Magnetic Particle Spray Mass Spectrometry.

In this work, the concept of magnetic particle spray mass spectrometry (MPS-MS) is reported for the first time. Magnetic sorbent particles are used to extract the analytes from a liquid sample. The particles are magnetically attracted to the tip of a magnetic probe that is positioned at the entrance of the mass spectrometer. A solvent is dispensed on the particles, and a high voltage promotes the formation of the Taylor cone around the particles agglomerate. Analytes are desorbed by the solvent, ionized, and analyzed by mass spectrometry. MPS-MS is totally in consonance with the green chemistry principle. A minimal consumption of sample (100 µL), solvent (34 µL), and magnetic sorbent (500 µg) is needed per analysis for an excellent performance of MPS-MS in terms of sensitivity and selectivity. The determination of amitriptyline, citalopram, clomipramine, chlorpromazine, doxepin, haloperidol, nortriptyline, and venlafaxine in human plasma samples using magnetic restricted-access carbon nanotubes was carried out as a proof of principle. Limits of quantification of 10 µg L-1 and correlation coefficients higher than 0.98 were obtained for all of the analytes. Limits of detection ranged from 0.43 to 2.82 µg L-1. Precision (as relative standard deviation) and accuracies (as relative error) ranged from 3.6 to 23.6%, as well as -12.8 to 18.7%, respectively. MPS-MS opens a new line of developments in the association of sample preparation with ambient ionization. New sorbents, device configurations, and physical and chemical conditions can also be analyzed for the analysis of many other analytes in different samples.

Online restricted access molecularly imprinted solid-phase extraction coupled with liquid chromatography-mass spectrometry for the selective determination of serum bile acids.

A rapid and sensitive online restricted access molecularly imprinted solid-phase extraction method coupled to a liquid chromatography-mass spectrometry (LC-MS) system for simultaneous determination of serum bile acids as well as their taurine and glycine conjugates was developed. Reversible liver damage of workers exposed to volatile organic solvents can be investigated based on the level of the analyzed molecules. A restricted access molecularly imprinted polymer coated with bovine serum albumin (RAMIP-BSA) was synthesized and used as the extraction phase. The column switching liquid chromatography system was able to exclude about 100% of the macromolecules and extract/separate nine bile acids from blood human serum samples, in a total time of 40 minutes. The developed method was validated based on the Food and Drug Administration (FDA) guidelines, being linear for all the analytes in their respective analytical ranges (coefficients of determination higher than 0.99), with limits of detection (LOD) and quantification (LOQ) ranging from 2.0 to 5.7 µg L-1 and from 10.0 to 25.0 µg L-1, respectively. Suitable results for precision (relative standard deviation ranged from 3.2 to 14.5% and 0.7 to 14.8%, respectively for intra and inter-assay) and accuracy (relative error ranged from -14.8 to 14.2%; -13.8 to 14.3%) were obtained. The validated analytical method was applied to determine bile acids in serum samples of five workers occupationally exposed to volatile organic solvent, demonstrating its applicability in the assessment of these toxicants.

Restricted access carbon nanotube for microextraction by packed sorbent to determine antipsychotics in plasma samples by high-performance liquid chromatography-tandem mass spectrometry.

This manuscript describes the development of the restricted access carbon nanotube (RACNT) as a selective stationary phase for microextraction by packed sorbent (MEPS) to determine antipsychotics (chlorpromazine, clozapine, olanzapine, and quetiapine) in untreated plasma samples from schizophrenic patients by ultra-high liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The synthesis was achieved by chemically covering commercial multi-walled carbon nanotubes with bovine serum albumin (BSA) to subsequently pack the material in a polyethylene conical tube (1000 µL). The RACNTs' sorbents were able to exclude about 97% of the plasma proteins, maintaining the same performance for about 100 assays. The MEPS variables (sample pH, draw-eject cycles, desorption and phase cleanup) were evaluated to improve sensibility and selectivity. The MEPS/UHPLC-MS/MS method was linear at concentrations ranging from the lower limit of quantification (10.0 ng mL-1) to the upper limit of quantification (200-700 ng mL-1) with coefficients of determinations higher than 0.99. The precision assays presented relative standard deviation (RSD) values lower than 13%, and the accuracy assays presented relative error (RE) values that ranged from - 8.01 to 11.53%. Neither significant matrix effects nor carryover was observed. The developed method was successfully applied to determine antipsychotics drugs for therapeutic drug monitoring of schizophrenic patients.

