Applications of the GeMSAEC Centrifugal Photometric Analyzer in Environmental Analysis the Determination Of Phosphate

Abstract

The ORNL GeMSAEC Photometric Analyzer is described briefly. The use of a small computer with this instrument, for data acquisition and handling and for automatic printout of the analytical results, is also described. The determination of orthophosphate by the molybdenum-blue procedure has been utilized in a statistical evaluation of the GeMSAEC system, and the results are presented. This study illustrates the considerations that are important in designing procedures for the GeMSAEC type of analyzer, and the advantages that accrue.     

Pyridoxal Nicotinylhydrazone as Fluorimetric Reagent for the Determination of Zinc by Ternary Complex FORMATION

Abstract

A new spectrofluorimetric method for the determination of zinc using pyridoxal nicotinylhydrazone as the reagent has been developed. This system forms a ternary complex with ammonia, ethylenediamine or pyridine with a stoichiometry ratio of 1:1:1. The interferences of foreign ions have been determined.     

Multiple Linear Regression Analysis Of The Retention Data For Several Polynuclear Aromatic Hydrocarbons

Abstract

The retention data for benzene, toluene, naphthalene, cumeme, biphenyl, and durene in ternary (methanol, tetrahydrofuran, water) and quaternary (methanol, tetrahydrofuran, acetonitrile, water) solvent systems has been reduced to linear equations relating the retention volume to solvent composition. In particular, attention is focused on the biphenyl, naphthalene, cumene system and comments are made as to the optimum separation conditions.     

Separation of Bufotalin and Cinobufotalin by Preparative Liquid Chromatography

Abstract

Complete resolution of bufadienolides by traditional column chromatography, or by thin-layer chromatography (TLC), is quite difficult. Separation of various bufadienolide conjugates by high performance liquid chromatography (HPLC) has been described, but not for resolution of the corresponding genins. A preparative HPLC procedure has been developed for resolving the difficultly separable bufotalin (1) and cinobufotalin (2). A Lobar B column packed with LiChromprep Si-60 was used to separate these bufadienolides employing a recycling procedure.     

Complex Formation Between Hydroxy Naphthol Blue and First Row Transition Metal Cyanide Complexes

Abstract

It has been found that cyanide complexes of first row transition metal elements exhibit enhanced binding to hydroxy naphthol blue (HNB) relative to the binding of corresponding aquo-ions. HNB forms a 2:1 complex with Fe³⁺ and Cu²⁺ cyanides, and 1:1 complexes with all other transition metal cyanide complexes studied; formation constants have been calculated from the spectrophotometric data in each case. It is possible to use HNB as a spectrophotometric reagent for transition metal cyanide complexes, lower limits of detection being determined for each complex.     

Molecular and crystal structure of cellulose acetate dipropanoate (CADP, 6-O-acetyl-2,3-di-O-propanoyl cellulose)

The molecular and crystal structure of cellulose acetate dipropanoate (CADP, 6-O-acetyl-2,3-di O-propanoyl cellulose) has been determined by using a constrained linked-atom least-squares refinement method, combined with X-ray and electron diffractograms and stereochemical refinement. The diffraction analysis indicated that CADP crystallized in a P2 ₁ monoclinic space group with unit cell parameters:a =1.088 nm,b (unique axis)=1.593 nm,c (fibre axis)=1.509 nm and =94.1°. The best model derived from combining the stereochemical refinement with the diffraction intensities gave R=0.217 (R=0.195) for the three-dimensional information from the X-ray fibre diagram and R=0.198 for the base plane data resulting from electron diffraction analysis. In the model, the crystal structure of CADP consisted of a system of right-handed threefold helices packed in an antiparallel fashion, with two molecules passing through the unit cell.     

Effect of HC1 Concentration on the Distribution Factors of Iron and Mercury in Foam Separation

Abstract

A recycling batch foam separation apparatus has been used for the measurement of the distribution factors, Γ/c, of the anionic metal chloro complexes of iron and mercury with the cationic surfactant, hexadecyltri-methylammonium bromide. As a function of HC1 concentration, optimum values in distribution factors occur at roughly 0.3N HC1 for Hg and roughly 8N HC1 for Fe. Separations are thus possible by control of HC1 concentration.     

A Spectrophotometric Study of the Molybdenum(VI)-1-Pyrrolidinecarbodithioate System

Abstract

A spectrophotometric study of the molybdenum-1-pyrrolidinecarbodithioate complex has shown that the meta1:ligand ratio is 1;2. Both molybdenum(VI) and molybdenum(V) form complexes with almost identical absorption spectra. The conditional extraction constant for the molybdenum(VI)-1-pyrrolidinecarbodithioate in chloroform system has been evaluated as 6.3 × 10¹⁶.     

