Infrared Microspectroscopy - Science method

Hi,

Maybe, this database: https://www.bruker.com/en/products-and-solutions/infrared-and-raman/opus-spectroscopy-software/database.html

Once, I saw this database, it is quite a good one, though, I don't know if it contains the material you are looking for.

David

The sloping is caused by the imperfect contact between the sample and ATR element. As you said, the effective penetration depth of IR is frequency dependent. Thus, if the sample/ATR element contact is not perfect, the IR radiation reflect at the sample surface without obtaining the information from the sample. However, the degree of this occurring for the long wavelength is less. This is the reason why the baseline goes up in the longer wavelength region in a exponential fashion. The supporting evidence of your sample not achieving good contact with the ATR element is your observation of the differential absorption band contour. If the contact is perfect, such contour should not appear. This is caused by the Christiansen effect when the contact at the interface is poor. Similar problem happens when you make a KBr pellet for a very hydrophobic sample. To minimize the contact problem (derivative contour and baseline shift), you may try one of the following. i) Use a IR transparent oupling liquid on the surface of ATR element (you can use only the frequency region the coupling liquid is transparent). For IR transparent material, Nujol mull or Fluorolube can be used.; ii) Use ATR element that is of smaller refractive index, such as KRS-5; iii) If your sample is not heat sensitive, warm up the sample immediately before contacting to ATR element so that the sample forms a good contact.

Many thanks Thomas Mayerhöfer , this is really helpful information.

Cheers,

Pjotr

Measure your sample at different locations (where you can specify the FTIR instrument to run several spectra in one run, e.g. 32 scans, which are automatically averaged into one spectrum), but since you’re doing ATR-FTIR you should not make an average of the spectra taken at different locations with different contact variations between the sample and the ATR crystal. Relatively hard surfaces complicate accurate quantitative measurements (height of absorbance peaks) due to varying contact with the ATR crystal for the different samples. Air between sample and ATR crystal results in a weaker absorbance signal. Unless other conditions indicate otherwise (e.g. inhomogenities, impurities, etc.), the FTIR curves with the largest absorbance peaks represent the most correct measurements on one and the same sample, and hence these curves should be chosen as they are assumed to be the most correct ones. Qualitative measurements (location of absorbance peaks at wave numbers) do not represent a problem as long as the contact area is large enough to ensure a sufficient strong measurement signal. Various details about the ATR-FTIR technique which may be helpful may be found in the following article (may be requested through Research Gate): B. P. Jelle, T.-N. Nilsen, P. J. Hovde and A. Gustavsen, ”Accelerated Climate Aging of Building Materials and their Characterization by Fourier Transform Infrared Radiation Analysis”, Journal of Building Physics, 36, 99-112, 2012.

I was co-chair of the conference, and am editing the proceedings. let me know if there is a more specific area of interest for you.

Hi Philippe,

We actually have access to an IR microscope (we're currently building and selling quantum cascade laser based microscopes at my company (see http://daylightsolutions.com/life-sciences/spero.htm), so we can perform spatially resolved spectroscopy on microfluidic devices.  But the issue is really time resolution.  The microscopes take several minutes to acquire a spectral cube, but we'd like to be able to monitor processes on the sub-second time scale.  Part of this is motivated by coupling with LC or capillary systems where elution times can be quite fast.   We're looking at a rapid tuning quantum cascade laser spectrometer that could have the optical power and tight focusing to couple into microfluidic channels, and want to see if there are any systems we can benchmark our performance against.

Thanks,

Miles

Here are two that I use:

Hi Rania, your spectrum looks like it might be a polysaccharide hydrogel such as sodium hyaluronate or another related compound. Can I ask where the sample came from? This context might help me nail down exactly what it is. Feel free to contact me at adam.lanzarotta@fda.hhs.gov.  Regards, Adam.

It will depend on what you want to transmit, if you want to transmit data, a spread-spectrum rf link at say ~900 MHz, will work very well. We have used these at low power (1-2 Watt) over several kilometres. Infra-red communication can easily be affected by atmospheric effects (e.g. rain) and will not be as reliable, it is very good for short distances in controlled environments, or when you do not want rf interference (e.g. next to large radio telescopes etc.).

due to the nature of the materials as a detector used in infrared cameras and atmospheric absorption it is impossible to find 5-12 um IR camera. most of LWIR cameras are produced in 7.5 - 11.5 um band. I can suggest FLIR SC 7000 series.