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111.
Different organic borates, phosphates, sulphates, and carboxylic acids are evaluated as extraction carriers in three-phase liquid-phase microextraction (LPME). Hydrophilic basic drugs form ion-pairs with the carriers and are extracted as ion-pair complexes into an organic liquid membrane of n-octanol or peppermint oil immobilized in the pores of a polypropylene hollow fiber. From this point, the basic drugs are released into a 20-microL solution of 50mM HCl placed inside the lumen of the hollow fiber (acceptor solution). Simultaneously, the carrier is neutralized by protons from the acceptor solution (protonated to maintain the charge balance). Both water-soluble and water-insoluble carriers are tested. One promising candidate among the water-soluble carriers is 1-heptanesulfonic acid. This is added to the sample solution to a final concentration of 25mM and served to ion-pair the analytes within the sample solution. Among the less water-soluble candidates, a mixture of di(2-ethylhexyl) phosphate (DEHP) and tris(2-ethylhexyl) phosphate (TEHP) serve as efficient carriers. Ten percent (w/w) of each of DEHP and TEHP are added to the organic liquid membrane, and these carriers principally worked through ion-pairing with the analytes at the interface between the sample solution and the organic liquid membrane. Several carriers are found to be compatible with human plasma samples, and bromthymol blue is particularly efficient in combination with these protein-containing matrices. Following optimization of the conditions for bromthymol blue, including saturation of the plasma samples with sodium sulphate, extraction recoveries between 45% and 75% are obtained for eight model drugs after 60 min of extraction. With bromthymol blue as the carrier, highly acceptable validation data are obtained for phenylpropanolamine and practolol extracted from human plasma.  相似文献   
112.
Basic drug substances were transported across a thin artificial organic liquid membrane by the application of 300 V d.c. From a 300 microl aqueous donor compartment (containing 10 mM HCl), the drugs migrated through a 200 microm artificial liquid membrane of 2-nitrophenyl octyl ether immobilized in the pores of a polypropylene hollow fiber, and into a 30 microl aqueous acceptor solution of 10 mM HCl inside the lumen of the hollow fiber. The transport was forced by an electrical potential difference sustained over the liquid membrane, resulting in electrokinetic migration of drug substances from the donor compartment to the acceptor solution. Within 5 min of operation at 300 V, pethidine, nortriptyline, methadone, haloperidol, and loperamide were extracted with recoveries in the range 70-79%, which corresponded to enrichments in the range 7.0-7.9. The chemical composition of the organic liquid membrane strongly affected the permeability, and may serve as an efficient tool for controlling the transport selectivity. Water samples, human plasma, and human urine were successfully processed, and in light of the present report, electrokinetic migration across thin artificial liquid membranes may be an interesting tool for future isolation within chemical analysis.  相似文献   
113.
The fluorescent properties of a new 1,3,5-cyclohexyltricarboxamide-based low-molecular-weight hydrogelator (1) derivatized with one hydrophobic fluorophore and two hydrophilic substituents have been investigated. Gels of 1 are composed of long, nonbranched fibers of uniform diameter, as shown by cryo-transmission electron microscopy (cryo-TEM). The aggregation of the naphthalene fluorophore moieties of the gelator molecules in the gel fibers favors the occurrence of a fast energy migration process that allows a very efficient sensitization of the fluorescence of a hosted fluorophore. Such processes have been investigated by the addition of propyldansylamide (PDNS), at two different concentrations, to gels of 1. Around 30% of the total PDNS added to the gels was found to be incorporated in the gel fibers, as confirmed by deconvolution of the fluorescence spectrum, excited-state lifetime measurements, and steady-state and time-resolved fluorescence anisotropy measurements. Moreover, anisotropy measurements show that the fluorophore that is incorporated within the gel fibers is almost completely immobilized, indicating that the interactions of PDNS with the gelator moieties are very strong. This particular configuration of donor (1) and acceptor (PDNS) molecules leads to a very efficient antenna effect, where 50% of the absorbed photons are funneled through to the dansyl derivative when one PDNS molecule is incorporated in the gel fibers for every 100 gelator molecules. A 5-fold higher concentration of PDNS increases the percentage of funneled photons to 75%.  相似文献   
114.
