8-Hydroxyquinoline derivative 1 as a fluorescent chemosensor for Zn²⁺ was synthesized. Because Cd²⁺ is often found with Zn²⁺ in the environment and can form fluorescent complexes with chelating fluorophores, a potentially important property of chemosensors for Zn²⁺ is their selectivity for Zn²⁺ over Cd²⁺. The Zn²⁺ or Cd²⁺ complexes of 1 gave an emission band from the 1:1 complex, but the fluorescence intensity for Cd²⁺ was a half of that for Zn²⁺. Ligand 1 is suited for use as a fluorescent chemosensor for Zn²⁺.

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In vitro screening assays are useful techniques for the determination of receptor-mediated activities in environmental samples. In order to define whether environmental chemicals act as an agonist or antagonist to the human estrogen receptor (hER), we have constructed a biosensor based on ligand-inducible interactions between hER and relative proteins on a quartz crystal microbalance (QCM). The his-tagged proteins, which were expressed in E. coli by recombinant DNA technology, were immobilized on an Au-electrode with Ni(II)-mediated chemisorption using the histidine tag and thiol-modified iminodiacetic acid. The resonance-frequency change of the protein-modified electrode was caused by association or dissociation with the hER relative proteins on the surface in the presence of estrogen. These results suggest that this sensor is applicable as a large-scale screening tool for estrogenic compounds.

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Isotope dilution analysis of the sub-μg l^-1 levels of selenite and selenate in natural water samples by microwave-induced nitrogen plasma mass spectrometry (MIP-MS) was performed. An appropriate amount of a spike solution containing ⁷⁸Se-selenite and ⁷⁸Se-selenate was added to the natural water sample to be analyzed. Both analytes in the water were then concentrated simultaneously by passing the sample through a column that was filled with an anionic exchange resin. After the concentration process, all of the selenite and some of the selenate on the resin were eluted by 0.03 M nitric acid. The residual selenate was eluted by 0.13 M nitric acid. The eluted sample solutions were injected into MIP-MS, and isotope dilution analyses were carried out. Selenite and selenate concentrations as low as 0.01 μg l^-1 in the natural water sample were successfully determined by the proposed method.

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A rapid and reproducible method is described that employs solid-phase extraction (SPE) using dichloromethane, followed by gas chromatography (GC) with flame ionization detection for the determination of benzene, toluene, ethylbenzene, xylene and cumene (BTEXC) from Buriganga River water of Bangladesh. The method was applied to detect BTEXC in a sample collected from the surface, or 5 cm depth of water. Two-hundred milliliters of n-hexane-pretreated and filtered water samples were applied directly to a C₁₈ SPE column. BTEXC were extracted with dichloromethane and the BTEX concentrations were obtained to be 0.1 to 0.37 μg ml^-1. The highest concentration of benzene was found as 0.37 μg ml^-1 with a relative standard deviation (RSD) of 6.2%; cumene was not detected. The factors influencing SPE e.g., adsorbent types, sample load volume, eluting solvent, headspace and temperatures, were investigated. A cartridge containing a C₁₈ adsorbent and using dichloromethane gave a better performance for the extraction of BTEXC from water. Average recoveries exceeding 90% could be achieved for cumene at 4°C with a 2.7% RSD.

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The major element composition, including two kinds of clay minerals and moisture content of sound-producing sand are reported for the first time. Sand from 33 beaches in Japan has been found to make sound. Ten sound-producing beaches were selected to compare with silent beach sand. Both sound-producing sand and silent beach sand are mostly composed of quartz and feldspar. The range of SiO₂ content of sound-producing sand is not different from silent sand samples. This indicates that a high quartz content is not necessary to produce sound, although more than 60 weight percent of quartz is necessary. One silent sand recovered its sound after a 3.5 percent HNO₃ treatment. Also, a small portion of clay minerals was found. A clean grain surface is a necessary factor for sand to produce sound. Illite was found in all silent sand samples.

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The effect of the temperature on the co-extraction of water molecules with Na⁺ from water to nitrobenzene (NB) in the presence of dipicrylaminate ion has been studied. The number (n) of water molecules co-extracted with a Na⁺ ion, as measured by the Karl Fischer method, increased from 3.1 to 5.2 with increasing temperature (6 - 65°C). This observation is in apparent contradiction to the expectation from simple thermodynamics because hydration is generally an entropically unfavorable process. Additional ¹H NMR experiments for the selective hydration of Na⁺ in deuterated NB have confirmed that the association constants of water with Na⁺ indeed decrease with increasing temperature. On the other hand, however, it has been shown that water solubility into NB substantially increases with temperature. We conclude that the latter effect overwhelms the former unfavorable entropy effect, which results in a net increase of the n-value, as observed.

