[Helen]

Why is n-propanol used as an internal standard when testing for alcohol in blood levels ?
Thanks
Helen

[Babcock_Hall]

Why do you ask?  Do you have any thoughts on the matter?

[Helen]

I have a report to write up on BAC levels that we determined from unknowns in the lab and one of the instructions for the report are

Explain why we use propanol as an insternal standard ?

i think that it is used to calibrate the machine and help to calculate the results ?

[Arkcon]

That's correct, but why?  What does an internal stand do?  How is n-propanol good in this regard?  These are answers the question is probably looking for.

Sorry to answer your questions with more questions.  But that's how we help people learn here.  Its all in the  Forum Rules{click}

[Helen]

an internal standard is used to to achieve accuracy and precision with each sample tested and keep consistent standards so we know that the concentration calculations are actually correct but i have no idea why n-propanol is good for this.

[Arkcon]

I can tell that you don't know why, because you're just copying the text book definition of internal standard, without explaining what you know about it, which is what this question wants.

Ok, lets talk some more about this topic.  You have some sort of assay.  What happens if there is no internal standard?

[Arkcon]

Also, try to consider what's good about n-propanal.  For example, could you also use glucose?  Or sodium chloride?  Why not?

[Helen]

If there is no internal standard then there is nothing to measure the analyte against, so you would not have an accurate measurment of concentration or absorbance.

[Arkcon]

That isn't true.  You could perform an analysis without an internal standard.  You could use an external standard, or use a calibrated instrument.  Why not start with the Wikipedia definition of internal standard: https://en.wikipedia.org/wiki/Internal_standard  A little too verbose, but its at least a starting point of useful facts.

[GCMASTER]

Some causes are:
1. It is alcohol that have nearest to ethanol's characteristics:
    m.w.,b.p, polarity - important for good repeatability
2. IPA is not naturally present in humans blood