A bit of background.

Okay, so I haven't exactly explained what I do at work, what EDB is, or anything like that.

As I've mentioned, I'm a summer intern at the U.S. EPA. I work in the Science and Ecosystem Support Division of Region IV-- in the Analytical Support Branch, more specifically. ASB is divided into organic and inorganic chemistry sections. I work in a pesticide lab (and sometimes the volatiles lab) in the Organic Chemistry Section. Basically the name of the lab describes what we are looking for in air/water/soil samples. So the analysts in Pesticides are looking for pesticide residues in samples that are given to us. Where are these samples coming from? They're generally taken by EPA (or privately employed) engineers in the field at sites that are either part of ongoing remediation projects or after someone has suspected illegal dumping or something gross like that.

Because this kind of analysis involves rather small minimum reporting limits and use of very sensitive instruments (GC/ECD), there is a lot of quality control involved. This data has to be defensible in court if required, and auditors are very picky about how things are done (with good reason). You can't just stick the samples on the GC and report the raw data without comparing it to controls. Examples of possible variables are things like matrix interference, column contamination, inconsistences in sampling methods, possible contamination of reagents or glassware, etc. So there are all kinds of what we call "blanks" to control for this interference and help nail down problems if we start getting weird numbers somewhere. We spike these samples with known amounts of the analyte of interest, as well as another compound called a surrogate that can (again) help weed out where problems are occurring. It works like this: if you know how much spike solution or surrogate you injected into a blank, and you get some weird percent recovery, it's time to investigate possible lab contamination. There are also bottle blanks where the engineers in the field rinse their glassware and send the liquid rinse as a separate sample-- this is a control measure that evaluates possible field contamination.

The DOC I've been blabbing about for the last MILLENNIA is a demonstration of capability that has to be performed any time there is some change in the method of analysis or personnel in a lab. Obviously a newbie summer intern counts as a change in personnel. ;) The idea is to prove that what you are doing is accurate, that it works, and that the method (or analyst) should be permitted to handle true samples unsupervised. There is no way a person could or should be able to handle real-world samples without demonstrating proficiency in the analysis-- again, EPA does handle criminal cases. The EDB method I've been learning is only about 6 months old and involves microextraction as well as the analysis itself (See EPA Method 8011 for the entire process). Basically what I did is make up a couple of blank spikes, an ICAL curve and initial calibration verification, run the whole thing and then turn in a packet consisting of about every kind of documentation you can imagine. I turned in my packet today and it's got stuff like my run sequence from the GC, copies of the extraction and GC logbooks, the raw data, a summary memo, draft report and a DOC checklist.

So what the hell is EDB? Ethylene dibromide (or 1,2-dibromoethane) is a highly toxic, colourless, chloroform-like compound that used to be an additive in leaded gasoline. It's been manufactured in this country since the 20's. I forget when leaded gasoline stopped being used in on-road vehicles (1997?), but EDB is still added to aviation gas and automobile racing fuel. It acts as a lead scavenger in engines, keeping lead from fouling them up. A smaller proportion of EDB produced in the U.S. (about 10-20% if I recall) was used in a nematicidal/fumigant capacity, added to soil shortly before planting, applied in grain storehouses, etc. The history of pesticide use in this country is depressing. People would get excited about new compounds and spray them all over shit before realizing those nasty little birth defects and cancer and stuff. Sad. EDB is considered by EPA to be a "known or suspected mammalian carcinogen." It is a severe eye, skin and mucosal membrane irritant, can cause internal organ damage, and it takes very little of this stuff to kill a human quite shortly (which is actually why it was applied to soil several days before planting of crops, to let the stuff kind of half-life itself out).

I may attempt some basic background on GC/ECD later. Sleep time now. I have an appointment tomorrow with one of my favourite teachers. :)