A new restricted access molecularly imprinted fiber for direct solid phase microextraction of benzodiazepines from plasma samples.

Restricted access molecularly imprinted polymers (RAMIPs) are hybrid materials that present selective binding sites for a template (or similar molecules), and an external hydrophilic layer that avoids the binding of proteins to the material, making them appropriate for the sample preparation of protein fluids. RAMIPs have been used successfully in online and offline solid phase extractions, but there is no application as a fiber in solid phase microextraction (SPME), to the best of our knowledge. In this paper, molecularly imprinted fibers were synthesized inside glass capillary tubes (0.53 mm i.d.), using diazepam and methacrylic acid as template and functional monomer, respectively. The MIP fibers were coated with a cross-linked bovine serum albumin (BSA) layer, resulting in RAMIP fibers that were used in the SPME of benzodiazepines directly from biological fluids. The BSA layer acts as a protective barrier that avoids the binding of proteins from the sample by an electrostatic repulsion mechanism. The protein exclusion capacity of the RAMIP fiber was about 98%, which is selective to benzodiazepines in comparison with other drugs (citalopram and fluoxetine). The SPME was optimized and the extraction conditions were set as follows: 1000 µL of the sample diluted with water (1 : 0.5, v : v), no pH adjustment, an extraction time of 20 min at 500 rpm, and elution with 200 µL of acetonitrile for 5 min at 500 rpm. The fibers were used in the SPME of benzodiazepines directly from plasma samples, followed by HPLC-DAD analyses. The method was linear for bromazepam (50-750 µg L-1), clonazepam (15-250 µg L-1), alprazolam (15-350 µg L-1), nordiazepam (100-2100 µg L-1) and diazepam (100-2600 µg L-1), with correlation coefficients higher than 0.97. Relative standard deviations (precision) and relative errors (accuracy) ranged from 0.5 to 20.0%, and -15.6 to 21.6%, respectively.

Biological sample preparation by using restricted-access nanoparticles prepared from bovine serum albumin: application to liquid chromatographic determination of ß-blockers.

Restricted-access nanoparticles (RANPs) were prepared from bovine serum albumin by coacervation. They have an average sized of 311 nm. They were characterized and used to capture the ß-blockers atenolol, metoprolol and propranolol from untreated biological samples. It is shown that both high protein affinity drugs (propranolol) and low protein affinity drugs (atenolol) could be rapidly extracted from plasma. This is revealed by kinetic and isothermal adsorption studies. On the other hand, almost all proteins from the sample were excluded. This demonstrates the efficiency of RANPs as restricted-access material. Sample preparation was carried out by solid phase microextraction using a probe obtained by the fixation of the RANPs at the end of a glass capillary. Atenolol (in concentrations from 100 to 1200 µg L-1), metoprolol (from 80 to 1000 µg L-1) and propranolol (from 15 to 200 µg L-1) were extracted from spiked plasma samples and analyzed by LC MS/MS without using a separation column. Correlation coefficients >0.99, good precision, accuracy, robustness, and lack of memory effects were observed for all of the analytes. The detection limits (at an S/N of 3) are 25.6, 14.6, and 3.8 µg L-1 for atenolol, metoprolol and propranolol, respectively. Ten samples can be simultaneously extracted within ∼15 min. Plasma samples of patients undergoing medical treatment were successfully analyzed with the method. Graphical abstract Schematic representation of a bovine serum albumin-based restricted access nanoparticle that exclude proteins from a human plasma sample but capture the small analytes.

Molecularly imprinted probe for solid-phase extraction of hippuric and 4-methylhippuric acids directly from human urine samples followed by MEKC analysis.

