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81.
Katiuska Araujo Marinela Colina Román Mazurek José Delgado Hilda Ledo Elizabeth Gutierrez Lenín Herrera 《Fresenius' Journal of Analytical Chemistry》1996,355(3-4):319-320
The mercury concentrations in wastewater and sewage sludge of a stabilization pond system have been evaluated. The system is built by three parallel facultative ponds followed by two systems of three maturation ponds in series. The samples of wastewater and sludge were digested using nitric acid and placed into a Parr-type bomb for 4 h at 110° C. Mercury was measured by Cold Vapour Atomic Absorption Spectrometry (CV-AAS) at 253.7 nm with sodium tetrahydroborate as reductant. The methodologies were checked with an USEPA quality control sample, a standard reference material from NIST and with another method of mineralization (cold mineralization) showing good results. Concentrations of mercury in wastewater between 1.47 ± 0.75 gl–1 have been found at the entrance of the system and 0.74 ± 0.0 gl–1 at the exit, while in sludge the results were between 0.29 ± 0.12 gkg–1 in the facultative pond and 0.04 ± 0.02 gkg–1 in the second maturation pond (exit). 相似文献
82.
Fluorimetric and UV methods of detection for liquid chromatographic determination of phenothiazines (chlorpromazine, acetopromazine and propionylpromazine) were developed. The effects of several experimental parameters on the separation and the sensitivity of the methods were evaluated. The detection limits ranged from 31 to 350 ng ml−1. Optimized methods were successfully applied to determination of the promazines in bovine liver samples. 相似文献
83.
[reaction: see text] The synthesis of four bioactive analogues of the somatostatin (SRIF-14) mimetic, beta-d-glucoside (+)-2, in which the C1 indole side chain is replaced with indole surrogates, has been achieved. These congeners, possessing the naphthyl, benzothiophene, benzyl, and benzofuran substituents, were predicted to satisfy the electrostatic requirements of the tryptophan binding pocket of SRIF. Unlike the previously described C4 picolyl and pyrazinyl congeners, these ligands bind the hSST4 receptor. 相似文献
84.
In this article we compare and contrast the strategies and tactics used in the syntheses of the amphidinolide T family of natural products that have been reported by Fürstner, Ghosh and ourselves. Similar approaches to the trisubstituted THF ring present in the targets are utilized in all of the syntheses, but each strategy showcases a different means of macrocyclization. 相似文献
85.
Cassandra T. Eagle David FarrarGrant N. Holder Michelle L. HatleyShirley L. Humphrey Elizabeth V. OlsonMaria Quintos Joseph SadighiTom Wideman 《Tetrahedron letters》2003,44(12):2593-2595
The catalytic activities of three structural isomers of Rh2[N(C6H5)COCH3]4 in cyclopropanation reactions were surveyed. These studies showed cis cyclopropanation selectivity with bulky alkenes for 2,2-cis- and 2,2-trans-Rh2[N(C6H5)COCH3]4. 相似文献
86.
Optically-gated injection of fluorescently-labeled DNA has been accomplished for the first time. Rapid, serial analysis of oligonucleotide ladders has been shown on a microchip using this injection technique. Separations of five- and six-component samples have been completed in 60 s or less with a capability to carry out serial injections of these samples every 15 s. The technique has been shown to have better than five base resolution for small oligonucleotides and excellent reproducibility in migration times (< or = 0.75% RSD). Currently, the limit of detection for the system is 0.23 microM. Additionally, multiple unique samples of DNA have been consecutively analyzed in a single separation lane using optical gating. Six consecutive injections of three different samples have been achieved with no sample carryover and a total analysis time of approximately 10 min. These results show the potential of optical gating as an alternative injection technique for high-throughput DNA applications, such as genotyping and monitoring dynamic processes. 相似文献
87.
A kinetic spectrophotometric method for the determination of hydrocortisone acetate based on its condensation with isonicotinic acid hydrazide is proposed. The method is applied to the determination of hydrocortisone acetate in a commercially available pharmaceutical preparation, presented as a pomade, that also contains another corticosteroid and additional active compounds. The operating procedure involves dissolving the pomade in chloroform and the addition of the reagent solution directly to the cuvette, in this way avoiding the previous extraction of analytes from the insoluble pomade matrix required by the alternative HPLC procedure. Calibration is performed by partial least-squares regression, using absorbance or first derivative spectra values recorded each minute during the first 30 min of reaction. Use of first derivative spectra overcomes possible scattered light problems produced by excipients precipitating, and produced slightly better results than absorbance data. The relative standard deviation obtained for 11 replicates analysed on different days was approx. 1.5%. The proposed method improves both accuracy and precision of the classical initial rate method and the precision of the HPLC procedure. 相似文献
88.
Santos E Schühle DT Jones H Schmickler W 《Langmuir : the ACS journal of surfaces and colloids》2005,21(14):6406-6421
The nonlinear optical properties of self-assembled monolayers obtained from bonding two different alpha-functionalized terthiophenes (alpha-T3) to (111) silver electrode surfaces have been investigated using second harmonic generation (SHG). The two (alpha-T3) compounds used were functionalized with alkane chains of different lengths (C8 and C4), and each was terminated with a thiol anchoring group. A nitrile group was attached to the terminal thiophene ring of the (alpha-T3) compound with the C4 chain. The orientation of the polarization of the incident beam was changed systematically and gradually between "p" and "s" orientation and the SH signal (isotropic and anisotropic contributions) analyzed in both directions ("P" and "S"). The symmetry of the system was reduced by the presence of the adlayers from C3v to C3. The dependence on the applied potential and the incident wavelength has also been studied. The relative magnitudes and phases of the various second-order tensor elements have been estimated and compared with the values for a bare surface. A resonance process in the (alpha-T3) pi moiety has been investigated, and from this, the effective "band-gap" energies of the organic semiconductor SAMs (i.e., the energy difference between the pi-pi bands) have been estimated. 相似文献
89.
A. Segura Carretero C. Cruces Blanco R. Estrada Fernández A. Fernández Gutiérrez 《Analytical and bioanalytical chemistry》1998,360(5):605-608
A method for the determination of the fungicide thiabendazole (TBZ) by micellar-stabilized room-temperature phosphorescence is described. It does not require any separation step and allows the direct determination of the fungicide in canned pineapple samples. The effect of various experimental conditions is discussed in detail. The analytical curve of thiabendazole gives a linear dynamic range of 23.8–500.0 ng mL–1 and a detection limit of 23.8 ng mL–1. Recoveries of 103.9 and 89.2% for syrup and canned pineapple pulp, respectively, were obtained for 250 ng mL–1 thiabendazole. 相似文献
90.
Micellar catalysis of the reaction of 2,4-dinitrofluorobenzene with phenoxide and thiophenoxide ions
H. Chaimovich A. Blanco L. Chayet L.M. Costa P.M. Monteiro C.A. Bunton C. Paik 《Tetrahedron》1975,31(9):1139-1143
The reactions of 2,4-dinitrofluorobenzene with phenoxide and thiophenoxide ion in water are strongly catalyzed by micelles of cetyltrimethylammonium bromide (CTABr) by factors of 230 and 1100 respectively. Nonionic micelles of Brij weakly catalyze the reaction with thiophenoxide ion. Spectral measurements show that phenoxide, and especially thiophenoxide, ions interact strongly with micelles of CTABr which also markedly change the acid dissociation of phenol under given buffer conditions. 相似文献