A Reliable and Straightforward Combination of vortex-assisted Dispersive Magnetic solid-phase Extraction with Direct Sorbent Sampling for Highly Sensitive Silver Determination in Water Samples Using Flame and Metal Furnace AAS.

In the present paper, the assessment of vortex-assisted dispersive magnetic solid-phase extraction using amino-functionalized mesoporous combined with direct magnetic sorbent sampling (DMSS) in flame or furnace atomic absorption spectrometry (FAAS or FF-AAS) was demonstrated for highly sensitive silver determination in water samples. The developed method showed significant enrichment factors compared to conventional pneumatic nebulization by FAAS, 607 for DMSS-FF-AAS and 114 for DMSS-FAAS. The analytical curve showed linearity in the range from 5.0 to 70.0 µg L- 1 and 1.0 to 15.0 µg L- 1 and limits of detection of 0.59 and 0.09 µg L- 1 for DMSS-FAAS and DMSS-FF-AAS, respectively. The intra and inter-day precision evaluated as a percentage of the relative standard deviation (RSD,%) ranged from 1.89 to 4.71% for levels of 25.0 and 65.0 µg L- 1. The method was applied in different kinds of water samples without matrix effects, yielding recovery values from 90 to 110%.

Interaction between modified magnetic nanoparticles and human albumin: Kinetics and isotherm studies and application in protein depletion.

Magnetic nanoparticles modified with tetraethyl orthosilicate (Fe3O4@TEOS) and bovine serum albumin (Fe3O4@TEOS@BSA) were evaluated as sorbent in albumin depletion from human serum samples by magnetic dispersive solid phase extraction. Characterization studies were carried out by X-ray diffraction, thermogravimetry, Fourier transform infrared spectroscopy, zeta potential, and scanning electron microscopy. Both nanoparticles also showed high thermal stability and pH-dependent surface charges. The human serum albumin adsorption protocol was optimized using a central composite rotatable design. Nanoparticle mass, pH, and albumin concentration were the most influential variables. Avrami's fractional order and Freundlich isotherm models best fitted the data for human albumin adsorption kinetic and isotherm studies for Fe3O4@TEOS and Fe3O4@TEOS@BSA, and the maximum adsorption capacities were 11.93 and 14.89 mg g-1, respectively. The protein desorption was influenced by the pH of samples and eluent volume. Electrophoresis in a polyacrylamide gel containing sodium dodecyl sulfate showed different patterns of serum protein bands when consecutive depletions were performed. The Fe3O4@TEOS showed greater affinity for HSA and efficiency in depletion. The process was versatile, and the depleted albumin proportion could be controlled by the nanoparticle masses. The proposed method is a powerful sample preparation technique for rapid, reliable, and specific depletion of albumin.

Magnetic particle spray mass spectrometry for the determination of beta-blockers in plasma samples.

Magnetic particle spray mass spectrometry (MPS-MS), an innovative ambient ionization technique proposed by our research group, was employed to determine beta-blockers in human plasma samples. A dispersive solid phase extraction of atenolol, metoprolol, labetalol, propranolol, nadolol, and pindolol was carried out using magnetic molecularly imprinted polymer (M-MIP) particles that were attached to the tip of a metal probe, which was placed in the mass spectrometer inlet. A solvent (1% formic acid in methanol) was dispensed on the particles, and the Taylor cone was formed around them (in high voltage). The analytes were desorbed/ionized and determined by a triple quadrupole mass spectrometer. M-MIP was synthesized with oxprenolol as a pseudo-template, demonstrating good selectivity to beta-blockers compared with no-analog molecules, with an adsorption process occurring in monolayers, according to isotherm studies. Kinetic experiments indicated chemisorption as the predominant M-MIP/analyte interaction. The analytical curves were linear (R2 > 0.98), and the limit of quantification was 3 µg L-1 for all the analytes. Limits of detection ranged from 0.64 to 2.41 µg L-1. Precisions (relative standard deviation) and accuracies (relative error) ranged from 3.95 to 21.20% and -17.05 to 18.93%, respectively. MPS-MS proved to be a simple, sensitive, and advantageous technique compared with conventional approaches. The analyses were fast, requiring no chromatographic separation and without ionic suppression. The method is aligned with green chemistry principles, requiring minimal sample, solvent, and sorbent amounts. MPS-MS successfully integrates sample preparation and ambient ionization mass spectrometry and holds great potential for application with other sorbents, samples, and analytes.

