Sequential injection lab-on-valve system for the determination of the activity of peroxidase in vegetables

Horseradish peroxidase (HRP) has been broadly used and investigated for many analytical purposes; it is an enzyme that catalyzes the reduction of hydrogen peroxide in the presence of a reducing compound. The objective of this work was to develop a methodology for the spectrophotometry determination of the activity of peroxidase in vegetable extracts using a flow method with a sequential injection lab-on-valve format. The developed system is based on the reaction between hydrogen peroxide (H₂O₂) and 2,2-azinobis(3-ethylbenzothiazoline-6)sulfonic acid (ABTS) catalyzed by the enzyme (HRP). The method presented a sample consumption of 15νL. per assay and a consumption of ABTS and H₂O₂ of 24 μg and 12 μg per assay, respectively. It was also possible to monitor online the thermal inactivation of peroxidase at different temperature ranges.