ICP-MS Training

Happy Friday again! This week ended up being a little bit intense because I attended three days' worth of training for ICP-MS and IC. I know--more acronyms. ICP-MS stands for inductively coupled plasma-mass spectrometry, and IC stands for ion chromatography. We are going to use both of these techniques in our lab and have new instruments to love. In order to keep this post from getting too complicated, today I'll focus mostly on the ICP-MS.

A good part of our training actually took place in front of the instruments, which are in the clean room. A clean room is exactly what it sounds like: a place that is very clean! Clean rooms can be designed for a variety of purposes. Our clean room has very low concentrations of particles and essentially no metal. Even the paint on the walls is not normal paint; it is specifically designed for use in a clean room. These conditions allow us to measure trace metals and other elements at very low levels, in some cases in the sub-part per billion (ppb) range. Without the clean room, the background concentrations would completely overwhelm the concentrations in our samples, and we would not be able to get any useful data. To enter the clean room, I have to get dressed up in my very clean, fancy duds.

I think the hair net is sexy.

Our ICP-MS instrument. It is an iCAP Q quadrupole mass spectrometer.

The autosampler. This allows the user to set up a run which the computer then executes automatically. It means that I could let a very long run go overnight and collect the data in the morning. Sleep! Zzzzz...

The sample inlet system. This is how the sample gets from the racks in the autosampler into the instrument. In the back is the peristaltic pump. On the lower right is the system that injects the sample, and on the lower left is the nebulizer (glass piece).

We will use our mass spectrometer to measure the concentrations of trace metals and other elements in natural water samples from lakes, rivers, etc.; sediment porewaters; and sediments.

A mass spectrometer separates and detects components of a sample having different masses.Technically, what the instrument measures is the mass-to-charge ratio (m/z), but mostly what reaches the detector has a +1 charge, so we are in effect looking at the mass. What this implies is that the sample must be ionized. There are several different ways of ionizing a sample, but ICP-MS uses an argon plasma to accomplish this. Fun fact: The argon plasma has a temperature approximately equal to that at the surface of the sun. The U.S. Geological Survey has a nice explanation of some of the more technical aspects of how an ICP-MS works here.

One of the important points about ICP-MS (or any other analytical technique, for that matter) is that the sample preparation and experiment design must be thoughtfully considered before putting a sample on the instrument. I think most scientists crack up and shake their heads at all the detective/cop shows on tv where the investigators grab the nearest instrument with an impressive-sounding name, put their sample in it, and two minutes later, the identity of the sample is printed out for them! Voila!

I can't believe it! I think it's dihydrogen monoxide!

In the real world, it doesn't work like that. First of all, the identity of the sample is almost never just given to the scientist. For example, with the mass spectrometer, all the user gets is the mass and the intensity of the signal at that mass. That's it. After that, it's up to the user to do something with it. However, most of the time the scientist already has some information about the sample--where it came from, what compounds or elements might be in it, etc. But to get good quality data from our mass spectrometer, I will have to dilute my samples to an appropriate concentration range, set up the method, prepare the correct calibration standards, optimize the instrument parameters, and a few other things. At the end of the day, it's fun. I enjoy listening to the hum of the instrument. Getting and analyzing data is like watching a story unfold.