Iron speciation by solid phase extraction and flame atomic absorption spectrometry using N,N′-bis-(2-hydroxy-5-bromobenzyl)-2-hydroxy-1,3-diiminopropane

A new Schiff base, N,N′-bis-(2-hydroxy-5-bromobenzyl)-2-hydroxy-1,3-diiminopropane, has been synthesized for the very sensitive determination of iron(III) and iron(II) in natural water samples. It enabled a very selective and rapid method for iron determination to be developed. The method has also been applied to total iron determination in sediment samples. In the preconcentration system, the Schiff base reagent is mixed with the samples and chelates containing iron(III). The complexes are then adsorbed on silica gel within a column system. Elution of the adsorbed chelate from the silica gel was performed with a small volume of acetone containing 2.5% nitric acid. The iron is measured off-line by flame atomic absorption spectrometry. The method can be applied to the preconcentration, separation and speciation of iron. The effects of parameters such as pH, sample flow rate, eluent flow rate, foreign ions and ligand concentration have been investigated. The effect of humic acid that can produce complexes with metal ions in natural systems has also been investigated. The results obtained indicate that the method is not affected by the presence of up to 10 ppm humic acid, which would be a very high concentration to be present in natural systems. The solid phase extraction method developed has been applied to the determination of iron in both natural water samples and sediment samples. The LOD was found to be 0.17 mg L⁻¹ when no preconcentration was used, although preconcentration factors of 100 could be achieved. The recovery values for spiked samples were between 100 and 104%. The results were compared statistically with those from the standard 1,10 phenanthroline method used for iron speciation in water systems. A Student’s t-test indicated no significant difference between the two methods. In addition, this method was applied to the analysis of a certified sediment sample, LGC 6156. Generally, a 10-fold preconcentration factor was required for the analysis of natural water samples.     

The temperature-composition phase diagram of the HgTe?HgI2 pseudobinary system on the HgTe rich side

The temperature-composition phase diagram of the HgTe? HgI₂ system was determined from 0 to 45 Mol-% HgI₂ between 25 and 670°C using Debye-Scherrer powder X-ray diffraction techniques and differential thermal analysis. Solid solutions of HgTe and HgI₂ with the cubic, zinc blende-type structure exist above 300°C, having a maximum solubility of 11.7 ± 0.8 Mol-% HgI₂ in HgTe at 501 ± 5°C. The known monoclinic compound Hg₃Te₂I₂ is formed by a peritectic reaction upon cooling at 501 ± 5°C, with the peritectic point at approximately 37 ± 4 Mol-% HgI₂.     

Fourier Transform Infrared Spectroscopy and Solid Phase Extraction Applied to the Determination of Oil and Grease in Water Matrices

 The solid phase extraction as a solvent-free method for the analysis of oil and grease in waters was studied. The use of a PTFE surface as a solid phase allows the retention of the volatile fraction of oil and grease, and further analysis of carbon–hydrogen bonds using infrared spectroscopy can be done on the surface. Various oils and grease samples were tested: n-hexadecane, n-tetradecane, n-nonadecane, n-docosane, isooctane, diesel oil and gasoline. Temperatures from 25° to 90 °C and a range of heating times were checked for extraction. Precision tests showed relative standard deviation values of around 10% in several samples of the same concentration. Calibration lines of n-hexadecane showed high correlation coefficients from 0.9 to 30 mg/l. Recoveries for the various oils using different calibration lines showed values from 90 to 110%. The method described here is fast and clean, and allows reproducible measurements of oil and grease in water that do not require the use of a solvent. Received March 1, 2001; accepted August 15, 2001; published online July 15, 2002     

An electropolymerized aniline-based fiber coating for solid phase microextraction of phenols from water

An aniline-based polymer was electrochemically prepared and applied as a new fiber coating for solid phase microextraction (SPME) of some priority phenols from water samples. The polyaniline (PANI) film was directly electrodeposited on the platinum wire surface in sulfuric acid solution using cyclic voltammetry (CV) technique. The efficiency of new coating was investigated using a laboratory-made SPME device and gas chromatography with flame ionization detection for the extraction of some phenols from the headspace of aqueous samples. The scanning electron microscopy (SEM) images showed the homogeneity and the porous surface structure of the film. The results obtained proved the ability of this polymer as a suitable SPME fiber coating for trapping the selected phenols. Influential parameters affecting the extraction process were optimized and an extraction time of 50 min at 50 °C gave maximum efficiency, when the aqueous sample was saturated with NaCl and adjusted at pH 2. This new coating can be prepared easily in a reproducible manner and it is rather inexpensive and stable against most of organic solvents. The PANI thickness can be precisely controlled by the number of CV cycles. At the optimum conditions, the R.S.D. for a double distilled water spiked with phenol and chlorophenols at ppb level were 4.8-17% (n = 3) and detection limits for the studied compounds were between 0.69 and 3.7 ng ml⁻¹, except for phenol and 4-chlorophenol. The optimized method was successfully applied to some real-life water samples.     

