pulse oximeter sensor

[tkw]

is there anyone who knows how's a pulse oximeter works?? I only know they uses infrared to measure.

 

[jbeng]

Try here: **broken link removed**

 

[tkw]

thanks jbeng. it really helps me a lot. Besides that i have another question, can i use the concept of the oximeter to detect trans fat?? Do u have any idea about it??

 

[jpanhalt]

If by concept, you mean infrared and/or visible spectroscopy, then yes, infrared spectroscopy can be used to determine trans fats. If you mean using red and near IR light through tissues, then the answer is "no." Pulse-oximetry works because there is big difference in absorption coefficients of the red light by oxygenated and non-oxygenated hemoglobin, yet the absorption coefficients for the infrared light are almost the same. In other words, the infrared absorption serves like a calibrator for the total hemoglobin. See isosbestic point (Isosbestic point - Wikipedia, the free encyclopedia) for more discussion on how that calculation is made.

John

 

[tkw]

If by concept, you mean infrared and/or visible spectroscopy, then yes, infrared spectroscopy can be used to determine trans fats. If you mean using red and near IR light through tissues, then the answer is "no." Pulse-oximetry works because there is big difference in absorption coefficients of the red light by oxygenated and non-oxygenated hemoglobin, yet the absorption coefficients for the infrared light are almost the same. In other words, the infrared absorption serves like a calibrator for the total hemoglobin. See isosbestic point (Isosbestic point - Wikipedia, the free encyclopedia) for more discussion on how that calculation is made.

John

jpanhalt, thanks for the explanation. Actually i'm planning to do that project,which is using a sensor to detect trans fat. But i have no idea where should i start to study in. Can u gv me some idea whether where should i start my research??

 

[tkw]

jpanhalt, thanks for the explanation. Actually i'm planning to do that project,which is using a sensor to detect trans fat. But i have no idea where should i start to study in. Can u gv me some idea whether where should i start my research??

 

[tkw]

jpanhalt, do u mean that the absorption for the red n infrared light is almost the same for the trans fat. As a result we cannot apply the concept??

 

[jpanhalt]

@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

 

[tkw]

i have jz study the information about trans fat from the link u gave me. I find out some explanation that i don't understand.
Firstly, during the hydrogenation process is it means that it will change the unsaturated fats into completely/partially saturated fats??
Secondly, is it after the hydrogenation process there will be two configuration form, either is trans fat or cis fat??
Thirdly, is trans and cis fat an saturated or unsaturated fat??