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    Hello


    I'm currently studying Advanced Higher Chemistry, and we need to come up with an investigation.

    I want to find the concentration of salicylic acid in different fruit, compared to aspirin and I'm just wondering if anyone has ideas of a suitable method?

    Oddly, this hasn't been done before at our school and our teacher is demanding a "tried-and-tested" method for it.

    Searching online has only shown me that we need an HPLC, which sounds expensive, etc... so that's not very viable.

    The problem, I think, is that salicylic acid is only present in small "volumes" compared to the big ones (if we take orange juice) such as citric acid/ascorbic acid. It also has very similar structures and molecular masses to the whole host of other acids present in fruit, which probably means any differentiation through physical properties (solubility, BP etc...) would be too inaccurate. I'm also 'guessing' that they have similar colours which makes colorimetry a pain.

    I just need to find a method to extract (or measure the concentration) of only salicyic acid.

    BUT finding the concentration of vitamin C in fruit juice is a popular experiment. So surely, I could tweak that method to make it fit salicylic acid?

    :ninja: except, I don't know how people find the concentration of ascorbic acid in the first place.

    I really really want to do this experiment. I'm honestly interested in it, so any help would be fantastic. I will also rep if you so wish.

    Thanks
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    http://chestofbooks.com/reference/He...ylic-Acid.html
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    (Original post by spacepirate-James)
    Hello


    I'm currently studying Advanced Higher Chemistry, and we need to come up with an investigation.

    I want to find the concentration of salicylic acid in different fruit, compared to aspirin and I'm just wondering if anyone has ideas of a suitable method?

    Oddly, this hasn't been done before at our school and our teacher is demanding a "tried-and-tested" method for it.

    Searching online has only shown me that we need an HPLC, which sounds expensive, etc... so that's not very viable.

    The problem, I think, is that salicylic acid is only present in small "volumes" compared to the big ones (if we take orange juice) such as citric acid/ascorbic acid. It also has very similar structures and molecular masses to the whole host of other acids present in fruit, which probably means any differentiation through physical properties (solubility, BP etc...) would be too inaccurate. I'm also 'guessing' that they have similar colours which makes colorimetry a pain.

    I just need to find a method to extract (or measure the concentration) of only salicyic acid.

    BUT finding the concentration of vitamin C in fruit juice is a popular experiment. So surely, I could tweak that method to make it fit salicylic acid?

    :ninja: except, I don't know how people find the concentration of ascorbic acid in the first place.

    I really really want to do this experiment. I'm honestly interested in it, so any help would be fantastic. I will also rep if you so wish.

    Thanks
    Hello.

    It's a very ambitious project considering that you're looking for a specific acid.

    May I suggest changing your practical plan a little?

    Fruit have very low concentrations of salicylic acid, shampoos on the over hand have more as salicylic acid is one of the main ingredients in anti-dandruff shampoos. Instead you could compare different shampoos?

    Quote me for more.
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    firstly, i've asked and chloroform is, surprisingly , not allowed to be used in our school which is a bit of a bummer...

    ... also, secondly, what does the chloroform act as in this case? does it separate the salicylic acid from all the other acids? and how?
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    (Original post by hollywoodbudgie)
    Hello.

    It's a very ambitious project considering that you're looking for a specific acid.

    May I suggest changing your practical plan a little?

    Fruit have very low concentrations of salicylic acid, shampoos on the over hand have more as salicylic acid is one of the main ingredients in anti-dandruff shampoos. Instead you could compare different shampoos?

    Quote me for more.
    poo. and i thought it was going to be easy at the start... ah well

    anyway, i could change it but since being an aspiring medic () i was going to try and see how much oranges (or other fruit) you would have to eat a day to equal one aspirin tablet.

    admittedly, i'd be willing to change if i honestly could not do the experiment. my teacher has given me the christmas break to find a method...

    i mean, don't berries have quite a 'high' concentration of the acid? 1mg per 100grams... or is that too small to be experimented on?

    Spoiler:
    Show
    I sound very stubborn and unmoving in terms of this... I know. I know. But I just want to have a shot, and try to see if it works or not. In the end of the day, it'll probably not work but hey ho.
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    (Original post by spacepirate-James)
    poo. and i thought it was going to be easy at the start... ah well

    anyway, i could change it but since being an aspiring medic () i was going to try and see how much oranges (or other fruit) you would have to eat a day to equal one aspirin tablet.

    admittedly, i'd be willing to change if i honestly could not do the experiment. my teacher has given me the christmas break to find a method...

    i mean, don't berries have quite a 'high' concentration of the acid? 1mg per 100grams... or is that too small to be experimented on?

