Mmol Dm Research Articles

Surfactant/carbon nanofibers-modified electrode for the determination of vanillin

Glassy carbon electrode (GCE) modified with carbon nanofibers (CNF) and surfactants has been tested for the determination of vanillin in Britton–Robinson buffer. Cationic cetylpyridium bromide (CPB), nonionic Triton X100, and anionic sodium dodecylsulfate surfactants under different concentrations have been tested as modifier of CNF/GCE. The best form of CVs and voltammetric characteristics of vanillin have been obtained on CPB (0.5 mmol dm−3)/CNF/GCE when the 1.4-fold increase of oxidation peak currents has been observed in comparison with CNF/GCE. The electrode has been characterized by scanning electron microscopy and electrochemical impedance spectroscopy. These data indicate that CPB/CNF coverage significantly increases the charge transfer (R ct = 0.24 ± 0.04 vs. 4.6 ± 0.1 kΩ for GCE). Mechanism of vanillin oxidation on CPB/CNF/GCE is suggested. The electrooxidation is diffusion-controlled irreversible process with participation of two electrons and two protons and formation of o-quinone. Differential pulse voltammetry has been used for the quantification of vanillin. The working conditions for the vanillin detection (pH 2.0, pulse parameters) have been found. The linear dynamic ranges of the vanillin determination are 0.50–75.0 and 75.0–750 μmol dm−3 with the limits of detection and quantification 0.14 and 0.46 μmol dm−3 of vanillin, respectively. The developed approach has been applied for the vanillin quantification in foodstuff (vanilla sugar, vanilla pods, and cream milk powder). The results obtained are in good agreement with the data of standard spectrophotometric method.

Corrosion Behaviour of AGR SIMFUELS

Pure UO2 pellets and, for the first time, AGR SIMFUEL pellets simulating 25 (pellet interior) and 43 GWd/tU burn-up (rim structure) have been fabricated. Using combined electrochemical and Raman spectroscopic studies, we have investigated the effect of the AGR SIMFUEL dopants on the structure of the UO2 crystal matrix and studied the effect of H2O2 on the SIMFUEL surface as a simulant for the effect of α radiolysis of water within intruding groundwater in the near field. Preliminary results of electrochemical studies of AGR SIMFUEL samples held in direct contact with the AGR fuel cladding material, 20/25/Nb stainless steel, in modified simplified groundwater (10 mmol dm-3 NaCl, 2 mmol dm-3 NaHCO3, pH 6.8) indicate that the open circuit potential of the coupled system is (i) negative of that adopted by the isolated SIMFUEL and (ii) positive of that adopted by the isolated cladding in electrolytes of the same composition. This implies that the SIMFUEL is protected against corrosion at the expense of the steel cladding, an observation that is currently the subject of further work in our laboratories.

Bimetallic Ag-Pd nanoparticles-decorated graphene oxide: a fascinating three-dimensional nanohybrid as an efficient electrochemical sensing platform for vanillin determination

In this work, a fascinating hybrid based on Ag-Pd bimetallic nanoparticles-decorated graphene oxide (Ag-Pd/GO) has been successfully synthesized by a green and in situ chemical reduction strategy. The resultant hybrid was particularly characterized by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, ultraviolet-visible spectroscopy and electrochemical techniques. The morphological results illustrate that Ag-Pd nanoparticles in microspheric appearances are highly dispersed and embedded on the GO layers, resulting in a rough surface and three-dimensional (3D) microstructure with a high Ag-Pd content in the matrix. The as-synthesized 3D Ag-Pd/GO hybrid displays distinctly enhanced electrocatalytic activity for the vanillin oxidation in comparison with that of the monometal-decorated GO, revealing a synergistic effect of the matrix GO and the doped bimetallic Ag-Pd. Therefore, the Ag-Pd/GO composite can be used as an enhanced electrochemical sensing platform for the sensitive determination of vanillin, and the fabricated sensor displays a wide detection range of 0.02–45 μmol dm−3, low detection limit of 5nmoldm−3 and satisfactory recoveries between 98.8 % and 103.5 %. All the results demonstrate that the 3D hybrids integrated graphene with bimetallic nanoparticles are promising candidates for the development of high-performance electrochemical sensors.

