Anyone familiar with Mass Spec?

This another shot in the dark. My last question didn't get a response. I don't blame you! It was boring as could be. This might be as well. Maybe I'll try to find a science specific forum. I figured I give you guys a go first.

Okay, I have these compounds I'm trying to test. I can't run them on LCUV (no chromophores). I don't have a GC. And there aren't ionizable forms (grrrrr). So, ESI doesn't work and I've tried APCI source with no luck. I'm trying to learn about forming adducts, but I have no idea how to go about this. Can anyone shed some light?

Thanks so much in advance!

~B

Braunwyn said:

I'm trying to learn about forming adducts, but I have no idea how to go about this. Can anyone shed some light?

Click to expand...

I have no idea what you're talking about but if you want there to be light you've come to the right place.

I suggest you start with Genesis 1:3.
I'm sure you can interpret the bible in such a way that it will give you an answer for your chromosomeless, non-ionizable compounds.

- Ectezus

Ectezus said:

I have no idea what you're talking about but if you want there to be light you've come to the right place.

I suggest you start with Genesis 1:3.
I'm sure you can interpret the bible in such a way that it will give you an answer for your chromosomeless, non-ionizable compounds.

- Ectezus

Click to expand...

I'm sure that's been done before, but

Ahh, we have comedians. lol And I was excited to see two responses.

Braunwyn said:

Ahh, we have comedians. lol And I was excited to see two responses.

Click to expand...

Sorreh.

Only mass spec I've used is quadrupole mass spec. And by sounds that doesn't sound like it'd work for your situation - think that only works on charged objects...

Cabal said:

Sorreh.

Only mass spec I've used is quadrupole mass spec. And by sounds that doesn't sound like it'd work for your situation - think that only works on charged objects...

Click to expand...

I think we have a quad some where. One of the compounds is a base, but it's structure is screwy. I'm just getting the hang of MS. The APCI source is supposed to deal with compounds that don't have groups that can be ionized, but it didn't work. Eh, maybe I didn't set it up right. I tried to tune but it noted low detection. I found the same thing on my single core with an ESI source. That's why I'm hoping I can form an adduct, maybe I'd get detection. I just don't know where to begin and don't have the time to educate myself.

Somebody in passing mentioned using Ammonium hydroxide (or something) so I set that up my mobile phases in the LC. Again, a whole lot of nothing.

Thanks for responding just the same, Cabal

Braunwyn said:

I think we have a quad some where. One of the compounds is a base, but it's structure is screwy. I'm just getting the hang of MS. The APCI source is supposed to deal with compounds that don't have groups that can be ionized, but it didn't work. Eh, maybe I didn't set it up right. I tried to tune but it noted low detection. I found the same thing on my single core with an ESI source. That's why I'm hoping I can form an adduct, maybe I'd get detection. I just don't know where to begin and don't have the time to educate myself.

Somebody in passing mentioned using Ammonium hydroxide (or something) so I set that up my mobile phases in the LC. Again, a whole lot of nothing.

Thanks for responding just the same, Cabal

Click to expand...

No worries, sorry I couldn't be more help.

By the sounds of things quad-MS won't really help, I seem to recall the experiment we were using it in only involved really simple molecules like dimers or threefold symmetric stuff like ammonia. Think with more complex stuff the electric dipole moment will start mucking things up perhaps.

Braunwyn said:

This another shot in the dark. My last question didn't get a response. I don't blame you! It was boring as could be. This might be as well. Maybe I'll try to find a science specific forum. I figured I give you guys a go first.

Okay, I have these compounds I'm trying to test. I can't run them on LCUV (no chromophores). I don't have a GC. And there aren't ionizable forms (grrrrr). So, ESI doesn't work and I've tried APCI source with no luck. I'm trying to learn about forming adducts, but I have no idea how to go about this. Can anyone shed some light?

Thanks so much in advance!

~B

Click to expand...

If you dont have a GC, build one. It sounds like it might be your best option. As I remember some early ones were built with glass tubes loaded with laundry detergent, and the flames recorded by a spectrograph.

Once you have the timing of the fractionating columns down, it should be possible to separate the compounds of interest.

It takes time, but saves money. It's the usual trade-off.

Uh, I know how a mass spectrometer works. But from the terminology you're using, it sounds like you're doing chemistry. Since I don't do chemistry and have never used a mass spec for my research, I don't know if I'd be of much help.

