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Is there any way to measure an acidity of a breath condensate? That is to measure a pH of an exhaled breath condensate. I would like to use such a sensor to daily measure my acid level in a breath condensate and correlate it with heartburn attacks as well as a measure of the impacts of my diet.

This can be very useful for patients with GERD (acid reflux) or those who suffer from a bad breath caused by the gastric acid in their stomach.

Note: ideally I would like to use it with the Raspberry Pi. For now the guys from Raspberry Pi SO sent me here saying it's a cool concept but sadly there is nothing off the shelf.

Edit: While doing the research on this question I found this interesting article on different ways of measuring the gastric acid secretion: http://www.researchgate.net/publication/49780488_Review_article_Methods_of_measuring_gastric_acid_secretion http://www.ncbi.nlm.nih.gov/pubmed/19279471

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    \$\begingroup\$ That's quite an uncommon question for an electrical design SE, I suspect this is off topic... Perhaps the Physics SE? In terms of sensors, first thing that pops in mind are the acidity sensors for plants, maybe you can hack one and stick it on your tongue. \$\endgroup\$ – Mister Mystère Sep 29 '15 at 15:05
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    \$\begingroup\$ I would suggest to relate that question first to some biophysics forums. After you find out which are the specific gases you need to measure look for any available sensors already in the market or try to ask here again. Personally I know that there are already sensors from the automotive industry able to measure gases like CO2, SOx, and etc. So you should be able to find something. \$\endgroup\$ – judoka_acl Sep 29 '15 at 15:21
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    \$\begingroup\$ Acidity (pH) is meaningless when applied to a gas. \$\endgroup\$ – Leon Heller Sep 29 '15 at 17:02
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    \$\begingroup\$ @LeonHeller have a read: Exhaled breath condensate pH assays So acidity of a gas makes no sense, but measuring the acidity of the condensate of it does - the title was not 100% accurate but I still think that saliva and breath condensate are different (in saliva you should not find much of the stuff from your lungs). \$\endgroup\$ – Arsenal Sep 29 '15 at 20:50
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    \$\begingroup\$ en.wikipedia.org/wiki/Esophageal_pH_monitoring \$\endgroup\$ – Fizz Sep 30 '15 at 21:05
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Two suggestions are to measure what's on your tongue or your saliva (I guess the result would be pretty much the same).

I suspect that the saliva has quite a different composition than the breath. What I found with a google search on "acidity breath" (because I never heard of it before) suggested to perform the analysis on breath condensate, which would probably give only very small quantities to analyse.

So maybe you could construct some apparatus where the pH electrodes are cooled so the breath will condensate on your actual sensing element and go from there. To prevent the droplets from slipping of, maybe you could trap them in a sort of U where the sensor sits at the bottom and gravity will help you keep the drops on the sensor.

For cooling you could use a Peltier element - it has no moving parts so might work quite reliable. Though the efficiency is low, don't know if that will work out for a portable device (should it be portable? in my mind it sounded like that but a raspberry isn't very portable to begin with).

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You're looking for a pH sensor. Sparkfun has a really nice little kit to get you started. Now this will need to be placed in your mouth and make contact with your saliva, but it should allow you to collect the data you're looking for.

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