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Low cost 235 nm ultra-violet light-emitting diode-based absorbance detector for application in a portable ion chromatography system for nitrite and nitrate monitoring

Citation

Murray, E and Roche, P and Harrington, K and McCaul, M and Moore, B and Morrin, A and Diamond, D and Paull, B, Low cost 235 nm ultra-violet light-emitting diode-based absorbance detector for application in a portable ion chromatography system for nitrite and nitrate monitoring, The Journal of Chromatography A, 1603 pp. 8-14. ISSN 0021-9673 (2019) [Refereed Article]

Copyright Statement

Copyright 2019 Elsevier B.V.

DOI: doi:10.1016/j.chroma.2019.05.036

Abstract

A low cost, UV absorbance detector incorporating a 235 nm light emitting diode (LED) for portable ion chromatography has been designed and fabricated to achieve rapid, selective detection of nitrite and nitrate in natural waters. The optical cell was fabricated through micromilling and solvent vapour bonding of two layers of poly (methyl methacrylate) (PMMA). The cell was fitted within a 3D printed housing and the LED and photodiode were aligned using 3D printed holders. Isocratic separation and selective detection of nitrite and nitrate was achieved in under 2.5 min using the 235 nm LED based detector and custom electronics. The design of the new detector assembly allowed for effective and sustained operation of the deep UV LED source at a low current (<10 mA), maintaining consistent and low LED temperatures during operation, eliminating the need for a heat sink. The detector cell was produced at a fraction of the cost of commercial optical cells and demonstrated very low stray light (0.01%). For retention time and peak area repeatability, RSD values ranged from 0.75 to 1.10 % and 3.064.19 %, respectively. Broad dynamic linear ranges were obtained for nitrite and nitrate, with limits of detection at ppb levels. The analytical performance of the IC set up with optical cell was compared to that of an ISO-accredited IC through the analysis of five various water samples. Relative errors not exceeding 6.86% were obtained for all samples. The detector was also coupled to a low pressure, low cost syringe pump to assess the potential for use within a portable analytical system. RSD values for retention time and peak area using this simple configuration were <1.15% and <3.57% respectively, highlighting repeatability values comparable to those in which a commercial HPLC pump was used.

Item Details

Item Type:Refereed Article
Keywords:low UV LED, analytical detection, ion chromatography
Research Division:Chemical Sciences
Research Group:Analytical Chemistry
Research Field:Separation Science
Objective Division:Manufacturing
Objective Group:Instrumentation
Objective Field:Scientific Instruments
UTAS Author:Paull, B (Professor Brett Paull)
ID Code:134568
Year Published:2019
Deposited By:Austn Centre for Research in Separation Science
Deposited On:2019-08-20
Last Modified:2019-12-05
Downloads:0

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