The 8270 is the EPA mandated test for semi volatiles.
The EPA 8270 is an analysis for materials that are extractable with methylene chloride
the initial step is -- add methylene chloride
extract into the methylene chloride
pour the methylene chloride off
add more methylene chloride
extract
pour it off -- add methylene chloride
extract
and pour it off
so the first stage of the 8270 results in a rather large container
of methylene chloride
like 100, 200 even 300 ml of methylene chloride
with very small amounts of whatever it is you're looking for
so the first step is--- "What are we going to do with all
this methylene chloride"?
it is like 99.99% methylene chloride and what you are looking for is kind of
is buried in all that methylene chloride
The key to the condensation (concentration)
lies in the boiling point of the materials you are
looking at
The semi volatile is called the semi volatile because
.. the 8270 is called the semi volatile because....
They boil ... they will turn into gas... but typically at
100 to 300 degrees centigrade
So a simple guess would be that...
if you took the methylene chloride, with the boiling point of about 40
and heated it up to 40
the methylene chloride would
come to a gentle bubble...bubble, bubble
and in the methylene chloride would boil off
leaving behind everything else
the way this is done in real life is not real different than this
you essentially boil it gently. the methylene chloride very quickly
boils off
and the other materials don't
the complication is that ....like... again
let's take naphthalene
it has a boiling point of 218°C
so it doesn't boil very easily all
it dissolves nicely methylene chloride
so the methylene chloride is bubbling off
naphthalene comes to the surface
naphthalene doesn't boil anywhere close to 40° but it will evaporate
the reality is that if you just blindly
heat the methylene chloride, the methylene chloride
will boil off nicely but you will lose a lot of your semi volatiles
the actual chemistry, the actual physical science behind
cleanly separating the methylene chloride from other things
is a complicated chemical engineering problem
petroleum engineers and chemical engineers are experts at this and maybe one will
come along and help us out with this
But in the meantime
the world of environmental science ......we're chemists
and we're trying to meet objectives ....We got things we are trying to do
we don't care too much about how it gets done
there is a trick which we use.
it is called the Kuderna Danish concentrator
the Kuderna Danish condenser consists of three pieces of glassware
the first one, or let me say, the middle one, is a glass vial
it looks like a separatory funnel
it it's not but it looks like one
it's kind of conical and pointed at the top
it has two ground glass fittings one at the top and one at the bottom
the ground glass fitting at the top
goes into a Snyder column
the Snyder column.....
it's kind of a low-tech kind of thing
it's not exactly condenser it's more like a filter or separator or something like that
but it isn't complicated
all it is, is a tube.
The tube has indentations and those indentations
Trap little balls
the balls are trapped
in the indentations and they
rattle around in the Snyder column
they come in different sizes but
a typical Snyder column is maybe about this long
the flask is maybe about this big
and then at the bottom of this conical flask
is a little graduated cylinder
it's pretty small... like maybe 10 milliliters altogether
maybe 20 milliliters altogether
but it's graduated
the bottom column is put into the top, the methylene chloride is
poured into the whole thing and then the Snyder column is put on top
sometimes they are held together with springs
sometimes not
And then this whole thing is put in a steam bath
The steam bath heats the methylene chloride
well above its boiling point
and methylene chloride starts screaming out of the flask going into the Snyder column
When it reaches the Snyder Column
the Snyder column... it is relatively cool
is like maybe 50°C or something like that
is a little bit cool
the methylene chloride fights its way through the balls
Snyder column kind of filters only the methylene chloride
and things that are very volatile are able to fight their way through the column
and get out and completely escape
everything else kind of gets stuck in the balls and kind of sticks
to the balls and of course,
the whole thing is coated with methylene chloride
but the vapors are able to find their way through
and escape into the air
this is done on a steam table in a hood
methylene chloride is moderately toxic so it's not something you want to breath.
its...hummm....
the people that do this are specialized in this
let's kind of run it as a scenario:
You have the tube, the little tube
the bigger flask
and then the Snyder column
it is full of methylene chloride
the methylene chloride is fairly clear
hopefully it's clear
sometimes is not
and you put it in a ring stand in the steam bath
the steam table heats it up
it starts bubbling fairly quickly
say within three quarters of an hour
or something like that the methylene chloride
is starting to be pretty much gone
as the methylene chloride goes down and down and down
the operator, using a water bottle with methylene chloride in it
it says "methylene chloride" on the water bottle
Squirts into the Snyder column
the methylene chloride percolates through the Snyder column
washing anything that's in the column down into the flask
it has to be evaporate again
everything you add has to be evaporate again
and as it goes down and down down down down
the operator gently
washes it down
and is it goes down below the big column
and goes into the graduated part
the operator makes one last rinse,,
quickly takes it apart, takes in the big flask away
puts the Snyder column right on the graduated cylinder
and keeps going and keeps going
carefully washing it
carefully watching it
washing and watching washing and evaporating it
and watching and washing and in evaporating it
and as soon as the liquid gets down to exactly 1 ml
there is mark on the graduated cylinder
As soon as it gets down to exactly one milliliter
the operator,,, the technician,, takes a Pasteur pipette disposable
draws it off and puts it in a labeled
autosampler vial... one of these little tiny bottles
those bottles hold about 1 ml and a half
or something like that
so it pretty well fills it
and then crimp seals it
And that's it..... he is done
And then it goes to the operator
The glassware is cleaned... yeah
and is it scrubbed...yeah...
the glassware is to put in a furnace and heated up to about.. maybe.. 800°C
and the furnace burns off all the organic material
so it's cleaned and scrubbed at all that
but...eh... not really
it's put in a furnace and burned it down to ... nothing
it's gone ....it's not cleaned
it's sterilized of organic material
The Kuderna-Danish concentrator which is the three pieces of glassware ....
they cost about ...
I want to say 150 to 300 American dollars
they're pretty extensive
they last a long time if you take care of them
the 8270 involves a complicated extraction
the extraction and condensation
let's look at this from the time real quickly
three samples come in from the Wal-Mart site
they want to build a Wal-Mart
the consultants "say we need an 8270 on this spot , this spot and this spot"
the lab gets three samples for 8270
the technician is going to do six samples
A blank..... I think it is intuitively obvious
that you check and make sure that your equipment is clean
the three samples and a spiked sample which is quality-control sample
and another spiked sample which is another quality-control sample
so the prep is typically, for three samples, six preparations
6 extractions,,,six condensations
the initial extraction will take the technician all morning
the concentration step will take the technician all afternoon and
then the six samples will go to the instrumentation people
the instrumentation is actually the area that I worked in
Instrumentation people.... it will take them ...
it's essentially all day
not all date continuously
but it will take an eight hour shift... pretty much to set these up
run them and process the data
I think the financial aspects are interesting
The typical 8270 cost $600
you want to have an 8270 run on your garden soil
not a problem but it'll cost 600 bucks
it's negotiable!!!
but it's kind of a big bucks deal