Ecd linearity for pesticides and pcbs

[sw340496]

Hi,
I'm running a 5890 with hydrogen carrier and nitrogen makeup for EPA 608/8081/8082. I'm having a linearity problem. It seems that I'm losing response in my high standards. I understand that ECD's have a limited linear range but it seems that that I should be able to go from 0.02ppm to 1ppm observed for the pesticides and 0.5 to 10ppm for the PCB's without the top end of the curve "bending". I've run in both split and splitless mode with split being slightly better at a 50:1 split ratio. Right now I'm running the makeup at approx 60ml/min withe the carrier flow at 2ml/min. The detector is a dual column setup with one detector being an old regular style ECD and the other an anode purge ECD with a rtx- cl pesticides clp2 column pair installed. Anyone have any thoughts?

Steve

[jss37992]

It looks to me like your are definitely overloading the detector. I run many Pesticides and PCB's daily and I do not calibrate that high. For pesticides I calibrate from 0.02-0.60ppm without any problems. I calibrate PCB's from 0.10-1.0ppm. Hope this helps.

[Bigbear]

We run our Agilent ECD's with 30 cc/min make up.