Publication Date

Spring 2023

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Moss Landing Marine Laboratories

Advisor

Maxime Grand

Subject Areas

Analytical chemistry

Abstract

Oceanographic nutrient monitoring efforts still largely rely on discrete sampling at irregular intervals, hindering the advancement of high-resolution biogeochemical observations and models. Benchtop analytical instrumentation for macronutrient analysis is expensive, complex, and requires large reagent volumes and highly trained operators. This thesis describes the development and optimization of a novel and commercially available class of automated nutrient analyzers called programmable Flow Injection (pFI) for benchtop and unattended in situ operations with a focus on phosphate and silicate analysis. While pFI is an ideal candidate for unattended deployments due to its compact size, low reagent volume requirements, and ability measure multiple analytes from a single device, this type of instrumentation has only been used for benchtop applications to date. The composition of reagents and standards were optimized to remain stable for more than 30 days at a range of temperatures. In addition, online dilutions were implemented to produce autonomous calibrations. A field-deployable pFI analyzer was developed using open-source software and low-cost commercially available hardware. The instrument was successfully deployed at a coastal shore station, revealing nutrient variability driven by the transport of high-nutrient water into the nearshore via internal tidal waves. The work presented in this thesis will showcase pFI as a robust technique for advancing the field of analytical chemistry and inspiring wider use of this technology.

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