Science Buddies: "Ask an Expert"

Hello,

For my project this year I need to be able to test the calcium levels in various freshwater samples. The samples will have Ca concentrations as low as 1.1 mg/L.

I am not sure how to go about testing the calcium levels when they are this low. Do you know if there a is portable digital device I can maybe rent somewhere to do my testing, or is there some mathematical calculation I can use to get my results? Strips testing calcium levels won't be accurate enough. Whatever I use will need to measure changes in the Calcium levels in small increments from 1.1 mg/L upwards.

Any advice you can provide me with would be appreciated.

Thank you.

Hi,

There is a lab method for determining calcium ion concentration (Ca2+) in water using EDTA titration. You can get the details here: https://www.google.com/#safe=active&q=c ... ation+edta

You do not need any special instrument to do this test but you would need some chemicals--EDTA, sodium hydroxide, dye reagent, distilled water, etc.--and some glassware that can be found in a chemistry lab, flasks, beakers, buret, graduated cylinders.

Check out the tutorials on the Google search. I also found a youtube video that gives some good instructions on how to do titrations if you have never done one https://www.youtube.com/watch?v=hTy9JBllUVg

I did not find any mention of the sensitivity of this titration so you will have to do some searching in the tutorials to see if it will read accurately in the 1 mg/L range.

There are instrumental methods of measuring very low Ca2+ concentrations but you would need access to a biochemistry lab with a UV spectrophotometer.

We'll be here to help you whatever you decide to do.

Good luck!

Sybee

Dear Sybee

Thank you very much for the information and the links.

Could you possibly send me the EDTA titration details link again? When I click on the link (the first one) in your message, it just takes me to the Google Search home page.

Thank you again for taking the time to answer my questions.

Hi Finsbury,

I think Sybee just searched "calcium ion titration edta" into Google. Hopefully you can find sources that are helpful. Good luck!

Hi,

I was going to just pick one link from the search to send to you but after reading the procedures on a dozen or so i thought i would send you the search URL and you could look for yourself. All the procedures that i read involve chemistry at an advanced high school or college level and I could not find one that could be done by an individual without supervision in a lab. Does your school have a fairly well-equipped chemistry lab that you can use? I so, I would ask the chemistry teacher if they know how to do an EDTA titration for determining calcium ion concentration in water.

In order to do this measurement successfully, you need to have someone help you in the lab who knows all the basic chemistry procedures. Some of the chemicals used in the procedure such as sodium hydroxide solution are corrosive and can cause burns if you get it on your skin. And whenever you work in a lab ALWAYS where approved safety glasses or goggles.

I wish I had a simpler answer for you, but if you want to measure Ca2+ in the 1 ppm range, I think this is your best option. Read through some of the links and try to understand the chemistry involved in the titration then show the procedure to your teacher and ask if there is someone who can help you do it. If you have specific questions, of course Scibuddies will always be here to try and guide you.

Good luck!

Sybee