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1.
Mikrochim Acta ; 188(11): 368, 2021 10 07.
Artigo em Inglês | MEDLINE | ID: mdl-34618242

RESUMO

The production of artificial anti-CB1 antibodies in nanoparticle format is described using the solid-phase imprinting approach. Instead of whole protein imprinting, a linear C-terminus sequence of the receptor comprising 15 amino acids (458-KVTMSVSTDTSAEAL-472) has been used as template, in accordance with the epitope imprinting approach. This sequence is located intracellularly, and it is involved in coupling to Gi/o proteins, being responsible for CB1 receptor desensitisation and internalisation. Developed molecularly imprinted materials were found to be in the nanometre scale, with a particle size of 126.4 ± 10.5 nm at pH 3 (25 ºC) and spherical shape. It was also observed that the size was sensible to temperature changes being reduced to 106.3 ± 15.2 nm at 35 °C. Lower critical solution temperature of this polymer was found to be ≈ 33.4 °C. The affinity and selectivity of the artificial antibody were assessed through dot blot and Western blot experiments. For the latter, recombinant fusion proteins GST-CB1414-472 and GST-CB1414-442 were produced to work respectively as target and negative control proteins. The control protein did not carry the target epitope for being devoid of last 30 amino acids at the C-terminus. The results demonstrated that the anti-CB1 material recognised selectively the target protein, thanks to the presence of the 15-amino acid sequence selected as epitope, which revealed that binding occurred at the C-terminus of the receptor itself. The methodology presented may pave the way for the development of novel imprinted nanomaterials for other proteins included in the superfamily of the G-protein-coupled receptors (GPCR).


Assuntos
Receptor CB1 de Canabinoide
2.
Analyst ; 142(7): 1157-1164, 2017 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-28262862

RESUMO

Environmental pollution by mercury in ambient water samples is a recognized problem worldwide. Sample preservation and transport to the laboratory lead to uncertain analytical results. This study outlines the development of a procedure for on-site electrodeposition of mercury from water samples on a screen-printed gold electrode (SPGE) using portable voltammetric techniques. Once in the laboratory, Hg is analyzed by laser ablation inductively coupled plasma-mass spectrometry (LA-ICPMS) in order to ensure that the required sensitivity and precision levels for environmental sample analysis are reached. A new ablation chamber was intentionally designed for the analysis of SPGE's gold electrode. This cell has a small internal volume of 15 cm3 and the SPGE device perfectly fits inside. This design assures signal stability, avoids elemental fractionation and reduces wash-out time to a few seconds, reducing the analysis time considerably. The proposed method is capable of measuring dissolved mercury at the ng L-1 level (quantification limit 200 ng L-1) with good precision (RSD < 7.6%). The proposed method was tested with the NCS ZC 76303 (NIM-GBW08603) Mercury in water Certified Reference Material.

3.
Anal Bioanal Chem ; 408(3): 747-60, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26537926

RESUMO

Chronic kidney disease (CKD) is a major epidemiologic problem which causes several disturbances in adults and in pediatrics. Despite being a worldwide public health problem, information available for CKD in the pediatric population is scarce. For that reason, an ion-pair reversed-phase liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) method has been developed and validated in order to analyze 16 amino acids, amino acid derivatives, and analogous compounds related to the arginine-creatine metabolic pathway that are suspicious of being increased or decreased in plasma from patients with CKD. The analytical method involved the addition of dithiothreitol, a reducing agent which reduces disulfide and thus giving total aminothiol concentration, as well as a simple precipitation of plasma proteins. Moreover, despite amino acids being usually derivatized to improve their retention time and to enhance their signal, for this method, an ion-pairing reagent was used, thus avoiding the need for derivatization. Subsequently, analysis of plasma from pediatric patients suffering from CKD and control pediatrics was carried out. As a result, glycine, citrulline, creatinine, asymmetric dimethylarginine (ADMA), and symmetric dimethylarginine (SDMA) were significantly increased in patients with CKD, regardless of their creatinine level, whereas in addition to these compounds dimethylglycine was also increased when CKD patients had plasma creatinine concentrations above 12 µg mL(-1), thus all are suggested as potential biomarkers for renal impairment.


