Bulk DPD Powder - worth it?

I know from info here DPD powder lasts a year. That would seem to be because it is opened often and exposed to the atmosphere (absorbs moisture I think).

I was thinking about buying 1/4 Lb and every year open it up to fill the 10 gram vial with enough for the year (or close to it) recapping the bulk container.

1/4 lb is 113 grams, so roughly I would be storing 10X what you get in the 10 gram vial for a little over 3X the cost (I roughly calc'd in shipping). If it lasted 3-4 years I would be even.

The price looks good on paper, but wonder if the bulk could last the several (10???) years it would take to use it up?

probably not. DPD is quickly oxidized by atmospheric oxygen in the presence of moisture. IF you had a way to store it with a dessicant and were able to replace the air in the container with carbon dioxide you might be able to extend it's useful life.

Bought a 1/4 # container a couple years ago. Keep it and other bulk test liquids in the fridge. After a couple years seems just fine. Time will tell. When you do have to open it make sure you let it come up to room temp first to avoid possible condensation. Also started a test a few days ago where I took some of the powder and am leaving it in an open container. When I see it get dark and lumpy I'll check it against good stuff and see if the test results are different.
Al

From my experience, it's hard to handle that way.

We buy in in 1 lb quantities, and have frequently had to discard powder purchased in the fall, when things would start up the following spring. This happened, in spite of opening the bottles only two times, and in spite of storing them carefully.

However, since adding desiccants to the DPD powder containers, we're seeing evidence that the powder sometimes remains good over the winter. Consequently, we're planning (later, after the kits are caught up) to offer 25g refill vials, with extra desiccant paks added, and with intructions to keep the powder indoors and opened as rarely as possible.

So, if you receive the powder in good condition (white or nearly so), add some bulk desiccant packs to your DPD powder containers, bag it along with additional desiccants, and open it rarely and only indoors . . . you might succeed.

Keep in mind, through, that the Taylor DPD powder in our kits is actually a Taylor's blend of powder, stabilizers and buffers for use in the FAS based testing. Pure DPD powder cannot be substituted, nor can the DPD powder HACH sells for use in colorimetric tests. So, you'll need to purchase from Taylor.

If you do, be sure to purchase during the summer, when they are blending and shipping immediately. I've gotten some old stock in the spring that I had to send back.

Ben

Thanks everyone -

And yes it would be Taylor chemicals.

I think I'll wait patiently for my ps234 and think more about this when I need refills. In the mean time if I come across some of those dessicant packs I'll save them, over the years I have thrown away so many. I understand they can be regenerated in an oven.

I got 1 dessicant packet today. I am starting my collection, to be ready for next year.:)