By Anonymous on Friday, April 16, 2004 - 04:02 am:
I try to analysis sunscreen by HPLC; but avobenzone and octinoxate peaks are overlaying, I couldn't get separate. HPLC condition: UV 300nm, mobile phase: methanol and water(85:15), C18, 5um bondapack(waters) column. Is anyone can help me? please advise! Thanks.
By Durk on Friday, April 16, 2004 - 04:54 am:
Can't you use a gradient of your mobile phase?
Durk
By syx_gf on Thursday, May 6, 2004 - 05:53 pm:
I use the same method: MeOH - water (85 - 15), but in 2 wavelengths: 310 and 360 nm. 360 nm is better for avobenzone. Just two minutes in front of avobenzone, there is a peak of octylmethoxycinnamate, which shows good shape: tf 4!
By syx_gf on Sunday, May 9, 2004 - 06:28 pm:
sorry, i meant avobenzone's tf > 4, but octylmethoxycinnamate's < 1.5. ;P
i have tried to use low pH using 0.1% TFA but still there is no correction. i won't use high pH because octylmethoxycinnamate can be degraded into acid and alcohol. i tried using other type of column (C8, CN), but avobenzone still in bad shape! i do not have any idea anymore...
do you have pKa value of avobenzone?
By Uwe Neue on Monday, May 10, 2004 - 04:20 pm:
My suggestion would be to use a modern C18 (or C8)instead of microBondapak C18. My suggestion is Symmetry C8 from Waters, or XTerra RP18 from Waters.