drilling fluid

[pueblito]

Dear chromatographers.

This chromatogram corresponds to a drilling mud ( or drilling fluid) that we have extracted according to EPA 3540.
After exchange to hexane we tried to clean up the extract with silica gel column procedure: 1mL sample extract, 5g silica gel, first 20mL hexane and finally 20mL Hexane:dichloromethane 8:2, This procedure works well with other samples but not in this case because the peak pattern is the same and no petroleum distillate pattern is evident.

Does anyone know how to deal with this kind of samples?

many thanks.
http://es.tinypic.com/r/2it0uow/7

[JTM]

i'm assuming this is some sort of sim dist?

it looks like your ramp is too fast. and possibly your starting temp too low.

[pueblito]

Well, Actually It´s a Total Extractables Petroleum hidrocarbons method in environmental samples, the GC conditions are:

column: MXT-1; 15m; 0.53mm; 0.5um
Constant Flow: 8mL/min
splitless time: 0.75min
Detector FID at 350°C
Injector 290°C

Oven:
40° ---- 2 minutes
at 12°C/min to 325°C hold 5 minutes.

We run a #2 Diesel and Motor Oil standards and the chromatograms look as usual.

I guess that the problem is related to the clean up procedure and It is especially frequent in this kind of samples.

thank you.

[AICMM]

Pueblito,

This just one of the collected fractions? I suspect you will get a much different pattern from the raw extract, probably a lot like diesel fuel.

Best regards,

AICMM

[chromatographer]

If your diesel and motor oil standards look good then the chromatogram for the drilling fluid is probably correct. Frequently the base oil used for drilling fluid is composed primarily of isomers of a couple carbon numbers with the straight chain paraffins removed to give the oil a low pour point.

[pueblito]

Dear JTM, AICMM and Chromatographer.

Thanks for replying.

Well, this extract corresponds to the two fractions and the raw extract looks very similar to the "clean" one.

And based on your opinions I think I will try a different a approach:

Alumina/silica clean up procedure.
And I will run a full scan mass spectrum (but in a narrower column to get better resolution ) in order to get more information about the composition.

best regards.