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).

Effective, convenient, and green sample preparation for the determination of retinol and retinol acetate in human serum using pipette tip microextraction.

An efficient sample preparation based on pipette tip microextraction that can be used for the analysis of retinol in human serum has been developed. Altogether, nine commercial pipette tips were compared based on recovery, sample volume, use of organic solvent, handling difficulty, duration of the preparation process, price, and greenness of the method. Retinol acetate was used as the internal standard. The extraction efficiency for both compounds was evaluated to optimize and select the best pipette tip for sample preparation, which was the WAX-S XTR pipette tip containing an ion exchanger and salt. This tip combined solid phase extraction and salting-out assisted liquid‒liquid extraction. Satisfying recoveries of 100 and 80% for retinol and retinol acetate, respectively, and good repeatability were demonstrated. The action of this pipette tip was based on the clean-up workflow in which the interferences were retained on the sorbent. The presence of residual interferences in the extracted samples did not affect the HPLC separation of compounds of interest. The simplicity of the clean-up workflow reduced the time of the sample preparation compared to the bind-wash-elute counterpart workflow. The advantages of our technique are its environmental friendliness and cost effectiveness. The selected pipette tip with an excellent microextraction efficiency enables sample preparation in both clinical research and practice.

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.

Molecularly imprinted polymer as sorbent phase for disposable pipette extraction: A potential approach for creatinine analysis in human urine samples.

Traditionally, creatinine determination is made by a spectrophotometric method; however, some compounds present in biological samples can interfere with creatinine determination, decreasing the sensitivity of the method in urine samples. Consequently, we report the development of a new molecularly imprinted polymer as a sorbent phase for disposable pipette extraction to determine creatinine in urine samples by high-performance liquid chromatography with UV detection. The synthesized polymer showed a high superficial area and presented a first-order kinetic reaction and a high selectivity for creatinine extraction compared to the non-molecularly imprinted polymer. The main disposable pipette extraction variables evaluated included the number of draw/eject cycles, the pH of the solution and desorption solvent type. The developed method showed an inter and intra-day precision from 1.3% to 2.0% and 0.8-1.6% respectively, accuracy values ranging from 82.3% to 102.1% respectively and recovery values ranging between 96.5% and 101.3%, with a limit of quantification of 0.302 g L-1. The application of the developed method in real urine samples showed creatinine concentrations ranging from 0.55 to 6.61 g L-1. Thus, the developed method was revealed to be an efficient strategy for creatinine determination, reducing analysis time (3 min) and solvent use, and increasing selectivity compared with DPX commercial sorbents.

Disposable pipette extraction: A critical review of concepts, applications, and directions.

Analytical chemistry has always been evolving towards techniques that are increasingly simple and effective and that conform to green principles. Disposable pipette extraction (DPX, also known as dispersive pipette tip solid phase extraction) is a recent technique that has become an interesting tool in sample preparation methodologies. The principle is based on a dynamic mixture between the matrix and the sorbent which allows rapid and effective extraction of analytes and provides vigorous clean-up of the samples. In the context of fitting in with green chemistry, DPX has contributed to replacing commercially available materials with natural alternative materials. The production of these materials is also simple, reduces sample/solvent volumes, consequently generates less waste and is less laborious and safer for the laboratory worker. This review is a source of information about the DPX technique, dealing with its basic concepts, procedure, optimizations, materials for the main applications published so far, which are in the food, environmental and biological (forensic) sciences.

Novel strategy for disposable pipette extraction (DPX): Low-cost Parallel-DPX for determination of phthalate migration from common plastic materials to saliva simulant with GC-MS.

In widespread use in commercial products as plasticizers, phthalic acid esters (phthalates) have worried researchers and society in general, given the negative impacts on living organisms, especially human health. Since they are not chemically linked to the polymeric matrix, their migration is evident for samples that come into contact with plastics that contain them, such as water, food and saliva. In this work, a new strategy is described, named parallel-disposable pipette extraction (Pa-DPX), in a fast, efficient and robust analytical method using five simultaneous extractions for the determination of migration of 6 phthalates from common plastic materials (children's toys, school supplies, dog toys and oral contact items) to saliva simulant, using gas chromatography-mass spectrometry (GC-MS). The optimized conditions were 5 extraction cycles with 1600 µL of saliva simulant and desorption with 200 µL of ethyl acetate using 5 cycles with the same aliquot. The calibration curves resulted in determination coefficients higher than 0.9915, limits of detection at 1.5 µg L-1, and the quantification limits were 5.0 µg L-1. Excellent results were obtained for repeatability (relative standard deviation ranging from 8.7% to 20.1% for 5 µg L-1) and intermediate precision, varying the day of analyses (7.9%-16.2%). The analyte recovery ranged from 75% to 114% for two different samples, in four different levels of concentration. The Pa-DPX-GC-MS method was successfully applied to determine the migration of PAE from 21 samples. At least one PAE was detected in 81% of samples, and di-n-octyl phthalate was found in higher concentration, achieving the migration of almost 30 µg per g of sample.

