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A lab-on-chip sensor for in situ spectrophotometric measurement of seawater pH

A lab-on-chip sensor for in situ spectrophotometric measurement of seawater pH
A lab-on-chip sensor for in situ spectrophotometric measurement of seawater pH
Accurate and high precision measurements of seawater pH are important for monitoring of ocean acidification and to fully understand the dynamics of the oceanic carbonate system. An optimisation and field testing of an in situ pH sensor, based on lab-on-chip technology, offers potential to address to this problem. The sensor employs a spectrophotometric method, with high precision (0.001 pH units) and accuracy (0.005 pH units) within the range of a certified TRIS buffer. In addition, it is a compact miniaturised field analyser that consumes minimal power (3 W) and uses low reagent consumption (2.2 μL per analysis). A newly developed Absorbance-Derivative method is used to eliminate indicator-induced pH perturbation; automatically correcting approximately ±0.08 pH units perturbation for each individual analysis. Another R-correction calibration method is also studied, resulting an accuracy of ±0.005 pH units, thereby providing an easy but also sufficiently accurate way to calibrate pH sensors. A recipe for preparing TRIS buffer with any pH value between 7.4 and 8.4, and with any salinity between 20 and 40 psu is resented, with initial verification suggesting an accuracy of ±0.004 pH units. The sensor has been field tested under various conditions, including vertical profiling, a brackish water moored deployment and a seawater moored deployment. A three-month pontoon deployment was performed, with an accuracy of ±0.003 pH units recorded over a 2 week period. However, biofouling in the inlet filter caused a diurnal offset up to 0.1 pH units, indicating that the next version of this pH sensor should focus on anti-biofouling technology.
University of Southampton
Yin, Tianya
fa5c7b87-1ffa-486a-b914-cfb008b8dd5a
Yin, Tianya
fa5c7b87-1ffa-486a-b914-cfb008b8dd5a
Mowlem, Matthew
6f633ca2-298f-48ee-a025-ce52dd62124f

Yin, Tianya (2017) A lab-on-chip sensor for in situ spectrophotometric measurement of seawater pH. University of Southampton, Doctoral Thesis, 123pp.

Record type: Thesis (Doctoral)

Abstract

Accurate and high precision measurements of seawater pH are important for monitoring of ocean acidification and to fully understand the dynamics of the oceanic carbonate system. An optimisation and field testing of an in situ pH sensor, based on lab-on-chip technology, offers potential to address to this problem. The sensor employs a spectrophotometric method, with high precision (0.001 pH units) and accuracy (0.005 pH units) within the range of a certified TRIS buffer. In addition, it is a compact miniaturised field analyser that consumes minimal power (3 W) and uses low reagent consumption (2.2 μL per analysis). A newly developed Absorbance-Derivative method is used to eliminate indicator-induced pH perturbation; automatically correcting approximately ±0.08 pH units perturbation for each individual analysis. Another R-correction calibration method is also studied, resulting an accuracy of ±0.005 pH units, thereby providing an easy but also sufficiently accurate way to calibrate pH sensors. A recipe for preparing TRIS buffer with any pH value between 7.4 and 8.4, and with any salinity between 20 and 40 psu is resented, with initial verification suggesting an accuracy of ±0.004 pH units. The sensor has been field tested under various conditions, including vertical profiling, a brackish water moored deployment and a seawater moored deployment. A three-month pontoon deployment was performed, with an accuracy of ±0.003 pH units recorded over a 2 week period. However, biofouling in the inlet filter caused a diurnal offset up to 0.1 pH units, indicating that the next version of this pH sensor should focus on anti-biofouling technology.

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Yin, Tianya PhD Thesis May 18 - Version of Record
Available under License University of Southampton Thesis Licence.
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Published date: September 2017

Identifiers

Local EPrints ID: 421151
URI: http://eprints.soton.ac.uk/id/eprint/421151
PURE UUID: 2cb1eb34-e709-4d4d-9734-d861bf694b26

Catalogue record

Date deposited: 23 May 2018 16:30
Last modified: 12 Dec 2021 08:30

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Contributors

Author: Tianya Yin
Thesis advisor: Matthew Mowlem

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