[Homer Jay]

Hello,

is it possible to quantify substances by MS/MS analysis or is chromatography required?

- homer

[chiralic]

Hello Homer Jay:

On this link you can find information about your question :

http://stinet.dtic.mil/cgi-bin/GetTRDoc?AD=ADA460865&Location=U2&doc=GetTRDoc.pdf
(start read on page 2)

Regards,

Chiralic

[Homer Jay]

Hello Chiralic,

thank you for your quick reply!

The paper was a quite funny example, although I didn't get why it's important to determine viagra in airplane crash victims.

To get back to MS-MS: one possibility is the use of deuterated standards (as mentioned in the paper) another appears to be a callibration with an external standard. Are the signals relative to the base peak of two measurmenets comparable among each other or how is external calibration possible? 


- homer

[enahs]

Yes, it is quite easy actually. I do it all the time. With our MSMS we get down to 1 part per trillion all the time and a 5 micro-liter injection without any column (no chromatography).

The key is an internal standard, not external. And doing a standard curve.

[Homer Jay]

Thank you enahs. What about an external standard (just out of curiosity). Is this possible?

If you've mass-spectra of the external standard and a spectrum of the analysis:  can they be compared quantitatively?

[JGK]

Thank you enahs. What about an external standard (just out of curiosity). Is this possible?

If you've mass-spectra of the external standard and a spectrum of the analysis:  can they be compared quantitatively?

The MS/MS response is quite variable adding a fixed amount of internal STD to both STDs and samples and plotting anlyte/IS ratio vs [analyte] will give a calibration which is much less affected by instrument variation. (the IS peak area should be affected similarly to the analyte and the ratio will be unchanged)

Using analyte peaks alone will produce a calibration heavily affected by instrument variation

[Homer Jay]

Looking good. Thank you.