Determination of chemical oxygen demand employed manganese as an environmentally friendly oxidizing reagent by a flow injection method based on microwave digestion and speciation coupled to ICP-OES

► A novel method for COD determination in water samples is evaluated. ► Using KMnO4 instead of K2Cr2O7 is evaluated in a Flow Injection-COD determination. ► This method joints the SPE and MW features into a new automated COD method. ► This FI-SPE method enables de determination of samples with high Cl− concentration. ► A noticeably reduction in time and wastes of analysis are remarked.