Flame atomic absorption spectrometric (FAAS) determination of copper, iron and zinc in food samples after solid-phase extraction on Schiff base-modified duolite XAD 761.

The present study involves the development of solid-phase extraction (SPE) procedure for the preconcentration of trace amounts of copper (Cu(2+)), iron (Fe(3+)) and zinc (Zn(2+)) ions on duolite XAD 761 modified by bis(2-hydroxyacetophenone)-2,2-dimethyl-1,3-propanediimine(BHAPDMPDI). The complexation between the metal ions and the proposed ligand was investigated potentiometrically. The metal ions retained on the sorbent were quantitatively determined via complexation with BHAPDMPDI. The complexed metal ions were efficiently eluted using 6 mL of 4 mol L(-1) nitric acid in acetone. The influences of the analytical parameters, including pH, amounts of the ligand and the solid phase, eluent conditions and sample volume, on the recoveries of the metal ions were optimized. Using the optimized parameters, the linear response of the SPE method for Cu(2+), Zn(2+) and Fe(3+) ions were in the ranges of 0.01-0.34, 0.01-0.28 and 0.02-0.31 µg mL(-1), respectively, and the detection limits for Cu(2+), Zn(2+) and Fe(3+) ions were 1.8, 1.6 and 2.4 µg mL(-1), respectively. The proposed method exhibits a preconcentration factor of 208 for all of the ions studied and an enhancement factor for Cu(2+), Fe(3+) and Zn(2+) ions of 34, 28 and 38, respectively. The presented results demonstrate the successful application of the proposed method for the determination of these metal ions in some real samples with high recoveries (> 95%) and reasonable relative standard deviation (RDS <5%).

Construction of a new Cu2+ coated wire ion selective electrode based on 2-((2-(2-(2-(2-hydroxy-5-methoxybenzylidene amino)phenyl)disufanyl)phenylimino)methyl)-4-methoxyphenol Schiff base.

In this article a new coated platinum Cu(2+) ion selective electrode based on 2-((2-(2-(2-(2-hydroxy-5-methoxybenzylideneamino)phenyl)disufanyl)phenylimino) methyl)-4-methoxyphenol Schiff base (L(1)) as a new ionophore is described. This sensor has a wide linear range of concentration (1.2 × 10(-7)-1.0 × 10(-1) mol L(-1)) and a low detection limit of 9.8 × 10(-8) mol L(-1)of Cu(NO(3))(2). It has a Nernstian response with slope of 29.54 ± 1.62 mV decade(-1) and it is applicable in the pH range of 4.0-6.0 without any divergence in potential. The coated electrode has a short response time of approximately 9s and is stable at least for 3.5 months. The electrode shows a good selectivity for Cu(2+) ion toward a wide variety of metal ions. The proposed sensor was successfully applied for the determination of Cu(2+) ion in different real and environmental samples and as indicator electrode for potentiometric titration of Cu(2+) ion with EDTA.

Hydrothermal synthesis, experimental and theoretical characterization of a novel cocrystal compound in the 2:1 stoichiometric ratio containing 6-methyluracil and dipicolinic acid.

This paper reports the hydrothermal synthesis, experimental and theoretical studies of a novel cocrystal compound in the 2:1 stoichiometric ratio of 6-methyluracil (6mu) and dipicolinic acid (pydcH(2)) formulated as [6mu](2)[pydcH(2)] (1), for the first time. DFT calculations were performed to access the most possible geometry of the title cocrystal compound. All calculations were carried out with the B3LYP hybrid density functional level and 6-311+G(d,p) basis sets. The vibrational frequencies together with the (1)H and (13)C NMR chemical shifts have been calculated on the fully optimized geometry of 1. The theoretical results are in good agreement with the experimental and solution data. The theoretical, solution, and experimental (elemental analysis, mass spectrometry, FTIR, (1)H and (13)C NMR spectroscopies) results confirmed our proposed structure for 1 in the 2:1 stoichiometric ratio of 6mu and pydcH(2), respectively. The protonation and equilibrium constants of 6mu and pydcH(2) and constituent systems were determined by potentiometric studies and the corresponding distribution diagrams depicted.

SDS-coated Sepabeads SP70-modified by 4-[(E)-3-phenylallylidene) amino] benzenethiol as new efficient solid phase for enrichment and determination of copper, nickel, chromium, and zinc ions in soil, plants, and mint water samples.

