How Dirty Are You? Part 1 Parafilm...Take a Quiz!
23 Feb 2014
image from about.com
A couple of years ago I gave a presentation about general lab practices.
How dirty are you? Common lab practices that may impact data quality are examined using various gas chromatography and gas chromatography-mass spectrometry techniques. (look for this presentation on the last How Dirty are You? blog...i cant give you the answers now!)
We work in very close quarters in our lab…we have grown in staff but not in space. This means that I sometimes have to squeeze into one of our hoods with a colleague or two. I started to notice little differences in the way each person goes about their work. For example, some people always place syringes on a clean paper towel while others don’t or some people will use a Pasteur pipette more than once while some won’t. I realized that I have lab habits that could be more ritualistic than meaningful.
One of the funniest things is rinsing a glass syringe- everyone has a number and a story- but we will get to that in a future “How Dirty Are You?” blog. There will be at least six subjects covered in this blog series. These will discuss other sources of contamination like gloves, syringes, pipet bulbs, tubing…etc. I will also post the percent of correct answers from the first audience to participate (FPRW 2012 Restek Vendor Seminar) and include answers I receive via email.
This blog is about Parafilm…personally, I love the stuff and have used it for years. One day a colleague of mine instructed to never use “that stuff” because it will contaminate your sample. Really, I thought…I have used it forever and it doesn’t seem like it would be too soluble in acetonitrile. I just couldn’t believe it. So I thought, “Heck, I am an analytical chemist, why don’t I test it?” Of course my colleagues were on board so this is what we did.
Parafilm is often used to store samples or temporarily top open containers like beakers so to mimic a worst case scenario, we soaked approximately 25 mg Parafilm directly in 3 mL of solvent for 60 minutes. The image below shows the eight solvents we tested and the Parafilm submerged in the each vial.
After the 60 minute soak time, we tested each sample using GC-FID. We used a hydrocarbon standard for signal intensity reference. As a teaser, I will tell you that the highest contamination peak was about 3 times higher than our 50 ppm hydrocarbon peak!!