I have read that PFOA can be detected at 220nm using UV Spectrophotometry. I am trying to test the effectiveness of a photocatalyst at reducing PFOA in pure water using our in-house UV Spectrophotometer and once I see the absorbance reduces reliable after a number of replicate tests, I plan to then send the samples to a lab for validation. The problem is lab testing for PFOA (and all the short chains down to F) is very expensive and in fact prohibitive. The results testing absorbance at 220nm so far have shown reduction from 0.140 to 0.091 within 1 hour. What is difficult to understand though, is when I test the pure water without PFOA, the absorbance is 0.111.

When I add 1mg/L of PFOA to the water, it raises to 0.140, then when I irradiate the photocatalyst for 1 hour, it drops to between 0.091 and 0.1 reliably. I have done this test several times with the same results. Additionally, I added 20mg/L PFOA to a clean sample and the absorbance was 0.334. This indicates to me that at 220nm I am detecting PFOA.

My specific questions then are:

Does this seem reliable enough to go to the next steps of getting lab validation?

Is there any way I can test for short chain PFAS with the spectrophotometer?

Thank you.