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941.
Ailing Zhu Yingying Guo Guangliang Liu Maoyong Song Yong Liang Yong Cai Yongguang Yin 《中国化学快报》2019,30(12):2241-2244
Dark formation of hydroxyl radical upon oxidation of reduced iron minerals plays an important role in the degradation and transformation of organic and inorganic pollutants. Herein, we compared the hydroxyl radical formation from various reduced iron minerals at different redox conditions. OH production was generally observed from the oxidation of reduced iron minerals, following the order: mackinawite (FeS) > reduced nontronite (iron-bearing smectite clay) > pyrite (FeS2) > siderite (FeCO3). Structural Fe2+ and dissolved O2 play critical roles in OH production from reduced iron minerals. OH production increases with decreasing pH, and Cl? has little effect on this process. More importantly, dissolved organic matter significantly enhances OH production, especially under O2 purging, highlighting the importance of this process in ambient environments. This sunlight-independent pathway in which OH forms during oxidation of reduced iron minerals is helpful for understanding the degradation and transformation of various inorganic and organic pollutants in the redox-fluctuation environments. 相似文献
942.
M. P. Shurygina S. A. Chesnokov M. A. Lopatin V. K. Cherkasov G. A. Abakumov 《Russian Chemical Bulletin》2004,53(11):2485-2489
A study of the kinetics of photoreduction of 9,10-phenanthrenequinone in the presence of hydrogen donors (para-substituted N,N-dimethylanilines and polymethylbenzenes) showed that plots of the quantum yield of photoreduction (H) and apparent reaction rate constant (k
H) vs. oxidation potential of hydrogen donors are extreme. In the presence of amines, k
H and H increase, as a whole, whereas they decrease in the presence of polymethylbenzenes. In coordinates H-G
e (G
e is the change in the free energy of electron transfer) for pairs quinone-H donor, H increases with G
e approaching to zero. For the amine series, this effect is mainly in the exothermic region of G
e (G
e < 0). For the series of polymethylbenzenes, this increase is observed in the endothermic region (G
e > 0).__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2381–2385, November, 2004. 相似文献
943.
Vanessa Gouge 《Tetrahedron letters》2004,45(4):773-776
2,2-Difluoro-3-(2-hydroxy-1 R-phenylethylamino)-3 S-phenylpropionic acid 3, obtained by a Reformatsky-type reaction of ethyl bromodifluoroacetate with (4R)-2,4-diphenyloxazolidine, was used as a classical carboxylic acid in the Ugi reaction to prepare various difluorinated pseudopeptides 5a-n. Compounds 5 were then deprotected by hydrogenolysis to furnish difluorinated pseudopeptides 6. 相似文献
944.
Tetrabutylammonium cyanide has been used as non-metallic catalyst for the diastereoselective cyanosilylation of α-hydroxyketones derived from the chiral pool. This affords α-substituted-α,β-dihydroxynitriles with high levels of asymmetric induction. 相似文献
945.
Three different types of SCD combustion source have been evaluated for use in the chromatographic analysis of atmospheric sulfur compounds. The conventional FID source and the newer inverted burner source were found to be less sensitive and less stable than the flameless design. Overall, the flameless source was superior for use with HRGC-SCD. 相似文献
946.
D. Harbach und H. Diehl 《Fresenius' Journal of Analytical Chemistry》1978,293(2):145-146
Ohne Zusammenfassung
Comparison of sample preparation methods for quantitative determination of heavy metals in fruit juices with flameless atomic absorption spectroscopy
Vortragender 相似文献
947.
Summary A comparison of the official EPA method 515.1 for determination of chlorinated acidic pesticides and a modification of it is illustrated. Extraction of the analytes from water and their determination and quantitation is by gas chromatography-electron capture detection (GC-ECD), liquid chromatography-UV detection and liquid chromatography-particle beam mass spectrometry. Although HPLC-PBMS was found to be less sensitive than the GC-ECD method, it was, nevertheless, more sensitive than HPLC-UV. The modified method is simpler, quicker and allows more accurate determination of pesticides in aqueous samples.Deceased July 31, 1996 相似文献
948.
On the Preparation of Di(i-propyl)thiosulfonium Salts [1] The preparation of the mercaptosulfonium salts (i-C3H7)2SSX+SbCl6? (X = H, D) and of the chlorothiosulfonium salts (i-C3H7)2SSCl+MF6? (M = As, Sb) and (i-C3H7)2SSSCl+SbCl6? is reported. They are formed by reaction of chlorinated or protonated (i-C3H7)2S with excess H2S or SCl2 and S2Cl2. The thiosulfonium compounds are characterized by vibrational and NMR spectroscopic methods. 相似文献
949.
Bis-citrato 1a-d , bis-citramalato 2 and bis-malato 3 germanate(IV) complexes were synthesized from germanium dioxide and citric acid, citramalic acid and malic acid respectively and were identified with IR, NMR and elementary analysis. Crystal 1a is triclinic, space group P1 with a = 7.919(2), b = 7.968(3), c = 9.605(3) Å, α = 94.25(3), β = 108.03(2), γ= 113.05(3)°, Z = 1, and the final residue, R(F), is 0.033 for 2583 reflections. Crystal 2 is monoclinic, space group C2 with a = 10.226(4), b = 12.802(4), c = 6.141(1) Å, β = 100.75(2)°, Z = 2, and the final residue, R(F), is 0.034 for 934 reflections. Both 1a and 2 have slightly distorted octahedral structures with citrate or citramalate ions as a tridentate ligand that forms five-, six- and seven-membered rings with the central metal. There is a two-fold axis through the central atom of compound 2 instead of the inversion center of 1a . Same structures for these six complexes are indicated because the spectral patterns of the other four compounds, 1b-d and 3 , are similar to those of compounds 1a and 2 . 相似文献
950.
W. Heinemann 《Fresenius' Journal of Analytical Chemistry》1976,280(5):359-364
Zusammenfassung Die atomabsorptionsspektroskopische Palladiumbestimmung wird vom Platin nicht und vom Rhodium nur wenig beeinflußt. Berücksichtigt man, daß ein Zusatz von Uran die Palladiumbestimmung neben Rhodium desaktiviert, so liegen allgemein die günstigsten Bedingungen für die Palladiumbestimmung vor, wenn Lanthan als spektroskopischer Puffer zugesetzt wird. Korrekturgleichungen werden gegeben.
Determination of noble metals by atomic absorption spectroscopy3. Effect of platinum and rhodium on the determination of palladium
The atomic-absorption determination of Pd is not affected by Pt, but there is a small influence by Rh. The aim of this investigation is to determine these effects quantitatively, furthermore under the releasing effects of uranium and lanthanum. Equations to correct the results are given.相似文献