Consideration of some sampling problems in the on-line analysis of batch processes by low-field NMR spectrometry.
Consideration of some sampling problems in the on-line analysis of batch processes by low-field NMR spectrometry.
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低场核磁共振谱在线分析间歇过程中一些采样问题的思考
DOI：
10.1039/b714266h
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
J. Wilkie
中科院分区：
文献类型：
--
作者：
A. Nordon;A. Diez;C. W. Wong;C. A. McGill;D. Littlejohn;M. Weerasinghe;D. A. Mamman;M. Hitchman;J. Wilkie
一个低场中分辨率NMR光谱仪，工作频率为29 MHz的1H，已被评估为在线过程分析。已经开发了包含预磁化区域的流动池，以最小化由于不完全极化效应而导致的信号降低。巴豆酸和2-丁醇的均相酯化反应使用一个简单的采样回路进行监测，它是可能的，通过丁醇和巴豆酸丁酯的CH信号区域的变化来监测反应的进展。非均相水-甲苯混合物的在线分析被证明更具挑战性，并设计了一种用于5 L反应器的快速取样回路系统。快速取样回路以8 L min（-1）的流速运行，二级取样回路用于使子样品以较慢（mL min（-1））的速率通过NMR分析仪。结果表明，即使在超等速取样条件下，由于反应器中混合不充分，也可能发生不具有代表性的取样。然而，仍然可以将在60 mL/min（-1）的流速下获得的1H NMR信号与反应器内容物的组成相关联。
A low-field medium-resolution NMR spectrometer, with an operating frequency of 29 MHz for 1H, has been assessed for on-line process analysis. A flow cell that incorporates a pre-magnetisation region has been developed to minimise the decrease in the signal owing to incomplete polarisation effects. The homogeneous esterification reaction of crotonic acid and 2-butanol was monitored using a simple sampling loop; it was possible to monitor the progression of the reaction through changes in CH signal areas of butanol and butyl crotonate. On-line analysis of heterogeneous water-toluene mixtures proved more challenging and a fast sampling loop system was devised for use with a 5 L reactor. The fast sampling loop operated at a flow rate of 8 L min(-1) and a secondary sampling loop was used to pass a sub-sample through the NMR analyser at a slower (mL min(-1)) rate. It was shown that even with super-isokinetic sampling conditions, unrepresentative sampling could occur owing to inadequate mixing in the reactor. However, it was still possible to relate the 1H NMR signal obtained at a flow rate of 60 mL min(-1) to the composition of the reactor contents.