Assuntos
Arginina/sangue , Cromatografia Líquida de Alta Pressão/métodos , Creatina/sangue , Espectrometria de Massas/métodos , Metabolômica/métodos , Insuficiência Renal Crônica/sangue , Adolescente , Adulto , Arginina/metabolismo , Biomarcadores/sangue , Criança , Pré-Escolar , Creatina/metabolismo , Feminino , Humanos , Masculino , Insuficiência Renal Crônica/metabolismo
4.
Analyst ; 139(23): 6232-41, 2014 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-25303642

RESUMO

A method based on scanning laser ablation and inductively coupled plasma-mass spectrometry (SLA-ICPMS) and Raman micro-spectroscopy for the detection and identification of compounds consistent with gunshot residue particles (GSR) has been developed. The method has been applied to the characterization of particles resulting from the discharge of firearms using lead-free ammunition. Modified tape lifts were used to collect the inorganic and organic residues from skin surfaces in a single sample. Using SLA-ICPMS, aggregates related to the composition of the ammunition, such as Cu-Zn-Sn, Zr-Sr, Cu-Zn, Al-Ti, or Al-Sr-Zr were detected, but this composition is only consistent with GSR from lead-free ammunitions. Additional evidence was provided by micro-Raman spectroscopy, which identified the characteristic organic groups of the particles as centralite, diphenylamine or their nitrated derivatives, which are indicative of GSR.


Assuntos
Armas de Fogo , Ciências Forenses , Lasers , Espectrometria de Massas/métodos , Metais/química , Pele/química , Humanos
5.
Sci Rep ; 14(1): 11549, 2024 05 21.
Artigo em Inglês | MEDLINE | ID: mdl-38773318

RESUMO

Pediatric chronic kidney disease (CKD) is a clinical condition characterized by progressive renal function deterioration. CKD diagnosis is based on glomerular filtration rate, but its reliability is limited, especially at the early stages. New potential biomarkers (citrulline (CIT), symmetric dimethylarginine (SDMA), S-adenosylmethionine (SAM), n-butyrylcarnitine (nC4), cis-4-decenoylcarnitine, sphingosine-1-phosphate and bilirubin) in addition to creatinine (CNN) have been proposed for early diagnosis. To verify the clinical value of these biomarkers we performed a comprehensive targeted metabolomics study on a representative cohort of CKD and healthy pediatric patients. Sixty-seven children with CKD and forty-five healthy children have been enrolled in the study. Targeted metabolomics based on liquid chromatography-triple quadrupole mass spectrometry has been used for serum and plasma samples analysis. Univariate data analysis showed statistically significant differences (p < 0.05) in the concentration of CNN, CIT, SDMA, and nC4 among healthy and CKD pediatric patients. The predictive ability of the proposed biomarkers was also confirmed through specificity and sensitivity expressed in Receiver Operating Characteristic curves (AUC = 0.909). In the group of early CKD pediatric patients, AUC of 0.831 was obtained, improving the diagnostic reliability of CNN alone. Moreover, the models built on combined CIT, nC4, SDMA, and CNN allowed to distinguish CKD patients from healthy control regardless of blood matrix type (serum or plasma). Our data demonstrate potential biomarkers in the diagnosis of early CKD stages.


