Abstract: A spectrometer equipped with an integrating sphere is used to measure a reflection spectrum from a suspension in a container when the suspension is irradiated with measurement light, of which wavelengths are selected from a wavelength range including near infrared. Reflection spectra of a number of types of standard samples, of which concentrations in the suspension are already known, are used to prepare a measurement model in accordance with an assay technique on the basis of a recursion. A concentration of the material in the suspension is found using the measurement model.

Abstract: A method and an apparatus that make an easy and quick measurement of the concentration of materials in a suspension possible with high precision and without essentially changing the structure of the conventional spectrometer for pre-dispersive spectrometry are provided by nullifying the limitation of a container of a sample as compared to transmission measurement. A spectrometer equipped with an integrating sphere is used to measure the reflection spectrum from a suspension in a container when the suspension is irradiated with measurement light, of which the wavelengths are selected from a wavelength range including near infrared, reflection spectra of a number of types of standard samples, of which the concentrations in the suspension are already known, are used to prepare a measurement model in accordance with an assay technique on the basis of a recursion, and the concentration of a material in the suspension is found using the measurement model.