See-through ID with Raman technology

Through-package identification of materials in white polyethylene (PE) bottles (a common packaging for solid chemicals) and other opaque packaging such as white and manila envelopes is demonstrated with 1064 nm Raman spectroscopy. The container contribution is removed with advanced identification algorithms, and the sample is correctly identified. Identification through colored plastic, multiple opaque layers, and thick glass can be made with TID1064ST. Identification of sodium benzoate inside a white PE bottle is given in Figure 1. 

Coated tablets can also be identified. ST technology penetrates the coating layer and measures the Raman spectrum of the underlying tablet. This allows the instrument to effectively sample through colored and dark materials, enabling reliable analysis without being obscured by surface effects. Figure 2 shows the Raman spectrum of a tablet with a very dark coating. Despite interference from the coating, signature peaks are still apparent. 

To demonstrate, we evaluated the ability of ST Raman at 1064 nm to identify several common excipients—varying in Raman scattering strength—through multi-layer paper bags used in pharmaceutical raw material packaging. As shown in Table 1, even trisodium phosphate, a notoriously low Raman scatterer, was correctly identified. A positive ID requires a hit quality index (HQI) above 85 that exceeds the second-best hit by at least 2 points. In contrast, trisodium phosphate could be identified only through white kraft paper using 785 nm excitation.

Figure 3 shows the spectrum of trisodium phosphate as measured through a two-ply bag of white and brown kraft paper, with a positive library search result. Although the spectrum is dominated by spectral features from the paper bag, TID1064ST is capable of reliably identifying trisodium phosphate.