    Spoiler:
    Show
    I sound very stubborn and unmoving in terms of this... I know. I know. But I just want to have a shot, and try to see if it works or not. In the end of the day, it'll probably not work but hey ho.
    Ah A level Chemistry, I remember the good ole days. :moon:

    Thinking about possible ideas is fine. Write all of this down, trust me, it gets you marks. Talk about how you considered doing this, but you would have problems with the method etc etc.

    Have you considered invesitigating white willow bark instead?

    'How much white willow bark would I need to eat a day to equal half an aspirin tablet?"

    For your prelim you would have to figure out how much salicylic acid there is in one aspirin. :holmes:

    Quote me for more... I'm getting some ideas now too
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    (Original post by spacepirate-James)
    poo. and i thought it was going to be easy at the start... ah well

    anyway, i could change it but since being an aspiring medic () i was going to try and see how much oranges (or other fruit) you would have to eat a day to equal one aspirin tablet.

    admittedly, i'd be willing to change if i honestly could not do the experiment. my teacher has given me the christmas break to find a method...

    i mean, don't berries have quite a 'high' concentration of the acid? 1mg per 100grams... or is that too small to be experimented on?

    Spoiler:
    Show
    I sound very stubborn and unmoving in terms of this... I know. I know. But I just want to have a shot, and try to see if it works or not. In the end of the day, it'll probably not work but hey ho.
    If it doesn't work then all the better More to write about, they don't care if your experiments work or not, just that you have carried it out in a valid way and considered all the aspects of variation/uncertainty etc.
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    Right, so I've gone and asked a chemistry scientist person,

    and he/she says, "An alternative approach may be just to try to determine the salicylic acid in the fruit juice directly using a colorimetric method, such as that involving use of Fe3+, to determine the salicylic acid impurity in aspirin.

    However, for this to be successful, you would have to be sure that the coloured complex formed was specific to salicylic acid, and not given by other acids present as well.
    "


    Right. So how specific should the reaction between salicylic acid and iron ions be?

    Is there anyway I can test this out?


    gah

    asdjhnfbwgrsjdn gbrwdsjnv gbwredsjvngbriefvdsnj. <-- my frustration :erm:
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    Having done the Vitamin C in fruit juice titration and written a report on it, iodide/iodate is the way to go if you can do that. There's an easy-to-follow method online if you'd like me to find it.
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    (Original post by addylad)
    Having done the Vitamin C in fruit juice titration and written a report on it, iodide/iodate is the way to go if you can do that. There's an easy-to-follow method online if you'd like me to find it.
    Is it possible that you could find it for me? It would really really be helpful Thanks



    well. Though vit c isn't the acid I'm searching for, the methods must be pretty similar.
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    (Original post by spacepirate-James)
    Is it possible that you could find it for me? It would really really be helpful Thanks



    well. Though vit c isn't the acid I'm searching for, the methods must be pretty similar.
    http://www.chemteach.ac.nz/investiga...inc_iodate.pdf

    I do recommend you do it though, it's a piece of piss and yet there is plenty of stuff going on (the KI and KIO3- getting it on for example). :awesome:

    Edit: there's also an n-bromosuccinimide one, there might be another chemical which reacts similarly with salicylic acid.

    By the way, if you have access to an IR spectrometer, you can determine salicylic acid that way I believe (the wavelengths are easy enough to find, and just do it by absorbance).
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    (Original post by spacepirate-James)
    Right. So how specific should the reaction between salicylic acid and iron ions be?

    Is there anyway I can test this out?
    It'll form a complex around the Fe3+ ion giving Iron (III) Salicilate.


    Metal complexes have distinct colours due to the d-d transitions.

    If you can get rid of any coloured impurities in the juice and ensure nothing else will complex with the Fe3+ ion it should work. This is a commonly used method for determining the yield of the esterification of salicylic acid.

    1 - Do you have access to a colourimeter?
    2- Investigate the effect of adding FeCl3 solution to your fruit juice, does it produce a quantitatively measurable absorbance difference? How dilute can you make the juice and still see a measurable effect (the more dilute, the more the absorbance will be down to the complex rather than anything in the juice). You might be able to get the colourimeter to subtract the absorbance of the juice itself by using it as the calibration solution. All this you can write into your prelim.
    IF all that goes well, you can start doing you calibration curve etc.

    (Original post by addylad)
    By the way, if you have access to an IR spectrometer, you can determine salicylic acid that way I believe (the wavelengths are easy enough to find, and just do it by absorbance).
    If the OP has no HPLC, chances are an IR spectrometer will be highly unlikely.

    Iodide/Iodate is a good backup option.
 
 
 
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