title: Simultaneous determination of ammonia nitrogen and L-glutamine in bioreactor media using flow injection.
abstract: A novel split stream flow injection (FI) system suitable for the simultaneous determination of L-glutamine and ammonia nitrogen (ammonia-N) in cell culture media is described. Potentiometric detection of ammonia-N in one portion of the manifold is achieved using a commercial ammonia gas-sensing electrode fitted with a wall-jet cap. L-Glutamine is quantified in the other part of the split sample by potentiometric detection of ammonium ions (by an ammonium-selective polymer membrane electrode), liberated from the hydrolysis of glutamine after the sample flows through a glass bead reactor containing immobilized glutaminase. Endogenous ammonia-N and potassium ions that would normally interfere with the glutamine measurement are removed upstream using a unique tubular cation-exchange unit. Using 50 microliters sample volumes and mixed solutions of ammonium chloride and L-glutamine in Iscove's Modified Dulbecco's Medium to calibrate the FI measuring system, values for ammonia-N and L-glutamine determined for 22 media samples obtained from a bioreactor growing retroviral producer cells correlate well with those measured with commercial, manual enzymic-spectrophotometric assay kits.
authors.affiliation: Department of Chemical Engineering, University of Michigan, Ann Arbor 48109-040.
authors.forename: B O
authors.initials: BO
authors.lastname: Palsson
authors.forename: B Q
authors.initials: BQ
authors.lastname: Shen
authors.forename: M E
authors.initials: ME
authors.lastname: Meyerhoff
authors.forename: M
authors.initials: M
authors.lastname: Trojanowicz
mesh_terms: D000641:Ammonia / Q000032:analysis*; D015374:Biosensing Techniques; D003470:Culture Media; D004566:Electrodes; D017022:Flow Injection Analysis / Q000379:methods*; D005973:Glutamine / Q000032:analysis*; D009584:Nitrogen / Q000032:analysis*; D011199:Potentiometry
chemical_list: D003470:Culture Media; D005973:Glutamine; D000641:Ammonia; D009584:Nitrogen