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The adsorption-desorption phenomena of surfactants were studied by measuring differential capacity-potential curves in a static solution and differential capacity-time curves in a flowing solution. The surfactants investigated were Aerosol OT, cetylpyridinium chloride, Hyamin 1622, tetrabutylammonium bromide, Triton X-100 and trioctylphosphineoxide. The differential capacity-potential and differential capacity-time curves for these surfactants showed different shapes, with and without peaks. The differential capacity-time curves were used to study the adsorption reversibility of the surfactants at a mercury electrode. The adsorptions of Hyamin 1622 and Triton X-100 were irreversible at all the potentials investigated. The adsorptions of Aerosol OT and trioctylphosphineoxide were irreversible except at the potential more positive than-0.2 V. The adsorption of tetrabutylammonium bromide was almost reversible at any potential investigated. The adsorption of cetylpyridinium chlolide was complicated, indicating different orientations of adsorption.

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A novel imidazole membrane sensor based on 2,4,6-triphenyl thiopyrilium perchlorate (TTP) as an excellent charged carrier, poly(vinyl chloride) (PVC), the plasticizer dibutyl phthalate (DBP) and oleic acid as an additive is described. The sensor responds to imidazole over a wide concentration range from 1.0 × 10^-5 to 1.0 × 10^-1 M with a slope of +33.5 ± 0.5 mV per decade. The detection limit of the electrode is 3.0 × 10^-6 M and it can be used for at least four weeks without any measurable change in sensitivity. The sensitivity of the electrode is high enough to permit the detection of as little as 0.2 μg/ml of imidazole without any significant interference from high levels of other components and especially, amino acids. The potentiometric selectivity coefficient data revealed negligible interference from common cations, anions and amino acids. The electrode has a relatively fast response time (<30 s), and good slope stability. The proposed sensor was successfully applied to the determination of imidazole in synthetic serum samples.

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A new type of ether-bonded packing for reversed-phase HPLC (RP-HPLC) was synthesized by reacting 1-octanol with β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, followed by coupling the product onto porous silica. The prepared packing was characterized by elemental analysis, solid-state ¹³C NMR, and Fourier transform infrared (FT-IR) spectroscopy. Chromatographic evaluations were performed by using a mixture of organic compounds as the analyte and methanol-water as binary mobile phase. The influence of the composition of organic modifier on the retention behavior of basic compounds was studied. The hydrolytic stability of the packing between pH 2.5 - 7.5 was also investigated. The results showed that the new stationary phase has excellent chromatographic properties and good hydrolytic stability.

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Capillary electrophoresis (CE) is a powerful separation technique that is peculiarly able to determine the fingerprints of traditional Chinese medicine. The Capillary Electrophoresis Fingerprints (CEFP) of compound liquorice tablets (CLTs) was established to evaluate the quality of CLTs. The background electrolyte was a 50 mM sodium borate solution. The detection wavelength was 228 nm and a 14 kV voltage was applied. Hydrochlorothiazide served as an internal standard and temperature was 24 - 25°C. The CLTs were extracted by a 50 mM borate solution containing 10% (v/v) methanol. The results showed that CE was a powerful tool for detecting of the fingerprints of traditional Chinese medicine and their constituents. The quality assessments were performed to compare the correlation coefficients (R) and cos θ (C) between each batch vector of CLTs and the total standard profile vector (TSPV), which was the mean vector of all the batch vectors of CLTs with 1.0. The nearer to 1.0 was the R or C, the higher was the similarity. The values of R and C between the TSPV and each batch vector of CLTs produced at different factories were all above 0.9150. The values of R and C between every two standard profile vectors (SPV) from different factories were all above 0.9420. A good stability and reproducibility of the CEFP of CLTs were obtained in the study. Further, we first put forward a new parameter Q to evaluate both the quantification accuracy and the qualitative accuracy for a CEFP, which was verified by determinations of GHIA, GHEA, MP and SB in CLTs. The CEFP was successfully employed to assess the quality of CLTs produced at Kunming Pharmaceutical Factory to be good.

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Bench-scale experiments were conducted in the laboratory, aiming to remove aluminum from water. They were based on the use of powdered marble wastes (PMW), which are inexpensive and produced in large quantity, and thus potentially cause environmental problems, as an effective inorganic sorbent and oleic acid (HOL) as surfactant. The main parameters (solution pHs, sorbent, surfactant and aluminum concentrations, shaking time, ionic strength and the presence of foreign ions) that influence the sorptive-flotation process were examined. Good results were obtained under the optimum conditions, for which nearly 100% of aluminum at pH 7 and at room temperature (∼25°C) was removed. The procedure was successfully applied to the recovery of aluminum spiked to some natural water samples. Moreover, a sorption and flotation mechanism is suggested.