Mechanism for the antibacterial activity of a mixture of 3,4,5-trihydroxy benzoic acid and magnesium oxide

In this paper, the mechanism for the antibacterial activity of a mixture of 3,4,5-trihydroxy benzoic acid (GA) and magnesium oxide (MgO) for Escherichia coli (JCM1649, E coli) is investigated. Antibacterial activity was assayed by the liquid dilution method against E coli. E coli in the logarithmic phase and the culture medium with pepton, yeast extract, NaCl, glucose, and MgSO4 7H2O were used in all experiments. The logarithmic phase culture of E coli (1x10 5 CFU cm -3 ) was added to the culture medium with GA and/or MgO. A Clark-type oxygen electrode with 1.1 cm -3 volume cell was used for the measurements of the oxygen consumption profile of a mixture of GA and MgO. The concentration of hydrogen peroxide (H 2O2) in the mixture was estimated by using porphyrinato-titanium complex. Efficient antibacterial activity was observed on a mixture of 2 mg cm -3 GA and 2 mg cm -3 MgO. The addition of 110 units cm -3 catalase, which is an enzyme of H2O2 decomposition, in a mixture of 2 mg cm -3 GA and 2 mg cm -3 MgO led to the decrease of the antibacterial activity as same as the case of 2 mg cm -3 MgO. Moreover, the production of H2O2 in the mixture was confirmed by the oxygen consumption profile under the addition of 500 units cm -3 catalase. The accumulation of 3-4 mmol dm -3 H2O2 was confirmed in a mixture of 2 mg cm -3 GA and 2 mg cm -3 MgO. The increase in the concentration of H2O2 from 3 mmol dm -3 to 4 mmol dm -3 led to a drastic increase in the antibacterial activity. Based on the results of this study, a possible mechanism for the antibacterial activity of a mixture of GA and MgO is discussed, concerning a synergy effect on the antibacterial action of MgO and that of H2O2.

Mathematical model for reactive recovery of invertase by chemical permeabilization of baker's yeast

BACKGROUND Cell permeabilization techniques allow selective release of an enzyme and specific reactions without breaking the cells. A mathematical model has been developed for selective permeabilization of Saccharomyces cerevisiae to recover invertase at high purity. The effect of thiols on the cell walls of S. cerevisiae was studied under different conditions of pH, cysteine concentration, speed of agitation and solid suspension density. RESULT The rate of release of invertase was a function of pH and cysteine (or thiolate ion) concentration.The maximum recovery of invertase was obtained at pH 10.0, 10 mmol dm−3 cysteine concentration and 15% (w/v) yeast loading. CONCLUSION Thiols are capable of permeabilizing the cell walls of S. cerevisiae and releasing the invertase under basic conditions. The insignificant effect of agitation shows that the external mass transfer resistance does not play any role in the release of invertase. © 2015 Society of Chemical Industry

Novel supramolecular system based on a cationic amphiphile bearing glucamine fragment: structural behavior and hydrophobic probe binding

The synthesized cationic surfactant bearing a glucamine fragment forms spherical micelles at about 0.7 mmol dm–3 and displays specific aggregation characterized by a sharp growth of micelles and a change in their properties within a narrow concentration range about 10 mmol dm–3.

