If that is your dominant carbon source you could use the TOC or CSB (Chemical oxigen demand). but of course if you want to go into the details HPLC and HPLC-MS/MS would be ultimative methods.

In Sweden photometric determination in UV using the quotient 260/280 nm was used. That may allow some differentiation between lignin substances and humic substances, which neither TOC or COD does. This worked for the sulphite process, but could possibly work for the sulphate process as well. Try out with water upstream and outlet.

Good luck

Look at St. Methods, the test for tannins ( also read lignins).