Although there are Maximum Residue Limits of pesticides determined for this plant, there is no legislation covering alimentary products from sugarcane. In this study, Disposable Pipette Tip Extraction (DPX) technique was evaluated as a sample preparation technique for simultaneous determination of eleven herbicides followed by LC-MS/MS analysis in three sugarcane-derived food matrices: juice, candy, and syrup. First, graphene oxide anchored to silica functionalized with octadecyl silane and endcapped was synthesized, which was evaluated as a sorbent in DPX. Then, after evaluating the parameters involved in DPX extraction, the method was validated following the ICH guide. As a result, the method showed acceptable linearity (r ≥ 0.99), limits of quantification (1.0 - 5.0 ng mL^-1 for juice and 5.0 - 25.0 ng g ^- 1 for candy and syrup, varying according to the pesticide), precision, and accuracy within the limits of the literature, and recoveries ranging from 48 - 69% (juice), 34 - 89% (candy), and 28 - 76% (syrup). Finally, the developed method was successfully applied in actual samples of the three studied matrices.

Polyvinyl alcohol-based hydrogel sorbent for extraction of parabens in human milk samples by in-tube SPME–LC–UV

In this work, we developed an in-tube solid-phase microextraction (SPME) device consisting of a fused silica capillary modified with a polyvinyl alcohol (PVOH) hydrogel. Methylparaben, ethylparaben, propylparaben, and butylparaben were determined in human milk samples by using the in-tube SPME device coupled with liquid chromatography with spectrophotometric detection in the ultraviolet region (LC-UV). The inner surface of the fused silica capillary was silanized to allow covalent modification with the PVOH-hydrogel, using glutaraldehyde as cross-linking agent. The developed device was used up to 250 times with no reduction in the analytes' peak areas or carryover effect, besides having a low production cost. The human milk samples showed a significant matrix effect for parabens with higher logKo/w. Low limits of quantification (LLOQ) between 10.0 and 15.0 ng mL-1 were obtained with RSD values in the range of 1.18 to 18.3%. For the intra- and inter-day assays, RSD values from 5.6 to 16.5% and accuracy from 74.5 to 128.8% were achieved. The PVOH-based hydrogel sorbent allowed the use of water as desorption solvent, eliminating the use of organic solvents, which follows the principles of green chemistry. The results showed a great application potential of the PVOH-based hydrogel sorbent for the extraction of organic compounds from high-complexity samples.

R. Rocha C, Teixeira JA, Pereira JAM. Green Extraction Techniques as Advanced Sample Preparation Approaches in Biological, Food, and Environmental Matrices: A Review

Green extraction techniques (GreETs) emerged in the last decade as greener and sustainable alternatives to classical sample preparation procedures aiming to improve the selectivity and sensitivity of analytical methods, simultaneously reducing the deleterious side effects of classical extraction techniques (CETs) for both the operator and the environment. The implementation of improved processes that overcome the main constraints of classical methods in terms of efficiency and ability to minimize or eliminate the use and generation of harmful substances will promote more efficient use of energy and resources in close association with the principles supporting the concept of green chemistry. The current review aims to update the state of the art of some cutting-edge GreETs developed and implemented in recent years focusing on the improvement of the main analytical features, practical aspects, and relevant applications in the biological, food, and environmental fields. Approaches to improve and accelerate the extraction efficiency and to lower solvent consumption, including sorbent-based techniques, such as solid-phase microextraction (SPME) and fabric-phase sorbent extraction (FPSE), and solvent-based techniques (μQuEChERS; micro quick, easy, cheap, effective, rugged, and safe), ultrasound-assisted extraction (UAE), and microwave-assisted extraction (MAE), in addition to supercritical fluid extraction (SFE) and pressurized solvent extraction (PSE), are highlighted.

Mechanical power driven SPME-SERS ultra-fast detection of illegal additives in aquaculture water

A dual-function (extraction and detection) porous silver fiber with high enhancement effect was constructed based on a convenient electrochemical etching method. The prepared silver fiber not only had high enrichment capacity and good Surface Enhanced Raman Spectroscopy (SERS) performance but also had good laser stability and uniformity. A strategy combining mechanical power and integration of solid phase extraction (SPME) and SERS detection was used. Driven by mechanical power, the analyte malachite green (MG) was enriched on the prepared silver fiber after 40 seconds, which can realize an ultra-fast and sensitive detection with a detection limit of 8.48 × 10-9 M. At the same time, this fiber can be regenerated after being treated with NaBH4. The silver fiber can be used for the detection of MG and CV after being immersed in NaBH4 solution for a few minutes. After 5 cycles of processing, the measurement signals of the silver fiber can reach 70% of the initial signals. The mechanical power driven SPME-SERS (MPD-SPME-SERS) integrated detection method can be used to analyse aquaculture water within 1 minute with a good linear relationship.

