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A solid phase extraction-based (SPE) procedure for simultaneous preconcentration of five tricyclic antidepressants (TCAs), amitriptyline hydrochloride (AMT), nortriptyline hydrochloride (NOR), doxepin hydrochloride (DOX), imipramine hydrochloride (IMI), and clomipramine hydrochloride (CLO) from water samples with determination by HPLC-DAD is proposed. Polymers were characterized by FT-IR, SEM, and thermogravimetric analysis. SPE-based methods were carried out by the preconcentration of 320.0 mL of TCAs at pH 7.0 (buffered with 0.01 mol L

A new analytical method exploiting supramolecular solvent-based microextraction (SUPRAS) combined with ultrasound-assisted extraction to preconcentrate cadmium from medicinal plant, with further determination by thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS), is proposed. The proposed method is based on the cadmium ultrasound-assisted extraction from Ginkgo biloba L. leaf samples with diluted acid (0.10 mol L−1 HNO3), followed by the metal complexation with diethyl dithiophosphate and preconcentration using a supramolecular solvent composed of inverted hexagonal aggregates of dodecanoic acid arranged in tetrahydrofuran/water medium. The limits of detection (LOD) and quantification (LOQ) were found to be 0.11 μg L−1 and 0.36 μg L−1, respectively. Intraday and interday precision assessed in terms of relative standard deviations (RSD, %) were lower than 8.50% to 0.70, 1.75 and 5.00 μg L−1 cadmium solutions. The efficiency of ultrasound-assisted extraction was comparable to microwave-assisted digestion and the method accuracy was checked by analysis of certified reference material (Tomato Leaves, SRM 1573a). Samples of Ginkgo biloba L. were analyzed and cadmium contents between 0.21 and 0.33 μg g−1 were found, thereby showing clearly the importance of investigating toxic metals in medicinal plants. The proposed method is simple, highly sensitive, environmentally friendly and has great potential to be applied in the quality control of medicinal plants aiming trace cadmium determination.

The present study demonstrates the development of a voltammetric sensor based on graphite/restricted access molecularly imprinted poly(methacrylic acid)/SiO2 composite for folic acid determination in pharmaceutical formulation. The insertion of hybrid molecularly imprinted polymer with restricted access (RAM-MIP) into the graphite paste provided enhance in the cathodic peak current for FA. As the electric conductivity of RAM-MIP is very poor, the optimum content was found to be very low (3%, w/w) in the composite. Under optimized conditions (0.1 mol L−1 Britton-Robinson buffer and pH 4.5) using square wave voltammetry (frequency of 150 Hz, pulse amplitude of 90 mV and potential increment of 7 mV) a limit of detection of 0.72 μg L−1 (1.63 nmol L−1) and a linear range from 5.0 to 100.0 μg L−1 (0.01 to 0.23 μmol L−1) were obtained. The method precision was assessed in terms of inter-day (n = 6) and intra-day precision (two consecutive days), whose relative standard deviations (RSD%) ranged from 3.56 to 5.01%. The developed method was applied for FA determination in pharmaceutical samples whose accuracy was attested by means of addition and recovery assays (97.7–105.0%) as well as by high performance liquid chromatography (HPLC) as a reference technique, thus indicating that RAM-MIP sensor might be successfully applied for quality control in the real samples.

Ethylone is a synthetic cathinone recently found in illicit drugs, due to its similar central nervous system-stimulation properties with ‘ecstasy’. Due to the necessity of a rapid and routine on-site determination of ethylone in illicit drugs, electrochemical techniques seem to be an advantageous analytical tool. In this report, a novel voltammetric method using a boron-doped diamond electrode to determinate ethylone was developed and applied in seized street drugs. Electrochemical behavior of ethylone was studied by cyclic, differential pulse (DPV) and square-wave voltammetry (SWV). Chemometric approach was applied for determining ethylone by DPV and SWV. Validation parameters, such as linear range, limit of quantification and detection, precision and accuracy, were evaluated by SWV. Adulterants typically found in seized street drugs were also evaluated as possible interfering compounds. It was observed that oxidation peaks of ethylone and caffeine overlapped, whose interference was further overcome by previous solid phase extraction with octadecyl silica (C18) as sorbent to eliminate the interfering effect of caffeine. The developed method was applied in seized samples and the accuracy was attested by comparison with HPLC-DAD. The results found using the developed electroanalytical methodology enabled to gather some information about the content and amount of ethylone present in seized street drugs found in Brazil.

A novel hybrid ion imprinted polymer (HIIP) is proposed aiming at the development of an online micro-solid phase preconcentration system of Cd2 + coupled to TS-FF-AAS. To evaluate the selective and adsorptive performance of HIIP towards Cd2 +, hybrid non-imprinted polymer (HNIP), organic ion imprinted polymer (OIIP), and the inorganic ion imprinted polymer (IIIP) were synthesized and compared with each other. Adsorption capacity of HIIP was 53% higher than HNIP, and dual-site Langmuir–Freundlich isotherm model showed the best fit for data of both polymers. The preconcentration system coupled to TS-FF-AAS was performed by loading 10.0 mL of Cd2 + solution at pH 7.5 through 80.0 mg of HIIP packed into a micro-column with posterior online elution using 1.0 mol L− 1 HCl/ethanol 1:1 (v/v) mixture. The developed method was highly tolerant for other metal ions Zn2 +, Pb2 +, Cu2 +, Co2 +, Fe2 +, and Hg2 + at analyte:interferent (1:50, m/m) ratio and Ca2 + and Mg2 + at 1:500 (m/m) ratio. Analytical curve ranging from 0.5 to 7.0 μg L− 1, limit of detection of 30 ng L− 1 and preconcentration factor of 14-fold were obtained. Intra-day and inter-day (3 days) experiment precision (n = 10) was, respectively, 3.9 and 0.6% (relative standard deviation, RSD), and 4.4 and 2.4% for concentrations of 0.7 and 6.5 μg L− 1. Sensitivity of method (Abs L μg− 1) was about 3.3, 2.2 and 1.9-fold higher when compared to preconcentration method using HNIP, OIIP and IIIP, respectively, thus clearly showing that hybrid polymer and imprinting process enhance Cd2 + adsorption. Addition and recovery experiments ranging from 94 to 106% in mineral, lake water and tap water, urine and cigarette samples attested the feasibility of method for analysis of matrices containing different components. Moreover, the accuracy of method was checked from analysis of certified reference material (DOLT-4, fish liver), being the obtained value of 23.9 ± 0.6 mg kg− 1 (n = 3) statistically equal to the certified value of 24.3 ± 0.8 mg kg− 1, by applying Student t-test at 95% confidence level.

