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Nitrate detection

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Exploratory pilot project for low-cost nitrate measurement

Assessing DIY spectrometry and open collaborative models for nitrate detection for field and in-home assays

December 2013


Nitrate contamination of drinking and surface water poses serious health risks, but affordable on-demand test- ing is not widely available. EPA Method 353.2 (http://www.caslab.com/EPA-Method-353_2/) outlines a cadmium reduction technique suitable for field testing of surface waters, and suggests the use of a spectrophotometric measurement of an indicator color change. While spectrophotometers are typically cost-prohibitive to consum- ers, several years of research into low-cost, open source spectrometer attachments to smartphones by the Public Lab network has resulted in several models of sub-$100 devices which may be suitable for more precise and geo-stamped measurements of surface water.

Public Lab proposes conducting a feasibility study of whether our spectrometer can replace existing colorimet- ric tools used in Method 353.2. If feasible, a re-usable testing kit for Method 353.2 could potentially cost as little as it currently costs to test several samples, given current lab fees of $35-40 per test -- and could yield on- demand data without the need to wait for lab results. A DIY or Open Hardware Method 353.2 additionally pro- vides an inexpensive means for developers to calibrate and verify in-line sensing systems. Lowering the barriers to entry in nitrate testing will support the development of a broader range of DIY tools and help launch a nitrate sensing program as diverse as those affected by nitrate pollution.


We propose an 8-week initial project to assess the potential for more in-depth proof of concept and prototyping stages. Topics will include:

  • brainstorming with domain "experts"
  • comparison of our prototype hardware with a needs assessment of our partners
  • acquisition and design of a hardware adaptations necessary for colorimetry
  • colorimetry initial proof of concept with minimally adapted spectrometer devices


Weeks 1-3:

  • Acquisition of equipment and supplies for reproducing EPA Method 353.2 with known sample concentrations
  • Feasibility interviews with domain "experts"
  • Spectrometry Lab Setup Prototype 1 for 353.2

Weeks 4-12:

  • Sample testing for 353.2
  • Matching samples submitted to certified lab
  • Prototype modification and experiment iteration

Weeks 13-18:

  • Write-up of results for 353.2 experiments
  • Hardware design and protocol documentation
  • Review of future research directions

Future phases

Contingent on the initial success of the exploratory pilot, next steps could include:

Proof of concept: further testing and modification of existing hardware;

Prototyping: construction of a series of iteratively refined prototypes based on colorimetric testing and data analysis; design work to refine the device and software design to the nitrate use case.

Field testing: increased work with partner community groups to assess the tool's utility in the field