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NIR Spectrometers with different spectral range

Zahra's picture
Forums: 

Hello everyone,

I am a beginner in NIR. I know that NIR uses region of electromagnetic spectrum from 700 to 2500 nm but I would like to know, why there are different kind of NIR spectrometers with different spectral range? For example in my case I work with NIR Spectrometer from PharmaTest and the whole spectral range of my devise is from 1000 to 1900 nm. 

Thank you in advance for your answers.

Katarzyna Kepka's picture

Hello,

Indeed there are many companies that expanded spectral range. Like Metrohm's analyzers cover from 400 nm up to 2500 nm, so visible and near-infrared region (VIS+NIR).

Best regards,

Katarzyna

hbrookechem's picture

The spectral range of an individual spectrometer is going to be based on a few things including the light source, the detector, and other optics. Which you choose is totally based on your application needs.

Cheers,
Heather Brooke, PhD

Yair Martinez's picture

Hi,

The truth is that most of the useful Chemical information in NIR are between 1000 and 2500 nm depending the samples. Sometimes, because of comertial things some companies build their instruments whit more or less spectrum range. 

Mathieu Jourdain's picture

Hi Zahra,

 

The difference in spectral range is due to instrument design : wavelength selection technology (filter, grating, interferometry, acoustic,…), NIR source (Tungsten lamp, LED, tunable Laser), detectors (Si, InGaAs, PbS,…).

The choice of the spectrometer must depend on your application and what you’re looking for (SNR, speed, resolution, … ?).

 

To my mind, useful information could be found below 1000 nm.

You could use the very near infrared (800 – 1100 nm) to measure solid sample in diffuse transmittance (since photons are more energetic in the low WL). You could select the 2nd or 3rd overtones in your model when the absorbance at higher WL are too huge (due to important water content for instance),...

The  visible range (400 – 800) nm could also helpful for qualitative application, for example to estimate the appearance (whiteness, translucency, color,..) of a sample, but also for quantitative application (aniline content in fuel for instance).

 

BR

Mathieu

Sus's picture

Hi,

Coming to your original question, the type of detector depends mainly on the range of wavelengths to be measured. There is no detector covering the whole NIR range from 780 to 2500. If you look at the history of the developemnet of spectroscopy you will understand.

Now, what is the best for each application - nothing best than trying with the spectrometer you have, try to understand what you are seeing in the spectra and move from there.

KR,

Sus

td's picture

Hi Zahra,

Could I suggest that if you want to understand more about NIR spectroscopy that You should read a book?

The best book for a beginner is "Practical NIR Spectroscopy: with applications in food and beverage analysis", by Osborne, Fearn and Hindle. It is available from this website!

Best wishes,

Tony