Hippuric acid (HA) and 4-methylhippuric acid (4-MHA) are metabolites as well as biological indicators for toluene and xylenes, respectively, and their determination in urine samples is very important, in order to monitor the occupational exposition to these solvents, ensuring a safe working environment. Thus, this paper describes the synthesis and characterization of a probe impregnated with molecularly imprinted polymers (MIPs) for the solid-phase extraction of HA and 4-MHA directly from untreated urine samples followed by micellar electrokinetic chromatography (MEKC) analyses. The MIP probe selectivity was compared to the non-imprinted polymer probe. The MEKC separations were carried out in 50 mmol/L sodium tetraborate pH 10.0/0.5 mmol/L cetyltrimethylammonium bromide aqueous solution, with a constant voltage of -15 kV. The system variables were optimized to provide ideal conditions for the extraction and desorption of the analytes, as well as for the MEKC analyses. The method was linear from 0.5 to 5.0 g/L for both analytes, with correlation coefficients > 0.994. Precisions and accuracies, expressed as relative standard deviation and relative error, were < 20.0 and within -15.4 to 16.6%, respectively, in accordance with the United States Food and Drug Administration recommendation. The MIP probe has proven to be simple, cheap, resistant, and synthetically reproducible, being successfully used to analyze both HA and 4-MHA from real samples.

Direct doping analysis of beta-blocker drugs from urinary samples by on-line molecularly imprinted solid-phase extraction coupled to liquid chromatography/mass spectrometry.

The use of beta-blockers to enhance performance in some sports is forbidden. Based on this regulation, there is a demand for dynamic analytical procedures for analyzing these compounds quickly and without manual sample preparation. Therefore, the use of a molecularly imprinted polymer (MIP) in a multidimensional liquid chromatographic system coupled to a mass spectrometer provides a good alternative for improving the selectivity and practicality of the beta-blocker analyses, as described in this paper. A water-compatible MIP for oxprenolol was synthesized by the precipitation method, using methacrylic acid as a functional monomer and 2-hydroxyethyl methacrylate and glycerol dimethacrylate as hydrophilic monomers. A column filled with MIP was coupled to an LC-MS/MS instrument under the multidimensional configuration, with 10.0 mmol L(-1) ammonium formate buffer (pH 5.0) as the loading and reconditioning mobile phase and a 0.01% formic acid aqueous solution-methanol (30 : 70 v : v) as the elution mobile phase. The system was used for on-line extraction and quantization of oxprenolol (from 1.0 to 75.0 µg L(-1)), atenolol, propranolol, nadolol, pindolol, labetalol and metoprolol (all from 3.0 to 50 µg L(-1)) simultaneously, from urine samples. The correlation coefficient was higher than 0.99 for all the analytes. Suitable precision and accuracy were obtained.

Restricted access molecularly imprinted polymers obtained by bovine serum albumin and/or hydrophilic monomers' external layers: a comparison related to physical and chemical properties.

Molecularly imprinting polymers (MIPs) can be modified with external layers in order to obtain restricted access molecularly imprinted polymers (RAMIPs) able to exclude macromolecules and retain low weight compounds. These modifications have been frequently achieved using hydrophilic monomers, chemically bound on the MIP surface. Recently, our group proposed a new biocompatible RAMIP based on the formation of a bovine serum albumin coating on the surface of MIP particles. This material has been used to extract drugs directly from untreated human plasma samples, but its physicochemical evaluation has not been carried out yet, mainly in comparison with RAMIPs obtained by hydrophilic monomers. Thus, we proposed in this paper a comparative study involving the surface composition, microscopic aspect, selectivity, binding kinetics, adsorption and macromolecule elimination ability of these different materials. We concluded that the synthesis procedure influences the size and shape of particles and that hydrophilic co-monomer addition as well as coating with BSA do not alter the chemical recognition ability of the material. The difference between imprinted and non-imprinted polymers' adsorption was evident (suggesting that imprinted polymers have a better capacity to bind the template than the non-imprinted ones). The Langmuir model presents the best fit to describe the materials' adsorption profile. The polymer covered with hydrophilic monomers presented the best adsorption for the template in an aqueous medium, probably due to a hydrophilic layer on its surface. We also concluded that an association of the hydrophilic monomers with the bovine serum albumin coating is important to obtain materials with higher capacity of macromolecule exclusion.