Fully automated graphitic carbon nitride-based disposable pipette extraction-gas chromatography-mass spectrometric analysis of six polychlorinated biphenyls in environmental waters.

A fully automated online emulsification-enhanced disposable pipette extraction-gas chromatography-mass spectrometry (EE-DPX-GC-MS) method has been developed for the extraction of six polychlorinated biphenyls (PCBs) from environmental waters. An in-house prepared material, graphitic carbon nitride (g-C3N4), was used as sorbent in a home-packed DPX device. The six PCBs studied include PCB 10, 28, 52, 153, 138 and 180. g-C3N4 was characterized successfully by X-ray diffraction, elemental analysis, scanning electron microscopy, Fourier-transform infrared and Raman spectroscopy. As a C-N analogue of graphite, the two-dimensional structure of g-C3N4 allows rapid analyte adsorption and desorption to take place. With a significant number of nitrogen functionalities in g-C3N4, the material dispersed well in aqueous sample, increasing the active surface area of contact between the sorbent and the sample. When coupled with a pre-emulsification step, PCBs in each portion of sample could be efficiently extracted by g-C3N4 within 20 s of gentle turbulence. Under the most favorable conditions, the automated online EE-DPX-GC-MS method achieved wide dynamic working ranges with good linearity (r2 ≥ 0.998) for all analytes. Limits of detection ranging between 4.35 and 7.82 ng L-1 were attained, with enrichment factors of between 34 and 57 and relative standard deviations (RSDs) for intra- and inter-day precision of ≤ 8.95% and ≤ 12.6%, respectively. Absolute recoveries were between 69.3% and 109%. The fully automated online EE-DPX-GC-MS approach was applied to industrial wastewaters and reservoir waters where good relative recoveries of PCBs of between 89.3% and 105% were obtained, with RSDs ≤ 11.6%.

Miniaturized Salting-Out Assisted Liquid-Liquid Extraction Combined with Disposable Pipette Extraction for Fast Sample Preparation of Neonicotinoid Pesticides in Bee Pollen.

As the main source of nutrients for the important pollinator honeybee, bee pollen is crucial for the health of the honeybee and the agro-ecosystem. In the present study, a new sample preparation procedure has been developed for the determination of neonicotinoid pesticides in bee pollen. The neonicotinoid pesticides were extracted using miniaturized salting-out assisted liquid-liquid extraction (mini-SALLE), followed by disposable pipette extraction (DPX) for the clean-up of analytes. Effects of DPX parameters on the clean-up performance were systematically investigated, including sorbent types (PSA, C18, and silica gel), mass of sorbent, loading modes, and elution conditions. In addition, the clean-up effect of classical dispersive solid-phase extraction (d-SPE) was compared with that of the DPX method. Results indicated that PSA-based DPX showed excellent clean-up ability for the high performance liquid chromatography (HPLC) analysis of neonicotinoid pesticides in bee pollen. The proposed DPX method was fully validated and demonstrated to provide the advantage of simple and rapid clean-up with low consumption of solvent. This is the first report of DPX method applied in bee pollen matrix, and would be valuable for the development of a fast sample preparation method for this challenging and important matrix.

Determination of anandamide in cerebrospinal fluid samples by disposable pipette extraction and ultra-high performance liquid chromatography tandem mass spectrometry.

This work describes the development and validation of an ultra-high performance liquid chromatography tandem mass spectrometry method that uses disposable pipette extraction (DPX-UHPLC-MS/MS) to determine the endocannabinoid anandamide (AEA) in cerebrospinal fluid samples (CSF). The DPX parameters sorption equilibrium time, sample volume, number of draw-eject cycles, washing solvent volume, and elution solvent volume were optimized by design of experiments (DOE) techniques. The simple DPX protocol proposed herein required a reduced amount of CSF sample and organic solvent. The DPX-UHPLC-MS/MS method presented linear range from 0.10 ng mL-1 (LLOQ) to 3.0 ng mL-1, inter- and intra-assay accuracy with EPR values varying from -8.2% to 9.6%, inter- and intra-assay precision with CV values ranging from 1.3% to 14.8% (except for the LLOQ), and no significant matrix effect. The innovative DPX-UHPLC-MS/MS method was successfully applied to determine AEA in CSF samples from Parkinson's disease (PD) patients and should therefore be used in clinical studies.