Corrosion Behaviour of Agr Simfuels

In the UK, the majority of spent nuclear fuel (SNF) is from indigenous Advanced Gas-cooled Reactors (AGRs). AGRs, whilst using UO2-based fuel, employ CO2 as coolant and are graphite moderated. Further, the fuel assembly cladding is comprised of 20/25/Nb stainless steel rather than zircalloy as is the case in Pressurised Water Reactors (PWRs). Consequently, AGR fuel has unique characteristics that need to be evaluated before disposal in an expected anoxic UK geological repository. Pure UO2 pellets and, for the first time, AGR SIMFUEL pellets simulating 25 (pellet interior) and 43 GWd/tU burn-up (rim structure) have been fabricated at the UK National Nuclear Laboratory. Using combined electrochemical and Raman spectroscopic studies, we have investigated the effect of the SIMFUEL dopants on the UO2 crystal matrix. We have also studied the effect of H2O2 on the SIMFUEL surface as a simulant for the effect of a radiolysis on intruding groundwater in the near field. Raman microscopy reveals an increase in the lattice damage (500 – 700 cm-1) with increasing burn-up, as the UO2 cubic fluorite lattice structure becomes more distressed and moves towards a tetragonal structure. Cyclic voltammetric studies of the AGR SIMFUELs reveal them to more susceptible to electrochemical oxidation then PWR SIMFUELs; in particular the peak associated with the in-grain UO2 to UO2+x oxidation (onset -0.2 V vs SCE, Ep = +0.14 V) is ~3X larger for AGR SIMFUELs than PWR SIMFUELs of similar simulated burnup. Importantly, analogous studies on PWR SIMFUELs have shown that UO2+x locations act as preferential corrosion sites. The open circuit potential (EOC) for UO2 and AGR SIMFUELs show a logarithmic dependence on [H2O2] in modified simplified groundwater(10 mmol dm-3 NaCl, 2 mmol dm-3 NaHCO3, pH 6.8). In contrast, the EOC of PWR SIMFUELs of ~0.1 V vs SCE in aqueous alkaline solution is near independent of [H2O2], an observation attributed to surface-catalysed H2O2 decomposition by non-stoichiometric U(IV)/U(V) sites. This suggests that, in contrast to the non-complexing alkaline conditions, carbonate complex-ation of U(VI) in groundwater simulant removes the H2O2 decomposition sites from the UO2 surface so resulting in a larger net [H2O2] and thus oxidative stress being induced at the SIMFUEL surface. At [H2O2] = 10 mmol dm-3, close to that encountered in an a dominated near field, H2O2 generates an oxidative stress of 0.05 V vs SCE on 43 GWd/tU AGR SIMFUEL in simplified modified groundwater. This corresponds to the near top of the voltammetric wave for the in-grain UO2 to UO2+x process, suggesting that near field peroxide may be capable of inducing a substantial population of anodically active UO2+x sites on AGR SNF and consequent localised site corrosion at the spent fuel surface. Extended duration Raman studies on the oxidation of UO2 on 25 GWd/tU SIMFUELs in 1 mmol dm-3 H2O2 (EOC = +0.19 V vs SCE) in O2-free deionised water reveal that, over a 1 week period, there is an increase over in the intensity of the peak at 540 cm-1, associated with the formation of defect sites in the UO2 fluorite lattice. Shorter term studies on undoped UO2 samples in 0.01 to 1 mmol dm-3 H2O2 solutions also reveal the in-growth of a peak at ~610 cm-1, a feature that has been attributed to O sublattice distortions due to the generation of UO2+x locations. This again indicates of the potential for near field concentration H2O2 to induce an increased susceptibility to corrosion for AGR SIMFUEL. The ultimate product of H2O2 induced corrosion of either UO2 or AGR SIMFUELs would be expected to be U(VI). The extended duration Raman studies show that a peak appears at 820 cm-1 after 5 hours exposure to 1 mmol dm-3 H2O2. This grows in intensity up to 50 hours exposure and has been assigned to metastudtite (UO2(O2) 2H2O), a uranium peroxide secondary phase formed at the SIMFUEL surface as a result of the reaction between H2O2 and UO2 2+ – the latter necessarily generated as a result of above-expected H2O2–driven corrosion of the AGR SIMFUEL UO2 matrix. Peroxide aside, open circuit potential measurements on 43 GWd/tU simulated burnup AGR SIMFUELs samples in intimate contact with 20/25/Nb stainless steel and in modified simplified groundwater electrolyte find that they exhibit a mixed potential of ~-0.12 V vs SCE. This corresponds to nearly a quarter of the way up the oxidation wave for in-grain UO2 to UO2+x process in the associated voltammogram – implying that UO2/steel coupling can induce UO2 corrosion even in the absence of a peroxide generated oxidative stress.

Isolation of 163Ho from dysprosium target material by HPLC for neutrino mass measurements

Abstract The rare earth isotope 163Ho is of interest for neutrino mass measurements. This report describes the isolation of 163Ho from a proton-irradiated dysprosium target and its purification. A Dy metal target was irradiated with 16 MeV protons for 10 h. After target dissolution, 163Ho was separated from the bulk Dy via cation-exchange high performance liquid chromatography using 70 mmol dm –3 α-hydroxyisobutyric acid as the mobile phase. Subsequent purification of the collected Ho fraction was performed to remove the α-hydroxyisobutyrate chelating agent and to concentrate the Ho in a low ionic strength aqueous matrix. The final solution was characterized by MC-ICP-MS to determine the 163Ho/165Ho ratio, 163Ho and the residual Dy content. The HPLC purification process resulted in a decontamination factor 1.4E5 for Dy. The isolated Ho fraction contained 24.8 ± 1.3 ng of 163Ho corresponding to holmium recovery of 72 ± 3%.