In the present paper an amperometric sensor based on graphite-SiO 2 /Al 2 O 3 /Nb 2 O 5 -methylene blue (GRP-SiAlNb-MB) composite has been successfully prepared for dopamine (DA) determination in real samples. The electrochemical behavior of DA at the GRP-SiAlNb-MB has been evaluated by employing cyclic voltammetry. The best ratio (m/m) of GRP-SiAlNb-MB composite was found to be 1:0.54. Under optimized conditions (pH 7.5 in 0.15 mol L −1 phosphate buffer) the amperometry method responds linearly to DA from 5.0 up to 500.0 μmol L −1 ( r = 0.995) with limits of detection and quantification of 1.49 and 4.97 μmol L −1 , respectively. The developed method was successfully applied for DA determination in real samples of pharmaceutical formulations and can be used for routine quality control analysis of pharmaceutical formulations containing DA. The use of inorganic matrix SiAlNb was found to be very useful to adsorb MB in the composite material with further improvement of the anodic peak current of DA.

The aim of this study is to evaluate the adsorptive performance of nano-carbon black for removing pesticides from aqueous media. The characterization of material was accomplished by SEM, FT-IR, TGA as well as by surface area measurements. Pesticide adsorption occurs in a wide pH range (2–7). The nano-carbon black presented a high surface area (306.9 m 2 g −1 ) and the maximum adsorption capacities were found to be 74.4, 63.1, 59.7, 89.5 and 105.2 mg g −1 for carbendazim, tebuthiuron, hexazinone, diuron and ametryn, respectively, obtained from dual site Langmuir-Freundlich isotherm model. From kinetic data, the equilibrium times were found to be 30 min for diuron, 80 min for ametryn and 45 min for the other pesticides, while experimental data were well adjusted to pseudo-second-order models, thus suggesting that the adsorption of pesticides takes place in binding sites with different energies. From thermodynamic adsorption parameters, it was observed for all pesticides negative values of ΔG and ΔH, thus suggesting that the adsorption process is spontaneous and of exothermic nature. Multiresidue adsorption was not affected by the presence of 1.0 mg L −1 humic acid. When compared to other carbonaceous adsorbent materials, nano-carbon black has as the main advantages the low equilibrium time, low cost and satisfactory adsorption capacity.

This work describes a novel methodology to analyze four tricyclic antidepressants (amitriptyline, doxepin, imipramine and, nortriptyline) in urine samples by combining supramolecular microextraction and paper spray ionization mass spectrometry (PS-MS). The proposed method uses a supramolecular solvent in which reverse micelles of 1-decanol are dispersed in tetrahydrofuran (THF)/water. The extraction of the tricyclic antidepressants at pH 9.0 requires a sample volume of 10.0 mL, short extraction time (1.0 min of extraction and 5 min of centrifugation), low amounts of organic solvent (50 μL of 1-decanol and 200 μL of THF), and provides high preconcentration factors: 96.9 to amitriptyline, 93.6 to doxepin, 71.3 to imipramine, and 146.9 to nortriptyline. The quantification by PS-MS is fast and straightforward because chromatographic separation is not required and all analytes were determined simultaneously. The limits of detection (LOD), quantification (LOQ), and the precision (RSD, %) of the developed method ranged between 5.2 and 8.6 μg L−1, 17.4–28.7 μg L−1 and 1.3–12.9%, respectively. Urine samples of five individuals (three males and two females) were used for accuracy evaluation. The accuracy obtained in these spiked urine samples at μg L−1 levels varied from 95.3 to 112.0%. The method also provided clean mass spectra with a high signal-to-noise ratio, which demonstrates the analytical appeal combination of supramolecular microextraction with determination by paper spray mass spectrometry.