A sensitive and simple method based on modification of Sepabeads SP70 by 4-((E)-3-phenylallylidene) amino) benzenethiol for the simultaneous preconcentration of trace amounts of copper (Cu), nickel (Ni), chromium (Cr), and zinc (Zn) ions in some real samples has been reported. The metal ions which are retained as respective complexes on solid phase were eluted with 8 ml of 4 M nitric acid. The influences of different analytical parameters including pH, ligand amount and Sepabeads SP70 and SDS amount, eluting solutions, and sample volume on metal ions recoveries were investigated. The effects of matrix ions on the retentions of the analytes were also examined. The recoveries of analytes were generally >95% with RSD between 0.74 and 0.88. The proposed method has been successfully applied for the determination of these metals in some real samples with complex matrices.

Preparation of a new chromium(III) selective electrode based on 1-[(2-hydroxy ethyl) amino]-4-methyl-9H-thioxanthen-9-one as a neutral carrier.

A new chromium carbon paste electrode sensor based on a carbon paste electrode containing 1-[(2-hydroxy ethyl) amino]-4-methyl-9H-thioxanthen-9-one (AMTX) as new carrier has been prepared. The influence of carbon paste ingredients including sodium tetraphenylborate (NaTPB), ionophore, Nujol and graphite powder on the electrode response has been investigated. The best performance characteristics for the electrode was obtained with a carbon:NaTPB:Nujol:AMTX in the mass ratio of (400:1.43:57.2:3mg) (86.65:0.31:12.39:0.65%). At the optimum value of all variables, the response of electrode is linear in range of 3.2x10(-7) to 1.0x10(-1)mol L(-1) with a Nernstian slope of 20.51 mV decade(-1) of Cr(3+) ion concentration with detection limit of 1.6x10(-7)mol L(-1). The electrode response is independent of pH in the range of 4.8-6.3, while the response time of the electrode was approximately 8 s. The potentiometric selectivity coefficients of proposed chromium-selective electrode towards various interfering ions were determined by fixed interference method (FIM), separate solution method (SSM) and matched potential method (MPM).

Preconcentration and separation of trace amount of copper (II) on N1, N2-bis(4-fluorobenzylidene)ethane-1,2-diamine loaded on Sepabeads SP70.

A sensitive and simple method for the preconcentration of copper (II) ions has been reported. The method is based on the adsorption of copper ion N(1), N(2)-bis(4-fluorobenzylidene)ethane-1,2-diamine loaded on Sepabeads. The sorpted copper content was eluted by 8 ml of 4M nitric acid in acetone. The influences of the analytical parameters including pH and sample volume were investigated. The interference effects of matrix ions on the retentions of the copper (II) ions were also examined. The recovery of understudy analyte was generally higher than 95%. The method has been successfully applied to the evaluation of copper contents in some real samples including water samples, vegetable samples and milk samples.

Flame atomic absorption spectrometric determination of zinc, nickel, iron and lead in different matrixes after solid phase extraction on sodium dodecyl sulfate (SDS)-coated alumina as their bis (2-hydroxyacetophenone)-1, 3-propanediimine chelates.

A sensitive and simple solid phase extraction method for the simultaneous determination of trace and toxic metals in food samples has been reported. The method is based on the adsorption of zinc, nickel, iron and lead on sodium dodecyl sulfate (SDS)-coated alumina, which is also chelated with bis (2-hydroxyacetophenone)-1, 3-propanediimine (BHAPN). The retained analyte ions on modified solid phase were eluted using 8 mL of 4 mol L(-1) HNO(3). The analyte determinations were carried out by flame atomic absorption spectrometry. The influences of some metal ions and anions on the recoveries of understudy analyte ions were investigated. The proposed method has been successfully applied for the evaluation of these trace and toxic metals in some traditional food samples from Iran.

Preconcentration and separation of trace amount of heavy metal ions on bis(2-hydroxy acetophenone)ethylendiimine loaded on activated carbon.

A sensitive and simple method for simultaneous preconcentration of trace heavy metal ions in some food samples has been reported. The method is based on the adsorption of Cr(3+), Fe(3+), Cu(2+), Ni(2+), Co(2+) and Zn(2+) on bis(2-hydroxy acetophenone)ethylendiimine (BHAPED) loaded on activated carbon (AC). The adsorbed metals on activated carbon were eluted using 2 mol L(-1) nitric acid in acetone. The influences of the analytical parameters including pH and sample volume were investigated. The effects of matrix ions on the recoveries of analyte ions were also investigated. The recoveries of analytes were generally higher than 94%. The method has been successfully applied for analysis of the metal contents in real samples including natural water samples.