Synthesis, characterization, and pharmacological evaluation of novel azolo- and azinothiazinones containing 2,4-dihydroxyphenyl substituent as anticancer agents.

We reported the synthesis and characterization of a series of azolo- and azino[1,3]thiazinones containing the 2,4-dihydroxyphenyl substituent. The compounds were prepared by a new one-step reaction of aryl-modified sulfinylbis[(2,4-dihydroxyphenyl)methanethione]s and the corresponding aminoazolo(azino)carboxamides. Their chemical structures were confirmed by IR, NMR: 1H, 13C, HSQC, and EI-MS spectral data. The compounds inhibited proliferation and viability of lung cancer A549, colon cancer HT-29, and glioma C6 cells in a structure- and concentration-dependent manner. The activity of some analogues was below 10 μmol dm−3 (IC50). Glioma C6 cells were the most sensitive to tested compounds. Generally, the derivatives were not toxic for the skin fibroblast HSF culture. Moreover, some of them exerted a protective effect on the treated normal cells. Evaluation of compound properties in silico showed that they possess significant drug-like characteristics and most of them display a low toxicity.Graphical abstract

Influence of Salt Stress on Growth and Frost Resistance of Three Winter Cereals

Abstract This paper presents results of a study on the influence of 0-150 mmol NaCl dm-3 Hoagland solution on growth, chlorophyll content, photosynthesis and frost resistance of seedlings of three winter cereals: wheat - cv. Almari, rye - cv. Amilo, and triticale - cv. Tornado. Sodium chloride at 25 mmol dm-3 caused better growth of wheat shoots and roots, both of fresh and dry matter. Higher concentrations of NaCl in the medium decreased the biomass of the tested seedlings. The influence of NaCl on the chlorophyll content in the seedlings varied. The conductometry method showed that the resistance of the cell walls of wheat and rye to low temperature decreased in the presence of NaCl in the growth medium. Luminescence has shown that seedlings that grew in NaCl-containing medium indicated an impediment of electron flow at a lower temperature than the control plants.

Synthesis and characterization of new Ti–Bi2O3 anode and its use for reactive dye degradation

This paper reports the synthesis, characterization and application of a Ti–Bi2O3 anode for the electrochemical decolorization of the textile dye Reactive Red 2. The anode was synthesized by electrodeposition on a Ti substrate immersed in an acidic bismuth (III) solution at constant potential, followed by calcination in air at 600 °C. Thermogravimetric Analysis (TGA), Energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analysis revealed that the electrodeposited material was predominantly metallic bismuth, which was oxidized to pure α-Bi2O3 during the calcination in air. SEM micrographs revealed that the Bi2O3 coat at the anode surface was inhomogeneous and porous. Reactive Red 2 was completely electrochemically decolorized at the synthesized anode in the presence of H2O2. The applied current density, H2O2 and Na2SO4 concentration, medium pH and initial dye concentration affected the dye decolorization rate. The optimal process parameters were found to be as follows: an applied current density of 40 mA cm−2 using a mixture of 10 mmol dm−3 H2O2 and 10 mmol dm−3 Na2SO4 at pH 7. The dye decolorization rate was shown to decrease as its initial concentration increased. The decolorization reactions were found to follow pseudo-first order kinetics.

Investigation of properties and structural characterization of the quercetin inclusion complex with (2-hydroxypropyl)-β-cyclodextrin

Quercetin is a typical plant flavonoid with a wide variety of pharmacological activities, including anti-inflammatory, anti-oxidative, anti-cancer and anti-age activity. It can be used for treatment of cardiovascular disorders. However, the application of quercetin in pharmacy is limited because of its poor aqueous solubility, low bioavailability, low permeability and instability. In order to overcome the mentioned limitations, an inclusion complex of quercetin with (2-hydroxypropyl)-β-cyclodextrin in a molar ratio of 1:1 have been prepared at room temperature by co-precipitation from ethanol solution. The inclusion complex was prepared at room temperature for 24 h by the co-precipitation method from ethanol solution. The obtained complex were evaporated and dried before the structural characterization. Based on the obtained results of FT-IR, DSC, 1H-NMR and XRD analysis, it can be concluded that the inclusion complex was formed by establishing the interaction between quercetin and (2-hydroxypropyl)-β-cyclodextrin. The phase solubility study indicates that the complexation of quercetin leads to increase the solubility of quercetin in water about 129-fold in the aqueous solution of HP-β-CD (10 mmol dm−3). Also, the photostability of quercetin was improved after its complexation with this cyclodextrin.

