Short communication3D-printed and CNC milled flow-cells for chemiluminescence detection
Graphical abstract
Introduction
For chemiluminescence detection involving fast chemical reactions, the analyte and the reagent must be reproducibly and efficiently mixed shortly prior to entering (or even within) a detection zone that permits the transfer of emitted light to a photodetector [1], [2], [3], [4], [5]. The most commonly used chemiluminescence flow-cells designed for this purpose comprise a flat coil of glass or polymer tubing connected to a T or Y-piece at which the reactant solutions merge and enter the coil [1], [2], [3], [4], [5], [6], [7], [8]. However, the recent fabrication of chemiluminescence flow-cells by etching or milling channels into polymer materials [9], [10], [11], [12], [13], [14], [15], [16] have enabled more reproducible construction, the introduction of features such as reversing turns to enhance mixing efficiency, and the exploration of alternative configurations and materials, in efforts to transfer a greater proportion of the emitted light to the photodetector. In this paper, we exploit these recent advances in construction techniques to develop a polymer flow-cell that divides the analyte stream towards two separate zones for reaction with two different chemiluminescence reagents. We also examine, for the first time, the feasibility of creating chemiluminescence detection flow-cells using a simple 3D-printing technique. We evaluate these novel analytical devices in direct comparison with conventional approaches to flow-cell construction and flow-splitting using the fast chemiluminescence reactions of permanganate with various phenolic amines (morphine, octopamine, synephrine, tyramine, and hordenine), utilizing flow injection analysis (FIA) and high performance liquid chromatography (HPLC) methodology.
Section snippets
Flow injection analysis
The instrument manifold was constructed as previously described [13], comprising a Gilson Minipuls 3 peristaltic pump (John Morris Scientific, Balwyn, VIC, Australia) with bridged PVC pump tubing (1.02 mm i.d.; DKSH) and Valco six-port injection valve (SGE, Ringwood, VIC, Australia) with 70 μL injection loop. With each change of flow-cell, the housing was re-sealed and left for 40 min to avoid the temporary increase in baseline signal that was observed under the most sensitive settings. All tubing
Selection of chemiluminescence reactions
For the FIA comparisons of flow-cells, we selected the widely used permanganate and morphine in acidic solution as an example of the many fast chemiluminescence reactions between oxidizing agents and organic analytes [3], [20], [21], [22], [23]. The rate (and therefore the chemiluminescence intensity) of this reaction can be enhanced by a preliminary partial reduction of permanganate to create a stable, high concentration of Mn(III) in the reagent solution [19], [24]. The operation of the
Conclusions
These findings show that 3D-printing is a viable option for the fabrication of chemiluminescence detection flow-cells, which under some circumstances provided greater detection of the emitted light than the conventional coiled tubing approach. It is likely that the 3D-printing of flow-cells using white polymer materials would produce even better performance, comparable with the best flow-cells constructed by high precision milling. The new flow-cell holder significantly improved the transfer of
Acknowledgments
The authors thank Deakin University and the Australian Research Council (Future Fellowship FT100100646) for funding this research.
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