Development of a selective and sensitive flotation method for determination of trace amounts of cobalt, nickel, copper and iron in environmental samples.

A simple, selective and rapid flotation method for the separation-preconcentration of trace amounts of cobalt, nickel, iron and copper ions using phenyl 2-pyridyl ketone oxime (PPKO) has been developed prior to their flame atomic absorption spectrometric determinations. The influence of pH, amount of PPKO as collector, type and amount of eluting agent, type and amount of surfactant as floating agent and ionic strength was evaluated on the recoveries of analytes. The influences of the concomitant ions on the recoveries of the analyte ions were also examined. The enrichment factor was 93. The detection limits based on 3 sigma for Cu, Ni, Co and Fe were 0.7, 0.7, 0.8, and 0.7 ng mL(-1), respectively. The method has been successfully applied for determination of trace amounts of ions in various real samples.

Cloud point extraction for the determination of copper, nickel and cobalt ions in environmental samples by flame atomic absorption spectrometry.

A cloud point extraction procedure was presented for the preconcentration of copper, nickel and cobalt ions in various samples. After complexation with methyl-2-pyridylketone oxime (MPKO) in basic medium, analyte ions are quantitatively extracted to the phase rich in Triton X-114 following centrifugation. 1.0 mol L(-1) HNO(3) nitric acid in methanol was added to the surfactant-rich phase prior to its analysis by flame atomic absorption spectrometry (FAAS). The adopted concentrations for MPKO, Triton X-114 and HNO(3), bath temperature, centrifuge rate and time were optimized. Detection limits (3 SDb/m) of 1.6, 2.1 and 1.9 ng mL(-1) for Cu(2+), Co(2+) and Ni(2+) along with preconcentration factors of 30 and for these ions and enrichment factor of 65, 58 and 67 for Cu(2+), Ni(2+) and Co(2+), respectively. The high efficiency of cloud point extraction to carry out the determination of analytes in complex matrices was demonstrated. The proposed procedure was applied to the analysis of biological, natural and wastewater, soil and blood samples.

Selective and sensitive spectrophotometric method for determination of sub-micro-molar amounts of aluminium ion.

A simple and accurate spectrophotometric method for determination of trace and ultra-trace amounts of Al3+ ion in tap and wastewater sample has been described. Using the eriochrome cyanine R (ECR) in the presence of N,N-dodecyltrimethylammonium bromide (DTAB) as cationic surfactant spectrophotometric determination of Al3+ ion has been carried out. The Beer's law is obeyed over the concentration range of 4-400 ng mL(-1) of Al3+ ion with the detection limits of 0.14 ng mL(-1), while the molar absorptivity of complexes is 1.19x10(5) L mol(-1) cm(-1). The influence of type and amount of surfactant, pH, and amount of ligand on sensitivity of spectrophotometric method were optimized. The method has been successfully applied for Al3+ ion determination in real sample.

The determination of some heavy metals in food samples by flame atomic absorption spectrometry after their separation-preconcentration on bis salicyl aldehyde, 1,3 propan diimine (BSPDI) loaded on activated carbon.

A sensitive and simple method for the simultaneous preconcentration of Cr3+, Fe3+, Cu2+, Ni2+, Co2+ and Zn2+ in real samples has been reported. The method is based on the adsorption of analytes on bis salicyl aldehyde, 1,3 propan diimine (BSPDI) loaded on activated carbon. The adsorbed metals on modified activated carbon were eluted using 8 mL of 2 mol L(-1) nitric acid in acetone or 10 mL of 4 mol L(-1) HNO3. The influences of the analytical parameters including pH and sample volume were investigated. The effects of matrix ions on the retentions of the analytes were also examined. The recoveries of analytes were generally quantitative. The method has been successfully applied for these metals content evaluation in some food samples.

Highly selective and sensitive spectrophotometric determination of trace amounts of silver ion in surfactant media using 2-mercaptobenzoxazole.

A simple and accurate spectrophotometric method for determination of trace amounts of silver ion in tap and wastewater solution and photographic solutions has been described. The spectrophotometric determination of silver ion using 2-mercaptobenzoxazole (MBO) in the presence of Triton X-100 as nonionic surfactant has been carried out. The Beer's law is obeyed over the concentration range of 0.1-9.0 microg mL(-1) of Ag+ ion with the detection limits of 1.6 ng mL(-1). The influence of type and amount of surfactant, pH, complexation time and amount of ligand on sensitivity of method were optimized. Finally the repeatability, accuracy and the effect of interfering ions on the determination of silver ion were evaluated. There is a good agreement between results of proposed method and atomic absorption spectrometry.