Screen printed paper-based diagnostic devices with polymeric inks.

A simple and low-cost fabrication method for paper-based diagnostic devices (PBDDs) is described in this study. Street-available polymer solutions were screen printed onto filter papers to create hydrophobic patterns for fluidic channels. In order to obtain fully functional hydrophobic patterns for fluids, the original polymer solutions were diluted with butyl acetate to yield a suitable viscosity range between 30-200 cP for complete patterning on paper. Typical pH and glucose tests with color indicators were performed on the screen printed PBDDs. Images of the PBDDs were analyzed by computers to obtain calibration curves for pH between 2 and 12 and glucose concentration ranging from 10-1000 mmol dm(-3). Detection of formaldehyde in acetone was also carried out to show the possibility of using this PBBD for analytical detection with organic solvents. An exemplar PBDD with simultaneous pH and glucose detection was also used to demonstrate the feasibility of applying this technique for realistic diagnostic applications.

Analysis of serum anion gap and osmolal gap in diagnosis and prognosis of acute methanol poisoning: clinical study in 86 patients

We performed a retrospective study in 86 patients from the Czech methanol outbreak in 2012 to determine the role of anion and osmolal gaps in diagnosis and prognosis of methanol poisoning. Methanol and ethanol were measured by a gas chromatographic method with flame ionization detection. Formate was measured enzymatically. Osmolality was measured by freezing point depression method. From 86 patients, 15 died, 47 survived without, and 24 survived with visual/CNS sequelae. There was a statistically significant correlation between the osmolal gap and serum methanol concentrations (R 2 = 0.704; p < 0.001); however, the sensitivity was low for the detection of serum methanol under 20 mmol dm−3. The survivors without sequelae had lower osmolal gap than those who survived with visual/CNS damage (p = 0.002). The correlation between the anion gap and serum formate on admission was significant (R 2 = 0.28; p 0.05). The measurement of the serum anion and osmolal gaps is a useful laboratory method of early diagnosis of acute methanol poisoning. Anion gap is a reliable indicator of the severity of poisoning in the late-presenting patients. Increased osmolal gap helps in diagnosing methanol poisoning at an early stage before the results of gas chromatography measurement are available.

Electrospray Ionization Mass Spectrometry for the Quantification of Inorganic Cations and Anions

Recent studies from our laboratory on electrospray ionization mass spectrometry (ESI-MS) for the quantification of inorganic cations and anions are reviewed. Metal ions were determined by ESI-MS in negative-ion mode as monovalent negative ions of their aminopolycarboxylate (APC) complexes, where excess amounts of the APC agents were added to sample solutions. Among the APCs studied, we found trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid (CyDTA, the chemical forms in a complex were expressed as H(n)cydta(n-4)) as the best chelating agent. A size exclusion column was used for on-line separation of the metal-APC complexes from matrix salts in samples. Total amounts of Al, Ni, Cu, Zn, and Pb in the biological certified reference materials (CRM), Olive Leaves (BCR-062) and Plankton (BCR-414), and in a soil CRM (JSAC-0401) were successfully determined by the proposed method. Halide ions (X(-) = F(-), Cl(-), Br(-) and I(-)) and cyanide (CN(-)) were determined by ESI-MS based on the formation of ternary complexes of metals, chelating agents and the analyte anions. Negative ions of the ternary complexes of group 13 elements, nitrilotriacetic acid (NTA, H(n)nta(n-3)), and halides, i.e., [AlF(nta)](-) for F(-), and [InX(nta)](-) for other halides, were measured; the limits of detection (LODs) were 10 nmol dm(-3) for F(-), 0.31 μmol dm(-3) for Cl(-), 3.8 nmol dm(-3) for Br(-), and 1.6 nmol dm(-3) for I(-), respectively. In the case of CN(-), an LOD of 20 nmol dm(-3) was obtained based on measurements of the ternary complex of Cu(II), CN(-) and 4-(2-pyridylazo)resorcinol (PAR, Hnpar(n-2)), i.e., [(63)Cu(II)(CN)(par)](-) (m/z 302). Moreover, quantitative methods for Cr(VI) and Cr(III) by ESI-MS were developed, where HCrO4(-) (m/z 117) for Cr(VI) and [Cr(III)(cydta)](-) for Cr(III) were used for measurements.