The conditions signaling the formation of bidisperse brushes in ordered block copolymers are investigated as an A(2) block is progressively grown onto an A(1)B diblock copolymer to form a series of molecularly asymmetric, isomorphic A(1)BA(2) triblock copolymers. Small-angle scattering and self-consistent field theory confirm that the microphase-ordered period decreases when the A(2) block is short relative to the A(1) block, but then increases as A(1)+A(2) bidisperse brushes develop. The mechanical properties systematically follow the spatial distribution of the A(2) block.  相似文献   
115.
Methods for the alkylation of di-tert-butyl hydrazine-1,2-dicarboxylate were investigated. It was found that under mild conditions mono- or di-substituted hydrazine derivatives were obtained in good to excellent yield. Furthermore, it was shown that one of the two Boc-groups of the disubstituted derivatives was selectively removed by heating, leading to precursors for trisubstituted hydrazines.  相似文献   
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A new method for the simultaneous determination of 11 synthetic musks and one fragrance compound in house dust was developed. The nitro musks included musk ketone (MK, 4-tert-butyl-3,5-dinitro-2,6-dimethylacetophenone), musk xylene (MX, 1-tert-butyl-3,5-dimethyl-2,4,6-trinitrobenzene), musk ambrette (1-tert-butyl-2-methoxy-4-methyl-3,5-dinitrobenzene) and musk moskene (1,1,3,3,5-pentamethyl-4,6-dinitroindane). The polycyclic musk compounds were 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta-(γ)-2-benzopyran (HHCB), 7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene (AHTN), 4-acetyl-1,1-dimethyl-6-tert-butylindane, 6-acetyl-1,1,2,3,3,5-hexamethylindane, 5-acetyl-1,1,2,6-tetramethyl-3-isopropylindane, 6,7-dihydro-1,1,2,3,3-pentamethyl-4(5H)-indanon. The one macrocyclic musk was 1,4-dioxacycloheptadecane-5,17-dione. The bicyclic hydrocarbon fragrance compound (1,2,3,4,5,6,7,8-octahydro-2,3,8,8-tetramethylnaphthalen-2yl)ethan-1-one (OTNE) and HHCB-lactone (4,6,6,7,8,8-hexamethyl-1H,3H,4H,6H,7H, 8H-indeno[5,6-c]pyran-1-one), a degradation product of HHCB, were also analysed. NIST SRM 2781 (domestic sludge) and SRM 2585 (organic contaminants in house dust) were analysed for these target compounds. The method was applied for the analysis of 49 paired samples collected using two vacuum sampling methods: a sample of fresh or "active" dust (FD) collected using a Pullman-Holt vacuum sampler, and a household dust (HD) sample taken from the participants' vacuum cleaners. Method detection limits and recoveries ranged from 12 to 48?ng/g and 54 to 117?%, respectively. AHTN, HHCB, OTNE and HHCB-lactone were detected in all samples, with median concentrations of 552, 676, 252 and 453?ng/g for FD samples, respectively; and 405, 992, 212 and 492?ng/g for HD samples, respectively. MX and MK were detected with high frequencies but with much lower concentrations. The two sampling methods produced comparable results for the target analytes. Widely scattered concentration levels were observed for target analytes from this set of 49 house dust samples, suggesting a wide variability in Canadian household exposure to synthetic musks.  相似文献   
120.
A biofuel cell incorporating a bienzymatic trehalase|glucose oxidase trehalose anode and a bilirubin oxidase dioxygen cathode using Os complexes grafted to a polymeric backbone as electron relays was designed and constructed. The specific power densities of the biofuel cell implanted in a female Blaberus discoidalis through incisions into its abdomen yielded maximum values of ca. 55 μW/cm(2) at 0.2 V that decreased by only ca. 5% after ca. 2.5 h of operation.  相似文献   
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