Herbicide Surrogate

[Bigbear]

I wonder if anyone is using an alternate surrogate for EPA 515.4. I do not like using 2,4-dichlorophenylacetic acid as it is not a useful marker for the other herbicides in my mix.
As an example of what I see, I ran one sample this week in duplicate and spiked it as well. The surrogate recoveries for the sample and dupe were both out ( 60% recovery) while the surrogate in the spike was 84%. The herbicide recoveries in the spike ranged from 95-105%.
Having a hard time understanding what is going on in the extracts. I have tried increasing the amount of diazomethane solution added with little or no effect.
I think the next thing I'll try is using an IPA/dry ice bath while collecting my diazomethane.

[Bigbear]

Follow up question. Anyone know what surrogate is used in ASTM D 5317.

[koba]

We had similar problem about six month ago and found out it was the amount of Add sodium sulfite crystals added to eliminates residual chlorine in the sample. I can't say for sure whether it would be the same for your lab nor explain why but I think it's worthwhile to try.

[Bigbear]

Thanks, worth a shot. We use 6 mg/ 60 ml now which is 2X what the method requires.

[NemosBucs]

Does anybody have a suggestion for an alternate surrogate as originally asked? My chemist is having the same issues with 2,4-DCAA as the surrogate also, erratic responses. I know of a lab that switched to 2,4,5-T, but that is a method analyte for us. Any other suggestions would be appreciated. Thanks.

[Bigbear]

Have your chemist try adding sodium sulfite to the blank water used to prepare calibration standards. This cured my problem. Still using 2,4-DCAA.

[twranger]

I have tried aciflurfen (late elution) and 2,4,6-trichlorophenol- they mimicked the DCAA recovery, so wasn't much help.
ASTM uses DCAA as well.