メニュー下のイメージ画像
HOME >NIR Technology

With NIR, the following components can be measured.

 ・Moisture
 ・Proteins/Lipids/Sugars, etc.
 ・Alcohol/Amino acids, etc.
 ・Solvent/Plastics, etc.
 ・Various organic matters


 NIR allows you to measure the concentration and/or thickness of above components instantly in non-contact and non-destructive way.

 Although the NIR sensor is an excellent choice for measuring components, it cannot measure anything as it is. It is necessary to create a calibration model for a measuring component. It is said to be difficult to create a calibration model without the specialized experiences. However, we have a graet news for you! With the software that comes standard with our NIR sensors, creating calibration model is a breeze without expertise.
  ※ The Unscrambler (multivariate analysis) model also available for researchers.

 Calibration model is a "NIR value"-"component concentration value" relation (see below).

  component concentration = intercept + slope x NIR value (light absorption)

 Once the calibration model is created, all you need to do operationally from then on is expose the samples to be measured to the light emitted by a NIR sensor, and component concentration values are displayed instantly.

 After the introduction of our sensor, reference values are needed to create a calibration model. (lab values)
  ・Moisture: e.g., Drying method
  ・Protein: e.g., Kjeldahl method
  ・Fat: e.g., Soxhlet method
  ・Organic matter: e.g., Chromatographic method
  ・Others: Accurate reference values are not a must. Calibration models can be created with the reference values of your own corporate choice (amount of additive or change in something, organoleptic value, etc.).

 BeatSensing is glad to help you create the calibration models.

What is NIR?

NIR is short for "near-infrared".
nir1.jpg(12485 byte)
NIR light has longer wavelength than visible light (VIS), and is invisible.

NIR absorption and Absorbance

A substance vibrates, and the frequency (beat) of this vibration vary from substance to substance.
shindou1s.jpg(8685 byte)
When the light wavelength and the frequency of the molecular vibration correspond with each other/meet, light of that wavelength gets absorbed by the substance, never to come back.
shindou2s.jpg(6633 byte)
This phenomenon exists in the infrared (IR) region, and is known to appear at the integral multiples of the wavelength. In the NIR region, 1st, 2nd, and 3rd overtones appear with the same absorption properties.

The graph below shows the NIR absorption properties of water.
 ・vertical axis: absorbance (light absorption rate)
 ・horizontal axis: wavelength (nm)
spect.jpg(30987 byte)
Two turning points on this graph (approximately 1450 and 1940 nm) are where light is absorbed by water.
Let's look at the absorbance at around 1450 nm.
 ・low moisture sample: light absorption is low
 ・high moisture sample: light absorption is high
This is explained by the following:
 ・Lambert-Beer law
 ・Kubelka-Munk formula
To put it into simple words,
 "absorbance changes linearly against the concentration change",
 and definitely, "absorbance can be translated into concentration".

Calibration model & Translation into concentration

NIR sensors are for measuring the beforementioned absorbance. In order to translate this absorbance into concentration, we need the following formula. The following calculation is always performed in the sensor.
 Predicted concentration = a + b x absorbance
"a" and "b" are calibration curve coefficients. When the NIR sensor is first installed, a calibration curve needs to be prepared following the steps below.
Cal.jpg(44383 byte)
Cal2.jpg(32288 byte)

Chemical assignment of absorption band

NIR light is absorbed by various substances besides water.

Chemical assignment Example substance
-OH water, alcohol
-NH proteins
-CH fats
-CO,-OH starches, cellulose, sugars

 Molecules above each absorbs light of different wavelength, therefore this technology can be applied to various substances with any of these molecular structures.

 

Using multivariate analysis (chemometrics)

 Grating polychromator type sensor acquires continuous wavelength (spectrum).

 ・3rd overtone type: 640 ~ 1050 nm
 ・2nd overtone type: 900 ~ 1700 nm

 There are hundreds of spectra in a continuous wavelength, and therefore it is difficult for us to select the best absorption wavelength.
 In recent years, the best wavelength is obtained by calculation. Technique called multivariate analysis (chemometrics) has been used, and it required expertise and a dedicated software.
 Our NIR sensor comes standard with a easy-to-use calibration software, and it enables you to prepare a PLS calibration curve using multivariate analysis without much expertise.

Source of error

 The accuracy of the NIR sensors goes up considerably when used with attention to the following aspects:

  ・effect of ambient temperature (please warm up well)
  ・effect of sample temperature (please keep the sample temperature constant)
  ・effect of measurement distance (please keep the measurement distance constant)

  We understand these are not always possible.
  BeatSensing is happy to work with you in finding a solution for the optimum operation. Please feel free to contact us!


 
サイドメニューの見出し(MENU)
link
Copy Right(C)2012 BeatSensing Co., Ltd. All rights reserved.