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Table 1 Summary of vibrational screening technologies

From: Substandard and falsified medicine screening technologies

Characteristic Infrared Near Infrared Raman
Principle Fundamental absorptions Overtone and combination absorptions Emissions
Chemical sensitivity Polar bonds Polar bonds Nonpolar bonds
Inherent selectivity High Low (modeling often required) High
Sampling mode Diamond ATR Diffuse reflectance 180o backscattering
Sampling configuration Intimate contact with sample required Stand-off detection possible but can be challenging Stand-off
Excitation source Broadband IR Broadband IR Monochromatic NIR i.e., 785 and 1064 nm
Interferences Water and any packaging Water, particle size/packing variability and opaque packaging Fluorescence and opaque packaging
Minimum sample size required At least 1 mg ~ 20–50 mg ~ 1 mg
Approximate penetration depths for solid dosage forms ~ 1–5 μm ~ 1–5 mm ~ 10–15 μm
  1. Content from table 1 is pulled from the following references – Kauffman et al. (2010), Neospectra (2019), Rodriguez et al. (2014), Shimadzu (2019) and Zou et al. (2018)