O desenvolvimento de materiais poliméricos adsorventes está diretamente relacionado com a energia de interação entre analito e monômero. Deste modo, um estudo empregado simulação computacional foi realizado com o intuito de avaliar dezoito monômeros funcionais, e a partir deste sintetizar polímeros reticulados contendo alta eficiência de adsorção para os antidepressivos tricíclicos [amitriptilina (AMT), clomipramina (CLO), doxepina (DOX), imipramina (IMI) e nortriptilina (NOR)] em meio aquoso. Entre os monômeros avaliados o ácido acrílico (AA) e ácido metacrílico (MAA) foram escolhidos para a síntese dos adsorventes poliméricos, devido à similaridade em suas estruturas e a discrepância nas energias de interação calculadas pela simulação computacional. Os polímeros obtidos foram caracterizados por espectroscopia na região do infravermelho (FT-IR), análise termogravimétrica (TGA), microscopia eletrônica de varredura (MEV), espalhamento dinâmico de luz (DLS), análise elementar (CHN), efeito Swelling (inchaço) e dados texturais. A adsorção dos antidepressivos tricíclicos (ADTs) foi favorecida em pH 7,0 para ambos os polímeros. No estudo de cinética de adsorção o poli(AA-co-EGDMA) se destacou em relação ao poli(MAA-co-EGDMA), devido à alta capacidade adsortiva em tempos reduzidos. A partir dos parâmetros termodinâmicos verificou-se que o processo adsortivo é caracterizado como endotérmico e espontâneo, acompanhado de um aumento na desordem na interface sólido-solução. Além do alto fator de pré-concentração o método desenvolvido apresentou baixos valores de limite de detecção e quantificação. Os limites de quantificação para a determinação de DOX, NOR, IMI, AMT e CLO empregando o poli(AA-co-EGDMA) foram de 0,17, 0,40, 0,55, 0,11 e 0,20, respectivamente. Os limites de quantificação para a determinação de DOX, NOR, IMI, AMT e CLO empregando o poli(MAA-co-EGDMA) foram de 0,19, 0,29, 0,37, 0,11 e 0,40, respectivamente. O método proposto foi aplicado em amostras de águas e testes de adição e recuperação foram realizados, sendo encontradas concentrações próximas as adicionadas, o que demonstra a eficiência de ambos materiais poliméricos para a determinação de ADTs em amostras aquosas. The development of polymeric adsorbents is directly related to the interaction energy between analyte and monomer. In this way, a computational simulation study was carried out with the aim of evaluating eighteen functional monomers, and from this synthesize crosslinked polymers containing high adsorption efficiency for the tricyclic antidepressants (TCAs) [amitriptyline (AMT), clomipramine (CLO), doxepin (DOX), imipramine IMI) and nortriptyline (NOR)] in aqueous medium. Among the evaluated monomers acrylic acid (AA) and methacrylic acid (MAA) were chosen for the synthesis of the polymeric adsorbents, due to the similarity in their structures and the discrepancy in the interaction energies calculated by the computational simulation. The obtained polymers were characterized by infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), dynamic light scattering (DLS), elemental analysis (CHN), swelling effect and textural data. The adsorption of tricyclic antidepressants (TCAs) was favored at pH 7.0 for both polymers. In the study of adsorption kinetics, the poly(AA-co-EGDMA) was highlighted in relation to the poly(MAA-co-EGDMA), due to the high adsorptive capacity in reduced times. From the thermodynamic parameters, it was verified that the adsorption process is characterized as endothermic and spontaneous, accompanying an increase in the disorder in the solid-solution interface. In addition to the high preconcentration factor, the developed method presented low limits of detection and quantification. The limits of quantification for the DOX, NOR, IMI, AMT and CLO determination employing the poly(AA-co-EGDMA) were 0.17, 0.40, 0.55, 0.11 and 0.20, respectively. The limits of quantification for the DOX, NOR, IMI, AMT and CLO determination employing the poly(MAA-co-EGDMA) were 0.19, 0.29, 0.37, 0.11 and 0.40, respectively. The proposed method was applied in water samples and addition and recovery tests were performed and concentrations close to those added were found, which demonstrates the efficiency of both polymeric materials for TCAs determination in aqueous samples.

This paper reports the synthesis of novel nanocomposite based on multi-walled carbon nanotubes (MWCNT) covalently bonded by molecularly imprinted poly(methacrylic acid-hemin) (MIP-MWCNT) using tert-butylhydroquinone (TBHQ) as template molecule and its use in the construction of electrochemical sensor. Chemical, physical and morphological structure of nanocomposite was characterized by FT-IR, TGA, SEM, TEM and textural analysis. The electrochemical sensor highly selective to TBHQ was prepared by drop-casting a suspension of nanocomposite on the surface of a glassy carbon electrode. From cyclic voltammetry, it was observed that the electrochemical sensor modified with MIP-MWCNT exhibited great recognition performance, higher analytical response and catalytic properties towards the TBHQ when compared to NIP-MWCNT (nanocomposite polymerized without adding TBHQ), MIP-MWCNT without hemin and MIP-hemin without MWCNT. Such results demonstrated the synergic effect of imprinting influence, MWCNT and hemin in improving the performance of electrochemical sensor. From chronoamperometric measures, the electrochemical sensor modified with MIP-MWCNT could recognize TBHQ selectively in the presence of electroactives and structurally similar compounds. Under optimized conditions by pulse differential voltammetry (pulse amplitude of 100 mV, pulse time of 25 ms and scan rate of 10 mV s−1) and measures in 0.15 mol L−1 H2SO4, the proposed method successfully enabled the simultaneous determination of TBHQ and butylated hydroxyanisole (BHA), yielding limits of detection of 0.85 and 0.50 μmol L−1, respectively. The feasibility of the method was checked by simultaneous determination of TBHQ and BHA in soybean oil, margarine, mayonnaise and biodiesel, whose results were statistically equal to those achieved by high performance liquid chromatography (HPLC).

Made available in DSpace on 2018-12-11T17:00:20Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-03-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) In the present study new molecularly imprinted adsorbents based on poly(methacrylic acid) and poly(acrylic acid) have been synthesized, characterized and evaluated as selective materials for the adsorption of diuron. Morphological, textural data and the presence of functional groups in the polymer have been evaluated by means of SEM, nitrogen adsorption-desorption assays and FT-IR, respectively. Two functional monomers were evaluated for the MIP synthesis, methacrylic acid (MIPMAA) and acrylic acid (MIPAA), and the first one showed higher selectivity and better adsorption towards diuron in the presence of competitor molecules, carbofuran and 2,4-D. The experimental adsorption isotherm of diuron has been obtained at pH 7.0 in phosphate buffer (0.05 mol L-1):acetonitrile (1:2, v/v) medium and equilibrium time of 180 min. The respective maximum adsorption capacities (MAC) of MIPMAA and MIPAA were found to be 14.58 and 7.32 mg g-1. One should note that MAC of MIPAA and its respective blank polymer (NIPAA) was very similar to each other, while for the MIPMAA its MAC was significantly higher (14.58 mg g-1) than the MAC of NIPMAA (6.12 mg g-1). Such result demonstrates the great influence of monomer on the adsorption and selectivity of MIP. Adsorption kinetic data were well fitted to pseudo-first-order and intraparticle diffusion models, while the adsorption isotherms showed good fit to the isotherm of Langmuir-Freundlich for two sites (LF-2) and one site (LF-1), but the former one allowed insight into the adsorption mechanism with more details. Departamento de Química Analítica Instituto de Química Universidade Do Estado de São Paulo (UNESP) Departamento de Química Universidade Estadual de Londrina (UEL) Campus Universitário, Rod. Celso Garcia Cid, PR 445 Km 380 Instituto Nacional de Ciência e Tecnologia (INCT) de Bioanalítica Universidade Estadual de Campinas (UNICAMP) Instituto de Química Departamento de Química Analítica, Cidade Universitária Zeferino Vaz s/n Departamento de Química Analítica Instituto de Química Universidade Do Estado de São Paulo (UNESP) FAPESP: 2011/03008-7 CNPq: 305552/2013-9 CNPq: 472670/2012-3 CNPq: 481669/2013-2

