期刊
JOURNAL OF CHROMATOGRAPHY A
卷 876, 期 1-2, 页码 37-50出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/S0021-9673(00)00179-5
关键词
sample introduction; sandwich injection; injection methods; polyamide; nylon; polymer
We report a method for reliable routine polymer sample introduction with minimal bias, a separation method of the first six linear and cyclic oligomers by liquid chromatography, quantification using group equivalents and long term method performance. Injecting a polymer sample in a mobile phase containing an aqueous non-solvent often results in blocked systems as the polymer precipitates in the connecting capillaries. In this first part we focus on a new injection technique, in which the dissolved polyamide is placed between two zones of formic acid, preventing the polymer to precipitate before it reaches the column. Development of this sandwich injection method makes direct injection of the polymer into an aqueous acetonitrile gradient feasible. The oligomeric polyamide recovery of this technique, extraction, dissolution/precipitation and direct injection on a hexafluoro-isopropanol (HFIP) gradient were compared. With the sandwich injection method the polymer remains on the column, slowly changing the stationary phase. The influence of this on resolution and retention was studied. Column stability allows sixty injections before cleaning or replacing the column is necessary. (C) 2000 Elsevier Science B.V. All rights reserved.
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