Electrospray ionization - ion trap - detector

[ChristofferB]

Hi all! So, this is an idea that's a bit out there, I just wanted some feedback if it might be worth pursuing.

I'm on an ongoing quest to construct inexpensive detectors for gas chromatography/ liquid chromatography/HPLC

There's a lot of development in this area, since most common detectors for liquid chromatography (UV-VIS diode array detector, mass spectrometers, conductivity, refractive index etc.) are usually very costly and bulky.

Basically, any detector that can detect peaks of dissolved molecules in a flow of liquid.

Here's the idea: Make a mass spectrometer without the spectrometer.

- Everything is housed in a very high vacuum chamber. Evacuated with a small turbo pump.
- An electrospray ionization source to create a jet of charged particles. most of the solvent is removed here.
- Maybe a simple electrostatic DC ion trap to suck away the lightest ions, acting as a mass low pass filter (might be needed to suppress solvent signal)
- Faraday cup detector, femtoampere-scale amplifier, ADC.

Do you see what I'm getting at? In theory, if you are certain only one compound will enter at a time you could in principle do away with the mass separation - you'd just want 'total amount ions other than solvent' as a function of time. Kinda like how a single wavelenght UV absorbance detector just detects "total amount of solutes at 255 nm" or similar.

This would be mechanically much more straight forward to construct.

--Chris
 
 

[vindoline]

Not "out there" at all. I'm pretty sure that this is what we call a "total ion chromatogram" or TIC. It's a pretty good universal detector.

[ChristofferB]

Thanks for the feedback!

Yeah the output would be the same, but that's usually just a data display type from a regular chromatography-coupled MS. I don't think I've ever seen a dedicated instrument that does only that.