Chromatography Forum

Hello, I am interested in performing PCB Aroclor analysis using SPE. I've done a few tests with it and so far have not gotten great recovery. I've followed the SPE source method and used a C18 disk and rinsed it with 20mL DCM followed by 20 mL of MeOH as the condition solvent. Finally, I used 5 mL of acetone and bottle rinsed with DCM. I was doing some research and found that some labs acidify the water prior to extraction and I was wondering if this makes a big difference. My percent recoveries are in the neighborhood of 50% for both Aroclor 1016/1260 and the surrogate (DCBP). I would like to see them much higher and was hoping people could provide some insight. Thanks in advance!

acidify to approx pH 2 with 1:1 HCL, rinse C18 with 10mLs of Et Acetate:Methylene Chloride, then 10 mLs methanol - leave the disk wet at this point! Don't filter all of the methanol through the disk......Add 5 mLs methanol to sample, mix and filter, approx 5-10 minutes to filter 1 Liter of sample. dry the disk for approx 5 minutes, then elute with 10 mLs ethyl acetate:methylene chloride, 5 mLs Methylene Chloride, then 5 mLs ethyl acetate. dry with sodium sulfate and blow down with nitrogen as usual...

I would skip the acetone rinse in the beginning. let us know how it works...

Thanks for the reply, I'll give it a try and let you know my results!

We don't acidify, agree the disk needs to stay wet after activation. We generally get 70-80% recovery, DCB sometimes is as low as 20% in blank DI water. Recovery seems to increase in actual samples, I suspect a salting out effect, but haven't proven.

Acidifying is absolutely essential for high recoveries. Don't be shy with the acid, it won't hurt anything. I have used 1 ml of conc sulfuric in the sample for over a decade with great success. Shake the sample. Make sure the pH is less than 2.

Don