Chromatography Forum

Hi everybody!

i'm new to this forum and I'm also quite new to chromatography, so I hope you can help me!!

I do analysis with a GC-MS from Perkin Elmer. I did some analysis and I saw that the blank of solvent I use, dichloromethane 99.99%, is not blank at all!!
I have to concentrate the dichloromethane (evaporation and then reconstitution), and the chromatogram of this concentrated DCM shows one phenol [Phenol-2,4-bis (1,1dimethylethyl)], some phthalates and alkanes from C22 to C29...
I did the analysis more than once, and I have always those contaminating agents;
Do you have an idea from where they can come??
Thanks a lot in advance for you answers!

Rinse the glove you use with a solvent, concentrate it and shoot it to your GC, you'll then know where it comes from.

you mean, it comes from the gloves??
Ok, I'll try tomorrow, thanks a lot!
But if it's the origin of those contaminations, it's quite annoying...

The contaminants you are describing come from all kinds of places. Look carefuly at the labware you are using, including lids. If you are using disposable glassware, these contaminants can come from the packaging. And watch out for lids to bottles and jars.

Be sure that your lab uses proper procedure on the use of solvents - take it out of the bottle into a clean container and what you do not use, discard. If sovents are poured out into a clean container and the unused materials are retuned to the bottle, even if the solvent has only been poured from the clean container - any contamination in the glassware will go into the bottle. Clean glass is not always that clean depending on the glass washing procedures - and bare hands used to put away glassware when dry...

I agree with all of the above.. Plastics are not the chromatographer's friend.....