Analysis of organic compounds in environmental samples by headspace solid phase microextraction

The analysis of samples contaminated by organic compounds is an important aspect of environmental monitoring. Because of the complex nature of these samples, isolating target organic compounds from their matrices is a major challenge. A new isolation technique, solid phase microextraction, or SPME, has recently been developed in our laboratory. This technique combines the extraction and concentration processes into one step; a fused silica fiber coated with a polymer is used to extract analytes and transfer them into a GC injector for thermal desorption and analysis. It is simple, rapid, inexpensive, completely solvent-free, and easily automated. To minimize matrix interferences in environmental samples, SPME can be used to extract analytes from the headspace above the sample. The combination of headspace sampling with SPME separates volatile and semi-volatile analytes from non-volatile compounds, thus greatly reducing the interferences from non-target compounds. This paper reports the use of headspace SPME to isolate volatile organic compounds from various matrices such as water, sand, clay, and sludge. By use of the technique, benzene, toluene, ethyl-benzene, and xylene isomers (commonly known as BTEX), and volatile chlorinated compounds can be efficiently isolated from various matrices with good precision and low limits of detection. This study has found that the sensitivity of the method can be greatly improved by the addition of salt to water samples, water to soil samples, or by heating. Headspace SPME can also be used to sample semi-volatile compounds, such as PAHs, from complex matrices.     

SPME-GC-MSD for Determination of Nine Phenyl Compounds in Snow Water in Beijing China

Solid phase microextraction (SPME) then capillary gas chromatography with mass spectrometric detection have been used for determination of nine phenyl compounds in snow water in Beijing City. Headspace extraction with a fiber coated with 100 µm PDMS was used to extract the compounds. Extraction and desorption times were optimized at 8 and 2 min, respectively. Relative standard deviation (RSD) of the analytical method was found to be less than 5%. The linear range was wide and limits of detection were less than 5 ng mL⁻¹ for the nine target analytes. Several phenyl compounds at ng mL⁻¹ levels were detected in snow samples in Beijing, indicating the corresponding air pollution.     

Synthesis,characterization, and application of griseofulvin surface molecularly imprinted polymers as the selective solid phase extraction sorbent in rat plasma samples

In present study, an investigation was carried out to develop and validate an analytical method for the selective extraction and determination of griseofulvin (GSF) from plasma samples. For this purpose, a rational approach was made to synthesize and characterize the surface molecularly imprinted polymers (SMIPs). The SMIPs were utilized as solid phase extraction (SPE) sorbents. The SMIPs were prepared by using GSF as template molecule on the surface of modified silica particles through a non-covalent technique. The particles demonstrated high adsorption capacity (119.1 µg/mL), fast adsorption equilibrium time (30 min) and good recognition selectivity for the template drug. The scanning electron microscopy and infrared spectroscopy were used to explain the structural and morphological characteristics of the SMIPs and surface non-imprinted polymers. The SPE method was combined with HPLC for plasma analysis. The method validation results demonstrated that the established method possessed good linearity for GSF ranging from 0.1 to 50 µg/mL (R² = 0.997). The limit of detection for this method was 0.02 µg/mL for rat plasma samples. The recoveries of GSF from spiked plasma samples were (90.7–97.7%) and relative standard deviations were (0.9–4.5%). Moreover, the SMIPs as selective SPE sorbent can be reused more than 8 times which is a clear advantage over commercial SPE sorbents. Finally, the usefulness of the proposed strategy was assessed by extraction and detection of GSF in real rat plasma samples.     

New Bio-Based Furanic Materials Effectively Absorb Metals from Water and Exert Antimicrobial Activity

Development of sustainable bio-based materials for removal of toxic contaminants from water is a high priority goal. Novel bio-based binary and ternary copolymers with enhanced ion-exchange, adsorption and antibacterial properties were obtained by using plant biomass-derived diallyl esters of furandicarboxylic acid (FDCA) as crosslinking agents and easily available vinyl monomers. The synthesized copolymer materials showed higher sorption capacities for Ni^II, Co^II and Cu^II compared to the commercial ion-exchange resins, and they maintained their high metal adsorption capacities for over 10 cycles of regeneration. The synthesized copolymer gels containing 1–5 wt % of the crosslinker showed excellent water absorption capacities. The synthesized copolymers with 1 % crosslinker content showed swelling ratios high enough to also act as moisture absorbents. Synthesized copolymers with crosslinker content of 10 wt % performed as contact-active antibacterials by inhibiting the growth of Gram-positive (S. aureus) and Gram-negative bacteria (E. coli, K. pneumonia) in suspension tests.     

REACTIONS IN SOLID STATE WITHIN POLYURETHANES. KINETICS AND POSTCURE REACTION MECHANISM IN CASTING POLYURETHANE ELASTOMERS

The solid state postcure reaction mechanism of polyurethane elastomers (PU) synthesized using a relatively small excess (up to 10%) of isocyanate was studied. The postcure process succeeds especially with the assistance of atmospheric humidity and, its process velocity depends on PU sample thickness. The polymer network is consolidated mainly by the formation of a new urea group. The formation of allophanate, uretidinedione, and isocyanurate groups and possible reticulations by the intermediary amine groups formed, play only a secondary role in the studied conditions. Kinetic equations regarding the postcure evolution were followed by means of the changes in mechanical properties. The evolution of the process was correlated to different kinetic measurements regarding the elementary processes involved like the consumption of NCO groups, absorption of water from the atmospheric humidity, and desorption of CO₂ resulted during the formation of urea group. The CO₂ desorption appears to be the slowest dynamic process.     

NOVEL POLYPHENYLENES CONTAINING ORTHOGONAL PHENYL AND BENZO-CROWN-ETHER GROUPS

The synthesis of a new class of polyphenylenes substituted with a large number of phenyl and benzo-crown-ether groups has been described. The polymers, prepared by Suzuki cross-coupling reaction between polyphenylated dibromide and benzene-1,4-diboronic acid, exhibit outstanding solubility in common organic solvents such as THF and chloroform. Preliminary results on molecular weights and thermal analysis of one representative polymer are discussed.