[lucy007]

hello, iv done a experiment for determining the concentrations in water of benzene, toluene, exlene and ethylbenzene
i need to know why u cant just inject the contaminated water in the GC-FID instead of going through the procedure of layers, removing . so n so , dont no anything bout this my thoughts were that if i was to do this to many things will get analysed and take far to long, im sure thers suttin more scientific to it thn this lol, regards

[Alpha-Omega]

If I understand your question correctly, you are asking why pretreatment of the samples you do is necessary..  Do I have that right...Without knowing exactly what the matrix is...where your water samples originate from....I am goiung to assume the matrix is complex.

In complex sample matrices, there are often too many overlapping compounds to allow resolution of the
compound(s) of interest, even with the highest resolution columns available.

You must use some approach which gives selectivity

Agilent offers a great FID system...might want to check it out...

It is a 2-D GC system:

Simplified 2-D GC can be used to accomplish the separation of specific analytes from very complex matrices where, on any single column, the analytes coelute with several other compounds, making their analysis difficult or impossible.