By giorgio on Wednesday, June 23, 2004 - 12:52 am:

i use gc/ms to analyze avobenzone in wwtp sludge. there is derivatization of the dibenzoyl group (CH3I + NaH / DMSO, the two hydrogens at alpha position are replaced by two methyle groups)and SG60 clean up prior to analysis. the problem is that the sensitivity of the column is drastically decreased after 2 - 4 samples, and becomes unusable after 10 - 15 samples. does anyone know where the problem is?

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By Consumer Products Guy on Wednesday, June 23, 2004 - 08:08 am:

I'd use HPLC for avobenzone (Parsol 1789), especially with your stated GC issues and matrix. With the UV detection wavelength of about 310nm, you should get plenty of specificity and sensitivity.

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By giorgio on Thursday, June 24, 2004 - 12:00 am:

thanks, we already tried that, but the limit of detection was beyond any sensible range... do you have any references?

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By Consumer Products Guy on Thursday, June 24, 2004 - 10:06 am:

You should be able to do low ppm or less easily with HPLC - what detection limits are you requiring? I've only worked with avobenzone 1 day (we don't use it) but have experience with other sunscreens, and use the same procedures. What's wwtp?

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By giorgio on Friday, June 25, 2004 - 12:23 am:

i need a detection limit of low ppm. did you inject avobenzone directly or was there a derivatization first? what hplc conditions did you use?
thanks

wwtp - waste water treatment plant

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By Consumer Products Guy on Friday, June 25, 2004 - 08:59 am:

We dissolve in DMF, or use ACN, or THF. No derivatization. Try 313 nm wavelength (or run scan of avobenzone standard to find better wavelength in that region, for specificity). Start with 50/50 THF/water on RP-18 column, can move to water-ACN, or water-methanol to lower background absorbance even more. We use THF without preservatives. You should be able to reach those detection limits.