Exploiting sequential injection analysis with lab-on-valve and miniaturized potentiometric detection: Epinephrine determination in pharmaceutical products

Miniaturized potentiometric units were constructed, evaluated and incorporated in a SIA-LOV manifold in order to the control of pharmaceutical analysis. The method validation was done with ephinefrine determinations in commercial pharmaceutical products. The optimization procedures were directed at potential versus epinephrine concentration. This approach was achieved by selecting 60 cm of reactor and a flow rate of 11 μL s⁻¹ and injecting 78 μL of epinephrine standard solutions in a 1.0 × 10⁻³ mol L⁻¹ IO₄⁻ solution. A linear range was found for epinephrine concentrations between 2.0 × 10⁻⁴ and 2.5 × 10⁻³ mol L^−l with a slope of 35528 mV L mol^−l and r² = 0.997. Under these conditions the analytical results for the commercial pharmaceutical formulations of 0.908 and 0.454 mg mL⁻¹, respectively, with a R.S.D. of 0.34 for both, was obtained. Through down scaling periodate-selective electrode it was possible to benefit from the recognized advantages of the lab-on-valve sequential-injection based systems, namely regarding equipment portability, reduced consumption of the sample and the reagents and the reduction of effluent waste. Furthermore, the new periodate electrode configuration is easy to achieve in common laboratories and enables the implementation of low volume detection cell where the electrical noise, that is frequently presented in potentiometric based procedures, is significantly reduced.