Assuntos
Biomarcadores , Insuficiência Renal Crônica , Humanos , Insuficiência Renal Crônica/diagnóstico , Insuficiência Renal Crônica/sangue , Biomarcadores/sangue , Criança , Feminino , Masculino , Pré-Escolar , Adolescente , Taxa de Filtração Glomerular , Metabolômica/métodos , Curva ROC , Estudos de Casos e Controles , Creatinina/sangue , Arginina/análogos & derivados
6.
Anal Chem ; 84(5): 2402-9, 2012 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-22304477

RESUMO

A new method based on scanning laser ablation and inductively coupled plasma-mass spectrometry (LA-ICPMS) for the detection and identification of gunshot residue (GSR) particles from firearms discharges has been developed. Tape lifts were used to collect inorganic residues from skin surfaces. The laser ablation pattern and ICPMS conditions were optimized for the detection of metals present in GSR, such as (121)Sb, (137)Ba, and (208)Pb. Other isotopes ((27)Al, (29)Si, (31)P, (33)S, (35)Cl, (39)K, (44)Ca, (57)Fe, (60)Ni, (63)Cu, (66)Zn, and (118)Sn) were monitored during the ICPMS analyses to obtain additional information to possibly classify the GSR particles as either characteristic of GSR or consistent with GSR. In experiments with real samples, different firearms, calibers, and ammunitions were used. The performed method evaluation confirms that the developed methodology can be used as an alternative to the standard scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) technique, with the significant advantage of drastically reducing the analysis time to less than 66 min.


Assuntos
Armas de Fogo , Lasers , Espectrometria de Massas , Metais/análise , Ciências Forenses , Humanos , Pele/química
7.
J Control Release ; 342: 81-92, 2022 02.
Artigo em Inglês | MEDLINE | ID: mdl-34974029

RESUMO

Secreted protein acidic and rich in cysteine (SPARC) is a matricellular glycoprotein overexpressed by several cancers. Because SPARC shows high binding affinity to albumin, we reasoned that pediatric sarcoma xenografts expressing SPARC would show enhanced uptake and accumulation of nanoparticle albumin-bound (nab)-paclitaxel, a potent anticancer drug formulation. We first evaluated the expression of SPARC in patient-derived xenografts (PDXs) of Ewing sarcoma, rhabdomyosarcoma and osteosarcoma, finding variable SPARC gene expression that correlated well with SPARC protein measured by immunoblotting. We revealed that the activity of the fusion gene chimera EWSR1-FLI1, the genetic driver of Ewing sarcoma, leads to lower expression of the gene SPARC in these tumors, likely due to enriched acetylation marks of the histone H3 lysine 27 at regions including the SPARC promoter and potential enhancers. Then, we used SPARC-edited Ewing sarcoma cells (A673 line) to demonstrate that SPARC knocked down (KD) cells accumulated significantly less amount of nab-paclitaxel in vitro than SPARC wild type (WT) cells. In vivo, SPARC KD and SPARC WT subcutaneous xenografts in mice achieved similar maximum intratumoral concentrations of nab-paclitaxel, though drug clearance from SPARC WT tumors was significantly slower. We confirmed such SPARC-mediated long-term intratumoral accumulation of nab-paclitaxel in Ewing sarcoma PDX with high expression of SPARC, which accumulated significantly more nab-paclitaxel than SPARC-low PDX. SPARC-high PDX responded better to nab-paclitaxel than SPARC-low tumors, although these results should be taken cautiously, given that the PDXs were established from different patients that could have specific determinants predisposing response to paclitaxel. In addition, SPARC KD Ewing sarcoma xenografts responded better to soluble docetaxel and paclitaxel than to nab-paclitaxel, while SPARC WT ones showed similar response to soluble and albumin-carried drugs. Overall, our results show that pediatric sarcomas expressing SPARC accumulate nab-paclitaxel for longer periods of time, which could have clinical implications for chemotherapy efficacy.


