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1,4-Dichlorobenzene-d4 retention time?

Discussions about GC and other "gas phase" separation techniques.

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I am using a Markes TD system attached to a Shimadzu GCMS to analyze air for VOCs on SS adsorbent tubes. I am working on building a calibration curve using a BTEX mix at varying known concentrations from 25ppb to 10ppm, and an internal standard of 1,4-dichlorobenzene-d4 at 10ppm in all the tubes.

I can “see” the BTEX on the chromatograms, but not the 1,4-DCB-d4. I think I selected an IS that is way outside of my BTEX mix range in terms of RT. Do you think that’s the case? I triple checked my concentration.

Benzene RT is about 2.25 minutes followed by TEX, ending with O-Xylene around 5 minutes. My entire run is about 12 minutes.

I can get details of the column specifics and GC method parameters (temps and He flow) when I get back to the lab.

(I am a retiree from 35 years in the environmental industry now pursing my PhD, have only a few months of hands-on GCMS experience, and our lab manager who I would ask is on vacation for the next week…)
You can try to check the database at restek.com.

Go to the resources hub and click on "chromatograms". You can type your analytes in and the database will be searched for chromatograms containing them. Find your column (or something close to it) and you can sort out where you might expect your IS to elute.
I think I selected an IS that is way outside of my BTEX mix range in terms of RT. Do you think that’s the case?

Possibly - bp of xylenes is 137-144 C; bp of 1,4-dichlorobenzene is 174 C.
On FID
Injector @ 260ºC
Split 25:1
HP-5 (30m x 0.320mm x 0.25um)
Average Velocity 35.743 cm/sec
Program
#1 Rate 2.5 °C/min
#1 Value 125 °C
#1 Hold Time 0 min
#2 Rate 20 °C/min
#2 Value 310 °C
#2 Hold Time 5 min

1,4-DCB elutes @ 14-15 minutes
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