Homemade FAS Titrating Reagent?

[tomvalois]

Has anyone tried making the R-0871 reagent at home? I can order deionized water and ferrous ethylenediamine sulfate from City Chemical or Fischer Scientific, and it would be a lot cheaper than buying the Taylor reagent. My preliminary calculations (admittedly based on a guess about the molar content of the DPD powder) lead me to believe that 10 liters of water and 13.5 grams of the sulfate will yield somewhere around 2,500 tests for less than $50. If anyone has tried this with either success or failure, please share your experience.

Thanks!

 

[Donldson]

You can buy 16 ounce bottles of R-0871 for $27 on Amazon, so $50 for 34 ounces isn't too much of a savings. Also you are talking a 7-10 year supply, so averaging out you are saving maybe $15 a year compared with buying the 2 ounce bottles from TF Test Kits if you assume the reagent you make stays fresh for a decade.

 

[tomvalois]

You can buy 16 ounce bottles of R-0871 for $27 on Amazon, so $50 for 34 ounces isn't too much of a savings. Also you are talking a 7-10 year supply, so averaging out you are saving maybe $15 a year compared with buying the 2 ounce bottles from TF Test Kits if you assume the reagent you make stays fresh for a decade.

My original post said 1 liter. It was supposed to be 10 liters (I have corrected it). So the savings are more substantial. Basically, $45 would buy 10 liters of deionized water and 15g of ferrous ethylenediamine sulfate, and would make about 340 ounces of reagent, so the cost would be about $0.14 per ounce, or $2.24 for a 16oz bottle. And I wouldn't make it all at once - I'd make small batches as I needed it. The sulfate won't go bad as long as it is kept in a dry place.

 

[Donldson]

Yes, that would make for a more substantial savings, but if you break it down it just doesn't make as much sense. You get about 70 tests per ounce of reagent, so you will pay about 0.2 cents per test. Buying the 2 ounce bottle from TF Test kits equates to about 7.9 cents per test. So your savings still only comes out to about $2.31 a month. If you buy the 16 ounce bottle for $27 it comes out to 2.4 cents per test, so you are only saving 66 cents a month over that.

So I will say the same thing I say to my friend who makes her own laundry detergent: if you want to do it more power to you, but if savings is your primary motivator there are easier ways to save a couple dollars a month.

 

[Patrick_B]

And as you say, part of your formulation is "admittedly based on a guess." That alone should deter you from trying to formulate your own reagent but you may be missing other pieces of the puzzle as well.

The bottom line is that any test we reccomend has a value 100X the miniscule cost of the reagent. Trying to save the pennies here is kind of like avoiding an oil change to save money on your car maintenance costs. It just isn't worth the possible downsides.

 

[JoyfulNoise]

The ferric ammonium sulfate titrating reagent is not stable. It reacts with oxygen in air where the ferric ion (Fe²⁺) gets oxidized to ferrous iron (Fe³⁺). So unless you have a setup to deoxygenate the DI water (typically done with a dry nitrogen gas bubble in a sealed glass container) and store the solution under a nitrogen blanket, you homemade reagent will not last very long. This is why Taylor puts a shelf life date on their bottles and only guarantees them for a year.

As others have said, you can certainly experiment for the fun of it, but I doubt the time you spend setting this all up will really be worth the extra money you save...