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HPLC DAD FL noisy baseline
Posted: Fri Jul 15, 2011 6:10 pm
by AMY2242
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Re: HPLC DAD FL noisy baseline
Posted: Fri Jul 15, 2011 7:12 pm
by JGK
What was the mobile phase you were working with?
Are IPA, acetone 7 methanol compaible with all of the MP components.
What happens if you try an aqueous wash?
Re: HPLC DAD FL noisy baseline
Posted: Fri Jul 15, 2011 7:37 pm
by AMY2242
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Re: HPLC DAD FL noisy baseline
Posted: Fri Jul 15, 2011 7:43 pm
by AMY2242
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Re: HPLC DAD FL noisy baseline
Posted: Sat Jul 16, 2011 9:07 am
by HW Mueller
Flow without column gives the same noise as with column and with no flow with or without column? All solvents give the same noise?
Did you try to push solvents, even air, through the cell with a syringe?
Re: HPLC DAD FL noisy baseline
Posted: Sat Jul 16, 2011 2:25 pm
by carls
What HPLC system are you using? Agilent systems include built-in tests for lamp intensity, flow cell transmittance, etc.
Poor sensitivity and noisey baseline sound like very little energy is getting to the detector. As you have suggested this is either a dirty flow cell or weak lamp. I would change one or the other. Instrument manufacturers have cleaning procedures for UV cells. Some use nitric acid but I dont recall the details.
What wavelength are you monitoring? Do the problems change at a different wavelength? Collect all spectra during a run and if there any structure in the data you either have a dirty flow cell or your solvents are contaminated.
Good luck!
Re: HPLC DAD FL noisy baseline
Posted: Sat Jul 16, 2011 9:24 pm
by AMY2242
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Re: HPLC DAD FL noisy baseline
Posted: Sun Jul 17, 2011 8:45 am
by HW Mueller
How did the baseline look during "manual" push of solvents through the cell? Just wondering whether you got some column stat. phase fines in the cell.
Re: HPLC DAD FL noisy baseline
Posted: Sun Jul 17, 2011 8:52 am
by HW Mueller
By the way, what do you mean with "the solvent bottle did run a LITTLE dry"?
And: did you do a stop flow or not? You didn´t do the baseline tests without a column on line?
Re: HPLC DAD FL noisy baseline
Posted: Thu Jul 21, 2011 8:16 pm
by AMY2242
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Re: HPLC DAD FL noisy baseline
Posted: Fri Jul 22, 2011 1:44 pm
by HW Mueller
Well one doesn´t do a no flow without having flow first, then compating to stopped flow. There are some questions you didn´t answer.
Re: HPLC DAD FL noisy baseline
Posted: Fri Jul 22, 2011 2:14 pm
by AMY2242
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Re: HPLC DAD FL noisy baseline
Posted: Fri Jul 22, 2011 2:26 pm
by carls
does the noise change when you remove the cell?
Re: HPLC DAD FL noisy baseline
Posted: Fri Jul 22, 2011 2:52 pm
by AMY2242
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Re: HPLC DAD FL noisy baseline
Posted: Sat Jul 23, 2011 8:24 am
by HW Mueller
It would be a strange coincidence if the lamp went bad just when you did non-LC with an LC. I don´t know your particular instrument and just found out from your last statement that FL stands for fluorescence. If this is correct and both use the same cell then you have another flow path (especially cell) testing possibility. Also different solvents and flow rates are helpful, and, furthermore, the use of a syringe for pushing solvents through.
My guess remains: Column fines in the cell.