Evaluation methods that employ the near infrared spectrum have generally had a low specificity and in particular have encountered difficulty in the evaluation of trace components, and the accurate measurement of coating quantity by methods using the near infrared spectrum has been quite problematic. The quantity of coating applied to a coating target, such as granules or uncoated tablets, is measured based on the absorption or scattering of light in the 800 to 1100 nm wavelength region by an additive coated on the coating target. The use of polyethylene glycol or a long-chain hydrocarbyl-containing compound as the additive is preferred.
