shana_kristel
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Extraction of Food coloring
Can anyone help me with my proposal now? I badly need you!
I will going to proposed a quantitative analysis of food coloring in noodles. Acording to my research, i am going to use (HPLC) High performance
liquid chromatography, but my sample is solid which is the noodle. how am i going to extract the food color on it for HPLC? please help me! i will
going to defend my proposal tomorrow 
Thank you very much if your gonna help me.!
Godbless!
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Dan Vizine
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It's not that simple. A noodle contains many compounds. If you "extract" it with a solvent and analyze the liquid, you'll see many peaks in an HPLC.
Unless you know exact retention times for the suspected colorings, you can't tell which peaks are coloring agents and which are dissolved organics (if
you use a thermal conductivity detector). This method isn't going to work very well.
This would be more suited for study by HPLC-MS, since the task requires separation plus identification.
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shana_kristel
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Thanks for replying
HPLC using mass spectro detectors?
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shana_kristel
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also, i'm going to quantify the amount of dye most especially tartrazine since it is a carcinogenic compound.
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Metacelsus
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You'll need to do a calibration, then.
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forgottenpassword
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It would be easier to use TLC. The food colouring presumably has a colour and will be visible to the naked eye. You could quantify it very easily and
precisely using standards of known concentration.
Unless the point of the exercise is to use HPLC, TLC would be a more appropriate method, and take far less time.
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unionised
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Depending on the equipment you have, there's a fairly obvious way to distinguish most food colours from most of the compounds in noodles.
Here's a hint; noodles are nearly white.
The bad news is that tartrazine is (like a lot of natural materials) yellow.
So if you have a detector that measures the absorption spectrum of the material as it comes off the HPLC column you can identify most coloured
materials relatively easily.
In my opinion TLC isn't great for quantitative analysis.
LC/ MS is great if you have the equipment.
The real problem you have is that you have left it too late if you need to talk about it tomorrow.
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forgottenpassword
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An opinion based on what?
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macckone
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A better question is how you identify the quantity of
the compound from the TLC media. HPLC is based on
when the compound exits the media as opposed to
where it lands in the media.
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forgottenpassword
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You compare the detection response with known standards, precisely as you do with HPLC.
For example: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3614699/pdf/IJBS...
Digital photography and image manipulation software has made this method much more accurate than when spots were simply measured in mm, where paper
chromatography had a distinct advantage.
Confirmation with a different solvent system allows for very accurate results. What's more, the standards can be run alongside the sample on the same
plate, rather than relying on extrapolations as with HPLC. Simple visual inspection of photographs of UV developed plates is usually sufficient.
[Edited on 21-10-2014 by forgottenpassword]
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macckone
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What you are describing is qualitative comparison
not quantitative analysis. HPLC is better for quantitative
analysis in that you can separate and weight a component.
With TLC the best you can do is estimate on spot size.
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forgottenpassword
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Typical HPLC quantitative analysis does not involve physically weighing the separated components. It involves comparing the magnitude of the signal
from a (usually UV) detector to a calibration curve made by injecting known weights of standards through the column separately.
Certainly pharmaceutical companies that routinely use such analysis do not call it "qualitative comparison".
If you insist on weighing the separated component, you can simply scrape off the spot on a TLC plate and quantitatively extract it. Educate yourself
on HPLC quantitative detection -- It does not involve physically weighing micrograms of substance.
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Dan Vizine
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It's interesting to me that digital image manipulation is being applied to quantative tlc.
When I was using quantitative tlc in the lab, the best we could hope to do with any confidence was to estimate the amount of a trace impurity, i.e.,
is it 0.5%, 1% etc.? It wasn't as accurate at determining the amount of materials present in relatively large amounts.
The condition for using it at all is having all of the things to be estimated as pure samples. If you don't have all of the components to be
determined or don't know what they are, the utility of tlc falls off quickly. Likewise, to be used, you need to find a solvent system that separates
the spots cleanly. This can usually be done, but not always.
[Edited on 21-10-2014 by Dan Vizine]
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unionised
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Quarter of a century working in an analytical lab.
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Little_Ghost_again
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Man I would of asked for a day off by now  . That cant make you work that long
in the uk without a break
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Dan Vizine
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I hope gardul reads this. It's bound to make him feel better.
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Dan Vizine
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Sorry for overlooking your earlier question. Just as it was found that coupling the output of a GC machine to a mass spec. to identify peaks was a
superb way of separating and identifying compounds, it later came about that the HPLC and the mass spectrometer were similarly paired.
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Famousroger
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Perhaps an application of my soxhlet
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