Extractable from rubber stopper

[Mattias]

Hi,

I struggling to identify an extractable from a rubber stopper by LC/MS (ESI, QTOF, positive mode, with lockspray)

The unknown has mass of 269.104 [M+H] and fragments into 135.06, 107.06, 92.05 and 80.04.
It has UVmax at 228 and 277 nm (aromatic)

Has anyone seen this one before?

[JMB]

Mattias,

What is the accurate mass of m/z 269, and from that the possible elemental compositions ?

Possibly m/z 135 is [CH3OC6H4C=O]+
and m/z 107 [CH3OC6H4]+

JMB

[dhdh]

This probably isn't it, but I notice there are some masses in common (or off by 1) with the the rubber additive benzothiazole. Prominent molecular ion 135 on GC-EI-MS, and fragments 108, 91, 82 and 69.

Hi,

I struggling to identify an extractable from a rubber stopper by LC/MS (ESI, QTOF, positive mode, with lockspray)

The unknown has mass of 269.104 [M+H] and fragments into 135.06, 107.06, 92.05 and 80.04.
It has UVmax at 228 and 277 nm (aromatic)

Has anyone seen this one before?

[JMB]

This raises the issue of whether m/z 269 is indeed [M+H]+ or is [2M+H]+ ?????

JMB

[JMB]

Also, 2-mercaptobenzothiazole is used as a vulcanization agent for rubber (Wikipedia).

Can you detect presence of S in m/z 269 ion, i.e. enhanced signal intensity at m/z 271 ??

JMB

[Mattias]

This raises the issue of whether m/z 269 is indeed [M+H]+ or is [2M+H]+ ?????

JMB

That is a good question! Even without MS/MS the 135.05 peak is much larger than the 269.10 peak. I also see some 291.1 peak which then would be [2M+Na].

But [M+H] of benzothiazole should weigh 136.0 and [2M+H] should weigh 271? Could it be possible to knock of an electron from the aromatic ring and get the [M+] ion instead?

[Mattias]

Also, when I perform fragementation on m/z 269, I do not see any fragments between 269 and 135.

So my molecular ion is most probably 135 (and not 269).

[Mattias]

The closest hit on 135.0552 (determined with accurate mass) is

C7H7N2O (protonated), calculated mass 135.0558.

Google on C7H6N2O + rubber chemical = 2-hydroxybenzoimidazole. I cannot find any ms/ms data on this one, but I have just ordered it

[JMB]

Mattias,

2-OH-benzimidazole is a good possible, although I cannot get m/z 80 from it.

Do you have these two sources; Massbank is very nice.

http://www.massbank.jp/index.html

http://www.lc-ms.nl/contaminants.htm

Regards,

JMB

[Mattias]

http://www.massbank.jp/jsp/Dispatcher.j ... 116&site=0

This is the fragmentation of 2-amino benzimidazole. It weighs one mass unit too little, but it fragments into 65, 80, 92 and 107. Exactly the fragments that I observe.

Will be very exciting when I get the reference substance

[Mattias]

http://rd.springer.com/article/10.1007% ... 11-1104-0#

In the bottom of page 305 the fragmentation of 2-OH-benzimidazole in ESI-MS is described. It fits perfectly to my observations.

But I assume that the fragmentation of small molecules can be quite similar, final confirmation will have to be done with retention time, UV-spectrum and MSMS fragmentation.

It is fun to work

[JMB]

I retired a couple of years ago, but still try to keep my brain ticking over by looking at these MS problems.
So much for..............
"Possibly m/z 135 is [CH3OC6H4C=O]+
and m/z 107 [CH3OC6H4]+"

Enjoy your work !!

JMB

[Mattias]

I have now confirmed that the peak is 2-hydroxybenzimidazole

It was a great help that you (JMB) made me aware that the 269.1 peak was not the molecular ion! Otherwise I would probably be still stuck in this problem.

[JMB]

Mattias,

Excellent, that was your starter question for 10 points..............

Regards,

JMB