Molecularly imprinted fibers with renewable surface for solid-phase microextraction of triazoles from grape juice samples followed by gas chromatography mass spectrometry analysis.

This paper describes the synthesis and characterization of a new molecularly imprinted solid-phase microextraction fiber able to renew its selective binding sites because of the gradual thermal decomposition of the polymeric network. The injector of the chromatograph operates at 300 °C, and during the desorption step of the analytes (in a short period), the polymeric network is degraded from the surface to the core in volatile compounds that do not interfere with the analysis. The renewable MIP fiber was successfully employed to extract triazole fungicides (triadimenol, tebuconazole, and metconazole) from grape juice samples followed by gas chromatography mass spectrometry analysis. The method was adjusted to the quadratic models from 100 to 2000 µg L(-1), with good precision and accuracy. The limits of quantification (100 µg L(-1) for all analytes) were sufficient to analyze triadimenol, tebuconazole, and metconazole in grape juice samples, where their maximum residue limits in Brazil are 100, 2000, and 1000 µg L(-1), respectively.

Magnetic carbon nanotubes modified with proteins and hydrophilic monomers: Cytocompatibility, in-vitro toxicity assays and permeation across biological interfaces.

Carbon nanotubes are promising materials for biomedical applications like delivery systems and tissue scaffolds. In this paper, magnetic carbon nanotubes (M-CNTs) covered with bovine serum albumin (M-CNTs-BSA) or functionalized with hydrophilic monomers (M-CNTs-HL) were synthesized, characterized, and evaluated concerning their interaction with Caco-2 cells. There is no comparison between these two types of functionalization, and this study aimed to verify their influence on the material's interaction with the cells. Different concentrations of the nanotubes were applied to investigate cytotoxicity, cell metabolism, oxidative stress, apoptosis, and capability to cross biomimetic barriers. The materials showed cytocompatibility up to 100 µg mL-1 and a hemolysis rate below 2 %. Nanotubes' suspensions were allowed to permeate Caco-2 monolayers for up to 8 h under the effect of the magnetic field. Magnetic nanoparticles associated with the nanotubes allowed estimation of permeation through the monolayers, with values ranging from 0.50 to 7.19 and 0.27 to 9.30 × 10-3 µg (equivalent to 0.43 to 6.22 and 0.23 to 9.54 × 10-2 % of the initially estimated mass of magnetic nanoparticles) for cells exposed and non-exposed to the magnets, respectively. Together, these results support that the developed materials are promising for applications in biomedical and biotechnological fields.

A new restricted access molecularly imprinted polymer capped with albumin for direct extraction of drugs from biological matrices: the case of chlorpromazine in human plasma.

A new restricted access molecularly imprinted polymer coated with bovine serum albumin (RAMIP-BSA) was developed, characterized, and used for direct analysis of chlorpromazine in human plasma samples. The RAMIP-BSA was synthesized using chlorpromazine, methacrylic acid, and ethylene glycol dimethacrylate as template, functional monomer, and cross-linker, respectively. Glycerol dimethacrylate and hydroxy methyl methacrylate were used to promote a hydrophilic surface (high density of hydroxyl groups). Afterward, the polymer was coated with BSA using glutaraldehyde as cross-linker, resulting in a protein chemical shield around it. The material was able to eliminate ca. 99% of protein when a 44-mg mL(-1) BSA aqueous solution was passed through it. The RAMIP-BSA was packed in a column and used for direct analysis of chlorpromazine in human plasma samples in an online column switching high-performance liquid chromatography system. The analytical calibration curve was prepared in a pool of human plasma samples with chlorpromazine concentrations ranging from 30 to 350 µg L(-1). The correlation coefficient obtained was 0.995 and the limit of quantification was 30 µg L(-1). Intra-day and inter-day precision and accuracy presented variation coefficients and relative errors lower than 15% and within -15 and 15%, respectively. The sample throughput was 3 h(-1) (sample preparation and chromatographic analysis steps) and the same RAMIP-BSA column was efficiently used for about 90 cycles.

Biomarkers in psychiatric disorders.

