Mike The Electronics Dismantles An Old Mass Spec

He buys it for 400 quid. It’s interesting to see how different designers approach the same problems. I had the opportunity to see how one company evolved the designs, but not as much exposure to competitive machines as I wanted.

This is an ion trap mass spec, which happens to be the only type that I haven’t worked on.  Still, everything forward of the ion trap is very familiar to me.   One thing that is obvious is the lengths that designers will go to not pay money to my former boss.  let’s start with the videos.

Part 2.

Here’s the manual for the LCQ



Here’s a schematic of an ion trap mass spectrometer.


And a video explaining how it works.

What a mass spectrometer does is ionize molecules and  send them into a vacuum to a detector.  There a number of different types of mass spectrometers, but the most popular machines right now are Quadrapole, Time of Flight and Ion trap. All off these instruments work by adding a fixed amount of energy onto a charged particle and then measuring the energy at which the particle hits a detector.  A quadrapole mass spec works by bouncing the ions between positive and negative electric fields.  A Time of Flight mass spec works by pulsing the ions and measuring the energy of the pulsed ions and the time they take to get to the detector.  An ion trap mass spec puts the ions on a revolving field where they separate themselves and then are output to a detector.  I was a bit surprised by the use of a Tesla coil for the high voltage on the detector. There are other ways to get DC HV that don’t have the high impedance that a Tesla coil does.

Now the reason I say that people were willing to go to great lengths to avoid paying money to my former boss is that just about every facet of the Finnegan’s design is to avoid, if possible, infringing on the patents held for the electrospray ionization that the company that I used to work for held. The design of the electrospray at an angle which is nonoptimal, the use of octopoles on the ion guides.  All of these things are done to get the same kind of performance without having to license the technology, most likely from my former boss. Which if you knew the man you could understand. Some of it was greed on his part, but I’m guessing most of it was pure spite.

Some of the design ideas make sense.  The source in the LCQ looks like definite improvement and I sort of wish that Mike had taken it apart in the video so that I could see how they did the heaters.  The heater design that we were using was clunky and needed improvement, but I never got a chance to work on that due to time constraints.  The rest of it was very interesting to me though. Especially the cast vacuum housing.

This was an interesting look at this complicated and not very often seen technology. Before I started to work on mass spectrometers I had never heard of them and I don’t think that most people have either.  It’s not often that you get a chance to see a technology carcass taken apart and methodically shown. Interesting videos, at least to me.



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