Simultaneous monitoring of glucose, lactic acid and penicillin by sequential injection analysis

A sequential injection analysis (SIA) system for measurement of glucose, lactic acid and penicillin has been developed. The system is built around a 10 port multiposition valve, a piston pump, and a chemiluminescence detector. The SIA-system may measure all three components using the same hardware, and it is therefore well suited for monitoring of penicillin cultivations, where glucose and lactic acid are typical substrates and penicillin is the major product. The analysis of glucose is based on an enzymatic conversion - using glucose oxidase - to glucono-δ-lactone with parallel formation of hydrogen peroxide. The formed hydrogen peroxide is detected by a chemiluminescence reaction involving luminol. The analysis of lactic acid using lactate oxidase is similar to that of glucose. The analysis of penicillin is based on formation of penicilloic acid by pumping the sample through a column of immobilized penicillinase upstream of the multiposition valve. When thereafter penicilloic acid reacts with iodine it prevents a simultaneous chemiluminescence generating reaction between iodine and luminol.