Triazine-based covalent porous organic polymer for the online in-tube solid-phase microextraction of polycyclic aromatic hydrocarbons prior to high-performance liquid chromatography-diode array detection

A triazine-based covalent organic porous polymer (COP) was synthesized from the monomers 1,3,5-triphenylbenzene and tricyanogen chloride via the Friedel-Crafts reaction and characterized in detail using Brunauer-Emmett-Teller analysis, X-ray photoelectron spectroscopy, elemental analysis, and scanning electron microscopy, which confirmed that the COP had a rough surface and suitable extraction site. It was then employed in in-tube solid-phase microextraction combined with a high-performance liquid chromatography-diode array detector. The COP adsorbent was evaluated with different types of analyte, including estrogens, polycyclic aromatic hydrocarbons (PAHs), and plasticizers. The COP produced its best performance with PAHs. In order to obtain the highest extraction efficiency for PAHs, the main influential factors were optimized. Furthermore, a sensitive analytical method was established with the limits of detection of 0.004-0.010 µg L^-1, high enrichment factor of 1110-2763, and wide linear ranges (0.013-20.0 µg L^-1, 0.016-20.0 µg L^-1 and 0.033-20.0 µg L^-1). The relative standard deviation in intra-day and inter-day tests was also controlled to be within 0.3-3.1%. The proposed method was employed in the online detection of trace PAHs in real water samples, with satisfactory results obtained.

In-situ synthesis of nanocubic cobalt oxide @ graphene oxide nanocomposite reinforced hollow fiber-solid phase microextraction for enrichment of non-steroidal anti-inflammatory drugs from human urine prior to their quantification via high-performance liquid chromatography-ultraviolet detection

The in-situ synthesis and application of nanocubic Co₃O₄-coated graphene oxide (Co₃O₄@ GO) was introduced for the first time to present a cost-effective, stable and convenient operation and a simple device for hollow fiber solid-phase microextraction (HF-SPME) of four selected nonsteroidal anti-inflammatory drugs (NSAIDs) including diclofenac, mefenamic acid, ibuprofen and indomethacin. The extracted analytes were desorbed by an appropriate organic solvent and analyzed via high-performance liquid chromatography-ultraviolet detection (HPLC-UV). The prepared sorbent was approved using different characterization methods such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The variables effective on the Co₃O₄@GO-HF-SPME method including extraction time, desorption time, desorption solvent volume, sample pH, stirring rate and ionic strength were screened via Plackett-Burman design and then optimized by Box-Behnken design. Under optimal condition, the calibration curves were linear within the range of 1.0-200.0 µg L^-1 of analyte concentration with detection limits of 0.18-1.1 µg L^-1 and the relative standard deviations less than 10.1%. The limits of quantification (LOQs) were in the range of 0.60-3.67 µg L^-1. Matrix effect was not observed with this method; therefore, standard addition is not necessary for quantification of target compounds. The enrichment factors were obtained in the range of 49-68. The relative recoveries of the urine sample analysis were calculated in the range of 93-102%. Finally, the presented method exhibited good sensitivity, excellent repeatability, high reusability and acceptable precision, which will be a promising method to analyze various nonsteroidal anti-inflammatory drugs in urine samples.

In-tube solid-phase microextraction: Current trends and future perspectives

In-tube solid-phase microextraction (IT-SPME) was developed about 24 years ago as an effective sample preparation technique using an open tubular capillary column as an extraction device. IT-SPME is useful for micro-concentration, automated sample cleanup, and rapid online analysis, and can be used to determine the analytes in complex matrices simple sample processing methods such as direct sample injection or filtration. IT-SPME is usually performed in combination with high-performance liquid chromatography using an online column switching technology, in which the entire process from sample preparation to separation to data analysis is automated using the autosampler. Furthermore, IT-SPME minimizes the use of harmful organic solvents and is simple and labor-saving, making it a sustainable and environmentally friendly green analytical technique. Various operating systems and new sorbent materials have been developed to improve its extraction efficiency by, for example, enhancing its sorption capacity and selectivity. In addition, IT-SPME methods have been widely applied in environmental analysis, food analysis and bioanalysis. This review describes the present state of IT-SPME technology and summarizes its current trends and future perspectives, including method development and strategies to improve extraction efficiency.