Assuntos
Neoplasias Ósseas , Osteossarcoma , Albuminas/metabolismo , Animais , Neoplasias Ósseas/tratamento farmacológico , Humanos , Camundongos , Osteonectina/genética , Osteonectina/metabolismo , Osteonectina/uso terapêutico , Osteossarcoma/tratamento farmacológico , Paclitaxel/uso terapêutico
8.
Environ Sci Technol ; 45(24): 10492-500, 2011 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-22050765

RESUMO

Hexavalent chromium (Cr(VI)) occurrence in soils is generally determined using an extraction step to transfer it to the liquid phase where it is more easily detected and quantified. In this work, the performance of the most common extraction procedure (EPA Method 3060A) using NaOH-Na(2)CO(3) solutions is evaluated using X-ray absorption near edge structure spectroscopy (XANES), which enables the quantification of Cr(VI) directly in the solid state. Results obtained with both methods were compared for three solid samples with different matrices: a soil containing chromite ore processing residue (COPR), a loamy soil, and a paint sludge. Results showed that Cr(VI) contents determined by the two methods differ significantly, and that the EPA Method 3060A procedure underestimated the Cr(VI) content in all studied samples. The underestimation is particularly pronounced for COPR. Low extraction yield for EPA Method 3060A was found to be the main reason. The Cr(VI) present in COPR was found to be more concentrated in magnetic phases. This work provides new XANES analyses of SRM 2701 and its extraction residues for the purpose of benchmarking EPA 3060A performance.


Assuntos
Cromo/análise , Poluentes do Solo/análise , Solo/química , Fracionamento Químico/instrumentação , Fracionamento Químico/métodos , Cromo/química , Poluentes do Solo/química , Estados Unidos , United States Environmental Protection Agency , Espectroscopia por Absorção de Raios X
9.
Biomed Chromatogr ; 25(1-2): 238-57, 2011 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-21058412

RESUMO

The antidepressant citalopram (CIT) is a potent and highly selective serotonin reuptake inhibitor (SSRI) which has been introduced in therapy as a racemic drug. CIT has been used to treat central nervous system affective disorders such as depression, anxiety, obsessive-compulsive disorders, various phobias, borderline personality disorders, bipolar disorders as well as indications wherein inhibition of serotonin reuptake is desired. CIT is demethylated to demethylcitalopram (DCIT) and didemethylcitalopram (DDCIT), which retain considerable activity as SSRIs. Therefore, in recent years, the monitoring of the levels of these analytes in biological fluids for toxicological and therapeutic purposes has been a target worthy of interest. In addition, the differences in activity between CIT enantiomers established the need to assess its behaviour in the field of pharmacological research. It is also necessary to develop analytical methodologies that make it possible to determine the levels of enantiomer concentrations. This review includes most of the published analytical methods for achiral assay of racemic CIT and its metabolites based on high-performance liquid chromatography coupled with UV, fluorescence and mass spectrometry detectors, capillary electrophoresis and gas chromatography with mass spectrometry detectors among others. With regard to the monitoring of enantiomers of CIT and of its metabolites, stereoselective methods based on chiral chromatographic columns, chiral additives in mobile phases and on the derivatization with a chiral reagent are also collected. In addition, different procedures of extraction are mentioned as well as liquid-liquid extraction, solid-phase extraction, solid-phase microextraction, automated online extraction or liquid-phase microextraction in different biological and environmental samples.


Assuntos
Antidepressivos de Segunda Geração/análise , Cromatografia Líquida de Alta Pressão/métodos , Citalopram/análise , Cromatografia Gasosa-Espectrometria de Massas/métodos , Inibidores Seletivos de Recaptação de Serotonina/análise , Antidepressivos de Segunda Geração/metabolismo , Citalopram/metabolismo , Humanos , Inibidores Seletivos de Recaptação de Serotonina/metabolismo , Extração em Fase Sólida , Estereoisomerismo
10.
J Forensic Sci ; 65(4): 1094-1101, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31943223

