The geologist’s guide to mass spectrometry

Mass spectrometry is important to geology. After all, rocks are made of atoms, and the different geologic processes can leave chemical clues behind that allow analysts to reconstruct a rock’s history. Despite this, the nitty-gritty details of using mass spectrometers and understanding the data they produce are often overlooked by many geologists. There seems to be some sort of false impression in the geological community that mass spectrometry is difficult, and perhaps even a bit dry and technical. While it is certainly technical, it is my intention to dispute the other claims. Mass spectrometry is wet and easy. You just need the correct frame of mind.

The basic principles of mass spectrometry are simple. First, you get some atoms or molecules so excited that they start losing their electrons. Then, before the excitement passes, you run the excited atoms (called “ions”) through an obstacle course of electric fields, magnetic fields, and physical barriers. This obstacle course separates the ions based on a particular attribute which is of interest to the analyst. For mass spectrometry, one of the attributes of interest in generally mass. Finally, you count the ions as they reach the end of the course.

There are lots of different types of mass spectrometers. The basic classifications are based on two factors: The method used for ionizing the molecules or atoms to be analysed is one basis for classification. The type of obstacle course used to separate the ions is another. Stay tuned for examples of different examples and explanations of how they work and what the results they produce actually mean.