Thread: Need Help in Chromatography

Yeah, basically I'm doing practicum HPLC in my college. I can use the machine and do the mathematical work, but I'm useless in understanding the concept. So, any help would be much appreciated.

1. What is "reproducibility" actually? And how can we see that we have done is reproducable?

2. When can we say that the internal standard methode has to be used instead of the external standard one to get a better result?

Thanks and sorry for my English.

I think your english is better than mine :?

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Reproducibility is simply the observation that repeating an experiment always yields the same result, within the limits of experimental error.

An experiment needs to be performed many times to give us confidence in its reproducibilty. Our confidence grows if the experiment is performed using different people and if they vary the equipment or chemical batches, and so on. Reproducibilty can fail in many ways, for example if the experiment has a strong element of probability, if there is experimenter bias, if the original experiment used flawed equipment. and so on.

Use of internal and external standards each have their own advantages. The external standard method avoids contamination or dilution of the original sample. The internal standard method gives better calibration of the equipment. I'm sure you can think of other reasons as well.

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Originally Posted by SteveF

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Reproducibility is simply the observation that repeating an experiment always yields the same result, within the limits of experimental error.

An experiment needs to be performed many times to give us confidence in its reproducibilty. Our confidence grows if the experiment is performed using different people and if they vary the equipment or chemical batches, and so on. Reproducibilty can fail in many ways, for example if the experiment has a strong element of probability, if there is experimenter bias, if the original experiment used flawed equipment. and so on.

Use of internal and external standards each have their own advantages. The external standard method avoids contamination or dilution of the original sample. The internal standard method gives better calibration of the equipment. I'm sure you can think of other reasons as well.

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Thanks for clearing that. But how much is the experimental error? Is that the same in every experiment?

experimental error is mainly due to the equipment you use. various instruments have there own uncertainity factors.
for example a metre rule has a 1mm uncertainity.

so no every experiment wont have the same experimental error. it is dependent on the human and the equipment