Sequential injection analyzer for glycerol monitoring in yeast cultivation medium

A smart and versatile flow system for the at-line monitoring of glycerol based on sequential injection analysis is proposed. Formaldehyde, generated by oxidation of glycerol with sodium periodate, is transformed into 2,4-diacetyl-1,4-dihydrolutidine applying the Hantzsch condensation reaction with acetylacetone and ammonium. Dual-wavelength detection was carried out to minimize the contribution of the schlieren effect using a single blue LED. In-line sample dilution is accomplished applying the concept of zone-penetration and a new concept of sample splitting. Under optimized physical and chemical variables, regression curves over two dynamic working ranges of 0.1–4 and 1–40 g l−1 were attained. The injection throughputs were 14 and 12 h−1, respectively. Applying on-line data evaluation and conditional inquiries, the smart and independent selection of the adequate analytical procedure for the required working range was accomplished. The system was successfully applied to the at-line monitoring of glycerol in a continuous, cell-free medium flow from a yeast cultivation process during batch and fed-batch phase with glycerol as the only carbon source.