[Ifeffit] Peak locations for Phosphorus in Carbon K-edge

Dear All, I have analysed some phosphoric acid activated carbons via NEXAFS and was wondering if anyone had come across any references or knew where the transition/peak for the C-O-P or C-P-O bonding arrangement occurs in the carbon K-edge region. The samples I am examining are a series at different heat treatment steps and lose a lot of oxygen functionality, so finding where C-O-P or C-P-O transitions occur would be very useful in understanding the chemical transitions that are occurring. Regards, Ken