Determination of β-alaninediacetic acid in waste waters and aquatic environment using GC-NPD

New chelating agents need to be applied to industrial purposes, because the conventional compounds, such as ethylenediaminetetraacetic acid (EDTA), have been demonstrated to cause adverse environmental effects. A promising compound in this respect is β-alaninediacetic acid (β-ADA). A reliable analytical procedure for the determination of β-ADA in waste waters and natural waters is presented in this study. The method is also applicable to sediments after extraction of β-ADA with phosphate. An aqueous sample was evaporated to dryness and treated with an esterification reagent containing ethanol, propanol or butanol. The resulting esters were determined by capillary gas chromatography using a nitrogen-phosphorus specific detector (GC-NPD). The best results were obtained by esterification with propanol at 86°C for 2 h. The response was linear up to 10 mg dm^-3. The limits of detection in distilled, waste, lake and sea waters were 2.0, 2.7, 2.5, 2.9 μg dm^-3, respectively, and 0.21 μg g^-1 in sediments. The relative standard deviation (RSD) values of retention times-did not exceed 0.46%. The run-to-run and day-to-day repeatabilities (calculated as RSD) in distilled water were below 7%, except near the limit of detection. In the natural waters studied the recoveries were 49-111%, in sediments only 19-21%. High concentrations (above 10 mg dm^-3) of Fe³⁺ interfere with the determination of β-ADA.