Lecture on Analytical Chemistry in BAC testing Part 9

The above is Part Nine from a lecture given by Attorney Justin J. McShane before the North Carolina Advocates for Justice “Advanced DWI Seminar”. This seminar happened on February 26, 2010. It was organized and hosted by John K. Fanney, Esquire of Fanney & Jackson, P.C. The following is a transcript of this video:

Let’s take a look at thin layer chromatography. I am going to cover it very quickly because it is just something to be exposed to. The first thing to do is extract the substance. You get the substance. The next thing you do is spot it on the plate. You fill at the bottom. Next you place in the solvent, the stuff you are going to be sucking up. After that you watch the solvent front as it elutes upward, causes that separation, hence the word chromatography. The next thing that happens is it is developed, meaning it is colorized. Then they read the distance, the color, and the resolution, against a known standard.

Let’s get very practical. This is from a particular case that we had that was a screening for THC. You are going to see this in urine related cases. You are going to see this in solid drug dose cases. They don’t particularly do it for blood but the important thing is to understand the process.

They take the known standard of THC, coming from a traceable source, meaning they absolutely know that it contains THC. Then they do those steps that we did, the spotting, and it elutes up, and then these are unknown from cases. So you have the standard but then you start to look over here and know that is what it is supposed to look like but nothing actually looks like that except for maybe that one. There are differences in the distance, the time that is related and it can be very subjective as far as the call as to whether or not it is THC.

The most instructive one to me is this one. This one means that someone got arrested for having pot, had to call one of you great folks up to defend them, no THC at all is present there. I wonder what happened with that guy’s case because my guy’s case was the nice beautiful one right there. This guy, who knows what happened to him. He might have pled guilty and it is just because they did the NIK kit on the side of the road but when it went into the lab maybe they didn’t get the lab results that came out of it. You have to be aware and you have to look for the raw data. The principle of thin layer chromatography, just think of the bounty commercials.

Now we are moving out of the realm of make believe and we are going to start to talk about forensic testing. What you have to understand is that molecules have different shapes and forms based upon the different bonding. On the left we have coca-juana molecules, on the right we have metho-juana molecules. Different things have different chemical structures.

This, if you have never seen one, is a gas chromatograph. When you hear those magic words, gas chromatograph, many attorneys think, ‘well that is it; we just have to work out a deal’. If you understand gas chromatography and you can be exposed to it, you can understand that’s not it. There is a lot more to it so let’s take a look at it and get a little background. Basically you have a sample vial, a head space vial, and this is the actual device, it is the gas chromatograph. This part is called a column; I actually have a column right here. I am going to pass it around so everyone can take a look at it. There are two different types of columns. The first type is called a packed column which no one ever uses unless they are in Michigan, maybe Wisconsin. The more prevalent one is called the capillary column. This is a capillary column. It is very thin. This is where things get pumped through and get separated out. Again, it is called chromatography, separation science. The process that goes along with it is very easy to understand. You just have to be exposed to it.

A couple of things, this is the vial, the head space vial that contains the blood and it contains an analyte of interest, a volatile organic compound, ethanol in our particular case. It exists here in the vial. The vial gets heated.  It might get shaken up a little and between the liquid phase and what is called the head space and it creates equilibrium which is called Henry’s Law. Henry’s Law depends on a closed system so if there are any leaks there are going to be problems with this. What is says is that the amount that exists in the head space is proportional to that which is in the liquid phase. What happens is, you have a needle that pierces the septum, the top part, it draws up a particular part of the analytes of interest into the column which hits a Flame Ionization Detector in this particular example and it gets burned after it separates out. The burning creates an electrical signal that gets recorded here as you see it separate out. As you see it hit the Flame Ionization Detector you see something that is called a chromatogram. This is what it looks like. You draw up two different molecules.  One goes through faster.  The other slower.  It hits the detector and that is how is comes out with a squiggly line. Let’s take a look at that one more time so everyone can take a look at it. It goes through, elutes out, hits the detector and that’s where you get the chromatogram.

This is to be distinguished from what is called direct injection. Direct injection is when the needle goes into the fluid itself and draws out the blood and can cause havoc. Your state doesn’t do it but it’s the same basic principle that as it elutes out and separates out.  It is there.

Retention time is the time it took to separate out, to come out at the end and hit the Flame Ionization Detector. That is the retention time as it elutes. I promise it will make sense in two slides. Why does it separate out? Why is it different? It is called sorption.

I want you to imagine that you are inside a mall but it is one of these George Jetson type of malls where there is a walkway like they have in the airport, that goes in only one direction. There are two analytes of interest in our particular example. There is the red one which is me and the blue one which is my wife. Different types of stores attract me and other types of stores I wouldn’t be caught dead in.  Same with my wife. For example, I love Sharper Image.  There is no way you could pay me enough to be in White House Black Market. You couldn’t pay me enough to spend time in Crate and Barrel. Nevertheless, my wife loves those types of stores. The bottom line is, this is the same exact process.  How quickly we get out is based upon the coating inside the capillary column and what it is made up of in terms of whether it absorbs or adsorbs, meaning it is attracted to it. Let’s take a look here. I am one and done.

I go into Sharper Image. I get out. She takes longer. She gets out. Changing the column is the same thing as changing the stores. Sharper Image, a tie store, I am going to spend a lot of time at my tailor shop.  There is a gadget store; you will not see me until next week. The bottom line is if you change the components inside the column there is not one universal column. So through the chemistry of it, you can cause things to go out faster and slower. In this one, I am the blue one.  It takes me more time to get out than my wife. There are times that there are things neither one of us like. We don’t need to go to the food court when we aren’t hungry. That is how it gets separated out and that results in what is called a chromatogram. A chromatogram is the representation that is there. The most important thing to take a look at with the chromatogram is understanding that you are comparing known times from a standard, meaning we know when we send in a standard, something as a known substance, and we pushed it through and it comes out at this relative point in time, called the retention time. That is how you can tell the difference between things that are like one another and things that are not like one another; methyl-juana and coca-juana in these circumstances.

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