Date of Award

6-1-2015

Document Type

Thesis - SCU Access Only

Publisher

Santa Clara University

First Advisor

Unyoung Kim

Abstract

Nitrate contamination is one of the most ubiquitous water contaminants worldwide. Consuming small amounts of nitrate has been linked to Blue Baby Syndrome, various cancers, and other reproductive health effects1. To combat this problem, the World Health Organization (WHO) has set nitrate limits in drinking water to 50 ppm. Frequent widespread testing of water sources in high-risk regions is critical to protecting public health. However, current nitrate detection methods are inherently inaccurate or too expensive for frequent use where they are needed most. To satisfy this unmet need, we present a novel point-of-use microfluidic sensor for the electrochemical detection of nitrate in drinking water for use in developing countries where this problem is prevalent. Our device is robust, inexpensive, and accurate, rendering it ideal for use in developing countries. Our proposed device utilizes a three-electrode system to detect nitrate electrochemically via inexpensive disposable chips. The working electrode is copper-plated copper ink, the counter electrode silver ink, and the reference electrode silver/silver chloride ink. The electrodes are painted onto a vinyl substrate, providing a cost-effective platform. The electrodes are housed in an acrylic casing. When the sensor is connected to an electrochemical analyzer and a small volume of water sample is deposited onto the sensor. Differential pulse voltammetry is performed with a potential range of 0 to – 0.8 V at a rate of 0.1 V/sec, producing a current peak for our analyte. Our electrochemical sensor detects nitrate in water with high sensitivity as low as 14 ppm, well below the maximum limit of the WHO requirement. The microfluidic sensor combined with a hand-held electrochemical analyzer represents one example of a growing trend towards point-of-care diagnostics. This proposed platform, combined with a mobile application as demonstrated by us and others2, is capable of delivering accurate and rapid readings at the water sources will contribute to identify the contaminated sources and to evaluate the efficiency of water treatment, as well as to inform public health regulatory agencies with this pertinent information.

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