In the present study a hybrid molecularly imprinted poly(methacrylic acid-trimethylolpropane trimethacrylate)-silica (MIP) was synthesized and modified with (3-glycidyloxypropyl)trimethoxysilane (GPTMS) with posterior opening of epoxy ring to provide hydrophilic properties of material in the extraction of folic acid from aqueous medium. The chemical and structural aggregates of hybrid material were characterized by means of Fourier Transform Infrared (FT-IR), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Thermogravimetric analysis (TGA) and textural data. Selectivity data of MIP were compared to non-imprinted polymer (NIP) through competitive sorption studies in the presence of caffeine, paracetamol or 4-aminobenzamide yielding relative selectivity coefficients (k′) higher than one unit, thus confirming the selective character of MIP even in the presence of structurally smaller compounds than the folic acid. The lower hydrophobic sorption by bovine serum albumin (BSA) in the MIP as compared to unmodified MIP proves the hydrophilicity of polymer surface by using GPTMS with opening ring. Under acid medium(pH 1.5) the sorption of folic acid onto MIP from batch experiments was higher than the one achieved for NIP. Equilibrium sorption of folic acid was reached at 120 min for MIP, NIP and MIP without GPTMS and kinetic sorption data were well described by pseudo-second-order, Elovich and intraparticle diffusion models. Thus, these results indicate the existence of different binding energy sites in the polymers and a complex mechanism consisting of both surface sorption and intraparticle transport of folic acid within the pores of polymers.

A new hybrid molecularly imprinted polymer (MIP) combined with restricted access (RAM) has been synthesized based on random free-radical polymerization and a sol–gel process. From competitive adsorption studies by using the RAM-MIP and RAM-NIP with folic acid and structurally similar molecules (caffeine, 4-aminobenzamide or paracetamol), relative selectivity coefficients (k) higher than one unit were achieved, indicating good recognition selectivity for folic acid. The percentage of BSA protein exclusion was higher for the RAM-MIP (55.3 ± 2.0) as compared to the MIP (35.9 ± 2.5%). The solid phase extraction (SPE) procedure was performed by loading the acid extract from milk powder samples previously submitted to saponification and acidification with 10% trichloroacetic acid (TCA) until pH 1.5, through 100 mg of RAM-MIP packed into SPE cartridge. The elution step was carried out by using a mixture of acetonitrile : 0.266 mol L−1 acetate buffer at pH 5.7 (15 : 85, v/v), the same composition of the mobile phase of HPLC. The intra-day precision (n = 10) of the procedure assessed as relative standard deviation (RSD) was 4.7 and 4.1% for the respective concentrations of 20.0 and 150.0 μg L−1. The applicability of the method was attested by analysis of different brands of milk powder samples fortified with folic acid, as well as by high recovery percentages 95.0–108.4% obtained upon addition and recovery tests. The cleanup process accomplished by RAM-MIP was so efficient that very few remaining matrix components were detected in the eluate by high performance liquid chromatography.

A SiO2/Al2O3/Sb2O5 mixed oxide was synthesized via a sol-gel method and applied to the on-line preconcentration of Ni(II) with determination by flame atomic absorption spectrometry. The mixed oxide was characterized by infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray fluorescence, thermogravimetric analysis, and the specific surface area. Analysis was performed by percolating 20.0 mL of sample at pH 7.1 through 100 mg of SiO2/Al2O3/Sb2O5 packed into a mini-column at 9.5 mL min−1. Under the optimum conditions, a preconcentration factor of 77.5-fold, linear dynamic range from 5.0 to 270.0 µg L−1, and limits of detection and quantification of 0.48 and 1.61 µg L−1 were obtained. The effects of several concomitant ions were evaluated and no interferences were observed. The method was employed for the analysis of water with good recoveries (92.9–100.6%) and the accuracy was verified by using a marine sediment certified reference material (MESS-3).

This work deals with simultaneous determination of hydrochlorothiazide (HCTZ) and valsartan (VAL) by square-wave voltammetry using a cathodically pretreated boron-doped diamond electrode. The method exhibits linear responses to HCTZ and VAL in the concentration range 1.97–88.1 μmol L −1 and 9.88–220 μmol L −1 , respectively, in a Britton–Robinson buffer solution (pH 5.0), with detection limits of 0.639 μmol L −1 and 0.935 μmol L −1 , respectively. The proposed method was successfully applied in the simultaneous determination of both antihypertensives in combined dosage forms and the results are in close agreement with those obtained using high performance liquid chromatography method.

The present study describes the synthesis of molecularly imprinted polyacrylamide and its applications for the selective adsorption of glyphosate (GP) and its degradation product, aminomethylphosphonic acid (AMPA). The molecularly imprinted polymers (MIPs) were prepared by polymerization in a homogeneous medium, which is known as the “in bulk” method. The reagents used for the synthesis were acrylamide (AAm) as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linking reagent, and azobisisobutyronitrile (AIBN) as the radical initiator. The selectivity of the MIPs was evaluated with non-imprinted polymers (NIPs) for each polymer synthesized without the template molecule. Polymer characterization was carried out by thermogravimetry (TG) analysis, Fourier-transform infrared spectroscopy (FT-IR), elemental analysis, and scanning electron microscopy (SEM). The experimental data on the adsorption kinetics were best explained by a pseudo-second-order kinetic model. The Langmuir–Freundlich nonlinear isotherm model for two adsorption sites had the best fit to the experimental data for glyphosate and AMPA. The maximum adsorption capacities were 3.37 and 4.74 mg g − 1 for MIP–GP and MIP–AMPA, respectively. According to the relative selectivity ( k ′) values, higher selectivities for the analytes were observed in aqueous medium for the MIPs than for the NIPs.