Immobilization of nanobeads on a surface to control the size, shape, and distribution of pores in electrochemically generated sol–gel films

Electrochemically assisted deposition of an ormosil film at a potential where hydrogen ion is generated as the catalyst yields insulating films on electrodes. When the base electrode is modified with 20-nm poly(styrene sulfonate), PSS, beads bound to the surface with 3-aminopropyltriethoxysilane (APTES) and using (CH3)3SiOCH3 as the precursor, the resulting film of organically modified silica (ormosil) has cylindrical channels that reflect both the diameter of the PSS and the distribution of the APTES-PSS on the electrode. At an electrode modified by a 20-min immersion in 0.5 mmol dm-3 APTES followed by a 30-s immersion in PSS, a 20-min electrolysis at 1.5 V in acidified (CH3)3SiOCH3 resulted in an ormosil film with 20-nm pores separated by 100 nm. Cyclic voltammetry of Ru(CN)64- at scan rates above 5 mVs-1 yielded currents controlled primarily by linear diffusion. Below 5 mVs-1, convection rather than the expected factor, radial diffusion, apparently limited the current.

Iron, copper, and manganese complexes with in vitro superoxide dismutase and/or catalase activities that keep Saccharomyces cerevisiae cells alive under severe oxidative stress

Due to their aerobic lifestyle, eukaryotic organisms have evolved different strategies to overcome oxidative stress. The recruitment of some specific metalloenzymes such as superoxide dismutases (SODs) and catalases (CATs) is of great importance for eliminating harmful reactive oxygen species (hydrogen peroxide and superoxide anion). Using the ligand HPClNOL {1-[bis(pyridin-2-ylmethyl)amino]-3-chloropropan-2-ol}, we have synthesized three coordination compounds containing iron(III), copper(II), and manganese(II) ions, which are also present in the active site of the above-noted metalloenzymes. These compounds were evaluated as SOD and CAT mimetics. The manganese and iron compounds showed both SOD and CAT activities, while copper showed only SOD activity. The copper and manganese in vitro SOD activities are very similar (IC50~0.4μmol dm–3) and about 70-fold higher than those of iron. The manganese compound showed CAT activity higher than that of the iron species. Analyzing their capacity to protect Saccharomyces cerevisiae cells against oxidative stress (H2O2 and the O2•– radical), we observed that all compounds act as antioxidants, increasing the resistance of yeast cells mainly due to a reduction of lipid oxidation. Especially for the iron compound, the data indicate complete protection when wild-type cells were exposed to H2O2 or O2•– species. Interestingly, these compounds also compensate for both superoxide dismutase and catalase deficiencies; their antioxidant activity is metal ion dependent, in the order iron(III)>copper(II)>manganese(II). The protection mechanism employed by the complexes proved to be independent of the activation of transcription factors (such as Yap1, Hsf1, Msn2/Msn4) and protein synthesis. There is no direct relation between the in vitro and the in vivo antioxidant activities.

Nitrogênio e potássio no crescimento de mudas de pitaia [Hylocereus undatus (Haw.) Britton &amp; Rose

