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6.
Anal Bioanal Chem ; 395(7): 2335-47, 2009 Dec.
Article in English | MEDLINE | ID: mdl-19787339

ABSTRACT

The capability of single-reflection near-IR (NIR) spectroscopy to differentiate, characterize and monitor the fate of a set of hydrocarbons spilled in the marine environment was compared with that of multiple-reflection horizontal attenuated total reflection mid-IR (ATR-MIR) spectroscopy. Multivariate pattern recognition techniques [principal component analysis (PCA), multivariate polynomial regression, cluster analysis and potential curves] were applied to unravel the major trends of the weathering processes of four generic types of crude oils and two heavy fuel oils spilled under controlled conditions for almost 4 months. A chemical interpretation of the NIR spectra related the weathering processes and the PCA loadings, which had not already been done in the literature. Weathering for both light and heavy products was characterized by a contrast among the linear aliphatic structures (more volatile and easy to degrade) and the branched and aromatic structures (more recalcitrant). Potential curves were applied to model each product and determine objectively whether unknown samples could be classified correctly. Polynomial regression on the PCA scores was employed to evaluate the time elapsed from the oil spillage to its sampling; this represents a new approach to assess the age of a hydrocarbon lump. In general, NIR spectroscopy yielded good results when light crude oils were studied, whereas ATR-MIR spectroscopy led to satisfactory results for both light and heavy products.

7.
Acta Crystallogr C ; 56 (Pt 8): 1028-9, 2000 Aug.
Article in English | MEDLINE | ID: mdl-10944316

ABSTRACT

The crystal structure of the title compound, C(19)H(16)N(2)O(2), displays a trans configuration of the azo moiety, which forms an intramolecular O-H.N=N hydrogen bond. The H.N and O.N distances are 1.81 (3) and 2.581 (4) A, respectively. The azobenzene moiety is approximately planar, and has a dihedral angle of ca 23 degrees with the substituted phenyl group.

11.
Talanta ; 42(1): 105-8, 1995 Jan.
Article in English | MEDLINE | ID: mdl-18966209

ABSTRACT

A sensitive spectrophotometric method was established for the determination of Diclofenac sodium (DS) with Methylene Blue (MB) as analytical reagent. It was found that DS reacts with an excess of MB in the pH range 9.2-9.4, to form a chloroform-extractable blue ion-association complex. Good agreement with Beer's law was found in the range of DS concentrations of 0.8-6.4 mug/ml with a detection limit of 0.37 mug/ml. The method was applied for the determination of DS in various tableted forms with a good precision.

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