Analysis of amphetamine and methamphetamine as emerging pollutants in wastewater and wastewater-impacted streams

The identification and quantitation of the non-ecstasy amphetamine-type stimulants (ATSs) amphetamine and methamphetamine in lakes, rivers, wastewater treatment plant influents, effluents, and biosolids are reviewed. Neither monitoring nor reporting is required of these ATSs, which are considered emerging pollutants, but they have been identified in the environment. Amphetamine and methamphetamine enter our water supply by human excretion after legal or illegal consumption and via manufacturing in clandestine laboratories. Analytical methodology for sampling, sample preparation, separation, and detection of ATSs is discussed. Reported occurrences of ATSs in the environment and their use in municipal sewage epidemiology are noted. Future research needs that challenge applications of analytical techniques are discussed. The review focuses on research reported from 2004 to 2009.     

Modeling the adsorption of Cd(II) onto goethite in the presence of citric acid

The adsorption of cadmium onto goethite in the presence of citric acid was measured as a function of pH and cadmium concentration at 25 degrees C. Potentiometric titrations were also performed on the system. Cadmium adsorption onto goethite was enhanced above pH 4 in the presence of 50 microM, 100 microM and 1 mM citric acid. While there was little difference between the enhancements caused by 50 and 100 microM citric acid below pH 6, above pH 6 further enhancement is seen in the presence of 100 microM citric acid. When 1 mM citric acid was present, the enhancement of cadmium adsorption was greater below pH 6, with increased Cd(II) adsorption down to pH 3.5. However, above pH 6, 1 mM of citric acid caused slightly less enhancement than the lower citric acid concentrations. ATR-FTIR spectra of soluble and adsorbed citrate-cadmium species were measured as a function of pH. At pH 4.6 there was very little difference between the ternary Cd(II)-citric acid-goethite spectrum and the binary citric acid-goethite spectrum. However, spectra of the ternary system at pH 7.0 and 8.7 indicated the presence of additional surface species. Further analysis of the spectra suggested that these were metal-ligand outer-sphere complexes. Data from the adsorption experiments and potentiometric titrations of the ternary Cd(II)-citric acid-goethite system were fitted by an extended constant-capacitance surface complexation model. The spectroscopic data were used to inform the choice of surface species. Three reactions in addition to those for the binary Cd(II)-goethite and citric acid-goethite systems were required to describe all of the data. They were [formula in text], [formula in text], and [formula in text]. Neither the spectroscopy nor the modeling suggested the formation of a ternary inner-sphere complex or a surface precipitate under the conditions used in this study.     

Dicholorbenzyl alkyl ether homologs as retention index markers and internal standards for the analysis of environmental samples using capillary gas chromatography

A homologous series of 2,4-dichlorobenzyl alkyl ethers (DCBEs) have been synthesized and purified for use as retention index calibrants and internal standards. They are stable, sensitive to ECD and FID and ideal for GC-MS, with base peaks at m/z 159/161. The retention index calibration against the n-alkanes for a linear temperature program (LTP) series is given and recommendations made for the most suitable members of the DCBE series for use as internal standards in organochlorine (OC) residue analysis.     

Cosorption of Zn(II) and 2-, 3-, or 4-aminopyridine by montmorillonite

Data from acid-base titrations at 25 degrees C of Zn(NO(3))(2) and 2-, 3-, or 4-aminopyridine in 10 mM KNO(3) as background electrolyte suggested that soluble complexes ZnL(2+) and Zn(OH)L(+) form, where L represents aminopyridine. Zinc-hydroxyaminopyridine complexes have not been reported previously. The cosorption of Zn(II) with each of the aminopyridines to K-saturated Wyoming (SWy-K) and Texas (STx-K), and Ca-enriched Texas (STx-Ca) montmorillonites was measured at 25 degrees C, with 10 mM KNO(3) or 3.3 mM Ca(NO(3))(2) as background electrolyte. Comparison with previous data for sorption of Zn(II) and the aminopyridines separately and surface complexation modeling of the cosorption data showed that under acid conditions competition between Zn(2+) and aminopyridinium ions for the permanent negatively charged sites of montmorillonite results in suppression of the uptake of each sorbate by the other, but only when a large excess of the competing sorbate is present. Under alkaline conditions the sorption of Zn(II) was not affected by the presence of even a large excess of aminopyridine, but the sorption of 4-aminopyridine in particular was slightly enhanced when a large excess of Zn(II) was present. The enhancement was attributed to the formation of metal-bridged ternary surface complexes at the variable-charge sites on the edges of the montmorillonite crystals.     

