Contrasting Methods for the Measurement of Dissolved Oxygen: A Case for Luminescent Dissolved Oxygen Sensors

Attempts to measure dissolved oxygen (DO) in water and wastewater are hampered by a lack of robust analytical techniques that are accurate, precise, easy to use, and resistant to matrix interferences. The two EPA methods currently approved to measure DO (Winkler titration and membrane electrode) often fail in delivering interference free readings that are accurate and precise across the BOD range of 1.0 to 20 mg/L, DO.As a counter measure to these deficiencies, Hach Company has developed a luminescence dissolved oxygen (LDO®) sensor to be used in water and wastewater for regulatory compliance and process control. As a result, an in-house LDO validation study was performed to evaluate and establish precision and accuracy from reference water and wastewater.This manuscript contrasts the theory and performance of DO measurement from Winkler titration and membrane electrodes with that LDO method. The underlying technology for each method is discussed along with determinant performance and interference pitfalls. Data is presented that demonstrates the superiority of LDO over the currently approved EPA methods.