RESUMO

Currently, aluminum stub with carbon adhesive devices are used to collect inorganic gunshot residues (GSR) from the hands of a shooter. In an ideal shooting case, the gunshot particles do not persist for more than 2 h in the hands of the shooter, provided that the hands have not been washed. However, for forensic analysis and inference, the extended persistence of GSR would be desirable. This study investigates a novel GSR sampling and detection protocol. Sampling was performed in the nostrils using swab devices impregnated in ethylenediaminetetraacetic acid (EDTA). The GSRs persisted for longer periods in nasal mucus than on the hands, and particles were detected 6 h after shooting occurred. The analytical determination was conducted by scanning laser ablation-inductively coupled plasma-mass spectrometry (SLA-ICPMS) which enable the identification of the number of particles and their elemental composition. Seventeen isotope signals corresponding to 13 C, 205 Tl and 15 analytes that are usually associated with the composition of GSR residues were monitored: 27 Al, 29 Si, 31 P, 33 S, 35 Cl, 39 K, 44 Ca, 57 Fe, 60 Ni, 63 Cu, 66 Zn, 118 Sn, 121 Sb, 137 Ba, and 208 Pb. The SLA technique enabled the reduction of the swab analysis time to 40 min. The effectiveness of this methodology was evaluated with two types of firearms: a pistol and a shotgun. The results indicated that the methodology proposed for the analysis of the nasal GSR was effective and that it can improve or complement the forensic analyses and inferences presented in a court.


Assuntos
Antimônio/análise , Bário/análise , Balística Forense/métodos , Chumbo/análise , Mucosa Nasal/química , Ácido Edético , Mãos , Humanos , Isótopos , Lasers de Estado Sólido , Espectrometria de Massas/métodos , Pele/química , Manejo de Espécimes , Ferimentos por Arma de Fogo
11.
J Sep Sci ; 32(20): 3449-56, 2009 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-19784946

RESUMO

A method based on sequential stir bar sorptive extraction followed by automated thermal desorption-GC-MS for the determination of pesticides in underground and superficial water samples has been developed. Retention time locked GC-MS and deconvolution Automated Mass Spectral Deconvolution and Identification System software allows the use of pesticide databases for identification and quantification in routine applications. Quantitation limits and repetitivity using full scan mass spectrometric determination guarantee the applicability of the method, which enables considerable savings to be made in total analysis time, with data processing times of around 2 min/sample.


Assuntos
Cromatografia Gasosa-Espectrometria de Massas/métodos , Praguicidas/análise , Poluentes Químicos da Água/análise , Água/análise , Água Doce/análise , Cromatografia Gasosa-Espectrometria de Massas/instrumentação , Resíduos de Praguicidas/análise , Software , Espanha , Abastecimento de Água/análise
12.
Sci Total Environ ; 687: 319-329, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31207521

RESUMO

Systematic fungicides treatments in vine-growing European ecosystems have been conducted for decades. The goal of this study was to determine the mobility and persistence of 20 fungicides used in two viticultural zones in Atlantic and Mediterranean climates, from the moment of their application until their distribution throughout different compartments of the ecosystem: soil, water, grapes, musts and wines. This study also sought to obtain valuable information to reduce the usage of these products without affecting the health of the vines. For this purpose, different phytosanitary treatments were applied, using dosing criteria based on data provided by meteorological stations, degree-day accumulation, phenological state, and growers' criteria. The observed differences between studied geographical areas were not significant with regard to chemical accumulation in the soil and water; however, they were significantly different regarding to grapes, musts, and wines.


Assuntos
Agricultura/métodos , Ecossistema , Meio Ambiente , Fungicidas Industriais/análise , Vinho , Vitis
13.
J Chromatogr A ; 1177(1): 170-4, 2008 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-18048045

RESUMO

A sensitive and specific method for determining fenitrothion and its main metabolites, 3-methyl-4-nitrophenol and fenitrooxon, in poplar leaves using deuterated isotopes as the internal standard is described. The analytes and the labeled isotopes were extracted from leaves by solid-phase microextraction and subsequently analysed by gas chromatography coupled with mass spectrometry. The method had a chromatographic run time of 17.0 min and good linearity over the range 0.01-10 mg kg(-1). The detection limits ranged between 2.5 and 0.6 microg kg(-1). The isotopic dilution technique allowed improving significantly the repetitivity even using different fibers with the same coating (RSD<5.1%). The method was applied successfully to study the persistence of fenitrothion in forestal matrices in a poplar forest after cannon spray application of the insecticide.


