Hi,
I would like to clarify regarding the usage of PDA detector.
In USP High Performance Liquid Chromatography -> General chapter -> Detectors section , mentioned as "PDA detectors will give less signal to noise than Variable wave length detectors" and also quoted as PDA detectors are less suitable for lower concentration components from analyte.

Please kindly give the clarification for the following;

In my case , based on the above statement, got the objection on the usage of PDA for routine analysis. They are restricting the PDA usage only for peak purity and spectral match applications( only for specificity study)
Ihave compared the results obtained from PDA &VWD which are most similar.
I have done one validation study using PDA detector, which is said to be invalid by QA department. Please kindly give the status of the above said document validity.

We are calibrating the PDA detector for wave length accuracy using holmium oxide and caffeine solution over the range of UV and Visible. The acceptance criteria for Wave length accuracy is + 2 nm. Based on this can i use PDA for routine analysis.

It is a fair statement to say the PDA will give higher noise that a VWD (although this is not always the case). If you have validated the method with a PDA the the method is VALID. The only reason I could see an objection is if you are consistantly looking down toward the detection limit with this method, then, perhaps a VWD might be more suitable. If I had to guess, your QA dept. is too cheap to buy a PDA or lack the ability to run a PDA.

Like much of the USP, that statement sounds a little dated. Certainly the first generation of PDA detectors had more noise than the VWD on the market at the same time.

However, PDA detectors have many more options regarding how they can be optimized (slit width, band width, peak width, etc.) It has been my experience that with relatively current instruments <5 years old Agilent and Waters systems the PDA parameters can be optimized to nearly match the performance of the VWD detectors.

Your method validation should stand on its own. We usually use a PDA for method development and a VWD as part of ruggedness (second analyst, second instrument). If you validate on the detector with the higher noise you shouldn't have problems when you transfer to the instrument with the lower noise. Good luck.

http://www.chem.agilent.com/Scripts/Generic.ASP?lPage=6563&indcol=N&prodcol=Y

Thank you u for your reply, got similar message from usp also