Enhanced Environmental Hydroxylamine Detection: A Chromatographic Adaptation to the Indooxine Approach

High Resolution Image Download MS PowerPoint Slide Hydroxylamine (NH 2 OH) plays an important role as an intermediate species in many nitrogen transformation reactions. Since it readily reacts with O 2, NH 2 OH is often present in submicromolar concentrations in environmental systems. Existing NH 2 OH quantification protocols are limited by sensitivity, cost, or both; consequently, the extent and role of NH 2 OH in many biological and abiotic processes are poorly understood. In the work presented here, a colorimetric method is improved and adapted for use in high-performance liquid chromatography (HPLC). The method entails the reaction of NH 2 OH with a reagent, 8-hydroxyquinoline, to form a larger compound, indooxine, that absorbs strongly in the visible range at 705 nm and at 261 nm in the UV window. Using a HPLC-UV system detecting at the 261 nm peak provided a significantly enhanced NH 2 OH detection limit and improved measurement reliability. This chromatographic method was tested for sensitivity and performance in wastewater and river water matrices, in addition to pure water cases, achieving reliable results in each solution. The protocol achieved accurate measurements of NH 2 OH concentrations as low as 0.05 μM, vastly improving previous detection limits. Sampling procedures that ensure the preservation of NH 2 OH were also established; samples acidified below a pH of 2.0 remained stable under room temperature conditions for up to two months. Given that HPLC-UV systems are relatively common in environmental laboratories, the adapted method reported here is expected to significantly improve the accessibility of accurate, highly sensitive NH 2 OH detection.