Psychiatric disorders represent a significant socioeconomic and healthcare burden worldwide. Of these, schizophrenia, bipolar disorder, major depressive disorder and anxiety are among the most prevalent. Unfortunately, diagnosis remains problematic and largely complicated by the lack of disease specific biomarkers. Accordingly, much research has focused on elucidating these conditions to more fully understand underlying pathophysiology and potentially identify biomarkers, especially those of early stage disease. In this chapter, we review current status of this endeavor as well as the potential development of novel biomarkers for clinical applications and future research study.

Lead determination in commercial juice samples by direct magnetic sorbent sampling flame atomic absorption spectrometry (DMSS-FAAS).

The direct magnetic sorbent sampling flame atomic absorption spectrometry (DMSS-FAAS), recently proposed by our research group, was applied to determine the lead in soy-based juice, whole grape juice, reconstituted grape juice, and orange nectar samples. A dispersive solid phase extraction (d-SPE) of lead was carried out using a magnetic orange peel powder, developed and optimized by Gupta et al (2012), that was inserted into flame by FAAS with a magnetic probe. The limits of quantification (<4.6 µg L-1) were smaller than maximum residue limits established in Brazil. Good precisions and accuracies were obtained. DMSS-FAAS presented a sensitivity at least 14 times greater than the d-SPE followed by conventional FAAS analysis, wherein the analytes were extracted and desorbed, and the eluate was introduced in FAAS via nebulization system. Lead was easily quantified in juice samples at very low concentrations, with satisfactory figures of merit, and without the need of a mineralization step.

Direct magnetic sorbent sampling flame atomic absorption spectrometry (DMSS-FAAS) for highly sensitive determination of trace metals.

A procedure of direct magnetic sorbent sampling in flame atomic absorption spectrometry (DMSS-FAAS) was developed in this work. Metal-loaded magnetic sorbents were directly inserted in the flame of the FAAS for direct metal desorption/atomization. Magnetic graphene oxide aerogel (M-GOA) particles were synthesized, characterized, and used as a proof-of-concept in the magnetic dispersive solid phase extraction of Pb2+ ions from water samples. M-GOA was selected because is a light and porous sorbent, with high adsorption capacity, that is quickly burned by the flame. Magnetic particles were directly inserted in the flame by using a metallic magnetic probe, thereby avoiding the need for a chemical elution step. As all the extracted Pb2+ ions arrive to the flame without passing through the nebulization system, a drastic increase in the analytical signal was achieved. The improvement in the sensitivity of the proposed method (DMSS-FAAS) for Pb2+ determination was at least 40 times higher than the conventional procedure in which the Pb2+ is extracted, eluted, and analyzed by conventional flame atomic absorption spectrometry (FAAS) via the nebulization system. The analytical curve was linear from 5.0 to 180.0 µg L-1 and the limit of detection was found to be 1.30 µg L-1. Background measurements were insignificant, and the atomic absorption peaks were narrow and reproducible. Precision assessed as a percentage of the relative standard deviation %RSD was found to be 17.4, 7.1, and 7.8% for 10, 70, and 180 µg L-1 levels, respectively. The method showed satisfactory results even in the presence of other ions (Al3+, Cr3+, Co2+, Cu2+, Fe3+, Mn2+, Ba2+, Mg2+, and Li+). The performance of the new system was also evaluated for Cd2+ ions, as well as by using other magnetic particles available in our lab: magnetic carbon nanotubes (M-CNTs), magnetic restricted access carbon nanotubes (M-RACNT), magnetic poly (methacrylic acid-co-ethylene glycol dimethacrylate) (M-PMA), magnetic nanoparticles coated with orange powder peel (M-OPP), and magnetic nanoparticles covered with SiO2 (M - SiO2). Analytical signals increased for both analytes in all sorbents (increases of about 4-37 times), attesting the high potential and applicability of the proposed method. Simplicity, high analytical frequency, high detectability and reproducibility, low cost, and possibility of being totally mechanized are the most relevant advantages.

Harnessing Small-Molecule Analyte Detection in Complex Media: Combining Molecularly Imprinted Polymers, Electrolytic Transistors, and Machine Learning.

