Method Development: different detector

[VJ]

Hi,
I have some interview type question for HPLC Method development:
1) What is the method development approch for finished product assay and impurities determination
2) How do you know which detector is the best for your analyte : UV, ELSD or RI
3) How do you know Reverse phase or normal phase or ion chromatography is appropiate for your analyte

[prepcolumn]

Hi,
I have some interview type question for HPLC Method development:
1) What is the method development approch for finished product assay and impurities determination
2) How do you know which detector is the best for your analyte : UV, ELSD or RI
3) How do you know Reverse phase or normal phase or ion chromatography is appropiate for your analyte

VJ
All your questions are about chemistry. Briefly;
1) For finished product you may start with searching literature about your product (papers, pharmacopoeias, drug substance DMF method, forums etc). Because possibly someone studies (or studied) what you study now. Then you may perform forced degradation studies with these methods to see the performance of the product with your formulation, and revise method accordingly. If you cannot find any of them, you may search method for similar products (eg: atorvastatin and rosuvastatin). If none works start to find pKa, polarity, solubility and other chemical and physicochemical properties to get a proper starting point of your method (actually, these points are also useful and required in all cases i mentioned above)
2) again a bit chemistry but you may also find answer with some trials. 80-90% of drug substances have UV activity. To understand this, you may scan your drug substance in UV spectrophotometer. If you cannot get any response then you may shift to other detectors.
3) again most pharmaceutical applications are reversed phase bacause they are generally not very polar and non-polar for octanol to water coefficient (log P) issues. But basically, if you work with very polar compounds normal phase is a better choice, otherwise go ahead with reversed phase.

I hope this helps

[Consumer Products Guy]

Hi,
I have some interview type question for HPLC Method development:
1) What is the method development approch for finished product assay and impurities determination
2) How do you know which detector is the best for your analyte : UV, ELSD or RI
3) How do you know Reverse phase or normal phase or ion chromatography is appropiate for your analyte

I can somewhat understand asking for help, if this is for a "first job" in the field. But if you've been employed in this field, you should already know this.

[VJ]

thanks prep column....
I found some information and wanted to share.... its always good to discuss, this is a great forum.

For detector choice if the compound is non chromophoric then use RI or ELSD. Usually ELSD is better choice than RI. RI has baseline instability, poor sensitivity and no gradient.

[prepcolumn]

thanks prep column....
I found some information and wanted to share.... its always good to discuss, this is a great forum.

For detector choice if the compound is non chromophoric then use RI or ELSD. Usually ELSD is better choice than RI. RI has baseline instability, poor sensitivity and no gradient.

[VJ]

Thanks

[rrm1987]

can you tell what compound you want to analyze?.The functional group present in it matters.