Pleural fluid pH validation on Siemens RAPIDPoint 500

We are taking on oversight of our Respiratory Therapy blood gas testing and need to validate pleural fluid pH on their Siemens RAPIDPoint 500 analyzers.  We just found out that they never validated the test using pleural fluid specimens.  Our main laboratory does body fluid pH testing but not on pleural fluid.  We would greatly appreciate any insight on how others have accomplished such a validation.

Thanks,

Theresa and Sherri