Chromatography Forum

Hi everyone,

I saw a mention in an archive post about environmental contamination. Would someone be able to give some input as to what kinds of problems might occur with HPLC from environmental contamination (like dust)?

I'm inquiring because I have had almost a week and half of assay results that are too high for octinoxate in my routine sunscreen samples, and for the life of me I can't pinpoint the problem. I have tried all my usual "fixes" that normally work to no avail. The only thing that has changed was that our maintenance department installed an air conditioner in my lab last weekend. Now, unfortunately they placed it in the wall high above the HPLC (not my preference of location). And in the nature of someone who isn't familiar with the delicate nature of an $$ piece of equipment, it didn't appear that they put a tarp down over the HPLC when cutting into the wall, etc. Therefore, I found some dust around the unit. I wiped up any surface dust and went on with my analyses. Since I thought it might be the a/c, I have tried running samples with and without the a/c on and I get the same results, so I don't figure it to be a temperature issue.

What kind of problems might one encounter with environmental dust, and how would I go about solving them? This is just about my last resort to try to figure out why none of my routine samples are coming out right, and the air conditioner being installed is the only thing that has changed.

Any input would be greatly appreciated!

Call the service guy!

You might have several problems arising - not only temp one, but the colling fans of pump and detector might be failing, the detector lamp might be full of dust, you might even have your check valves dirty of the eluent beakers were untapped - well, I only give 60 seconds tought to find all those, now imagine if we start wondering for a couple of days!

Are your peaks from multiple injections from the same vial reproducible? If so, I doubt that it's an HPLC issue. If OK, have a second operator make up standard and samples independently. Sunscreens are straightforward due to low 300nm region UV detection wavelength and the high levels used in products. I'll assume you're within the linear range for your octyl methoxycinnamate, sorry name changed to ethylhexyl methoxycinnamate, sorry name changed to octoxinate.

You've probably already checked this, but are your blanks clean? If the problem is contamination, it should show up there.