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Determination of trace zinc in seawater by coupling solid phase extraction and fluorescence detection in the Lab-On-Valve format

Determination of trace zinc in seawater by coupling solid phase extraction and fluorescence detection in the Lab-On-Valve format
Determination of trace zinc in seawater by coupling solid phase extraction and fluorescence detection in the Lab-On-Valve format

By virtue of their compactness, long-term stability, minimal reagent consumption and robustness, miniaturized sequential injection instruments are well suited for automation of assays onboard research ships. However, in order to reach the sensitivity and limit of detection required for open-ocean determinations of trace elements, it is necessary to preconcentrate the analyte prior its derivatization and subsequent detection by fluorescence. In this work, a novel method for the determination of dissolved zinc (Zn) at subnanomolar levels in seawater is described. The proposed method combines, for the first time, automated matrix removal, extraction of the target element, and fluorescence detection within a miniaturized flow manifold, based on the Lab-On-Valve (LOV) concept. The key feature of the microfluidic manipulation of the sample is flow programming, designed to pass sample through a mini-column where the target analyte and other complexable cations are retained, while the seawater matrix is washed out. Next, zinc is eluted and merged with a Zn selective fluorescent probe (FluoZin-3) at the confluence point of the LOV central channel using two high-precision stepper motor driven pumps that are operated in concert. Finally, the thus formed Zn complex is transported to the LOV flow cell for selective fluorescence measurement. This work describes the characterization and optimization of the method including Solid Phase Extraction using the Toyopearl AF-Chelate-650M resin, and detailed assay protocol controlled by a commercially available software and instrument. The proposed method features a LOD of 0.02 nM, high precision (<3% at 0.1 and 2 nM Zn levels), an assay cycle of 13 min and a reagent consumption of 150 ?L FluoZin-3 per sample, which makes the method highly suitable for oceanographic shipboard analysis. The accuracy of the method has been validated through the analysis of seawater reference standards and comparison with ICP-MS determinations on seawater samples collected in the upper 1300 m of the subtropical south Indian Ocean. This work confirms that integration of sample pretreatment with optical detection in the LOV format offers a widely applicable approach to trace analysis of seawater.
GEOTRACES, Zn, Lab-On-Valve, FluoZin-3, Oceanography, Trace analysis
0003-2670
45-54
Grand, Maxime M.
659acbde-d639-42b7-9fab-52fa1b3655ff
Chocholouš, Petr
4ccbd9d7-034d-41ff-9cd6-245ec8d26473
Růžička, Jarda
3b4397fc-ca97-4eb2-8f99-96d65b19fba4
Solich, Petr
4a44b848-2455-4b83-bab9-b433e178f076
Measures, Christopher I.
bee0ab0a-cbec-491e-bcfa-e0cec9df67bb
Grand, Maxime M.
659acbde-d639-42b7-9fab-52fa1b3655ff
Chocholouš, Petr
4ccbd9d7-034d-41ff-9cd6-245ec8d26473
Růžička, Jarda
3b4397fc-ca97-4eb2-8f99-96d65b19fba4
Solich, Petr
4a44b848-2455-4b83-bab9-b433e178f076
Measures, Christopher I.
bee0ab0a-cbec-491e-bcfa-e0cec9df67bb

Grand, Maxime M., Chocholouš, Petr, Růžička, Jarda, Solich, Petr and Measures, Christopher I. (2016) Determination of trace zinc in seawater by coupling solid phase extraction and fluorescence detection in the Lab-On-Valve format. Analytica Chimica Acta, 923, 45-54. (doi:10.1016/j.aca.2016.03.056).

Record type: Article

Abstract


By virtue of their compactness, long-term stability, minimal reagent consumption and robustness, miniaturized sequential injection instruments are well suited for automation of assays onboard research ships. However, in order to reach the sensitivity and limit of detection required for open-ocean determinations of trace elements, it is necessary to preconcentrate the analyte prior its derivatization and subsequent detection by fluorescence. In this work, a novel method for the determination of dissolved zinc (Zn) at subnanomolar levels in seawater is described. The proposed method combines, for the first time, automated matrix removal, extraction of the target element, and fluorescence detection within a miniaturized flow manifold, based on the Lab-On-Valve (LOV) concept. The key feature of the microfluidic manipulation of the sample is flow programming, designed to pass sample through a mini-column where the target analyte and other complexable cations are retained, while the seawater matrix is washed out. Next, zinc is eluted and merged with a Zn selective fluorescent probe (FluoZin-3) at the confluence point of the LOV central channel using two high-precision stepper motor driven pumps that are operated in concert. Finally, the thus formed Zn complex is transported to the LOV flow cell for selective fluorescence measurement. This work describes the characterization and optimization of the method including Solid Phase Extraction using the Toyopearl AF-Chelate-650M resin, and detailed assay protocol controlled by a commercially available software and instrument. The proposed method features a LOD of 0.02 nM, high precision (<3% at 0.1 and 2 nM Zn levels), an assay cycle of 13 min and a reagent consumption of 150 ?L FluoZin-3 per sample, which makes the method highly suitable for oceanographic shipboard analysis. The accuracy of the method has been validated through the analysis of seawater reference standards and comparison with ICP-MS determinations on seawater samples collected in the upper 1300 m of the subtropical south Indian Ocean. This work confirms that integration of sample pretreatment with optical detection in the LOV format offers a widely applicable approach to trace analysis of seawater.

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Accepted/In Press date: 25 March 2016
Published date: 7 June 2016
Keywords: GEOTRACES, Zn, Lab-On-Valve, FluoZin-3, Oceanography, Trace analysis
Organisations: Ocean and Earth Science

Identifiers

Local EPrints ID: 396477
URI: http://eprints.soton.ac.uk/id/eprint/396477
ISSN: 0003-2670
PURE UUID: 9de1624a-6a17-46bc-a5d3-41af67d98abe
ORCID for Maxime M. Grand: ORCID iD orcid.org/0000-0001-9338-694X

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Date deposited: 06 Jun 2016 14:31
Last modified: 09 Jan 2022 07:01

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Contributors

Author: Maxime M. Grand ORCID iD
Author: Petr Chocholouš
Author: Jarda Růžička
Author: Petr Solich
Author: Christopher I. Measures

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