A pitaia ainda é uma cultura carente de estudos e informações que subsidiem a definição/adaptação de sistemas de produção mais adequados às condições edafoclimáticas brasileiras, embora nos últimos anos tenha havido aumento de sua expansão agrícola, tanto no Brasil quanto em outros países. Assim, o objetivo deste estudo foi avaliar o efeito da adubação mineral sobre o crescimento de mudas de pitaia e, dessa maneira, obter informações direcionadas para a definição de manejos de fertilização adequados à exploração agrícola da cultura. Para isto, foram testadas cinco doses de nitrogênio (N) (0; 150; 300; 450 e 600 mg dm-3) e potássio (K) (0; 75; 150; 225 e 300 mg dm-3), sendo os níveis de cada nutriente arranjados em esquema fatorial 5x5, com quatro blocos. Para a interação significativa a (p&lt;0,05), procedeu-se ao ajuste em superfícies de resposta do tipo Y = β0 + β1(A) + β2(A)² + β3(B) + β4(B)² + β5(A).(B) + e. As estimativas das correlações fenotípicas foram obtidas considerando apenas o intervalo das doses de N e K, que promoveram as melhores respostas do acesso de pitaia para os caracteres estudados. Ao término do presente estudo, foi constatado que a aplicação de doses crescentes de N e K, e a interação NxP afetam os teores de ambos os nutrientes no solo, o sistema radicular e a parte aérea, influenciando, desse modo, sobre o crescimento inicial das plantas de pitaia. Os rendimentos mais satisfatórios ocorrem quando há 0,7 mmol dm-3 de K no solo, e 20 - 25 g kg-1 de N com 30 - 40 g kg-1 de K na parte aérea. Esses valores foram obtidos para a aplicação de 300 - 450 mg dm-3 de N com 150 - 225 mg dm-3 de K. O somatório do comprimento dos cladódios (SCC) e a massa seca do sistema radicular (MSSR) são as variáveis explicativas que apresentam maiores efeitos diretos sobre a massa seca dos cladódios (MSC).

A palladium imprinted polymer for highly selective and sensitive electrochemical determination of ultra-trace of palladium ions

We report on the design of a palladium(II)-selective electrode based on the use of palladium(II) imprinted polymer nanoparticles (IP-NPs), and its application for the anodic stripping deferential pulse voltammetry determination of palladium ions. The IP-NPs were obtained by precipitation polymerization of 4-vinylpyridine (the functional monomer), ethylene glycol dimethacrylate (the cross-linker), 2,2'-azobisisobutyronitrile (the initiator), eriochrome cyanine R (the palladium-binding ligand), and palladium ions (the template ion) in methanol solution. After polymerization, the Pd2+ in the polymer nanoparticles were leached out with dilute hydrochloric acid to create cavities for hosting Pd2+. The new sensor showed high selectivity for palladium ions in the presence of common potential interferences according to the specific recognition nature of the synthesized imprinted material. A carbon paste electrode was modified with the IP-NPs, and differential pulse stripping voltammetry was applied as the detection technique after open-circuit sorption of Pd2+ ions and its reduction to the metallic form. An explicit difference in the response was observed between the electrodes modified with IP-NPs and electrodes modified with non-IP-NPs. The modified electrode responses to Pd2+ was linear in the 0.01 nmol dm−3 to 1.0 nmol dm−3 (with sensitivity of 92.25nA/nmol dm−3) and in the 1.0 nmol dm−3 to 1.0μmol dm−3 (with sensitivity of 16.12μA/μmol dm−3) concentration ranges. The limit of detection (LOD) of the sensor was 3.0pmol dm−3 (at S/N=3). The sensor was successfully applied to the trace determination of Pd2+ in spiked environmental water and soil samples.

New method for visualization of silica phytoliths in Sorghum bicolor roots by fluorescence microscopy revealed silicate concentration-dependent phytolith formation

Silica phytoliths are microscopic structures of amorphous hydrated silica (SiO2 · nH2O) formed by specialized plant cells. Besides their biological roles, physical, chemical, and structural properties of biogenic silica offer a wide spectrum of applications in many fields of industry and technology. Therefore, processes involved in their formation recently become a very interesting topic to study. However, optical transparency and microscopic sizes of silica phytoliths do not allow their visualization and localization by classical light microscopy methods. Their observation thus requires phytolith isolation, technically difficult or lengthy sample preparation procedures, or a work with toxic chemicals. In this paper we are proposing a novel method for visualization of silica phytoliths in Sorghum bicolor root endodermal cells by fluorescence microscopy using alkali mounting solution (pH 12). This method offers an easy and quick preparation of the samples and high contrast imaging. Based on our results we can assume that the proposed fluorescent method for silica phytolith investigation allows observation of multiple samples in relatively short time period and thus might be applicable also for high-throughput screenings. Using this method we found out that after a 3-day cultivation of sorghum plants the minimal needed concentration of sodium silicate, limiting the formation of silica phytoliths in the root endodermis, was 25 µmol dm(-3). The positive correlation of sodium silicate concentration in the substrate with the phytolith diameter was also observed.