Matrix Effect Assessment of an Ion Chromatographic Method to Determine Inorganic Anions in Wastewater

Inorganic anion monitoring is essential for bioreactor operation and is related for pollution control or energy and products recovery. However, there is a lack of studies validating methods for inorganic anions analyses in conditions compatible to those in bioreactor operations treating different types of wastewater. This paper provides a systematic statistical study and matrix-effect assessment for sugarcane vinasse, leachate, sewage and synthetic sewage. Sample preparation consisted of only a filtration and sample dilution. Cl−, NO2 −, NO3 −, PO4 3− and SO4 2− were determined in a Dionex ICS 5000® equipped with a chemical conductivity suppressor. Calibration curves were linear and well-adjusted between 2.5 and 50 mg L−1 for all the anions in all the tested matrices, except PO4 3− and SO4 2− in vinasse. A calibration range for PO4 3− in all tested matrices was 5.0 to 100 mg L−1, whereas a range from 5.0 mg L−1 to 50 mg L−1 was obtained for SO4 2− in vinasse. All the anions yielded recoveries in the range of 85–115% for all the tested matrices. Relative standard deviations lower than 10 and 2% were achieved for peak areas and retention times, respectively. A signal enhancement was observed for all the tested matrices and all the anions. The matrix effect level varied from −1.7 (NO2 − in vinasse) to −33.9% (Cl− in leachate). Sewage was the less affected matrix, while leachate gave higher matrix effects. Validation results and the matrix effect assessment showed that a simple sample preparation is suitable for multi-elemental analyses of inorganic anions for complex environmental samples.