Hi,
I work with a HPLC-MS-MS almost daily. I tried to get an answer for your last question but your question was vague as could be.

Same here.

what kind of compounds do you have?
If you don´t have a chromophore, maybe you could use an ELSD?
In an MS you could get almost anything ionized, but it depends on what compounds you want to measure.

Gracchus said:

If you dont have a GC, build one. It sounds like it might be your best option. As I remember some early ones were built with glass tubes loaded with laundry detergent, and the flames recorded by a spectrograph.

Once you have the timing of the fractionating columns down, it should be possible to separate the compounds of interest.

It takes time, but saves money. It's the usual trade-off.

Click to expand...

Time is the problem. To start, I wouldn't be able to fit this type of project into my schedule unless I spoke with my boss and made into an official project in my objectives. And maybe I should do that. It's always good to have other methods. My problem now is that I started my experiment on thurs and it called for a 24 hour incubation. This is 100% my fault. I knew these compounds were problematic, thought I found an easy fix with APCI at the advice of a MS expert, and now I've put myself in a pickle. My head cold has held common sense hostage.

Any way, I've always wanted to learn more about GC.

just another skeptic said:

Hi,
I work with a HPLC-MS-MS almost daily. I tried to get an answer for your last question but your question was vague as could be.

Same here.

what kind of compounds do you have?
If you don´t have a chromophore, maybe you could use an ELSD?
In an MS you could get almost anything ionized, but it depends on what compounds you want to measure.

Click to expand...

They are small molecules. Two have MW in the 400's. The third was around 1300 but I ran out of material. I'm trying to measure concentration.

ELSD? Light scattering is an idea I haven't considered. I don't have anything like that in my lab but one of my colleagues is doing some work using light scattering. I don't know how I would hook that up to HPLC but may he's know. Thanks!

I wish I could post the structures here but I can't. I'll see if I can find something similar. But, yea, in MS almost anything could be ionized with an APCI source, right? Maybe I set it up wrong. It's on our tripple core and I just learned how to use that software so maybe I did something wrong.

Thanks for responding. I'm so appreciative. If anything else comes to mind please let me know. In the mean time, I'll try to find some structures on the net that may help. Off to work!

Braunwyn said:

This another shot in the dark. My last question didn't get a response. I don't blame you! It was boring as could be. This might be as well. Maybe I'll try to find a science specific forum. I figured I give you guys a go first.

Okay, I have these compounds I'm trying to test. I can't run them on LCUV (no chromophores). I don't have a GC. And there aren't ionizable forms (grrrrr). So, ESI doesn't work and I've tried APCI source with no luck. I'm trying to learn about forming adducts, but I have no idea how to go about this. Can anyone shed some light?

Thanks so much in advance!

~B

Click to expand...

Like Gracchus said: Build a GC,

A GC is not that hard to locate. I can get access to a few right-a-way (not mine). What I mean is: why don't you go to someplace where a GC is available? May be it is the easiest way.

Or, apply some stimulus fund from Obama to buy one.

I'm sure some dept. has a GC. Although, I've kind of given up looking for help outside my lab. People are so busy and I feel like I'm bothering them.

Any way, I realized today that when I tried using the Ammonium phase that I forgot to add the Mass. der. Also, these two compounds are steroids. There are a couple of -OH groups on them so I'm going to test a range of Masses. I didn't have time today, unfortunately. I'll update tomorrow in case anyone is interested.

Braunwyn said:

Time is the problem. To start, I wouldn't be able to fit this type of project into my schedule unless I spoke with my boss and made into an official project in my objectives. And maybe I should do that. It's always good to have other methods. My problem now is that I started my experiment on thurs and it called for a 24 hour incubation. This is 100% my fault. I knew these compounds were problematic, thought I found an easy fix with APCI at the advice of a MS expert, and now I've put myself in a pickle. My head cold has held common sense hostage.

Any way, I've always wanted to learn more about GC.


They are small molecules. Two have MW in the 400's. The third was around 1300 but I ran out of material. I'm trying to measure concentration.



ELSD? Light scattering is an idea I haven't considered. I don't have anything like that in my lab but one of my colleagues is doing some work using light scattering. I don't know how I would hook that up to HPLC but may he's know. Thanks!