A natural and renewable biosorbent phase as a low-cost approach in disposable pipette extraction technique for the determination of emerging contaminants in lake water samples.

This study proposes an efficient analytical methodology using a biosorbent (cork) as an extraction phase in disposable pipette extraction technique for the rapid determination of the emerging contaminants methyl paraben, ethyl paraben, benzophenone, 3-(4-methylbenzylidene) camphor and 2-(ethylhexyl)-4-(dimethylamino) benzoate in lake water samples using high-performance liquid chromatography with diode array detection. The optimized conditions were comprised of 800 µL of sample, three cycles of 30 s each for the extraction, pH 6, addition of 30% w/v of NaCl. For the desorption step, the optimized desorption conditions were achieved with 100 µL of a mixture comprised of 50% methanol and 50% acetonitrile v/v, using one cycle of 30 s. Excellent analytical performance was achieved with limits of detection of 0.6 µg/L for methyl paraben to 1.4 µg/L for 3-(4-methylbenzylidene) camphor, and the limit of quantitation varied from 2 µg/L for methyl paraben to 4.3 µg/L 3-(4-methylbenzylidene) camphor, respectively. The correlation coefficients ranged from 0.9962 for ethyl paraben to 0.9980 for methyl paraben. The method accuracy varied from 71-132%, and the intraday precision ranged from 3 to 23% (n = 3) and interday from 9 to 23% (n = 9). The robustness was evaluated through Youden and Lenth's methods and indicated no significant variations in the results.

An effective and high-throughput analytical methodology for pesticide screening in human urine by disposable pipette extraction and gas chromatography - mass spectrometry.

In this paper, the use of disposable pipette extraction (DPX) for the determination of pesticides in human urine in possible cases of poisoning is proposed for the first time. The pesticides studied were oxamyl, propoxur, carbofuran, 3­hydroxycarbofuran, carbaryl, methiocarb, terbufos, parathion methyl, malathion, chlorpyrifos and endosulfan. The pipette tip used for the extraction of these compounds was commercially acquired. It has a capacity of 5 mL and contains 20 mg of sorbent material (styrene-divinylbenzene). The optimization of the main parameters that can influence the extraction efficiency of this sample preparation technique was performed with univariate and multivariate approaches. The analytes were separated and identified by gas chromatography coupled to mass spectrometry (GC-MS). The optimal extraction conditions were 5 extraction cycles of 30 s and 5 desorption cycles of 15 s with 250 µL of ethyl acetate. Elution of the extract was performed in a vial containing 100 mg of anhydrous sodium sulfate. The method developed was validated, providing correlation coefficients higher than 0.9955 for all analytes, limits of detection (LOD) of 0.76 to 1.52 µg L-1, limits of quantification (LOQ) of 2.5 to 5.0 µg L-1, relative recoveries of 63 to 118%, intra-day precision of 0.7 to 15.3% and inter-day precision of 4.9 to 13.1%. An effective and rapid method for the analysis of human urine for the identification of possible cases of poisoning by pesticides was successful developed.

Determination of drugs in plasma samples by disposable pipette extraction with C18-BSA phase and liquid chromatography-tandem mass spectrometry.

This work describes restricted access material (RAM) constituted of porous octadecylsilane particles with the outer surface covered with bovine serum albumin (C18-BSA) as a stationary phase to extract drugs from plasma samples by disposable pipette extraction (DPX) for further analysis by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The C18-BSA phase simultaneously excluded macromolecules by chemical diffusion barrier (BSA network) and enrichment of the interior phase (C18) with drug traces by sorption. The hydrophilic barrier of the C18-BSA allows small molecules (drugs) to permeate through the hydrophobic part (C18), while at the same time it excludes the macromolecules by chemical diffusion barrier (BSA network). Optimization of the DPX variables (sorption equilibration time, exclusion of endogenous compounds, and elution step) improved the sensitivity and selectivity of the method, which presented a linear range from the lower limit of quantification (0.5-20.0ngmL-1) to the upper limit of quantification (32.5-10,500ngmL-1), inter- and intra-assay precision with coefficients of variation (CV) lower than 15%, and relative standard error (RSE) of the accuracy ranging from -12% to 11%. The developed method was successfully used to determine five antipsychotics (olanzapine, quetiapine, clozapine, haloperidol, and chlorpromazine) in combination with seven antidepressants (mirtazapine, paroxetine, citalopram, sertraline, imipramine, clomipramine, and fluoxetine), two anticonvulsants (carbamazepine and lamotrigine), and two anxiolytics (diazepam and clonazepam) in plasma samples from schizophrenic patients for therapeutic drug monitoring.