Assuntos
Fenitrotion/análise , Cromatografia Gasosa-Espectrometria de Massas/métodos , Praguicidas/análise , Folhas de Planta/química , Árvores , Indicadores e Reagentes , Padrões de Referência , Reprodutibilidade dos Testes
14.
J Pharm Biomed Anal ; 46(4): 763-70, 2008 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-18222055

RESUMO

A liquid chromatography method was developed for the determination of some frequently prescribed selective serotonin re-uptake inhibitors (SSRI) - citalopram and fluoxetine - and its main metabolites - demethylcitalopram, didemethylcitalopram and norfluoxetine - in human urine samples, using a previous stage of solid-phase microextraction. All the extraction parameters influencing adsorption (extraction time, temperature, pH, ion strength and organic modifier addition) and desorption (desorption time and desorption solvent mixture composition) of the analytes on the fiber have been studied. A satisfactory reproducibility for extraction from urine samples (R.S.D.<10%) was obtained. The linearity for urine ranged from 0.05 to 2 mg l(-1) with limits of detection close to 0.01 mg l(-1), which cover the typical urinary concentrations obtained for citalopram, fluoxetine and their metabolites.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Citalopram/análogos & derivados , Citalopram/urina , Fluoxetina/análogos & derivados , Fluoxetina/urina , Extração em Fase Sólida/métodos , Humanos , Concentração de Íons de Hidrogênio , Concentração Osmolar , Temperatura
15.
J Chromatogr B Analyt Technol Biomed Life Sci ; 852(1-2): 519-28, 2007 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-17329174

RESUMO

Fluoxetine (FLX) and norfluoxetine (NFLX) racemic mixtures were determined by reversed-phase liquid chromatography with fluorescence detection (lambda(exc)=227 nm, lambda(em)=305 nm). The calibration curves prepared from drug-free plasma and brain were linear in the range of 5-1000 ng ml(-1) and 100-40,000 ng g(-1) for doped samples, with detection limits of 3.2 and 2.1 ng ml(-1) in plasma and 31.5 and 26.1 ng g(-1) in brain tissue for FLX and NFLX, respectively. Enantiomer determination was carried out through normal phase HPLC-FD (lambda(exc)=224 nm, lambda(em)=336 nm) after precolumn chiral derivatization with R-1-(1-naphthyl)ethyl isocyanate. Standard curves also prepared in a drug-free matrix were linear for each enantiomer over the range of 2-1000 ng ml(-1) and 20-7000 ng g(-1) with detection limits for the four compounds ranging between 0.2 and 0.5 ng ml(-1) in plasma and between 3.0 and 8.2 ng g(-1) in brain tissue. In both methods the analytes were isolated from the biological matrix by a new solid-phase extraction procedure with recovery in plasma and brain over 90 and 87%, respectively. The repeatability of this extraction procedure was satisfactory within-day and between-day with CV<9.1%. This study also offered the opportunity to obtain an assessment of the potential relationships between the concentration of individual enantiomers of FLX and NFLX in plasma and brain tissue after chronic treatment with racemic FLX at a dose intended to mimic the human plasma concentration of FLX in standard clinical conditions, and therefore should make for more reliable extrapolation of neurochemical findings in other species.


