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Question: Quantitative analysis using paper-based kits

fieldlab is asking a question about nitrate
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by fieldlab | May 06, 2016 07:01 | #13083

Can anyone answer some questions for me about quantitative analysis using paper based kits? I'm interested in the idea of using cameras (or a spectrometer) to provide quantitative data by transmitting light though paper rather than solution.

For example, the following url is a link to a 2009 paper from Analytical Chemistry: "Quantifying Colorimetric Assays in Paper-Based Microfluidic Devices by Measuring the Transmission of Light through Paper"

I am part of a group of people interested in measuring agricultural contamination of waterways. The key chemical parameters that I am interested in are nitrate and phosphorus, with measurement accuracy needing to be ppm-ppb. The following quote from the paper suggests that paper-based kits may be something we could use. I realise that the application in the paper is quite different, but I'd appreciate a chemist having a look with our application in mind and receiving their views on the matter.

"This prototype transmittance colorimeter is inexpensive, rugged, and fully self-contained, and thus potentially attractive for use in resource-limited environments and developing countries" (Ellerbee et al. 2009). - Sounds like us!


Hmm, interesting. I don't know much about paper assays, but this kit available online says:

Smallest Increment: Steps: 0, 0.15, 0.3, 1, 1.5, 3 ppm

would that be sensitive enough? It's available for $21.39. What are the drawbacks or limitations, if any, to paper based tests?

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Thanks for your reply @warren. There is pretty good discussion going on about this concept on hackaday for Pb detection in drinking water a la Flint.

Main advantage is objective digital measurement under controlled lighting. What about cheap cell phone screens a flat bed light source?

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Hmm, interesting!

Would a cell phone screen be a really consistent spectrum? I wonder how much variability there is in manufacturing.

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Yes, a good question @warren - possibly not, and I'm not sure how to find out, apart from buying a whole lot of cheap cell phones. I'll keep thinking about it!

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We're starting to compile a lot of different sensors and testing methods here -- could be of help!

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