Thursday, August 4, 2011

Solid Phase Extractions

It has been a while since I have written a science post -- so I want to share with everyone how we are actually processing some of the water while we are in Alaska.  I will end with some wildlife pics, I promise!

We are using a common method to isolate dissolved organic matter from water called solid phase extraction (SPE) cartridges.  Each of these cartridges is a plastic collumn with a small amount of porous material at the bottom that bonds to organic material (ours contain 5g of solid phase, but they come in all different sizes). 

Our extraction set-up!
We have developed a system of tubes that allow us to pass water from the 20L carboy into the top of the cartridge.  As the water drips through the solid phase, the organic matter bonds to the material and is removed from the water (a process called "loading" the collumn).  Since no solid phase material completely removes 100% of the organic material from the water, we are using 2 types of solid phase material: C18 and DVB.  These two types of solid phase bond to slightly different types of organic matter, which will hopefully give us a representative picture of organic matter composition.

As the organic matter is loaded onto the collumn, a dark band appears at the top of the solid phase.  Throughout the process we monitor the water that comes out of the collumn to determine when a significant amount of the organic matter is no longer bonding to the collumn and is actually just flowing through the solid phase (this is known as "break through").  At this point, we stop dripping water through the collumn and it is time to get our organic matter out!

Two completed C18 Cartridges after 15L of water were passed through each collumn

In order to remove the organic matter from the solid phase material in the collumn, we need to pass some liquid through that the organic matter will be more soluble in than water - which will allow the organic matter to dissolve in the liquid and be released from the solid material.  In our case, we use methanol to flush out the organic matter.  It is actually quite fun to watch the band of material moving down the collumn as we pull the methanol through!

The beginning of the extraction

The band of organic matter is moving down!!

... almost to the syringe...

Here it comes!  Look at that golden color :-)

... and out comes the organic matter!

At the end of this long process, we have a gorgeous amber brown material that will later be dried down to a powder for all of my experiments at OSU!!

The syringe at the end of the extraction full of our precious organic matter

Okay, so now for the promised animal pictures :-).  Allison and I headed out a couple of days ago to the Oksrukuyik Creek (pronounced Oxy-curic) to collect more water.  As we were driving, we spotted a muskox, which looked like a mass of fur moving along the river!

Unfortunately the muskox is a little out of focus, but he looked like a walking long haired wig!
While scoping out field sites we also spotted an Alaskan Lake Trout!

1 comment:

  1. Interesting! But what is a Collumn? Is it similar to Column?