The present paper describes the feasibility of on-line preconcentration of nickel ions from aqueous medium on Ni(II)-imprinted cross-linked poly(methacrylic acid) (IIP) synthesised through a double-imprinting method and their subsequent determination by FAAS. The proposed method consisted in loading the sample (20.0 mL, pH 7.25) through a mini-column packed with 50 mg of the IIP for 2 min. The elution step was performed with 1.0 mol L−1 HNO3 at a flow rate of 7.0 mL min−1. The following parameters were obtained: quantification limit (QL) – 3.74 µg L−1, preconcentration factor (PF) – 36, consumption index (CI) – 0.55 mL, concentration efficiency (CE) – 18 min−1, and sample throughput – 25 h−1. The precision of the procedure assessed in terms of repeatability for ten determinations was 5.6% and 2.5% for respective concentrations of 5.0 and 110.0 µg L−1. Moreover, the analytical curve was obtained in the range of 5.0–180.0 µg L−1 (r = 0.9973), and a 1.64-fold increase in the method sensitivity was observed w...

The main purpose of this research was to synthesize crosslinked poly(4-vinylpyridine-ethylene glycol dimethacrylate) and evaluate its feasibility for highly sensitive and selective determination of Cd in water samples by using flow injection flame atomic absorption spectrometry. The crosslinked polymer, prepared by bulk polymerization, was characterized by FTIR spectrometry and scanning electron microscopy. The flow injection solid-phase method was based on preconcentration of 20.0 mL of sample through 100 mg of the polymer packed into a minicolumn at pH 8.25 using a flow rate of 6.0 mL/min, followed by elution with 1.0 M HNO3. The sample solution parameters influencing the preconcentration behavior of Cd ions, such as pH, buffer concentration, and flow rate, were simultaneously studied and optimized using a Doehlert matrix. Values of 0.10 μg/L, 2.0–210 μg/L, 32.3, 18/h, 9.7/min, and 0.62 mL were obtained for LOD, linear range, preconcentration factor, sample throughput, concentration efficiency, and consumption index, respectively. The effect of the presence of the inorganic cations Pb(II), U(IV), Co(II), Hg(II), Cu(II), As(III), Mg(II), Sb(III), Ni(II), Th(IV), Ba(II), and Ca(II) on the method was studied, and the preconcentration of Cd was observed to have no interference. The accuracy of the method was assessed by analysis of natural water samples using addition and recovery tests and inductively coupled plasma/MS as a reference technique, as well as by analysis of a standard reference material of trace elements in water.

Computational simulations of eighteen functional monomers to produce cross-linked polymers containing high adsorption efficiency to tricyclic antidepressants [amitriptyline (AMT), clomipramine (CLO), doxepin (DOX), imipramine (IMI) and nortriptyline (NOR)] in aqueous medium were evaluated and selected to polymers synthesis. Among them, acrylic acid (AA) and methacrylic acid (MA) were chosen to synthesize the poly(AA-co-EGDMA) and poly(MA-co-EGDMA) adsorbents due to their contrasting calculated interaction energies and to their similar chemical structures. The polymers were characterized by dynamic light scattering (DLS), elemental analysis, swelling effect and textural data. Higher tricyclic antidepressants adsorptions were obtained at pH 7.0 to both polymers, with superior results to poly(AA-co-EGDMA). From the adsorption kinetics the pseudo-second order, Elovich and intraparticle diffusion models showed good adjustments on experimental data of both polymers. The adsorptive predicted by the pseudo-second order model for the poly(AA-co-EGDMA) were 537, 480, 441, 522, 542 μmol g−1 to AMT, CLO, DOX, IMI and NOR, respectively, while to poly(MA-co-EGDMA) were 243, 120, 226, 205 and 178 μmol g−1. By the thermodynamic parameters, the adsorption process was characterized as endothermic and spontaneous, accompanied by an increase of disorder at the solid-solution interface. The higher adsorption capacity of poly(AA-co-EGDMA) to the antidepressants than to the poly(MA-co-EGDMA) demonstrates agreement with the interaction predicted by the computational simulation, showing its efficiency on predict the best functional monomer to synthesize polymeric adsorbents.

Nickel hydroxide films were electrosynthesized in the presence of different diluted surfactant solutions by galvanostatic electroprecipitation. Lamellar α-Ni(OH)2 films are obtained using cationic surfactant cetyltrimethylammonium bromide (CTAB), anionic surfactant sodium dodecyl sulfate (SDS), and also neutral surfactant Tween® 80. The films were structurally and morphologically characterized by X-ray diffraction, thermal gravimetric analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy, and electrochemically by cyclic voltammetry and electrochemical quartz crystal microbalance (EQCM). The results evidenced that SDS remains intercalated between the lamellae of α-Ni(OH)2. Albeit the presence of CTAB and Tween® 80, it was noticed in FTIR spectra that the surfactants did not intercalate. The morphology was affected by the presence of different surfactants. All studied surfactants displaced the oxidation potential (E O) of Ni2+/Ni3+ process to less positive values. Also, the presence of surfactants improved the electrode charge efficiency and the charge response for the same number of moles of nickel ions deposited. The ratio of the charge and frequency change is 4.4 times bigger for films deposited with SDS when compared with pure α-Ni(OH)2 films.

