Advances in On-line Monitoring and Control of the Morphological and Polymorphic Forms of Organic Crystals Grown from Solution
Advances in On-line Monitoring and Control of the Morphological and Polymorphic Forms of Organic Crystals Grown from Solution
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DOI：
10.14356/kona.2005011
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发表时间：
2005
影响因子：
4.1
通讯作者：
X. Wang;J. D. Anda;K. Roberts;Ruifa Li;G. Thomson;G. White
中科院分区：
文献类型：
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作者：
X. Wang;J. D. Anda;K. Roberts;Ruifa Li;G. Thomson;G. White
已知从溶液中生长的有机晶体表现出多种形态和习性，这对产品的最终使用特性（如生物利用度）和下游处理（如过滤和干燥）非常重要。晶体形态也可以决定其他质量指标，如尺寸。与利用各种光谱技术在线测量粒度和浓度等其他质量指标的大量研究工作相比，关于晶体形貌的在线测量和操作的文献很少。过去曾尝试使用激光衍射和超声光谱法进行形状监测。由于难以从受噪声和多重散射干扰的信号中提取详细的形状信息，这些方法并不是很成功。本文描述了一种基于在线成像、多尺度图像分析和晶体形态建模相结合的在线晶体形态测量与控制新方法，并给出了将该方法应用于(L)-谷氨酸的间歇结晶的结果。在线成像被证明能够实时捕获高保真的晶体形状和多态转变。提出了一种多尺度图像分析方法，从图像背景中提取晶体并计算形状描述符，然后将其用于形状识别，并导出实时显示不同晶型比例和晶体面相对平均生长速率的监测图。研究了针状晶体生长速率的计算和动力学参数的估计。最后，提出了一种集成在线成像和晶体形态建模的“相机模型”方法。
Organic crystals grown from solution are known to exhibit multiple morphology as well as habits which are of great importance to the end-use property of the product such as the bioavailability and the downstream processing such as in filtration and drying. The crystal morphology can also dictate other quality measures such as the size. Compared with the great amount of research work that has been done on the on-line measurement of other quality measures such as the size and concentration using various spectroscopy techniques, the literature on the on-line measurement and manipulation of crystal morphology is scarce. Attempts were made in the past to use laser diffraction and ultrasound spectrometry for shape monitoring. These methods have not proved to be very successful due to the difficulty in extracting detailed shape information from the signals corrupted by noise and multiple scattering. In this paper, we describe a new approach for on-line crystal morphology measurement and control which is based on the integration of online imaging, multi-scale image analysis and crystal morphology modelling, and present the results obtained on applying the approach to the batch crystallisation of (L)-glutamic acid. Online imaging proved capable of capturing high fidelity crystal shapes and polymorphic transitions in real time. A multi-scale image analysis method was proposed to extract the crystals from the image background and to calculate shape descriptors which were then used for shape recognition and to derive monitoring charts showing the ratios of different polymorphs in real time as well as the relative average growth rates of facets of crystals. Calculating crystal growth rates and estimating kinetics parameters for needle-shaped crystals was also investigated. Finally, a methodology called ‘camera model’ for integrating on-line imaging and crystal morphology modelling was presented.