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A laboratory-made micro-cryogenic chromatographic oven was mainly improved in size, which was controlled at 6 × 6 × 2.5 cm. A thermoelectric system was used to cool the capillary column instead of the traditional liquid cryogen. A cold block connected to the cryogenic module was directly solidified at room temperature with thermally conductive adhesive so that the uniformity of transferring heat was greatly improved, and the size of the system was reduced. Moreover, this system was inexpensive and convenient for both operation and control. The newly developed device coupled with headspace solid-phase microextraction (SPME) was successfully applied to the determination of methyl tert-butyl ether (MTBE) and its degradation products. During the analysis procedure, a 65 μm polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber was used to extract MTBE and its degradation products. The extraction was controlled at 50°C for 30 min and the NaCl content in the sample was maintained at 35%. The limits of detection (LODs) ranged from 0.006 μg mL^-1 (for MTBE) to 0.206 μg mL^-1 (for methyl acetate) and the relative standard deviations (RSD%) were below 4%. The spiked recoveries for the developed method were evaluated using various water samples as a matrix.

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Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was used to determine the Pb/Ca ratios in the enamel of deciduous incisors, a biomarker of in utero Pb exposure, using pelletized bone certified reference materials (CRMs) as calibrants. The detection limit for Pb by LA-ICP-MS was 11 μg kg^-1 demonstrating an adequate sensitivity for Pb in the teeth of unexposed individuals (0.1 - 10 mg kg^-1). The precision for the Pb/Ca ratios in NIST SRM 1486 Bone Meal was 3.4%. The correlation between Pb/Ca ratios obtained by LA-ICP-MS and those obtained by a digestion method was highly significant. We found one point calibration by a CRM was applicable for the quantification of Pb in tooth enamel. This method will be valuable for the assessment of in utero Pb exposure levels.

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The adsorption behavior of gold (Au), silver (Ag) and palladium (Pd) on nanometer-size titanium dioxide (NSTD) at low concentrations was studied using inductively coupled plasma atomic emission spectrometry (ICP-AES). A preconcentration procedure of the analytes was carried out using NSTD as a solid-phase extractant before their determination by ICP-AES. The optimum conditions for adsorption were studied in detail, and under the condition that Au, Ag and Pd ions could be adsorbed and recovered quantitatively. The static adsorption capacities of Au, Ag and Pd on NSTD were 22.63, 14.06 and 11.82 mg/g, respectively. For the elution of gold, silver and palladium, a mixture of 5% thiourea solution and 3 mol L^-1 HNO₃ was used. The parameters tested included: pH conditions, contact time of the analytes with NSTD, flow rate, adsorption capacity and sorption kinetics. According to the definition of IUPAC, the detection limits (3σ) of this method for Au, Ag and Pd with an enrichment factor of 50 were (0.016), (0.006) and (0.012) μg mL^-1, respectively, the relative standard deviations (RSD) were 8.7%, 4.5% and 7.4%, respectively (n = 6). Some geological samples were determined with satisfactory results.

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Gold-deposited optical fiber sensors with film thicknesses from 30 to 60 nm were prepared, and the responses to a wide range of a refractivity (1.33 - 1.54 refractive index (RI) units) were investigated both experimentally and theoretically. The response curve of the sensor has two minima in the refractivity range from 1.33 to 1.44 and at 1.462 RI units. The former minimum is due to surface plasmon resonance (SPR) in the thin gold film, and shifts to a lower refractivity as the film becomes thicker. The response curves of the sensors with film thicknesses of 45 and 60 nm agreed well with those calculated from SPR theoretical equations. Morphology observations of the surfaces of deposited gold films on glass by atomic force microscopy (AFM) and a variation in resistance of the films with various thicknesses show the structure of the gold films. We concluded that the thin deposited gold films have many defects, and that the core of the gold-deposited optical fiber leaks light through the defects to the sample solution with the same refractivity (1.462 RI units) as that of the core.

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A simple and rapid method for the analysis of trace amounts of gold(III), palladium(II), and platinum(IV) by the combined use of graphite furnace atomic absorption spectrometry and anion-exchange separation was proposed, and successfully applied to the rapid determination of metals in industrial waste solutions obtained from the final process of noble-metal recovery factories, because noble metals can be selectively and quantitatively separated to a high degree by using a small column containing only a 0.7 g-portion of a common anion-exchange resin and a dilute thiourea solution.

