I need to know when Chromatography was origanated how,why,and where. I also need 4 types of chromatography. I need you all to tell me something about 4 types of chromatography
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By Post on Wednesday, February 21, 2001 - 01:24 pm:
Maybe you could look it up in an encyclopedia. Or on m-w.com. Saying "please" is also usually seen as good form.
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By alex on Friday, February 23, 2001 - 03:24 am:
there are several types of chromatography, but you could say a sentence or two about
1. normal-phase liquid chromatography, where the stationary phase (column) is polar and the mobile phase non polar. Thus analytes are separated based on their polarity. Non polar, organic compounds are attracted to the mobile phase and come out of the column sooner, thus separated from the polar analytes, which are attracted to the stationary phase and stay longer in the column.
2. reverse-phase liquid chromatography is the opposite. It uses a polar mobile phase with non-polar stationary phase, so non-polar analytes take longer to elute. This technique is the most popular for routine, reproducible analytical procedures.
I am very familiar with reverse-phase chromatography, but I do not want to tell you about other types as I am not sure that what I know is correct, or what level of depth you require. I recommend looking for 'gas chromatography' in an encyclopaedia. this is very useful as is usually a pre requisite for mass spectrometry.
Of course, there is the simple 'paper chromatography' (ink & filter paper)
or TLC, thin layer chromatography, which follows the same principle but uses a plate coated with a layer of aluminium oxide instead of paper. this technique is usually used to identify compounds during lab practicals. different compounds will travel different distances up the plate (called an rf value) depending on how much they are attracted to the solvent. Thus compounds can be identified via their rf values
there are several websites which will give you a simplistic explanation - this website is possibly a bit advanced for your needs?
I hope this helps a bit!
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