An Effective Approach for the Silylation of Hydroxyl Compounds in Room Temperature Ionic Liquids

Abstract

The room temperature ionic liquid (RTIL) 1-n-butyl-3-methylimidazolium hexafluorophosphate (BMImPF₆) is used as a “green” recyclable alternative to conventional solvents for the silylation of a series of hydroxyl compounds (alcohols and phenols) with t-butyldimethylchlorosilane (TBDMCS), which has some advantages such as simplicity of the synthetic procedure, the potential for recycling of the ionic liquid and the environmentally benign.     

Apparatus for the Determination of Mercury by Plasma Emission Spectrometry

Abstract

A cold vapor introduction system has been developed for the rapid detection of sub-nanogram amounts of mercury by plasma emission spectrometry. Operational parameters affecting response have been evaluated and optimum values are presented. The system appears to be free of spectral interferences. It has been applied to the analysis of marine sediments and organisms and coastal seawater.     

Predictive abilities of scaled quantum mechanical molecular force fields: application to 2,3-dimethylbuta-1,3-diene

In connection with the appearance of new experimental vibrational data on the high-energy rotational isomer of 2,3-dimethylbuta-1,3-diene (I) in a low-temperature matrix and in neat crystals, the ab initio-based vibrational analysis of this molecule has been re-evaluated. Calculated wavenumbers derived from a scaled quantum-mechanical force field analysis at the MP2(FC)/aug-cc-pVDZ//MP2(FC)/aug-cc-pVDZ computational level are compared with experimental data. Several reassignments of the fundamental wavenumbers for I have been suggested in the course of the current analysis, and the existence of a high-energy non-planar s-gauche conformer of 2,3-dimethylbuta-1,3-diene has been confirmed.     

Determination of Ammonia in Water Using Flow Injection Analysis with Automatic Pervaporation Enrichment

Abstract

An automated ammonia monitoring system has been developed by putting a pervaporation unit in an enrichment cycle used in flow injection analysis mode. In the proposed system, an enrichment cycle was equipped to enable the adjustment for the measuring range of ammonium by controlling the duration of the enrichment circulation. Therefore, the system was capable to determine ammonia in both the surface water with low ammonia concentration and the ammonia-rich wastewater with the linear dynamic range of 0.05–15 mg l^?1 and 15–50 mg l^?1, respectively. The relative standard deviations were less than 1.9% and the quantification limit is as low as 0.03 mg l^?1. The sampling frequency is 8–10 h^?1.     

The Non-Grid Technique for Modeling 3D QSAR Using Self-Organizing Neural Network (SOM) and PLS Analysis: Application to Steroids and Colchicinoids

Abstract

A novel method for modeling 3D QSAR has been developed. The method involves a multiple training of a series of self-organizing networks (SOM). The obtained networks have been used for processing the data of one reference molecule. A scheme for the analysis of such data with the PLS analysis has been proposed and tested using the steroids data with corticosteroid binding globulin (CBG) affinity. The predictivity of the CBG models measured with the SDEP parameter is among the best one reported. Although 3-D QSAR models for colchicinoid series is far less predictive, it allows for a discussion on the relative influence of the structural motifs of these compounds.     

Analysis of Resin-Bead Loaded U And PU Samples with a Single-Stage Mass Spectrometer

Abstract

The resin bead sample loading technique has been applied to a conventional single-stage mass spectrometer equipped with pulse counting. Isotopic data obtained for U and Pu are comparable to those obtainable from similar instruments using conventional techniques.     

Recycling concepts for polyurethanes and polycarbonate

The opinion is that all thermoplastics are infinitely recyclable, while crosslinked polyurethanes (PUR) and thermosets are not recyclable. The present paper uses comparative data to show that the waste management problem associated with crosslinked PUR materials has been largely overcome on a pilot-plant scale. Direct and indirect material recycling as well as thermal recycling are discussed. A direct recycling method in which granulated PUR-RIM scrap is made to “flow” under heat and pressure to re-mould it, is quoted as evidence that crosslinked polyurethane elastomers can be reclaimed and reused in a similar manner to thermoplastics. This process is called “compression molding”. Recycling methods for thermoplastics under consideration from an early stage, as well as entirely new possibilities that are emerging, are demonstrated, using polycarbonate Makrolon® as an example.     