A novel poly(methacrylic acid) material (IIP/CTAB) was prepared by a hierarchical double-imprinting process with Ni2+ ion and cationic surfactant—cetyltrimethylammonium bromide (CTAB) as templates, and it was employed to adsorb Ni2+ ions from aqueous medium. Other poly(methacrylic acid) materials— single-imprinted (IIP/no CTAB) and nonimprinted (NIP/no CTAB) were investigated in adsorption studies. All the synthesized polymers were characterized by FTIR, SEM, and nitrogen adsorption–desorption isotherm. The maximum Ni2+ adsorption capacities of IIP/CTAB and NIP/no CTAB were found to be 33.31 and 18.64 mg g–1, respectively, at pH 7.25. The relative selectivity coefficient (k′) values for Ni2+/Cu2+, Ni2+/Mn+, Ni2+/Co2+ and Ni2+/Pb2+ systems were higher than 1, thus confirming the significant improvement in the selectivity of the polymer. The kinetic data were described very well by the pseudo-second-order model, thereby confirming the chemical nature of the Ni2+ adsorption (chemisorption), whereas the dual-...

Carbon black (CB) grafted with 3-mercaptopropyltrimethoxysilane (3-MPTMS) was used as solid phase extractor for Cd2+ in a flow injection system coupled to flame atomic absorption spectrometry (FAAS). The influence of pH, buffer concentration, preconcentration flow rate and eluent concentration on preconcentration of Cd2+ were investigated by means of chemometric tools. The characterization of the adsorbent chemically modified was performed by Fourier transform infrared, scanning electron microscopy, energy dispersive X-ray spectroscopy, thermogravimetric analysis, Raman spectroscopy and textural analysis. To perform the on-line preconcentration, 20.0 mL of a pH 7.0 Cd2+ solution at a flow rate of 4.0 mL min−1 was loaded through 30.0 mg of modified CB and then eluted with 1.0 mol L−1 HCl toward the FAAS instrument. The limits of detection and quantification were found to be 0.20 and 0.66 µg L−1, respectively. Addition and recovery tests carried out in real samples (mineral, tap and saline waters, and cigarette sample) and the analysis of certified reference material (TORT-2, lobster hepatopancreas reference) attested the applicability of proposed method.

The present paper describes the synthesis of a new chemically modified cellulose microfiber through oxidation with sodium periodate and functionalization with N,N'-bis (2-aminoethyl)-1,2-ethanediamine for the fast and selective preconcentration of Cd(II) ions in flow system analysis. The new sorbent was characterized by FTIR, SEM, and surface area values. The uptake behavior of Cd(II) ions onto this sorbent was evaluated from kinetic data, pseudo-first-order and pseudo-second-order models, as well as from Langmuir, Freundlich and Langmuir-Freundlich adsorption isotherms. The maximum sorption capacity of 4.59 mg g(-1) was estimated by the Langmuir-Freundlich model with fast kinetics for the sorption of Cd(II) described by the pseudo-second-order kinetic model. After characterization, the sorbent was packed in a mini-column, and a fast flow injection preconcentration system for Cd(II) determination by FAAS was developed. The best Cd(II) preconcentration condition, obtained by means of factorial design and response surface methodology, was achieved at pH 9.36 and a flow rate of 10 mL min(-1) followed by elution with 1.0 mol L(-1) nitric acid. By using 78 s preconcentration time, fast and highly sensitive determination of Cd(II) ions could be achieved with a limit of quantification of 0.20 μg L(-1), preconcentration factor of 26, consumption index of 0.5 mL, concentration efficiency of 20 min(-1), and sample throughput of 39 h(-1). The repeatability for 10 replicate determinations was found to be 7.8 and 2.5% for Cd(II) ion concentrations of 5.0 and 100.0 μg L(-1), respectively. The new sorbent efficiency for the interference-free preconcentration of Cd(II) ions was assessed by analysis of tap, mineral and lake waters, as well as synthetic seawater and normal saline waters. Furthermore, complex samples, such as biological samples, could be analysed by the proposed method in accordance with the accuracy attested by analysis of certified reference materials, TORT-2 (lobster hepatopancreas), and DOLT-4 (dogfish liver).

The present study describes the adsorption characteristic of Cd(II) onto Nb2O5/Al2O3 mixed oxide dispersed on silica matrix. The characterization of the adsorbent has been carried out by infrared spectroscopy (IR), scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS), energy dispersive X-ray fluorescence analysis (EDXRF) and specific surface area (SBET). From batch experiments, adsorption kinetic of Cd(II) was described by a pseudo-second-order kinetic model. The Langmuir linear isotherm fitted to the experimental adsorption isotherm very well, and the maximum adsorption capacity was found to be 17.88 mg g−1. Using the effective material, a method for Cd(II) preconcentration at trace level was developed. The method was based on on-line adsorption of Cd(II) onto SiO2/Al2O3/Nb2O5 at pH 8.64, in which the quantitative desorption occurs with 1.0 mol L−1 hydrochloric acid towards FAAS detector. The experimental parameters related to the system were studied by means of multivariate analysis, using 24 full factorial design and Doehlert matrix. The effect of SO42−, Cu2+, Zn2+ and Ni2+ foreign ions showed no interference at 1:100 analyte:interferent proportion. Under the most favorable experimental conditions, the preconcentration system provided a preconcentration factor of 18.4 times, consumption index of 1.08 mL, sample throughput of 14 h−1, concentration efficiency of 4.35 min−1, linear range from 5.0 up to 35.0 μg L−1 and limits of detection and quantification of 0.19 and 0.65 μg L−1 respectively. The feasibility of the proposed method for Cd(II) determination was assessed by analysis of water samples, cigarette sample and certified reference materials TORT-2 (Lobster hepatopancreas) and DOLT-4 (Dogfish liver).