A distinct intermediate of RNase A is induced by sodium dodecyl sulfate at its pK(a).

The chemical denaturation of RNase A was found to be mediated by sodium dodecyl sulfate (SDS) at various pH. The characterization of the unfolding pathway was investigated by spectrophotometry and differential scanning calorimetry (DSC), and was analyzed by multivariate curve resolution (MCR) as a chemometric method. The spectrophotometric titration curve of RNase A upon interaction with SDS indicated a distinct complex intermediate in glycine buffer at pH 3.3. This was accompanied with the catalytic activation of the enzyme and was concurrent with maximum population of the intermediate, determined by MCR. This was confirmed by the DSC profile of RNase A in the presence of SDS, indicated by two transitions in thermal unfolding. The kinetic data on the unfolding process of RNase A upon addition of SDS showed a two-phase pathway under the same conditions. The intermediate appeared at low pH especially at the pK(a) of SDS (pH 3.3). These results provide strong evidence of the influence of low pH (around the pK(a) of SDS) on the existence of an intermediate upon interaction of RNase A with SDS.

Predator-driven phenotypic diversification in Gambusia affinis.

Predation is heterogeneously distributed across space and time, and is presumed to represent a major source of evolutionary diversification. In fishes, fast-starts--sudden, high-energy swimming bursts--are often important in avoiding capture during a predator strike. Thus, in the presence of predators, we might expect evolution of morphological features that facilitate increased fast-start speed. We tested this hypothesis using populations of western mosquitofish (Gambusia affinis) that differed in level of predation by piscivorous fish. Body morphology of G. affinis males, females, and juveniles diverged in a consistent manner between predatory environments. Fish collected from predator populations exhibited a larger caudal region, smaller head, more elongate body, and a posterior, ventral position of the eye relative to fish from predator-free populations. Divergence in body shape largely matched a priori predictions based on biomechanical principles, and was evident across space (multiple populations) and time (multiple years). We measured maximum burst-swimming speed for male mosquitofish and found that individuals from predator populations produced faster bursts than fish from predator-free populations (about 20% faster). Biomechanical models of fish swimming and intrapopulation morphology-speed correlations suggested that body shape differences were largely responsible for enhanced locomotor performance in fish from predator populations. Morphological differences also persisted in offspring raised in a common laboratory environment, suggesting a heritable component to the observed morphological divergence. Taken together, these results strongly support the hypothesis that divergent selection between predator regimes has produced the observed phenotypic differences among populations of G. affinis. Based on biomechanical principles and recent findings in other species, it appears that the general ecomorphological model described in this paper will apply for many aquatic taxa, and provide insight into the role of predators in shaping the body form of prey organisms.

First anionic 1,10-phenanthroline-2,9-dicarboxylate containing metal complex obtained from a novel 1:1 proton-transfer compound: synthesis, characterization, crystal structure, and solution studies.

The new 1,10-phenanthroline containing 1:1 proton-transfer compound LH(2), [pyda.H(2)](2+)[phendc](2-), was synthesized from the reaction of 2,6-pyridinediamine, pyda, and 1,10-phenanthroline-2,9-dicarboxylic acid, phendc.H(2), and characterized by elemental analysis, ES-Ms, IR, (1)H, (13)C NMR, and UV/vis spectroscopies. Subsequently, the first example of [phendc](2)(-) containing anionic complex [pyda.H](2)[Co(phendc)(2)].10H(2)O, was prepared, using the above novel proton-transfer compound, and structurally characterized by single-crystal X-ray diffraction. The complex crystallizes in the space group P2(1)/n of the monoclinic system with four molecules in a unit cell of dimensions a = 11.877(3) A, b = 31.473(9) A, c = 12.915(4) A, and beta = 116.223(5) degrees. The structure has been refined to a final value for the crystallographic R factor of 0.0524 based on 9021 observed independent reflections. The complexation reactions of pyda, phendc.H(2), and LH(2) with H(+) as well as LH(2) with Co(II) in aqueous solution were investigated by potentiometric pH titrations, and the equilibrium constants for all major complexes formed are described. The results are presented in the form of distribution diagrams revealing the concentrations of individual complex species as a function of pH. The results revealed that, at a pH range of 5.2-6.2, the major complex species is [(pyda.H)](2)[Co(phendc)(2)], similar to the isolated crystalline complex.