I wish I could post the structures here but I can't. I'll see if I can find something similar. But, yea, in MS almost anything could be ionized with an APCI source, right? Maybe I set it up wrong. It's on our tripple core and I just learned how to use that software so maybe I did something wrong.

Thanks for responding. I'm so appreciative. If anything else comes to mind please let me know. In the mean time, I'll try to find some structures on the net that may help. Off to work!

Click to expand...

From my point of view those are big molecules. How polar are they? For example what solvents do they dissolve in?

the best way I found of posting pics was to copy and paste a chem draw image onto paint and then post that.

I've spoken to a coworker who works with molecules very close to steroids and he freqently uses MALDI in his mass spec but he hasnt really had any problems with other techniques though.

One thing I was thinking about regarding detection using LC is maybe you could stick on a chromophore like a benzyl group on to your OH.

Braunwyn said:

Time is the problem. To start, I wouldn't be able to fit this type of project into my schedule unless I spoke with my boss and made into an official project in my objectives. And maybe I should do that. It's always good to have other methods. My problem now is that I started my experiment on thurs and it called for a 24 hour incubation. This is 100% my fault. I knew these compounds were problematic, thought I found an easy fix with APCI at the advice of a MS expert, and now I've put myself in a pickle. My head cold has held common sense hostage.

Any way, I've always wanted to learn more about GC.


They are small molecules. Two have MW in the 400's. The third was around 1300 but I ran out of material. I'm trying to measure concentration.

Click to expand...

Is concentration all you are after? Do you have access to a GPC (aka Size Exclusion Chrom.)? A low-Mw range GPC column (200-20,000 Mw) might work... Odds are, it wouldn't fully resolve your two 400's if they are within ~25 amus of each other, but it'll give you a concentration on the two 400's vs. the 1300 for sure. Most research GPCs have multi-detectors installed by default (UV, LALS, SLS, viscosity, yadda yadda); they're mostly for polymers, and polyolefins don't typically show up on UV detectors, either.

TemperateSeaIsland said:

From my point of view those are big molecules. How polar are they? For example what solvents do they dissolve in?

Click to expand...

There are a few hydroxy groups that I hoped would fragment. I have them in DMSO and dilute with 50:50 ACN/H20. I'll post a cholesterol pic that I'm sure you're all familiar with. Maybe that will spark some ideas.

the best way I found of posting pics was to copy and paste a chem draw image onto paint and then post that.

Click to expand...

It's not that I don't know how to post the pic, I'm just not allowed to. These are new chemical entities under patent. I still haven't done a search for similiar looking compounds. It's a been a busy week!

TemperateSeaIsland said:

I've spoken to a coworker who works with molecules very close to steroids and he freqently uses MALDI in his mass spec but he hasnt really had any problems with other techniques though.

Click to expand...

I'll have to look into that. Perhaps one of the MS's in our lab uses MALDI.

One thing I was thinking about regarding detection using LC is maybe you could stick on a chromophore like a benzyl group on to your OH.

Click to expand...

That's a good idea. Maybe I'll give that a go, though I'm not sure what I should use.

atomweaver said:

Is concentration all you are after? Do you have access to a GPC (aka Size Exclusion Chrom.)? A low-Mw range GPC column (200-20,000 Mw) might work... Odds are, it wouldn't fully resolve your two 400's if they are within ~25 amus of each other, but it'll give you a concentration on the two 400's vs. the 1300 for sure. Most research GPCs have multi-detectors installed by default (UV, LALS, SLS, viscosity, yadda yadda); they're mostly for polymers, and polyolefins don't typically show up on UV detectors, either.

Click to expand...

I'm testing these compounds seperately. The larger one is out.


I tried the APCI source again on the tripple core. I set it to neg. polarization and the detection was low. I've played around on my single core (ESI source) this week. It's just easier to deal with software wise. As per suggestion of a colleague, I made up a new batch of mobile phase -10mM Ammonium formate and adjusted the pH with ammonium hydroxide to pH 9. The other phase is ACN with 0.1% formic acid. Again, I was hoping to be left with charge but I didn't come up with much, as best as I understood. I got a lot of junk. I probably should use something acidic. Of course, I have no idea if any of this will degrade the compound.

Using my normal two phases (water/formic and ACN/formic) with neg. pol. I detected the Mass but cannot quantitate. So, I'm thinking my method is off. This weekend I'm going to find a method for steroids/cholesterol and give that a go.

Any way, thanks for the continued input!