@post#5
You were given a lead in your other thread about measuring trans fat, namely FT infrared spectroscopy. Aside from that, try Google or your favorite search engine.
@post#6
I was referring only to the absorption of near infrared by hemoglobin and oxyhemoglobin. At the wavelength used, the two forms of hemoglobin have about the same absorption coefficient. Did you read and understand the Wikipedia link I gave on that subject? Were there any parts of that explanation that were unclear? Finally, ask yourself why the two wavelengths used for pulse oximetry with the typical finger or ear clamp were chosen rather than one that was right at an isosbestic point.
You have two very similar threads going. In the other thread, you ask where to start. It is not clear whether you want to measure trans fat in pure oils
in vitro or whether you want to measure their concentration is complex biological fluids, perhaps even in a living person.
First, I think you need to understand the chemical/configurational difference between trans fat and biologically produced cis-fat (
Trans fat - Wikipedia, the free encyclopedia). Also, read about cis-trans isomerization (
Cis).
Read an introductory text on infrared spectroscopy to learn how that technique works and what it measures. You will need to learn how the out-of-plane twisting and wagging vibrations in the 1000 to 900 cm-1 region are related to cis or trans configurations of alkyl disubstituted ethylenes (i.e., a carbon-carbon double bond in a long chain alkene). You will need to know how to convert wavenumbers (reciprocal centimeters, cm-1) used in infrared spectroscopy to wavelengths used often in other discussions (See:
Wavenumber - Wikipedia, the free encyclopedia). So, what is the wavelength of an infrared absorption at 900 cm-1? Did you get 11.1 microns? If not, check your units. Remember, you are going from cm units to microns.
Then read about current spectroscopic methods to measure trans fat. Here are two links on that subject:
Overview of infrared methodologies for trans fat d... [J AOAC Int. 2004 Mar-Apr] - PubMed result
Determination of total trans fats and oils by infr... [Anal Bioanal Chem. 2007] - PubMed result
Now that you know about measuring trans fat
in vitro, you can more clearly define what you want to do.
John