Electrospray ionization mass spectrometry studies of noncovalent myosin VI complexes reveal a new specific calmodulin binding site

Among the myosin superfamily, myosin VI differs from all others by a reverse directionality and a particular motility. Little structural information is available for myosin VI. It is known that it binds one calmodulin (CaM) by means of a single "IQ motif" and that myosin VI contains a specific insert located at the junction between the motor domain (MD) and the lever arm, likely to play a critical role for the unusual motility previously observed. Electrospray ionization mass spectrometry (MS) was used to determine the CaM and Ca2+ stoichiometries in several myosin VI constructs. In particular, the experimental conditions required for the observation of multiprotein/Ca2+ noncovalent assemblies are detailed for two truncated MD constructs (less than 20 kDa) and for three full MD constructs (more than 90 KDa). The specificity of the detected stoichiometries is discussed for each construct and the resolving power of Time of Flight mass spectrometry is stressed, in particular for the detection of metal ions binding to high molecular weight complexes. MS reveals a new CaM binding site for myosin VI and highlights a different behavior for the five myosin VI constructs versus Ca2+ binding. In addition to these stoichiometry based experiments, gas-phase dissociation analyses on intact complexes are described. They reveal that Ca2+ transfer between protein partners occurs during the dissociation process for one construct with a full MD. Charge-transfer and dissociation behavior has allowed to draw structural assumptions for the interaction of the MD with the CaM N-terminal lobe.     

Adsorption of aspartic acid on kaolinite

The interaction of aspartic acid with kaolinite was studied by potentiometric titrations and by adsorption measurements both at constant aspartate concentration (but varying pH) and at a constant pH of 5.5. The temperature was 25 degrees C, and the ionic medium 5 mM KNO3. Aspartic acid dissociation constants estimated from titrations agreed with those from the literature. The adsorption of aspartic acid to kaolinite was weak and varied only slightly with pH; 10-18% of 100 microM aspartic acid adsorbed to kaolinite at 100 m(2)L(-1) between pH 3 and 10. Data from the titrations and adsorption experiments were fitted closely by an extended constant-capacitance surface complexation model, in which monodentate outer-sphere complexes formed between deprotonated aspartic acid molecules and protonated sites on the variable-charge edges of the kaolinite crystals. There appeared to be no adsorption to the permanently charged crystal faces.     

Measurement of cell migration on surface-bound fibronectin gradients

A novel technique for the quantitative observation of cell migration along linear gradient substrates functionalized with adhesive proteins is presented. Gradients of the cell adhesion molecule fibronectin are generated by the cross diffusion of functionalizable alkanethiols on gold and characterized by X-ray photoelectron spectroscopy and surface plasmon resonance. Two distinct migration assays are described that characterize the movement of either sparsely populated noncontacting cells or a confluent monolayer of cells into free space. The drift speed of bovine aortic endothelial cells is measured and shown to increase along a fibronectin gradient when compared to a uniform control substrate using both assays. The results of these experiments establish reproducible conditions for studies of cell migration on gradients of surface-bound ligands.     

Octylgermane on gold: synthesis, oxidation, and pattern formation

Chemisorbed monolayers of octylgermane (C8H17GeH3) on gold have been formed by vapor deposition in ultrahigh vacuum. The monolayer has been characterized by X-ray photoelectron and reflection absorption infrared spectroscopies (XPS and RAIRS) and scanning tunneling microscopy (STM). XPS data indicate the monolayer can be oxidized by exposure to ozone. STM images exhibit a complex pattern which can be modeled as strain-mediated spinodal decomposition.     

Theoretical study on the structure, stability, and electronic properties of the guanine-Zn-cytosine base pair in M-DNA

M-DNA is a type of metalated DNA that forms at high pH and in the presence of Zn, Ni, and Co, with the metals placed in between each base pair, as in G-Zn-C. Experiments have found that M-DNA could be a promising candidate for a variety of nanotechnological applications, as it is speculated that the metal d-states enhance the conductivity, but controversy still clouds these findings. In this paper, we carry out a comprehensive ab initio study of eight G-Zn-C models in the gas phase to help discern the structure and electronic properties of Zn-DNA. Specifically, we study whether a model prefers to be planar and has electronic properties that correlate with Zn-DNA having a metallic-like conductivity. Out of all the studied models, there is only one which preserves its planarity upon full geometry optimization. Nevertheless, starting from this model, one can deduce a parallel Zn-DNA architecture only. This duplex would contain the imino proton, in contrast to what has been proposed experimentally. Among the nonplanar models, there is one that requires less than 8 kcal/mol to flatten (both in gas and solvent conditions), and we propose that it is a plausible model for building an antiparallel duplex. In this duplex, the imino proton would be replaced by Zn, in accordance with experimental models. Neither planar nor nonplanar models have electronic properties that correlate with Zn-DNA having a metallic-like conductivity due to Zn d-states. To understand whether density functional theory (DFT) can describe appropriately the electronic properties of M-DNAs, we have investigated the electronic properties of G-Co-C base pairs. We have found that when self-interaction corrections (SIC) are not included the HOMO state contains Co d-levels, whereas these levels are moved below the HOMO state when SIC are considered. This result indicates that caution should be exercised when studying the electronic properties of M-DNAs with functionals that do not account for strong electronic correlations.