Assuntos
Encéfalo/metabolismo , Cromatografia Líquida de Alta Pressão/métodos , Fluoxetina/análogos & derivados , Fluoxetina/metabolismo , Espectrometria de Fluorescência/métodos , Animais , Fluoxetina/sangue , Ratos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
16.
J Chromatogr A ; 1508: 53-64, 2017 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-28599860

RESUMO

The work presented here explores the grafting of molecularly imprinted nanoparticles (MIN) on silica beads for the development of new chiral stationary phases (CSP). Both solid-phase imprinting and precipitation polymerisation were tested for MIN synthesis though the latter approach was the only one that provided efficient chiral selectors. MIN particles were prepared by iniferter polymerisation initiated by UV radiation, using itaconic acid as functional monomer and ethylene dimethacrylate as cross-linker. This resulted in particles with an average size of 249.0±4.0nm which were covalently immobilised onto chromatographic silica beads. The resultant CSP based on the composite silica beads-MIN was capable of resolving the racemate of the antidepressant drug citalopram and also separating its major metabolites by liquid chromatography, with better efficiency and peak symmetry than other MIP based CSP. The methodology presented here allowed for the quantification of the pharmacologically active enantiomer (+)-(S)-citalopram (SCIT) and its main metabolites (+)-(S)-desmethylcitalopram (SDCIT) and (+)-(S)-didesmethylcitalopram (SDDCIT) in urine, registering mean recoveries that ranged from 91.5 to 103.7% with RSD values that were below 10% in all tested concentration levels (0.1, 0.75 and 5µgmL-1), which confirmed method suitability for the intended application.


Assuntos
Cromatografia Líquida/instrumentação , Polímeros/química , Dióxido de Silício/química , Impressão Molecular/métodos , Nanopartículas/química , Polímeros/síntese química , Porosidade , Dióxido de Silício/síntese química , Estereoisomerismo
17.
Talanta ; 154: 255-62, 2016 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-27154672

RESUMO

In recent years, Cr speciation in dietary supplements has become decisive in the evaluation of their health risks. Despite being an beneficial micronutrient, Cr(III) can be toxic at living organisms at high concentrations, while Cr(VI) is known to be highly toxic and carcinogenic. The main objective of this work was to optimize an analytical methodology for the extraction and accurate quantification of Cr(III) and Cr(VI) in dietary supplements. The extraction of Cr species was carried out with 50mM EDTA solution on a hotplate under optimized conditions. Special attention was paid to bidirectional species transformations. No noticeable oxidation of Cr(III) into Cr(VI) was observed and the reduction to Cr(III) only occurred at very high Cr(VI) concentrations. Cr(III) as Cr(EDTA)(-) complex was chromatographically separated from Cr(VI), retained as CrO4(2-), on an anion exchange column coupled to inductively coupled plasma mass spectrometry (LC-ICP-MS). The limit of quantification (0.08µgg(-1)) was below the limit established for Cr enriched yeasts by the European Union. Eleven dietary supplements were analyzed and Cr(III) and Cr(VI) quantification was carried out by external calibration monitoring (52)Cr isotope and by speciated isotope dilution mass spectrometry (SIDMS) adding (50)Cr(III) and (53)Cr(VI) spikes. Total Cr was also quantified by ICP-MS and mass balance between total Cr and the sum of Cr(III) and Cr(VI) was achieved. In eight of the eleven tested supplements Cr(III) calculated amounts were higher than those indicated by the manufacturer, but only one of them exceeded the 250µgday(-1) recommended by World Health Organization (WHO). In contrast, it is worth noting that Cr(VI) amounts beyond the recommendations of the European Union for Cr enriched yeasts were found in five supplements. These results revealed that more accurate and rigorous quality assurance protocols should be applied to the testing of the final products, including the analysis of both Cr(III) and Cr(VI).


