Which sensors should O use to measure salinity and chlorine in sweat?

Hi! I am doing a project in school, in which I need to measure the salimity leves and also the chlorine levels in sweat, is there any sensor that could give me any of this values? Or maybe any other idea to get to this results?

Chlorine...that's a tough one. Reading CL2 is done either optically after exposing sample to a reagent. It changes color in presence of CL2 (usually pink) then compared to clear as the zero standard

...or done amperometrically by adding reagent, two chemicals (sodium hydroxide and one I can't recall) plus acetic acid, then measuring conductance and comparing with "zero" water, water with absolutely no CL2. Not sure how you would add reagent to sweat and do either method. Amperometric is a continuous "in process" method. DPD (N,N Diethyl-1,4 Phenylenediamine Sulfate) or optical is a sample type - the one you would be most interested in.

Salinity might be measured with something like a soil moisture meter for plants but not sure how that would work. They connect to Arduino analog inputs. You'd have to have another "zero" sensor as well by maybe cleaning part of the skin with alcohol to remove salt. Just thinking out loud.

ElHefe: Chlorine...that's a tough one. Reading CL2 is done either optically after exposing sample to a reagent. It changes color in presence of CL2 (usually pink) then compared to clear as the zero standard

...or done amperometrically by adding reagent, two chemicals (sodium hydroxide and one I can't recall) plus acetic acid, then measuring conductance and comparing with "zero" water, water with absolutely no CL2. Not sure how you would add reagent to sweat and do either method. Amperometric is a continuous "in process" method. DPD (N,N Diethyl-1,4 Phenylenediamine Sulfate) or optical is a sample type - the one you would be most interested in.

There's not going to be any chlorine in sweat. It's not worth testing for it. It's a poison and you wouldn't be alive if it was being secreted from your skin.

There will be chloride in sweat which is a totally different issue to test for.

The difference between chlorine and chloride would be a good place to start looking for your solution.

Do you want something that tests on the skin? OR are you going to collect a bucket of sweat?

Chloride you MAY find in someone's sweat after they visited the pool.

Salinity of a liquid is normally measured using an EC probe (and be aware that I'm simplifying things here badly as while EC is a direct measure of salinity, it's not a simple direct relationship) but I don't know of any that would work with just a few drops, let alone with drops that have been soaked up by a towel or so. You may not literally need buckets, but close to, to make it work with regular EC probes.

Chloride you MAY find in someone's sweat after they visited the pool.

Chloride would be there all the time from the salt in the sweat. Chlorine is what you're thinking of at the pool though that's actually hypochlorite. The chlorine that is produced from that hypochlorite is in small small quantities and dissipates really fast.

Mmm... So much for being a chemical engineer... Mixing them up again...

Anyway. There are chloride probes available - they're similar to pH probes in that it uses an ion selective glass membrane. Those again are meant for larger volumes - enough to stick the probe in. They're expensive, a couple hunderd USD a piece, without the sensor amplifier board (the same as you would use for a pH sensor). Probably out of budget of a school project.

Chlorine, the best probe may be your nose, but it'd have a digital output (it's there or it's not there). Qualitative only, not quantitative. There must be chlorine gas probes out there as well but not sure how to measure the amount in sweat - after all it evaporates really quickly and then gets diluted in the surrounding air.