Prediction of pollutant emission characteristics in ISO50001 energy management in the Americas: Uni and multivariate machine learning approach.

The American continent is experiencing significant economic and industrial development driven by sustainability principles. In this context, discussions on improving energy consumption have become increasingly frequent and dynamic across various sectors of civil society, including the implementation of energy efficiency measures as advocated by the ISO50001 energy management standard. However, there is a pressing need to investigate which socioeconomic aspects are responsible for the issuance of this certification in the Americas and how these factors relate to characteristic industrial emissions, especially particulate matter. This study aims to evaluate the socioeconomic factors influencing ISO50001 standard issuance and how these adjusted factors correlate with particulate matter of 2.5 µm and 10 µm dimensions. To achieve this, machine learning techniques were employed, considering the complex nature and risk of data overfitting. Model fitting was performed through multiple lasso regression, and the relationship between the adjusted factors was examined through cross-correlation analysis. The analyses indicate a strong correlation of adjusted macroeconomic indicators, especially with PM2.5, suggesting an association with cardiorespiratory problems and methane-related origins. This work is of great relevance to academia as it proposes new concepts regarding the interaction between energy efficiency standards and particulate matter. For the industrial sector, the adjusted factors provide guidance for standard implementation while also helping to mitigate health issues. Additionally, for the government, these results can assist in formulating policies to address specific health problems related to this area.

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.

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.

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.

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.

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.

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.

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.

Evaluation of the nicotine metabolite ratio in smoking patients treated with varenicline and bupropion.

Background: Smoking is the leading cause of preventable death worldwide. It is responsible for several types of cancer, cardiovascular diseases, and diseases of the reproductive system, among others. Therefore, advances in research are increasingly necessary in order to make smoking cessation treatment more effective. Some studies have investigated the association of the nicotine metabolite ratio (NMR) with general characteristics and treatment outcomes. In the present study, the main aim was to evaluate the NMR in smoking patients from an Assistance Program of a tertiary cardiology hospital. Methodology: Serum samples were collected from 185 patients at T0 (while patients were still smoking and before starting pharmacological treatment). Cotinine and hydroxycotinine analytes were measured using liquid-chromatography tandem mass-spectrometry (LC-MS/MS). By looking at the relationship between hydroxycotinine and cotinine, we can obtain the NMR, with which it is possible to classify patients into slow metabolizers (NMR < 0.31), as well as normal or fast metabolizers (NMR ≥ 0.31). Results: From 185 patients, 55 were considered slow metabolizers and 130 as normal/fast. The metabolite averages were associated with the number of cigarettes smoked per day (p < 0.001 for cotinine and 0.023 hydroxycotinine). However, we were unable to analyze the association of the NMR with general and clinical characteristics of patients under smoking cessation treatment. Conclusion: We were able to evaluate the NMR, and to observe categories of metabolizers in Brazilian patients under pharmacological treatments. Thus, this study can contribute to the indication of a form of analysis, which might form part of the customization of smoking cessation treatments and, consequently, improve the success rates.

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.

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.

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.

Restricted Access Molecularly Imprinted Polymers.

The use of conventional molecularly imprinted polymers (MIPs) for biological sample preparation is a difficult procedure due to the presence of high concentrations of proteins which can obstruct the selective binding sites, decrease the adsorption capacity, and compromise the analytical validation. In this way, modifications of conventional MIPs have been carried out in order to give them the ability to exclude macromolecules. Superficial coverings with hydrophilic groups and/or proteins have been the main procedures to obtain these restricted access molecularly imprinted polymers (RAMIPs ). These materials have been efficiently used for the selective extraction of small molecules from untreated complex matrices (e.g., blood, plasma, serum, and milk), without the need of a pre-deproteinization step. In this chapter, we describe a generic synthesis protocol to obtain RAMIPs as well as the assays to evaluate the protein exclusion efficiency and possible applications in offline and online procedures.

Use of magnetic Fe3O4 nanoparticles coated with bovine serum albumin for the separation of lysozyme from chicken egg white.

