Component spatial pattern analysis of chemicals by use of two-dimensional electro-optic terahertz imaging

Yamashita, Minoru; Usami, Mamoru; Fukushima, Kazushiro; Fukasawa, Ryoichi; Otani, Chiko; Kawase, Kodo

doi:10.1364/ao.44.005198

Cited by 16 publications

(6 citation statements)

References 9 publications

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“…48,49 This technique has attracted a lot of interest as regards THz applications, and is useful for analyzing the distribution and the concentration of chemicals in targeted materials. 20,21 THz imaging detects absorption caused by weak inter-and intramolecular vibrational modes, which makes identification possible by using the unique information. Moreover THz imaging can be used to analyze samples covered with invisible materials that are transparent to THz waves, since THz waves can pass through a wide variety of non-polar materials, such as paper and plastics, 2 which are commonly used as packaging substances, as described in the previous section.…”

Section: Terahertz Imagingmentioning

confidence: 99%

“…This approach is useful for tomographic studies and for analyzing the distribution and concentration of chemicals in targeted materials. 20,21 Many applications using the unique merits of THz spectroscopy are expected to be developed, and these include security inspection, industrial process control, medical diagnosis, food inspection, and biological and biomedical imaging. Commercial THz imaging systems are already available.…”

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Analytical Terahertz Spectroscopy

Ueno

Ajito

2008

ANAL. SCI.

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Section: Terahertz Imagingmentioning

confidence: 99%

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confidence: 99%

Analytical Terahertz Spectroscopy

Ueno

Ajito

2008

ANAL. SCI.

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“…It has been also applied to chemical mapping to identify a drug substance or some components chemically in a drug product. 18,19) This new imaging technique is a unique and novel tool for the formulation and manufacturing process research of drug products, and is potential for at line or in line inspection as the process analytical technology. 20) In this study, THz pulsed imaging was applied to evaluate the topographical pattern of hydration and dehydration process of theophylline in drug product.…”

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confidence: 99%

Chemical Mapping of Hydration and Dehydration Process of Theophylline in Tablets Using Terahertz Pulsed Imaging

Hisazumi

Suzuki

Wakiyama

et al. 2012

CHEMICAL & PHARMACEUTICAL BULLETIN

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The purpose of this research is to investigate the topographical pattern of hydration and dehydration (also known as pseudo-polymorphic change) of drug substance in drug product using terahertz (THz) pulsed imaging. Emphasis is placed on (1) applicability of THz pulsed imaging and (2) kinetic analysis in the pseudo-polymorphic change. Either anhydrous or monohydrated form of theophylline was used as the drug substance, leading to initially anhydrous or monohydrated tablets. These tablets were stored at 25°C to keep the relative humidity constant at 84% (anhydrous tablets) or 45% (monohydrated tablets), respectively. The THz pulsed imaging was confirmed to enable visualization that the hydration of the anhydrous form or the dehydration of the monohydrated form began on the surface of the tablets and gradually progressed to the core side in the tablets with storage. Kinetic studies indicated that these pseudo-polymorphic changes followed the phase boundary mechanism. Since the other imaging techniques has been scarcely achieved to show the topographical pattern of pseudo-polymorphic change of drug substances in drug products directly and visually, it is considered that THz pulsed imaging has a potential ability to solve complicated issues in pharmaceutical development.Key words terahertz pulsed imaging; theophylline; hydration; dehydration; polymorph; kinetic It is well known that many pharmaceutical solids can exist in more than one crystalline form as polymorphism. 1)Polymorphism also includes solvation or hydration products (also known as pseudo-polymorphs) and amorphous, 2) which generally have different physical and physicochemical properties. These may also affect the pharmaceutical properties of drug products, for example, difference in the dissolution rates and/or bioavailability.3) Polymorphic change may occur due to stress during the manufacturing process and storage. Since polymorphic change of drug substance in a drug product has the possibility to affect the safety and efficacy of the drug product, it is needed for detecting polymorphism in the drug product, to evaluate the impact of polymorphic change on the pharmaceutical properties. However, the evaluation often shows difficulty in detecting polymorphic change of drug substance in a drug product due to an interference of excipients.X-Ray powder diffraction (XRPD) method is the most popular technique for detecting and quantifying polymorphs. Recently, vibrational spectroscopic analyses, such as Raman and near-infrared (NIR) spectroscopies, have been used for the same purpose as nondestructive measuring methods. 4-7)Terahertz (THz) spectroscopy has become popular as a novel technique to determine the crystallinity and polymorphism of drug substances. [8][9][10][11][12][13] The absorption spectrum of the THz region is largely affected by the intermolecular vibrations rather than the intramolecular vibrations. Since the intermolecular vibration has a strong correlation with the molecular conformation (i.e., polymorphism), THz spectroscopy is considered...

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“…[5−7] Two-dimensional THz imaging can be obtained from point-to-point scanning, [8,9] or from CCD real-time imaging by using a pulsed THz wave from a terahertz time domain spectroscopy system (THz-TDSS). [10,11] It can also be obtained from continuous THz wave scanning. [12] Recently, some compressed and fast imaging methods have been demonstrated.…”

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A Compressed Terahertz Imaging Method

Zhang¹,

Pan²,

Xiong³

et al. 2012

Chinese Phys. Lett.

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A compressed terahertz imaging method using a terahertz time domain spectroscopy system (THz-TDSS) is suggested and demonstrated. In the method, a parallel THz wave with the beam diameter 4cm from a usual THz-TDSS is used and a square shaped 2D echelon is placed in front of an imaged object. We confirm both in simulation and in experiment that only one terahertz time domain spectrum is needed to image the object. The image information is obtained from the compressed THz signal by deconvolution signal processing, and therefore the whole imaging time is greatly reduced in comparison with some other pulsed THz imaging methods. The present method will hopefully be used in real-time imaging.

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Component spatial pattern analysis of chemicals by use of two-dimensional electro-optic terahertz imaging

Cited by 16 publications

References 9 publications

Analytical Terahertz Spectroscopy

Analytical Terahertz Spectroscopy

Chemical Mapping of Hydration and Dehydration Process of Theophylline in Tablets Using Terahertz Pulsed Imaging

A Compressed Terahertz Imaging Method

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