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Determination of total dissolved cobalt in UV-irradiated seawater using flow injection with chemiluminescence detection

Determination of total dissolved cobalt in UV-irradiated seawater using flow injection with chemiluminescence detection
Determination of total dissolved cobalt in UV-irradiated seawater using flow injection with chemiluminescence detection

A sensitive flow-injection method with chemiluminescence detection (FI-CL) for the determination of dissolved cobalt in open ocean samples, suitable for shipboard use has been developed. To date, FI methods for dissolved cobalt have been used only in coastal and estuarine waters. Therefore, significant modifications to existing methods were required, including (1) the use of a commercially available iminodiacetate (IDA) resin (Toyopearl AF-chelate 650M) in place of resin immobilized 8-hydroxyquinoline for online preconcentration and matrix removal, (2) the introduction of acidified ammonium acetate (pH 4) as a column-conditioning step before sample loading and rinse steps, and most importantly, (3) UV irradiation of acidified seawater samples to determine total dissolved cobalt, rather than an operationally defined fraction. This method had a detection limit of 4.5 pM (3σ of the blank). The accuracy of the method was evaluated by determining total dissolved cobalt in acidified North Pacific deep seawater (1000 m) samples from the Sampling and Analysis of Iron (SAFe) program and NASS-5. The method yields a mean (± SD) value of 40.9 ± 2.6 pM (n = 9), which is in excellent agreement with the SAFe consensus value of 43 ± 4 pM, and 208 ± 30 pM for NASS-5 (certified value 187 ± 51 pM). This study demonstrates that UV irradiation is an essential step for the determination of total dissolved cobalt in seawater by FI-CL. The method was applied to vertical profiles from the Sargasso Sea, indicating that total dissolved cobalt is influenced by both biological and physical processes.

1541-5856
352-362
Shelley, Rachel U.
da7abad3-b5c8-4e11-aeda-7a0256a6fab9
Zachhuber, Bernhard
eea5a80d-f586-435d-96c4-006227b10011
Sedwick, Peter N.
4f6c2a8e-afe2-4b89-a971-e8b086d40b48
Worsfold, Paul J.
27675f89-7eee-45c5-821e-a381d8db9693
Lohan, Maeve C.
6ca10597-2d0f-40e8-8e4f-7619dfac5088
Shelley, Rachel U.
da7abad3-b5c8-4e11-aeda-7a0256a6fab9
Zachhuber, Bernhard
eea5a80d-f586-435d-96c4-006227b10011
Sedwick, Peter N.
4f6c2a8e-afe2-4b89-a971-e8b086d40b48
Worsfold, Paul J.
27675f89-7eee-45c5-821e-a381d8db9693
Lohan, Maeve C.
6ca10597-2d0f-40e8-8e4f-7619dfac5088

Shelley, Rachel U., Zachhuber, Bernhard, Sedwick, Peter N., Worsfold, Paul J. and Lohan, Maeve C. (2010) Determination of total dissolved cobalt in UV-irradiated seawater using flow injection with chemiluminescence detection. Limnology and Oceanography: Methods, 8 (7), 352-362. (doi:10.4319/lom.2010.8.352).

Record type: Article

Abstract

A sensitive flow-injection method with chemiluminescence detection (FI-CL) for the determination of dissolved cobalt in open ocean samples, suitable for shipboard use has been developed. To date, FI methods for dissolved cobalt have been used only in coastal and estuarine waters. Therefore, significant modifications to existing methods were required, including (1) the use of a commercially available iminodiacetate (IDA) resin (Toyopearl AF-chelate 650M) in place of resin immobilized 8-hydroxyquinoline for online preconcentration and matrix removal, (2) the introduction of acidified ammonium acetate (pH 4) as a column-conditioning step before sample loading and rinse steps, and most importantly, (3) UV irradiation of acidified seawater samples to determine total dissolved cobalt, rather than an operationally defined fraction. This method had a detection limit of 4.5 pM (3σ of the blank). The accuracy of the method was evaluated by determining total dissolved cobalt in acidified North Pacific deep seawater (1000 m) samples from the Sampling and Analysis of Iron (SAFe) program and NASS-5. The method yields a mean (± SD) value of 40.9 ± 2.6 pM (n = 9), which is in excellent agreement with the SAFe consensus value of 43 ± 4 pM, and 208 ± 30 pM for NASS-5 (certified value 187 ± 51 pM). This study demonstrates that UV irradiation is an essential step for the determination of total dissolved cobalt in seawater by FI-CL. The method was applied to vertical profiles from the Sargasso Sea, indicating that total dissolved cobalt is influenced by both biological and physical processes.

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More information

Published date: July 2010
Organisations: Marine Biogeochemistry, Southampton Marine & Maritime Institute

Identifiers

Local EPrints ID: 406475
URI: http://eprints.soton.ac.uk/id/eprint/406475
ISSN: 1541-5856
PURE UUID: 43c7323e-5a84-4c5f-a4c2-b5e440184f53
ORCID for Maeve C. Lohan: ORCID iD orcid.org/0000-0002-5340-3108

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Date deposited: 18 Mar 2017 02:20
Last modified: 07 Oct 2020 02:02

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