[missaturn]

im using GCMS chemical ionization mode for my compoud. how to confirm my compound if there is only one fragment ion in the standard? in the real sample, there might be other  compound with the same fragment. Thanks.

[Alpha-Omega]

I have no idea of what you are working with....What is the phase of your species, etc...

However, you could look into isotopic labeling with NMR (assuming your compound can be determined using NMR).

MS gives you the fragments...putting them together can require further confirmational analysis.

Structural determination may require several analyses used in tandem.  NMR, FTIR, UV/Vis, MS, etc...

Of course, I would always go with XRF and XRD whenever possible (faster and sample prep is simple).

[missaturn]

Thanks Alpha-Omega.

Im doing a nitrosoamines test in water. Unfortunately, I dont have instrument options of tandem MS etc. Another question is can we use the same surrogate standard for internal standard? I just affraid that after the extraction, the surrogate standard will become less.

[Alpha-Omega]

A surrogate is something you know is definitly NOT in your samples...if you use it in the standards....yes you can spike your samples....that is what it is for.....DCA is commonly used as a surrogate by EPA in IC.

Thes links will take you take to EPA documents redarding running samples-including spiking with a surrogate:
http://www.mass.gov/dep/cleanup/laws/d8paper.pdf
http://www.epa.gov/ttn/emc/promgate/m-321.pdf
http://www.epa.gov/nerlesd1/chemistry/vacuum/training/pdf/run_samples.pdf

Do you know your MDLs (minimum detection limits) and LODs (limits of detection)?  If you know those you know how much surrogate to use....even if you do not know your MDLS...the LODs for your method should be a good enough indicator...

If you had the option you could do GC/FTIR