ONLINE SIMULTANEOUS MONITORING OF AMMONIA AND GLUTAMINE IN A HOLLOW-FIBER REACTOR USING FLOW-INJECTION ANALYSIS

A FIA method has been developed and fully characterized for the simult aneous detection of ammonia and glutamine in culture media. Ammonia de tection is based upon a chemical method and does not require an electr ode. This species diffuses across a hydrophobic porous membrane into a n indicator solution, the absorbance of which is continuously monitore d using a LED and a phototransistor. Glutamine was determined by a dif ference method in which ammonia was measured before and after passage through a module containing immobilized glutaminase. Very good lineari ty was observed in the range 0-4 mM for both species, Total analysis t ime was 22 min. This FIA method was used to accurately monitor ammonia and glutamine on line for over 600 h for a hybridoma culture performe d in a hollow-fiber reactor. FIA measurements were in good agreement w ith off-line measurements. No instrument failures occurred, thanks to systematic cleaning and maintenance procedures. This FIA method is a v ery attractive tool for the monitoring, and possibly control, of conti nuous cultures over extended periods.