Quantification of cannabinoids and their free and glucuronide metabolites in whole blood by disposable pipette extraction and liquid chromatography-tandem mass spectrometry.

Identifying recent cannabis intake is confounded by prolonged cannabinoid excretion in chronic frequent cannabis users. We previously observed detection times ≤2.1h for cannabidiol (CBD) and cannabinol (CBN) and Δ(9)-tetrahydrocannabinol (THC)-glucuronide in whole blood after smoking, suggesting their applicability for identifying recent intake. However, whole blood collection may not occur for up to 4h during driving under the influence of drugs investigations, making a recent-use marker with a 6-8h detection window helpful for improving whole blood cannabinoid interpretation. Other minor cannabinoids cannabigerol (CBG), Δ9-tetrahydrocannabivarin (THCV), and its metabolite 11-nor-9-carboxy-THCV (THCVCOOH) might also be useful. We developed and validated a sensitive and specific liquid chromatography-tandem mass spectrometry method for quantification of THC, its phase I and glucuronide phase II metabolites, and 5 five minor cannabinoids. Cannabinoids were extracted from 200µL whole blood via disposable pipette extraction, separated on a C18 column, and detected via electrospray ionization in negative mode with scheduled multiple reaction mass spectrometric monitoring. Linear ranges were 0.5-100µg/L for THC and 11-nor-9-carboxy-THC (THCCOOH); 0.5-50µg/L for 11-hydroxy-THC (11-OH-THC), CBD, CBN, and THC-glucuronide; 1-50µg/L for CBG, THCV, and THCVCOOH; and 5-500µg/L for THCCOOH-glucuronide. Inter-day accuracy and precision at low, mid and high quality control (QC) concentrations were 95.1-113% and 2.4-8.5%, respectively (n=25). Extraction recoveries and matrix effects at low and high QC concentrations were 54.0-84.4% and -25.8-30.6%, respectively. By simultaneously monitoring multiple cannabinoids and metabolites, identification of recent cannabis administration or discrimination between licit medicinal and illicit recreational cannabis use can be improved.

Disposable pipette tips extraction: Fundamentals, applications and state of the art.

Disposable pipette tips extraction consists of a solid-phase extraction in which the sorbent is poorly dispersed in a pipette tip, which allows a quick and dynamic contact between the aspirated analyte from the sample and the solid phase. It is a technique used particularly in food and forensic analysis, since it requires a small amount of sample and solvent. This article highlights the principles, advantages and disadvantages of the disposable pipette tips extraction method and reviews recent applications.

The development of a new disposable pipette extraction phase based on polyaniline composites for the determination of levels of antidepressants in plasma samples.

In the present work, a new stationary phase for disposable pipette extraction (DPX) based on composites of polyaniline and a styrene-divinylbenzene (SD) copolymer was applied to the analysis of fluoxetine and norfluoxetine in plasma samples using liquid chromatography and fluorescence detector (LC-FD). The DPX variables, such as number of draw/eject cycles, sample pH, type and volume of the desorption solvent, were optimized to established the sorption equilibrium and shorten the analysis time. Among the DPX evaluated variables, the higher extraction efficiency were obtained with 200 µL of plasma mixed with 200 µL of borate solution (pH 9), followed by liquid desorption of the drug with 200 µL acetonitrile in a single cycle. The DPX/LC-FD method demonstrated a linear response over the dynamic range from 10 to 1000 ng mL(-1) for fluoxetine and from 80 ng mL(-1) (LOQ) to 1000 ng mL(-1) for norfluoxetine with r(2)=0.997 and 0.998, respectively. The limit of quantification (LOQ) was 10 ng mL(-1) for fluoxetine and 80 ng mL(-1) for norfluoxetine. Based on the analytical validation results, the proposed method can be a useful tool for determining the fluoxetine and norfluoxetine levels in plasma samples from patients receiving therapeutic dosages.