Made available in DSpace on 2018-12-11T16:58:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-11-10 An electrochemical sensor modified with a molecularly imprinted polymer (MIP) and carboxyl-functionalized multi-walled carbon nanotubes (MWCNT-COOH) was developed for the sensitive and selective detection of diuron in river water samples. An MIP was obtained by bulk polymerization using the best monomer (methacrylic acid) selected by computational simulation. The surface characteristics of the MIP and NIP (control polymer) samples were evaluated by means of surface area and pore volume determinations, using the BET method. The adsorption efficiency of the MIP was determined in adsorption tests that revealed high adsorption, relative to the control polymer. In addition, MWCNTs functionalized with carboxyl groups were used to enhance the performance of the sensor. Electrochemical studies of diuron using the MIP and MWCNT-COOH immobilized on a carbon paste electrode were performed with wave square voltammetry (SWV). The analytical parameters pH, buffer composition, and amounts of MWCNT-COOH and MIP were investigated and optimized. Excellent results were obtained with a linear range of between 5.2 × 10-8 and 1.25 × 10-6 mol L-1, detection limit of 9.0 × 10-9 mol L-1, and sensitivity of 5.1 × 105 μA L mol-1. The MWCNT-COOH-MIP/CPE showed an enhanced electrochemical response, with sensitivity 7.9-fold greater than for a plain carbon paste electrode (CPE). Application of the sensor using river water samples resulted in recoveries between 96.1 and 99.5% and RSD

O presente trabalho descreve a síntese de um polímero híbrido molecularmente impresso contendo acesso restrito como um novo material sorvente para a extração de ácido fólico em amostras de leite. A caracterização do material foi realizada por FT-IR, TGA, SEM, TEM e análise de área superficial, volume e tamanho de poros, cujos resultados confirmaram a presença da rede orgânica e inorgânica, como também a presença de mesoporos. A partir dos estudos cinéticos obteve-se o tempo de equilíbrio de 390 minutos, resultando em uma sorção de 5,6 mg de ácido fólico (AF) por grama de sorvente. A formação de sítios de sorção seletivos foi confirmada pela sorção competitiva de soluções binárias de AF:concomitante (cafeína, ácido úrico, 4-aminobenzamida e paracetamol), na qual os coeficientes de seletividade relativos encontrados foram de 1,82, 1,33, 4,37 e 1,53, respectivamente. A porcentagem de exclusão de albumina sérica bovina para o MIP-RAM foi de 55 ± 2 e para o MIP de 35 ± 2%. Os estudos utilizando o polímero molecularmente impresso em extração em fase sólida (MISPE) demonstraram satisfatória limpeza dos cromatogramas sem a necessidade de lavagem do cartucho para remoção de interferências, tornando possível a injeção direta do eluato no sistema cromatográfico. O método MISPE apresentou limite de detecção de 1,45 µg L-1 e limite de quantificação de 4,83 µg L-1 e foi aplicado em amostras de leite em pó fortificadas com ácido fólico. As quantidades de ácido fólico obtidas foram similares aquelas declaradas no rótulo. Ainda, foram obtidos, após testes de adição e recuperação, percentuais de 95 a 108%, o que atesta a exatidão do método. The present work describes the synthesis of a hybrid molecularly imprinted polymer containing restricted access as a new adsorbent material for the extraction of folic acid in milk samples. The characterization of the material was performed by means of FT-IR, TGA, SEM, TEM and analyzes of surface area, pore volume and size pore, whose results confirmed the presence of organic and inorganic network, as the presence of mesopores. From the kinetic studies the equilibrium time was found to be 390 minutes yielding adsorption of 5.6 mg of folic acid per gram of adsorbent. The formation of selective adsorptive sites was confirmed by the competitive adsorption of binary solutions of AF:possible interfering (caffeine, uric acid, 4-aminobenzamide and paracetamol), in which the relative selectivity coefficients were found to be 1.82, 1.33, 4.37 and 1.53, respectively. The percentage of bovine serum albumin exclusion for the MIP-RAM was 55 ± 2 and for the MIP was 35 ± 2%. Molecularly Imprinted Solid Phase Extraction (MISPE) studies has shown excellent clean-up of chromatograms without the need to wash the cartridge for removal of interfering, thus making possible the direct injection of eluate into the chromatographic system. The MISPE method showed limit of detection of 1.45 µg L-1 and limit of quantification of 4.83 μg L-1 and it was applied to the powder milk samples fortified with folic acid. The amounts of folic acid were similar to those stated in the label. In addition, it was obtained upon addition and recovery tests, percentages of 95 to 108%, which attest the accuracy of method.

The present study proposes a method for cloud point preconcentration of copper ions at pH 2.0 based on complexes formed with [4,5-dimercapto-1,3-dithyol-2-thionate] and subsequent determination by flame atomic absorption spectrometry (FAAS). Under optimal analytical conditions, the method provided limits of detection of 0.84 and 0.45 µg L-1, by preconcentrating 12.0 and 24.0 mL of sample, respectively. The method was applied for copper determination in water samples, synthetic saliva, guarana powder, tea samples and soft drinks and the accuracy was assessed by analyzing the certified reference materials Dogfish Liver (DOLT-4) and Lobster Hepatopancreas (TORT-2).

The determination of heavy metal ions in environmental, clinical and food samples has been a common concern for several researchers and in special case of aquatic environment, there has been a more stringent regulation standards pertaining to the discharge of heavy metals. Some efforts have been carried out to develop many treatment processes to reduce the disposal of heavy metal ions mainly in water bodies. The different treatment processes include precipitation, membrane filtration, ion exchange and adsorption (Tokalioglu et al. 2009), however, the levels of heavy metals disposal into water bodies are still rising, mainly in aqueous effluents discharged into aquatic bodies (Mello et al. 2005). As example, lead is considered as the major environmental pollutant and has become the most widely scattered toxic heavy metal in the world as a result of anthropogenic action. It is very well known that lead enters the environment through several industrial activities, such as industrial ammunition, paper board mill, battery manufacturing and coal burning and pigments (Zhan & Zhao, 2003). Lead can cause several effects on central nervous system, blood pressure, kidneys and reproductive system (Needleman, 2004). Similarly to lead, cadmium is also considered as toxic for animals and humans, and it is classified by the International Agency for Research on Cancer as a human carcinogen (IARC, 1993). The National Council for the Environment in Brazil (CONAMA, 2005) established 0.2 mg L-1 as the maximum level of cadmium for effluent discharge in aquatic bodies, while 5.0 and 3.0 μg L-1 are the maximum contaminant levels in potable water allowed by EPA(EPA, 2003) and ANVISA (ANVISA, 2004), respectively. Even at low concentration levels (≤ g L-1), there is bioaccumulation of heavy metals in aquatic organisms, so there is a growing need for their monitoring in different types of water samples. In addition, the heavy metal ions monitoring can provide both important aspects in water quality and controlling the industrial processes (Martinotti et al. 1995). Thus, the development of analytical methods based on preconcentration systems has commonly been the aim of choice for the determination of trace metals in water and

