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Proceedings Paper

Raman spectroscopy method for subsurface detection of food powders through plastic layers
Author(s): Sagar Dhakal; Kuanglin Chao; Jianwei Qin; Walter F. Schmidt; Moon S. Kim; Diane E. Chan; Abigail Bae
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Paper Abstract

Proper chemical analyses of materials in sealed containers are important for quality control purpose. Although it is feasible to detect chemicals at top surface layer, it is relatively challenging to detect objects beneath obscuring surface. This study used spatially offset Raman spectroscopy (SORS) method to detect urea, ibuprofen and acetaminophen powders contained within one or more (up to eight) layers of gelatin capsules to demonstrate subsurface chemical detection and identification. A 785 nm point-scan Raman spectroscopy system was used to acquire spatially offset Raman spectra for an offset range of 0 to 10 mm from the surfaces of 24 encapsulated samples, using a step size of 0.1 mm to obtain 101 spectral measurements per sample. With increasing offset distance, the fraction of information from the deeper subsurface material increased compared to that from the top surface material. The series of measurements was analyzed to differentiate and identify the top surface and subsurface materials. Containing mixed contributions from the powder and capsule, the SORS of each sample was decomposed using self modeling mixture analysis (SMA) to obtain pure component spectra of each component and corresponding components were identified using spectral information divergence values. Results show that SORS technique together with SMA method has a potential for non-invasive detection of chemicals at deep subsurface layer.

Paper Details

Date Published: 1 May 2017
PDF: 9 pages
Proc. SPIE 10217, Sensing for Agriculture and Food Quality and Safety IX, 1021706 (1 May 2017); doi: 10.1117/12.2262102
Show Author Affiliations
Sagar Dhakal, Agricultural Research Service (United States)
Kuanglin Chao, Agricultural Research Service (United States)
Jianwei Qin, Agricultural Research Service (United States)
Walter F. Schmidt, Agricultural Research Service (United States)
Moon S. Kim, Agricultural Research Service (United States)
Diane E. Chan, Agricultural Research Service (United States)
Abigail Bae, River Hill High School (United States)


Published in SPIE Proceedings Vol. 10217:
Sensing for Agriculture and Food Quality and Safety IX
Moon S. Kim; Kuanglin Chao; Bryan A. Chin; Byoung-Kwan Cho, Editor(s)

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