Fe3O4 magnetic nanoparticles modified with tetraethyl orthosilicate and bovine serum albumin (Fe3O4@TEOS@BSA) were synthesized and efficiently used to separate lysozyme from egg white. Glutaraldehyde was used to crosslink the bovine serum albumine molecules around the nanoparticles. The surface modifications were attested by transmission electron microscopy, infrared spectroscopy, thermogravimetry analysis, and zeta potential. The material was thermally stable, and its surface charge was pH-dependent. The best lysozyme adsorption and desorption were obtained at pHs 10.0 and 5.0, respectively. The pseudo-second-order model fitted well into the lysozyme adsorption kinetic data and the time for the equilibrium was 15 min. The adsorption equilibrium results were best described by the Freundlich model. Fe3O4@TEOS@BSA particles were very efficient to extract lysozyme from chicken egg, according to the SDS-PAGE analyses. The extracted molecules maintained their enzymatic activity in about 90%. Fe3O4@TEOS@BSA particles were easily recycled, with their reuse being possible 5 times with the same performance.

Magnetic restricted-access carbon nanotubes for the extraction/pre-concentration of organophosphates from food samples followed by spectrophotometric determination.

In this work, magnetic restricted-access carbon nanotubes (M-RACNTs) were synthesized, characterized and used in the dispersive solid-phase extraction (d-SPE) of organophosphate pesticides (OPPs) from food samples (broccoli, eggplant, cauliflower, and soy milk), followed by spectrophotometric determination in a flow injection analysis system. Fe3O4 nanoparticles were incorporated in the multi-walled carbon nanotubes employing dimethylformamide. The dimethylformamide was used as a solvent in the incorporation process, forming the suspension of both particles. The resulting M-CNTs were covered with an external bovine serum albumin (BSA) layer, chemically crosslinked. M-RACNTs were able to efficiently capture OPPs, excluding about 95% of the proteins from food matrices. The analyses were carried out in a flow injection analysis system (FIA), with the spectrophotometric detection (at 560 nm) of the complex formed by the reaction between OPPs, N-bromosuccinimide and rhodamine B. A fractional factorial design method was used to optimize the experimental parameters. The addition/recovery test showed results from 95.5% to 108.9%. Accuracies were checked by comparing the results obtained with the proposed and standard HPLC methods, which were in agreement. The proposed method was linear from 5 to 90 µg L-1 of OPPs, with limits of detection and quantification of 0.74 and 5 µg L-1 and precision of 3.67%, expressed as relative standard deviation. The pre-concentration factor was about 164 times.

Magnetic restricted-access carbon nanotubes for dispersive solid phase extraction of organophosphates pesticides from bovine milk samples.

Magnetic restricted-access carbon nanotubes (M-RACNTs) were synthesised and used for dispersive solid phase extraction of organophosphates (chlorpyriphos, malathion, disulfoton, pirimiphos) from commercial bovine raw milk samples. Due to their magnetic susceptibility, M-RACNTs were easily separated from the samples/solvents using a neodymium magnet, and the extracted organophosphates were analysed by gas chromatography-mass spectrometry. The protein exclusion capacity was about 100%. Kinetic and isotherm data (for M-RACNTs - malathion interaction) were adequately adjusted to the pseudo-second order and Sips models, respectively, and the maximum adsorption capacity was about 0.55 mg g-1. The method presented linear ranges from 5.0 to 40.0 µg L-1 for all analytes, with determination coefficients from 0.9902 to 0.9963. The intra-assay precisions (as relative standard deviation) and accuracies (as relative error) ranged from 10.47 to 19.85% and from -0.18 to -18.80%, respectively, whereas the inter-assay precisions ranged from 6.48 to 18.76% and from -0.22 to 19.49%, respectively for 5.0, 20.0 and 40.0 µg L-1 organophosphates levels. The organophosphates were not stable at 4 and 24 h (relative errors ranged from -39.30 to 72.07% and -69.64 to 75.95%, respectively). Limits of detection ranged from 0.36 to 0.95 µg L-1, and 5 µg L-1 was defined as the limit of quantification for all the analytes. The proposed method was applied in the determination of organophosphates in five commercial milk samples, and no pesticides were detected.

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.