Multidimensional capillary liquid chromatography-tandem mass spectrometry for the determination of multiclass pesticides in "sugarcane spirits" (cachaças)

Cachaça or "sugarcane spirit" is a Brazilian beverage considered the third most consumed beverage worldwide. Sugarcane, its raw material, is one of the main crops developed in the country, placing Brazil as the largest producer of this commodity on a global scale. Considering the growth in sugarcane production, many farmers use pesticides in their crops. However, excess pesticides can be accumulated in products derived from sugarcane, creating an environmental and public health concern. In this context, the development of analytical methods capable of identifying residues of pesticides in cachaças and other sugarcane-derived products is essential to ensure the beverage's quality. This work presents a method to quantify multiclass pesticides in Brazilian sugarcane spirits (cachaças) through an automated multidimensional system. The first dimension consists of an extraction column packed with a graphene-silica phase, followed by a capillary liquid chromatography-tandem mass spectrometry system as the second dimension. The method was optimized by an experimental design, in which the influence of three variables was evaluated on the extraction process: percentage of acetonitrile, loading flow, and loading time. Afterward, twenty-two cachaças were analyzed to ascertain the applicability of the proposed method. The analyses reported five samples containing clomazone (a type of herbicide widely used in sugarcane production). The method showed good linearity under optimized conditions, with correlation coefficients greater than 0.981, and limits of detection and quantification of 5 μg L^-1 and 10 μg L^-1, respectively. The herein discussed results suggest that the proposed method could be a practical option for identifying pesticides in beverages. Graphical Abstract.

The Current Role of Graphene-Based Nanomaterials in the Sample Preparation Arena

Since its discovery in 2004 by Novoselov et al., graphene has attracted increasing attention in the scientific community due to its excellent physical and chemical properties, such as thermal/mechanical resistance, electronic stability, high Young's modulus, and fast mobility of charged atoms. In addition, other remarkable characteristics support its use in analytical chemistry, especially as sorbent. For these reasons, graphene-based materials (GBMs) have been used as a promising material in sample preparation. Graphene and graphene oxide, owing to their excellent physical and chemical properties as a large surface area, good mechanical strength, thermal stability, and delocalized π-electrons, are ideal sorbents, especially for molecules containing aromatic rings. They have been used in several sample preparation techniques such as solid-phase extraction (SPE), stir bar sorptive extraction (SBSE), magnetic solid-phase extraction (MSPE), as well as in miniaturized modes as solid-phase microextraction (SPME) in their different configurations. However, the reduced size and weight of graphene sheets can limit their use since they commonly aggregate to each other, causing clogging in high-pressure extractive devices. One way to overcome it and other drawbacks consists of covalently attaching the graphene sheets to support materials (e.g., silica, polymers, and magnetically modified supports). Also, graphene-based materials can be further chemically modified to favor some interactions with specific analytes, resulting in more efficient hybrid sorbents with higher selectivity for specific chemical classes. As a result of this wide variety of graphene-based sorbents, several studies have shown the current potential of applying GBMs in different fields such as food, biological, pharmaceutical, and environmental applications. Within such a context, this review will focus on the last five years of achievements in graphene-based materials for sample preparation techniques highlighting their synthesis, chemical structure, and potential application for the extraction of target analytes in different complex matrices.

Evaluation of Two Fully Automated Setups for Mycotoxin Analysis Based on Online Extraction-Liquid Chromatography-Tandem Mass Spectrometry

Mycotoxins are secondary metabolites of fungi species widely known for their potentially toxic effects on human health. Considering their frequent presence in crops and their processed food, monitoring them on food-based matrices is now an important topic. Within such a context, the sample preparation step is usually mandatory before the chromatographic analysis, due to the complexity of matrices such as nuts, cereals, beverages, and others. For these reasons, we herein present the evaluation of two greener setups, based on the automation and miniaturization of the sample preparation step for mycotoxin analysis in different beverages. Firstly, we describe an analytical method based on a multidimensional assembly, coupling a lab-made microextraction column (508 µm i.d. × 100 mm) to a UPLC–MS/MS for the analysis of ochratoxin A in beverages. This configuration used a synthesized sorbent phase containing C18-functionalized graphene–silica particles, which exhibited excellent extraction performance, as well as being reusable and cheaper than commercially available extractive phases. Sequentially, a second setup, based on a multidimensional capillary LC coupled to MS/MS, was assessed for the same purpose. In this case, a graphene oxide-based capillary extraction column (254 µm i.d. × 200 mm) was used as the first dimension, while a C18 analytical capillary column performed the mycotoxin separation in beverages. Although this second one has similarities with the first, we focused mainly on the benefits related to the link between a miniaturized/automated sample preparation device with a capillary LC–MS/MS system, which made our analysis greener. Additionally, the chromatographic efficiency could even be enhanced.