A novel ion imprinted polyvinylimidazole-silica hybrid copolymer (IIHC) was synthesized and used as a selective solid sorbent for Pb 2+ ions preconcentration using an on-line solid phase extraction (SPE) system coupled to TS-FF-AAS. The ionic hybrid sorbent was prepared using 1-vinylimidazole and 3-(trimethoxysilyl)propylmethacrylate as monomers, Pb 2+ ions as template, tetraethoxysilane as reticulating agent and 2,2′-azobis-isobutyronitrile as initiator. The best on-line SPE conditions concerning sorption behavior, including sample pH (6.46), buffer concentration (9.0 mmol L −1 ), eluent (HNO 3 ) concentration (0.5 mol L −1 ) and preconcentration flow rate (4.0 mL min −1 ), were optimized by means of full factorial design and Doehlert matrix. The analytical curve ranged from 2.5 to 65.0 μg L −1 ( r = 0.999) with limit of detection of 0.75 μg L −1 ; the precision (repeatability) calculated as relative standard deviation ( n = 10) was 5.0 and 3.6% for Pb 2+ concentration of 10.0 and 60.0 μg L −1 , respectively. From on-line breakthrough curve, column capacity was 3.5 mg g −1 . Preconcentration factor (PF), consumptive index (CI) and concentration efficiency (CE) were 128.0, 0.16 mL and 25.6 min −1 , respectively. The selective performance of the sorbent, based on relative selectivity coefficient, was compared to NIC ( non imprinted copolymer ) for the binary mixture Pb 2+ /Cd 2+ , Pb 2+ /Cu 2+ and Pb 2+ /Zn 2+ . The results showed that ion imprinted polyvinylimidazole-silica hybrid polymer had higher selectivity for Pb 2+ than NIC at 64.9, 16.0 and 8.8 folds. The developed method was successfully applied for highly sensitive and selective Pb 2+ determination in different kinds of water samples, parenteral solutions and urine. Accuracy was also assessed by analyzing certified reference fish protein (DORM-3) and marine sediment (MESS-3 and PACS-2) with satisfactory results.

Nowadays there are many sun-protection cosmetics incorporating chemical and/or physical UV filters as active ingredients and there are no official methods to determine these kinds of compounds in sunscreen cosmetics. The objective of this work is to estimate TiO(2) concentration, without sample preparation, employing a portable energy dispersive X-ray fluorescence (EDXRF), aiming to estimate the sun protection factor (SPF) due to the physical barrier in sunscreen composition, and also identify the metals present in the samples. A portable EDXRF system was used for the analysis of fifteen commercial samples. It was also prepared three formulations estimated in FPS-30 using TiO(2) at 5%. Quantification was performed using calibration curves with standards from 1 to 30%. The physical barrier contribution in the SPF, associated to Ti concentration, was determined for all samples. The presence of some elements, like K, Zn, Br and Sr was detected in the sunscreen, identifying chemical elements that were not cited in the formulations. Three commercial samples were analyzed for total SPF determination and the result shows that the measured value is 10% lower than the nominal one.

No presente trabalho e descrito um metodo voltametrico por redissolucao anodica utilizando um eletrodo de pasta de nanotubos de carbono modificado com filme de bismuto para determinacao simultânea dos metais Zn 2+ , Cd 2+ e Pb 2+ em amostras de etanol combustivel. Os ions metalicos foram pre-concentrados no filme de bismuto no tempo e potencial de deposicao de 500 s e -1,2V, e a etapa de redissolucao realizada por voltametria de onda quadrada (frequencia 15 Hz, amplitude de pulso 25 mV e incremento de potencial de 5 mV). Como eletrolito suporte foi utilizado tampao acetato 0,1 mol L -1 em pH 4,5. O metodo apresentou linearidade incluindo o branco analitico ate 48,39 ?g L -1 para os metais e os limites de deteccao obtidos foram 3,36, 0,32 e 0,47?g L -1 para Zn 2+ , Cd 2+ e Pb 2+ , respectivamente. O metodo proposto foi aplicado em amostras de etanol combustivel.

The present study describes the development of a preconcentration method for manganese determination by FAAS using poly(protoporphyrin-co-vinylpyridine) as a sorbent. To synthesize this material, 4-vinylpyridine and protoporphyrin were copolymerized in the presence of ethylene glycol dimethacrylate as a cross-linker and 2,2-azobisisobutyronitrile as an initiator. The factors affecting the flow injection preconcentration system were optimized by employing 25 fractional factorial and Doehlert matrix designs. The proposed on-line preconcentration method was performed by percolating 18.0 mL aliquots of Mn(II) solutions (pH 8.3) at a flow rate of 6.0 mL min−1 through a mini-column, packed with 100 mg of poly(protoporphyrin-co-vinylpyridine); the Mn(II) ions were then on-line eluted with 1.5 mol L−1 HNO3 into the FAAS nebulizer. Under these conditions, it was possible to yield a linear curve in the concentration range of 0.0–120.0 μg L−1, with a correlation coefficient of 0.997. Besides, the following system parameters were obtained: sampling frequency of 15 h−1, preconcentration factor of 53, consumptive index of 0.34 mL, concentration efficiency of 17.6 min−1, detection limit of 0.34 μg L−1, and quantification limit of 1.13 μg L−1. The method precision (repeatability) estimated for ten measurements of 1.0 and 50.0 μg L−1 Mn(II) standard solutions was found to be 5.2 and 4.9%, respectively. Moreover, the protoporphyrin incorporation into the poly(vinylpyridine) network caused a remarkable 323% increase in the method's sensitivity. Finally, the proposed procedure was not affected by potentially interfering ions. Thus, it was successfully applied to the Mn(II) determination in water, food and sediment samples.