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The determination of stoichiometries and stability constants of complexes by means of UV-visible spectrophotometry applying traditional methods does not evaluate the quality of the values obtained, since the classic application of these methods does not provide coverage intervals. However, the use of chemometric techniques in different steps of the application of these methods makes it possible to obtain not only a real value of the characteristics of the complexes but a validation of such a value. In this paper a methodology is proposed that combines some traditional methods, three different regression models (LMSR, LSR and LSPR) and a small number of mathematical algorithms. This methodology is able to estimate, in a simple and rigorous way, the stoichiometry and stability constant of a complex and its corresponding uncertainties.

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Multidimensional T₁ρ-, diffusion-filtered and diffusion-ordered NOESY techniques were applied to identify segments of a ligand binding with a protein receptor. These experiments can easily provide intermolecular NOEs of the complex, which are of great significance for characterizing the binding epitopes of a ligand. This information cannot be obtained by high-throughput 1D NMR experiments, used for determining the binding affinity, although multidimensional NMR experiments require more experiment time. The present results indicate that the current experiments using T₁ρ- and diffusion-edited techniques are very suitable for identifying segments of a ligand binding with a protein receptor in the drug discovery process.

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A novel compound, N,N"-bis(2,4-di-sulfobenzyl)tolidine tetrasodium salt (SBT), was synthesized for use as a chromogenic indicator for oxidizing substances, and its applicability to the colorimetric determination of chlorine in water was examined.

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A sensitive, selective and rapid method for the determination of nickel based on a rapid reaction of nickel(II) with 2-(2- quinolylazo)-5-diethylaminoaniline (QADEAA) has been developed. In the presence of pH = 6.0 ammonia-ammonium chloride buffer solution and sodium dodecyl sulfonate (SDS) medium, QADEAA reacts with nickel to form a violet complex having a molar ratio of 1:2 (nickel to QADEAA). The molar absorptivity of the complex is 1.38 × 10⁵ l mol^-1 cm^-1 at 595 nm. Beer"s law is obeyed in the range of 0.01 - 0.4 μg/ml. This method had been applied to the determination of nickel with good results.

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A rapid, sensitive and accurate atomic absorption method for Cr(III) and Cr(VI) ions was developed based on the cloud-point extraction (CPE) technique. Cr(III) reacts with a new Schiff"s base ligand to form the hydrophobic complex, which is subsequently entrapped in the surfactant micelles. The Cr(VI) assay is based on its reduction to Cr(III) by the addition of concentrated H₂SO₄ and ethanol to the sample solution. The condensed surfactant phase containing the metal chelates is introduced into an atomic absorption spectrometer. The relative standard deviations were 2.1% for both species and the limits of detection were around 0.17 μg l^-1.

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A simple, accurate and sensitive method for the microdetermination of benzocaine, lignocaine and procaine hydrochlorides in pure forms and in pharmaceutical formulations is described. The procedure is based on the reaction of those drugs in an aqueous acidic medium with p-benzoquinone to form charge-transfer complexes. The method has been used for the determination of 5.0 - 70, 5.0 - 60 and 5.0 - 90 μg ml^-1 of benzocaine, lignocaine HCl and procaine HCl, respectively. The complexes have apparent molar absorptivities of 1.70 × 10³, 2.79 × 10³ and 2.42 × 10³ L mol^-1 cm^-1 and Sandell sensitivities of 9.72, 10.34 and 11.25 ng cm^-2, respectively. The proposed procedure of analysis is as accurate as the British Pharmacopoeial method (2003). The method was successfully used for the determination of those drugs in the presence of their degradation products, additives and excipients, which were normally encountered in pharmaceutical formulations.

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The structure of an S₂O mixed-donor macrocycle incorporating para-substituted xylyl subunit was characterized by a single crystal X-ray analysis. The crystal structure shows an exo-dentate orientation of sulfur and oxygen donor atoms due to the fully stretched aliphatic ring conformation. Thus all of torsional angles between donor atoms are arranged anti and S···S distance in a ring is 6.764(1)Å, which is larger than those values of ortho- and meta-type analogs. The observed high rigidity of the ring conformation may induce the extraordinary behaviors in chelation.

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The title compound was extracted from the natural product of plant origin. It crystallizes in tetragonal space group P4₁ or P4₃, with cell parameters a = 15.795(2)Å, c = 11.970(5)Å and Z = 4. The structure exhibits intermolecular hydrogen bonds of the type C-H···O.

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