Towards chemiluminescence detection in micro-sequential injection lab-on-valve format: a proof of concept based on the reaction between Fe(II) and luminol in seawater

Hugo M Oliveira; Maxime M Grand; Jaromir Ruzicka; Christopher I Measures

doi:10.1016/j.talanta.2014.06.076

Towards chemiluminescence detection in micro-sequential injection lab-on-valve format: a proof of concept based on the reaction between Fe(II) and luminol in seawater

Talanta. 2015 Feb:133:107-11. doi: 10.1016/j.talanta.2014.06.076. Epub 2014 Jul 10.

Authors

Hugo M Oliveira¹, Maxime M Grand², Jaromir Ruzicka², Christopher I Measures²

Affiliations

¹ Department of Oceanography, University of Hawai'i at Manoa, 1000 Pope Road, Honolulu, HI 96822, USA. Electronic address: hmoliveira@icbas.up.pt.
² Department of Oceanography, University of Hawai'i at Manoa, 1000 Pope Road, Honolulu, HI 96822, USA.

PMID: 25435235
DOI: 10.1016/j.talanta.2014.06.076

Abstract

Micro-sequential injection lab-on-valve (µSI-LOV) is a well-established analytical platform for absorbance and fluorescence based assays but its applicability to chemiluminescence detection remains largely unexplored. In this work, we describe a novel fluidic protocol and two distinct strategies for photon collection that enable chemiluminescence detection using µSI-LOV for the first time. To illustrate this proof of concept, we selected the reaction between Fe(II) and luminol and developed a preliminary protocol for Fe(II) determinations in acidified seawater. The optimized fluidic strategy consists of holding 100 µL of the luminol reagent in a confined zone of the LOV and then displacing it with 50 µL of sample while monitoring the chemiluminescent product. Detection is achieved using two strategies: one based on a bifurcated optical fiber and the other based on a customized detection window created by mounting a photomultiplier tube atop of the LOV device. We show that detection is possible using both strategies but that the window strategy yields significantly enhanced sensitivity (355×) due to the larger detection area. In our final experimental conditions and using window detection, it was possible to achieve a limit of detection (LOD) of 1 nmol L(-1) and to quantify Fe(II) in acidified seawater samples up to 20.00 nmol L(-1) with high precision (RSD<6%). These analytical features combined with the long-term stability of luminol solution and the full automation and low reagent consumption make this approach a promising analytical tool for shipboard analysis of Fe(II). The intrinsic capacity of the LOV to operate at a low microliter level and to handle solid phases also opens up a new avenue for chemiluminescence applications. Moreover, this contribution shows that LOV can be a universal platform for optical detection, capable of absorbance, fluorescence and luminescence measurements in a single instrument setup.

Keywords: Chemiluminescence; Iron; Lab-on-valve; Luminol; Seawater.