Chromatography Forum

The question is this is 1,2-EDB by 8260 SIM equivalent or better than doing it by EPA 8011 (GC-ECD)? I've developed a SIM method that fits from 5000 to 10 ppt with an RSD of 9.1%.
Cal levels 5K, 4K, 2K, 1K 800, 400, 200, 120, 80, 50, 40, 20, 10 ppt

Response 136768 for 5000 ppt
Response 24320 for 1000 ppt
Response 8969 for 400 ppt
Response 1152 for 50 ppt
Response 487 for 20 ppt
Response 181 for 10 ppt

I am using 400 ppt as my CCV. Fluorobenzene and Chlorobenzene-d5 at 5 ppm as my internal standards. I tried 1 ppm but could not get consistent passing of BFB tune. 5 ppm passes without a problem. Fluorobenzene response is 650,000 and Chlorobenzene-d5 response 2,000,000 and 4-BFB response is 200,000.

I figure with my 5mL sample and a 40:1 split inlet that purge and trap puts ~5 times less 1,2-EDB on the detector than method 8011. But then ECD may also be much more senstive than an MSD.
Any comparisons would be welcome.

Can you share your method for the curious?

How do the peaks look at the low end?

We can achieve 25x lower detection limits by using ECD than by using 8260.

For BFB, ensure you're getting enough mass to the detector. I came across an 8260 instrument that was struggling to pass BFB routinely. Turns out due to the high 50x split ratio the detector was only receiving about 1.0 ng BFB. We increased the concentration of the solution by 10-20x and BFB started passing every time.

We can achieve 25x lower detection limits by using ECD than by using 8260.

For BFB, ensure you're getting enough mass to the detector. I came across an 8260 instrument that was struggling to pass BFB routinely. Turns out due to the high 50x split ratio the detector was only receiving about 1.0 ng BFB. We increased the concentration of the solution by 10-20x and BFB started passing every time.

Wow, that is really impressive. I had figured a factor of 5 more ng delivered to the ECD system but had no idea how sensitivity the ECD would add to that factor. For regular 8260 SIM/Scan I'm spiking 5uL of 70 ppm with a 40:1 split so I am getting 8.75 ng at the column. But for the straight SIM method I'm spiking 5uL of 5 ppm of ISS at the instrument with a 40:1 split which comes to 0.625 ng of 4-BFB at the column. But I am passing BFB with no issues with a 25ms integration on all the affected peaks.

Isn't 20 ppt drinking water trigger levels? Why are you trying to hit it with 8260? Are you shooting a second shot for EDB only or doing sim scan all in one go? we run 524 and roughly 10% of those are looking for low EDB levels and we use 504 for that. There is a prep but it's quick and the 524 data looks cleaner. Perk with 504 is ECD cals can last forever, mine has been in range since May 2022.

Isn't 20 ppt drinking water trigger levels? Why are you trying to hit it with 8260? Are you shooting a second shot for EDB only or doing sim scan all in one go? we run 524 and roughly 10% of those are looking for low EDB levels and we use 504 for that. There is a prep but it's quick and the 524 data looks cleaner. Perk with 504 is ECD cals can last forever, mine has been in range since May 2022.

Yeah its groundwater from Oil Petroleum Storage releases. So I run the regular 8260 SIM/SCAN (MDL's ~0.2 ppb) then run a second 8260 SIM-only method just to pick off 1,2-DCA and 1,2-EDB.

EDIT: It turns out the problem was activated carbon not an ozidizer)
A problem we have locally is that the state lead contractors have injected wells with a soluble oxidizer to try and destroy the petroleum contamination. This means that purging at temperatures higher than 40C result in the loss of the internal standards and surrogates. I have purged for years at 70C and get really great fits across the whole 8260 list but I might have to run the DCA/EDB analysis with a 40C P&T to try and avoid the oxidative degradation of the ISS.

"There is a prep but it's quick and the 524 data looks cleaner."
Are you suggesting that the 524 data is cleaner looking than the 504 data or is that a typo?
So you do not use 524 SIM to run EDB; just the 504 method? I know of at least one other commercial lab that is developing an 8260 SIM method because its getting hard to get ECD's for the older instruments.