Explain why an Internal Standard is used and what criteria might be used to choose one.?

Question

I used caffeine as an internal standard in this experiment and i used this experiment is HPLC instrument

Answer 1

Typically the internal standard should be as similar to the analyte as possible in terms of structure, behaviour etc. In fact, using a deuterated version (as the internal standard) of the molecule you are trying to determine is best as it will behave exactly the same.

Internal standard method of quantification is very common in branches of science where sample work up is required before quantification e.g. biological matrices. This is because sample work up leads to losses of your unknown so spiking a known amount of an internal standard before work up allows you to know how much is lost during work up and account for it.

Internal standardisation is a method used to quantify a species in a sample. Other quantification methods include external standardisation (where you have a separate solution of a different molecule) that brackets your samples and standard addition (where you add an exact known amount of the molecule you are trying to determine to your unknown samples and back-extrapolate to determine what was already there.

All of this is applicable to HPLC and GC...

Answer 2

An internal standard is a compound whose behavior is known, and whose results in the same test as the unknown give the chemist assurance of the accuracy and precision of the result. The chemist uses a known amount of the standard, measures the area under the caffeine peak on the chart paper, then uses that response to estimate the amount in the unknown peak. The chemist should have some assurance that the response of caffeine is the same as the unknown.

The internal standard can sometimes be the same as the unknown. For example, if you add a known amount of caffeine to the sample solution while analyzing coffee or tea, you can measure how much more the same peak is with added caffeine as without it. This is called spiking the sample.

Answer 3

positioned up theory: (i ought to confess, however. i do no longer consume McDonald's or KFC very lots. quickly foodstuff isn't wholesome.) while will the muslim international settle for us and consume our hamburgers and chicken and not whinge? as quickly as we decrease the value to 21 sheckels? you're too religious of a human beings. you know why a woman wears lipstick. She is finding for a guy. Why is that a sin? What if she is finding for a husband and wearing lipstick makes her sense exceedingly? Why are you human beings so judgemental and caught in 2000 B.C. ? If she starts wearing intense heel footwear below her gown then i'm going to agree that she has long gone too a techniques. this is basically no longer prominent. Western international looks on the pig as very tastey. OUR prophet, Paul, reported it grew to become into o.k. to consume beef. this is why we consume it. because of the fact of this we can't get alongside interior the international? you think of we are unclean and we expect of you're loopy! you think of we've no morals. we are only such as you, however. we'd desire to stay, fall in love, stay wholesome, please a God it quite is good to all and sundry.