Measurement of nano molar ammonium with a cyclic olefin copolymer microchip and low-power LED

Abi Kaed Bey, Samer K.; Mowlem, Matthew C.. 2023 Measurement of nano molar ammonium with a cyclic olefin copolymer microchip and low-power LED. Sensing and Bio-Sensing Research, 43, 100611.

Full text not available from this repository.


In oligotrophic regions, ammonium (NH4+) concentrations can be below 50 nM, however, few existing instruments can measure below this level with high confidence. This work, based on the o-pthaldialdehyde (OPA) fluorescence assay, is applied to measure nanomolar NH4+ in a novel optofluidic Cyclic Olefin Copolymer (COC) microchip using a low-power (20 mW) Light Emitting Diode (LED) as the excitation source. The optical arrangement was first modeled using ray tracing software to determine the initial detection volume size. Ammonium standards made with artificial seawater of 5 nM to 1000 nM, were run in triplicates. The limit of detection (LOD) obtained was 1.5 nM (3 x σ of the blank) or a LOD of 15 nM when the y-intercept and the vertical variation of each measured concentration on the calibration curve were taken into consideration (y-intercept +3. S y/x). Precision at 5 nM and 1000 nM was 3.3% and 0.5% respectively. The optofluidic system was also compared to an off-the-shelf fluorometer (Jasco FP2020) and an existing high-resolution shipboard analyser using five different standard concentrations. The LOD and the ammonium concentrations uncertainty for the Jasco FP2020, shipboard analyser, and current microsystem were 217 nM, 39 nM, and 15 nM and ± 232 nM, ± 48 nM, and ± 16 nM respectively. The optical setup was also validated using real samples from the Atlantic. This optical design, without optical fibres, makes the system simple and suitable for use with other fluorescent assays when compact, rugged, low-cost, and low-power consumption instrumentation is required.

Item Type: Publication - Article
Digital Object Identifier (DOI):
ISSN: 22141804
Additional Keywords: Marine, Ocean, Biogeochemical cycle, Ammonium, Chemical analysers, Seawater
Date made live: 24 Apr 2024 11:38 +0 (UTC)

Actions (login required)

View Item View Item

Document Downloads

Downloads for past 30 days

Downloads per month over past year

More statistics for this item...