Assessment of Organic Source Contributions in Coastal Waters by Principal Component and Factor Analysis of the Dissolved and Particulate Hydrocarbon and Fatty Acid Contents

Abstract

Principal component (PCA) and factor analysis (FA) are evaluated for the interpretation of the information contained in large datasets resulting from the study of environmental samples by gas chromatography (GC) and GC coupled to mass spectrometry (GC-MS). A case involving the identification and quantitation of 64 variables (hydrocarbons and fatty acids) in 87 water samples (dissolved and particulate fractions) of a coastal system (Ebre Delta) has been selected for examination.

PCA has evidenced important differences between the dissolved and particulate materials, as well as between the particulates collected in the bays and those obtained in the river and channels. PCA has also allowed the identification of outlier samples in the dissolved fraction. Independent application of FA to each of these groups has provided a useful method for the characterization of diverse algal, terrestrial, microbial and anthropogenic inputs. Direct correspondences between these source inputs and factor loadings have provided a selection of representative components of each contribution in the coastal system.     

Molecular logic circuits and a security keypad lock based on a novel colorimetric azo receptor with dual detection ability for copper(II) and fluoride ions

A novel azoimine dye-based colorimetric chemosensor (1) has been designed and synthesised for dual recognition of copper(II) and fluoride ions in aqueous media. Significantly, the outstanding dual-ion recognition properties along with the excellent reversibility prompted us to consider 1 as an ideal candidate for fabrication of multiple logic circuits. According to the response profile of 1 towards Cu²⁺ and F^? inputs, we developed a unique tunable system integrated with one INHIBIT logic gate as well as one OR gate. Also, 1 behaved as a molecular keypad lock with sequential addition of Cu²⁺ and F^? inputs. In accession, a reversible ‘Write–Read–Erase–Read’ function with complementary ‘IMP/INH’ logic gate has been demonstrated through a feedback loop using F^? and trifluoroacetic acid as two chemical inputs. To the best of our knowledge, this is the first report where the symmetrical bis azo-azomethine dye has been exploited as a molecular keypad lock.     

Crystalline inclusion compounds of a new diol host featuring a combination of anthracene and 9-fluorenol units

The diol host compound 2 has been synthesised and its behaviour to form crystalline inclusion compounds is discussed in comparison with an analogous ethynylene spaced host compound 1. The rotation around the fluorenol–anthracene bonds in 2 is highly restricted as indicated by solution NMR spectroscopy, molecular mechanics and semi-empirical calculations. Single-crystal X-ray structures of the inclusion complexes of 2 with 1-BuOH (2a), morpholine/H₂O (2b) and DMSO (2c) are in agreement with the bent geometry of the anthracene ring system suggested by the calculations. The structures exhibit specific modes of hydrogen bond interactions.     

Enzyme Electrodes For L-Glutamate Using Chemical Redox Mediators and Enzymatic Substrate Amplification

Abstract

L-glutamate was determined by recycling in a bienzyme system consisting of glutamated dehydrogenase and glutamate pyruvate transaminase. The NADH produced in the dehydrogenase reaction was determined either by direct oxidation at a modified graphite electrode or by reoxidation with oxygen through a N-methylphenazinium ion mediator. The oxygen was determined with an oxygen electrode. The former system resulted in an amplification of 15 and the latter of 60 times.The detection limits became 5-10^?7 and 1-10^?7 M L-glutamate for the respective systems.     

Synthesis,spectra, crystal structure and thermal properties of a polymeric 1-D cobalt(II) cyanato complex with hexamethylenetetramine

A new cobalt(II) cyanato complex, [Co(NCO)₂(H₂O)₂(hmt)] (I) where hmt is hexamethylenetetramine, has been synthesized and structurally characterized. The electronic spectra of the solid compound suggest octahedral cobalt and IR spectra revealed monodentate N-cyanato groups and aqua ligands, while hmt is a bridging N, N′-bidentate leading to a 1-D infinite polymeric chain. The structure has been confirmed from single crystal X-ray diffraction. Crystal data for I : Fw 319.20, a = 9.234(2), b = 11.252(2), c = 12.576(3) Å, β = 107.75(3)°, V = 1244.5(4) ų, Z = 4, T = 100 K. Crystal system : monoclinic, space group : C2/c. Hydrogen bonds of the type O–H ··· O and O–H ··· N between aqua molecules and O atom of the terminal N-cyanato groups or an N atom of hmt ligands consolidate and extend the structure to a 3-D network. The thermal properties of I are reported.