Assuntos
Suplementos Nutricionais , Cromo , Isótopos do Cromo , Espectrometria de Massas
18.
J Chromatogr A ; 1451: 23-32, 2016 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-27207580

RESUMO

This paper reports the development of stir bars with a new MIP based coating, for the selective sorptive extraction of the herbicide glyphosate (GLYP). Molecular imprinting of the polymer has directly been carried out employing underivatised GLYP as the template molecule. Due to the poor solubility of the target compound in organic solvents, the MIP methodology has been optimised for rebinding in aqueous media, being the synthesis and the rebinding steps carried out in water:methanol mixtures and pure aqueous media. The coating has been developed by radical polymerisation initiated by UV energy, using N-allylthiourea and 2-dimethyl aminoethyl methacrylate as functional monomers and ethylene glycol dimethacrylate as the cross-linker. Mechanical stability of the coating has been improved using 1,3-divinyltetramethyldisiloxane in the polymerisation mixture. Under the optimised conditions, the MIP has demonstrated excellent selectivity for the target compound in the presence of structural analogues, including its major metabolites. The applicability of the proposed method to real matrices has also been assessed using river water and soil samples. Registered mean recoveries ranged from 90.6 to 97.3% and RSD values were below 5% in all cases, what confirmed the suitability of the described methodology for the selective extraction and quantification of GLYP.


Assuntos
Glicina/análogos & derivados , Herbicidas/química , Herbicidas/isolamento & purificação , Impressão Molecular/métodos , Água/química , Glicina/química , Glicina/isolamento & purificação , Glicina/metabolismo , Herbicidas/metabolismo , Compostos Orgânicos/química , Polimerização , Polímeros/química , Rios/química , Siloxanas/química , Solo/química , Solubilidade , Solventes/química , Glifosato
19.
Forensic Sci Int ; 246: 79-85, 2015 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-25481775

RESUMO

The identification of characteristic organic gunshot residues (OGSR) provides conclusive evidence in the elucidation of elemental profiles when lead-free ammunition is fired. OGSR also prevents false negatives. Toward this aim, a quick and efficient method based on liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF) was developed to detect and identify 18 gunpowder additives in gunshot residues (GSR). The unequivocal identification of target analytes was assured by using MS/MS mode. Swabs were compared with home-modified tape lift supports covered with a PTFE layer to determine the better sampling technique. The modified tape lift provided better extraction recoveries and enabled the analysis of inorganic and organic GSR simultaneously. The developed method was applied to the analysis of GSR from four different lead-free ammunitions. Diphenylamine and its nitrated degradation products and centralites were identified in all samples, providing strong evidence of GSR.

20.
Talanta ; 116: 448-53, 2013 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-24148428

RESUMO

This paper reports the application of a chiral imprinted polymer (CIP)-coated stir bar for the selective extraction of (+)-(S)-citalopram (SCIT) and its main metabolites, (+)-(S)-desmethylcitalopram (SDCIT) and (+)-(S)-didesmethylcitalopram (SDDCIT), from urine samples. The developed device has been demonstrated to be capable of selectively extracting the three target analytes from urine samples without saturating the imprinted sites. A CIP-coated stir bar sorptive extraction procedure (CIP-SBSE) is proposed for the isolation of SCIT, SDCIT and SDDCIT followed by their subsequent analysis using liquid chromatography ion trap mass spectrometry (LC-ITMS). Deuterated SCIT-d6 was used as an internal standard. The method was validated using a standard procedure, which revealed that a quantification of 5 ng mL(-1) was obtained in urine samples and that the accuracy and precision were within the established values while no matrix effect was observed.


Assuntos
Antidepressivos de Segunda Geração/urina , Citalopram/análogos & derivados , Citalopram/urina , Polímeros/química , Extração em Fase Sólida/normas , Adsorção , Cromatografia Líquida , Humanos , Impressão Molecular/métodos , Padrões de Referência , Sensibilidade e Especificidade , Extração em Fase Sólida/métodos , Espectrometria de Massas por Ionização por Electrospray , Estereoisomerismo , Espectrometria de Massas em Tandem
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