Small-molecule analyte detection is key for improving quality of life, particularly in health monitoring through the early detection of diseases. However, detecting specific markers in complex multicomponent media using devices compatible with point-of-care (PoC) technologies is still a major challenge. Here, we introduce a novel approach that combines molecularly imprinted polymers (MIPs), electrolyte-gated transistors (EGTs) based on 2D materials, and machine learning (ML) to detect hippuric acid (HA) in artificial urine, being a critical marker for toluene intoxication, parasitic infections, and kidney and bowel inflammation. Reduced graphene oxide (rGO) was used as the sensory material and molecularly imprinted polymer (MIP) as supramolecular receptors. Employing supervised ML techniques based on symbolic regression and compressive sensing enabled us to comprehensively analyze the EGT transfer curves, eliminating the need for arbitrary signal selection and allowing a multivariate analysis during HA detection. The resulting device displayed simultaneously low operating voltages (<0.5 V), rapid response times (≤10 s), operation across a wide range of HA concentrations (from 0.05 to 200 nmol L-1), and a low limit of detection (LoD) of 39 pmol L-1. Thanks to the ML multivariate analysis, we achieved a 2.5-fold increase in the device sensitivity (1.007 µA/nmol L-1) with respect to the human data analysis (0.388 µA/nmol L-1). Our method represents a major advance in PoC technologies, by enabling the accurate determination of small-molecule markers in complex media via the combination of ML analysis, supramolecular analyte recognition, and electrolytic transistors.

Molecularly imprinted solid-phase extraction and high-performance liquid chromatography with ultraviolet detection for the determination of urinary trans,trans-muconic acid: a comparison with ionic exchange extraction.

A new molecularly imprinted polymer (MIP) has been synthesized for the selective extraction of trans,trans-muconic acid (ttMA) from urine samples, followed by high-performance liquid chromatography analysis with ultraviolet detection. The synthesis was based on non-covalent interactions, and 4-vinylpyridine was used as a functional monomer. The analytical calibration curve was prepared using a pool of five urine samples of non-smokers spiked with ttMA standards with concentrations that ranged from 0.3 to 10 mg L(-1) (r(2) = 0.999). The limit of quantification was 0.3 mg L(-1) (lower than the biological exposure limits suggested by the ACGIH). The within-day and between-day precision and accuracy presented relative standard deviations and relative errors of less than 15%. The analytical frequency was 4 h(-1) (considering extraction and separation/quantification steps), and the same MIP cartridge was efficiently used for approximately 100 cycles. All figures of merit were similar or better than those obtained by the procedure based on ionic exchange extraction. The proposed method could be an interesting alternative for the routine analysis of ttMA in urine for biological monitoring procedures of human exposure to benzene.

Application of the molecularly imprinted solid-phase extraction to the organophosphate residues determination in strawberries.

This study describe an analytical method employing gas chromatography (GC) using flame photometric detection that has been developed for the simultaneous determination of organophosphate pesticides (diazinon, disulfoton, parathion, chlorpyrifos and malathion) in strawberry samples. For this purpose, molecularly imprinted solid-phase extraction was applied as a sample preparation technique. The method was linear in the ranges from 0.10 to 1.00 µg g(-1), for diazinon, disulfoton, parathion and chlorpyrifos, and 0.10 to 2.00 µg g(-1) for malathion with r > 0.99. The detection limits (LD) ranged from 0.02 to 0.05 µg g(-1). Recovery studies yielded average recoveries in the range of 65.25 to 87.70 %. These results showed the potential of this technique for organophosphate residue monitoring in strawberry samples.

Molecularly Imprinted Solid Phase Extraction Aiding the Analysis of Disease Biomarkers.

Low concentrations of biomarkers as well as the complexity of biological samples make the clinical diagnoses of several diseases a challenging task. Sample preparation protocols remain a fundamental piece in the puzzle of analytical processes, and smart sorbents including molecularly imprinted polymers (MIPs) have been successfully used in this case. In this review, we depict the state of art for the rational design of MIPs to be used in solid phase extraction of disease biomarkers from biological samples. The topics are divided into (1) strategies for MIP syntheses, (2) setups for sample preparation protocols with MIPs, (3) the applications of these combined principles in the analyses of different classes of disease biomarkers, and (4) remaining challenges and future trends for the application of Molecular Imprinting Technology in sample preparation for clinical diagnosis.

