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it says there that ph affects aspriin in urine.after plotting your first calibration curve you'll tehn do one for different phs. and you don'[t need to know how it works,or have used it before,just explain in your plan.if you find teachers books,they help...or in the plan you could just say 'use a colorimeter as normal'
parag
Yea I've decided to use known concs of aspirin and use a colorimeter to get a calibration curve and then use that to calculate aspirin in the urine. The problem is, we've never used colorimeters before and google hasn't been amazingly helpful on the subject either. My biology teacher said he wasn't sure if it was school/college apparatus (we haven't got one) but it makes the most sense to use one. My major beef though is with how on earth you're meant to use aspirin in urine to work out what's left in the body, as I've discovered that most the aspirin you take gets metabolised to things that don't give the violet complex with iron (III) :confused:


when you know how much is going in,and you know how much came out,you know what's left in the body duh :p: lol
but that means you need to make standard solution based on a normal conc of an aspirin tablet,how much urine is normally excreted at a go in the body etc etc etc.i'm still trying to figure that one out.
Reply 22
my god how hard is this coursework , its even worse than the garlic one last year, pile of crap.
heeeeellp, some teachers has mentioned using a filter on the colorimeter cos of the colour of urine but wont that mess it up when u try and compare against your solution absorbances cos wont that be colourless or do i use a filter the opposite of the purpley colour its meant to go ahhhhhhh panicking
xxx
you don't use real urine! you use aspirin solutions.when you add the iron,it becomes red.and then you put it in the colorimeter,you get the percentage absorbance...then you plot the calibration curve.
Reply 24
Thanks. i think that will work. :smile:
Reply 25
ok im really confused in this coursework.

i got a D in my AS biology and i need help!

please can some one start me off..... or just point me the right direction----->
Ok this is what I think you have to do...

1. you make up different concentrations of aspirin solution. (aspirin tablets and different volumes of distilled water depending on the needed concentration. leave for 24 hours for hydrolysis)

2. Using each concentration you add the same volume to a volume of urine (keep it constant each time) and a volume of iron chloride (again keep it constant each time).
The solutions will appear different shades of purple.... the stronger the conc of aspirin the darker purple

3. Use a cuvette filled with urine to set the colorimeter at 0 (you have to do this to take into account the colour of urine when measuring the light transmission). Then for each solution containing different conc of aspirin use the colorimeter to find out light transmission.

4. Plot this on a graph (aspirin amount against % light transmission)

5. from this if you have a reading for % light transmission of urine you can read off the graph the amount of aspirin likey to be in the urine and work out how much remains in the body by taking the values away..

Then there are the obvious limitations to chat about...

I think this is what you do....
Anybody who has any ideas please help each other by posting!!! :>
can i just say something....did you lot read the question paper,you're not supposed to use actual urine! read properly. use urine and you'll fail. you only need the standard solutions of different concentrations.that'll act as your urine,and that's how you'll get your calibration. so if you make solutions eg at 1M,0.5M,0.2M and add the Fe,you'll get different shades of the purple which you put into the colorimeter and get your different absorbances and then you can plot your calibration curve. you'll doing this at pH7 as they said it's the highest volume of aspirin that can be obtained. then you use buffers to change the pH,according the question,there is less amount of aspirin in the urine at lower pHs so supposedly,i haven't gotten this far yet,if you have add the Fe to your aspirin solution,somehow the Fe reacts or something,but your colour won't be the same as it was at lets say pH7.

please please do not usee actual urine. you can say at the end,the aspirin aolution will obvisouly be replaced with urine,if an actual test was being carried out in a medical lab.

the actual words of the plan say right at the bottom in bold: You should not trial your plan using human subjects or actual urine so please people,read properly!
Reply 28
suzukiescudo
ok im really confused in this coursework.

i got a D in my AS biology and i need help!

please can some one start me off..... or just point me the right direction----->


you did better than me i got an E. we haven't even been given the planning exercise in our school yet.
any help appreciated thanks!
Reply 29
we haven't even been given the planning exercise in our school yet.
any help appreciated thanks!


you should have been given it on the 15th of march..
________________________________________________________________

for the write up what do write in the introduction??
Shylock
can i just say something....did you lot read the question paper,you're not supposed to use actual urine! read properly. use urine and you'll fail. you only need the standard solutions of different concentrations.that'll act as your urine,and that's how you'll get your calibration. so if you make solutions eg at 1M,0.5M,0.2M and add the Fe,you'll get different shades of the purple which you put into the colorimeter and get your different absorbances and then you can plot your calibration curve. you'll doing this at pH7 as they said it's the highest volume of aspirin that can be obtained. then you use buffers to change the pH,according the question,there is less amount of aspirin in the urine at lower pHs so supposedly,i haven't gotten this far yet,if you have add the Fe to your aspirin solution,somehow the Fe reacts or something,but your colour won't be the same as it was at lets say pH7.

please please do not usee actual urine. you can say at the end,the aspirin aolution will obvisouly be replaced with urine,if an actual test was being carried out in a medical lab.

the actual words of the plan say right at the bottom in bold: You should not trial your plan using human subjects or actual urine so please people,read properly!


I thought that meant you should just not TRIAL it at school but you can write it in your plan! has anyone asked a teacher??
Shylock

please please do not usee actual urine. you can say at the end,the aspirin aolution will obvisouly be replaced with urine,if an actual test was being carried out in a medical lab.


isn't the aspirin solution added to the urine, not replaced by it!??? me confused now
Swimmer88
I thought that meant you should just not TRIAL it at school but you can write it in your plan! has anyone asked a teacher??


the aspirin is in the urine.so you can't write it in your trial. you're using the different aspirin solutions as your urine...
Swimmer88
isn't the aspirin solution added to the urine, not replaced by it!??? me confused now


you don't add it to the urine :rolleyes: it's replaced by urine.
Reply 34
suzukiescudo
you should have been given it on the 15th of march..

no my teacher is giving it to us after easter i think.
it 's supposed tobe issued on or after 15th march.
some school's do it differently,some before,some after easter
Reply 36
we had ours later last year aswell. which was why i joined TSR.
Reply 37
Shylock
when you know how much is going in,and you know how much came out,you know what's left in the body duh :p: lol
but that means you need to make standard solution based on a normal conc of an aspirin tablet,how much urine is normally excreted at a go in the body etc etc etc.i'm still trying to figure that one out.


Au contraire mon chere! What I was trying to get at is if 50% of the aspirin you took leaves your body in your urine, you may only be able to detect say 10%, so that'd lead you to thinking you still had 90% of what you took left in you, even if it was 50%. I think that makes sense....or at least it did in my head :elefant:
parag
Au contraire mon chere! What I was trying to get at is if 50% of the aspirin you took leaves your body in your urine, you may only be able to detect say 10%, so that'd lead you to thinking you still had 90% of what you took left in you, even if it was 50%. I think that makes sense....or at least it did in my head :elefant:


lol that's a bit confusing but i think i know what you're getting at mon cheri :p: and what you have to do is research how much aspirin actually comes out and can be detected in normal urine.then you'll know how much you should be detecting
Reply 39
Aye, j'ai fait ca, mais j'ai trouve that the amount that's detectable varies from person to person between like 3% and 10% (okay my french skills aren't that good :laugh:)

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