Without the O2 scavenger, the obtained charges are low and non-linear with respect to glucose concentration. In contrast, in the presence of the integrated O2-scavenger, the electrical charges are about 3 times higher and proportional to the glucose concentrations. This demonstrates that the O2 scavenger is effective for suppressing O2 interference even in complex sample matrices such as blood, qualifying it for point-of-care sensing applications. The value of the glucose concentration obtained from the analysis of the internal standard addition method is very low (0.187 mM), which is typical of blood samples upon storages since glucose is metabolized in whole blood over time . Figure . Blood samples analysis using internal standard addition method. Charge from the chronocoulometry of modified SPEs in ambient air with paraformaldehyde only (red dots) and with all components of the O2 scavenger (blue dots) Eapp = 0.6 V vs. pseudo RE for 10 minutes. Glucose (5, 7, and 10 mM) was added to the blood. The screen-printed electrodes were modified with Os-complex modified polymer (50 wt%), GOx (40 wt%), and PEGDGE (10 wt%) with total loading 200 μg cm -2 . The scavenger containing AOx (40 U mL -1 ), CAT (4000 U mL -1 ) and paraformaldehyde (saturating concentrations ~50 mg mL -1 ) is integrated within the capillary channel of the SPE. Data are the average of n = 3 repetitions and error bars show standard deviation.