Magnetic restricted-access carbon nanotubes for SPME to determine cannabinoids in plasma samples by UHPLC-MS/MS.

This manuscript describes the development of magnetic restricted-access carbon nanotubes (M-RACNTs) for use as SPME sorbent to determine cannabidiol (CBD) and delta-9-tetrahydrocannabinol (THC) in human plasma samples by UHPLC-MS/MS. The adsorptive phase was immobilized on an SPME device by electromagnetic interactions between the M-RACNTs and a cylindrical neodymium magnet (3-mm diameter x 8-mm height) attached to a stainless-steel rod (3-mm diameter x 40-mm height). The M-RACNTs were synthesized by incorporating Fe3O4 magnetic nanoparticles (MNPs) into commercial carbon nanotubes (CNTs); then the surface of the resulting sorbent was further coated with a layer of bovine serum albumin (BSA). Characterization techniques (SEM, FTIR, and Zeta potential) confirmed the presence of both MNPs and BSA layer dispersed through the structure of the CNTs. The M-RACNTs presented adequate sorption capacity, stable physical/chemical characteristics, and appropriate magnetic properties. Protein exclusion capacity (about 98.5%) was attributed to the chemical diffusion barrier created by the BSA network at the outer surface of the sorbent. The SPME parameters (sample pH, equilibrium time, and desorption conditions) were optimized by design of experiments (fraction factorial planning). The method (validated according to the FDA guidelines) presented adequate selectivity and linearity (coefficient of determination higher than 0.99) at concentrations ranging from the lower limit of quantification (LLOQ) (10 ng mL-1) to the upper limit of quantification (ULOQ) (300 ng mL-1) for both CBD and THC. Precision and accuracy varied from 4.47 to 19.84% (LLOQ) and -6.90 to 17.78% (LLOQ), respectively. Carry-over and matrix effect were not significant. The method was successfully applied to determine plasmatic CBD levels in healthy volunteers attending a single session of oral drug administration and THC levels in frequent cannabis smokers.

Online biological sample preparation with restricted access hybrid carbon nanotubes for determination of anti-smoking drugs.

Untreated samples were injected directly into a column switching system, an online SPE technique, using an extraction column packed with restricted access hybrid carbon nanotubes (RAHCNTs), a novel type of restricted access material, in an ultra-high performance liquid chromatography, coupled to a mass spectrometer (UHPLC-MS/MS). The synthesis of used restricted access material was relatively simple, quick, and reproducible, and had a high material yield. Compared to its predecessor, which is covered with bovine serum albumin (Restricted Access Carbon Nanotubes-RACNTs), RAHCNTs have improved performance when used for the analysis of organic compounds. These molecules have a greater adsorption capacity due to the insertion of hydrophilic monomers (tetraethyl orthosilicate (TEOS), 3-(trimethoxysilyl)propyl methacrylate (MPS), glycerol dimethacrylate (GDMA), and hydroxyethyl methacrylate (HEMA)) in the external layer. In addition, the formation of the hybrid material provides greater chemical and thermal stability, supporting wide pH and temperature ranges, and high concentrations of acidic and basic solutions. It also supports high proportions of organic solvents in the medium. Another significant advantage of the material is its longer lifetime, as it can be reused for approximately 500 analytical cycles without any loss of efficiency, versus 300 for RACNTs. In the method developed to determine anti-smoking drugs (varenicline and bupropion) simultaneously, as well as nicotine and some of their metabolites in human blood serum, the RAHCNTs were capable of retaining the analytes efficiently, whereas the macromolecules were excluded (almost 100%). The method was linear for all the determined analytes (coefficients of determination higher than 0.99), with limits of detection and quantification ranging from 0.6 to 2.5 µg L-1 and from 1.0 to 5.0 µg L-1, respectively. High extraction recovery values were obtained (higher than 88%), as well as inter and intra-assay accuracy and precision results that are in accordance with values recommended by the FDA. The method is promising for therapeutic monitoring and new personalized strategies for patients under antismoking treatment, using a small sample volume (100 µL). In addition, RAHCNTs are capable of simultaneously extracting analytes with very different physical-chemical characteristics.