Conflicting results between different bottles of R-0871

[MITBeta]

I have a Taylor kit with R-0871 with best by date of 9/21.

I recently bought a refill from TFTestkits of the TFTestkits labeled R-0871 (no expiration date indicated).

I lent the refill bottle to a friend who is in the midst of a SLAM and she keeps reporting significantly higher values than I am expecting.

Today I went over and ran 2 tests side by side, 1 with my bottle, 1 with hers:

Mine: 9.5ppm
Hers: 15ppm

This suggests to me that the concentration in the bottle from TFTestkits is weaker.... But which one is correct?

I diluted 12.5% bleach 10,000:1 and get 13ppm (lots of opportunity for errors in dilution here...) so consider that to be close enough.

So do I now have to run a sample check against diluted bleach on each new reagent refill, or am I missing something here?

 

[ajw22]

Swap the tips in the bottle. There have been reports of tips that had a bit of a blockage.

Drop size matters. Hers higher ppm says she used more drops that may have been smaller.

Before you go looking at the concentrations test both bottles using the same tips.

 

[MITBeta]

I don't currently have access to the other bottle. Are the tips from Taylor and TFTestkits interchangeable?

Regardless of whether it's the concentration, tip, moon phase, or whatever, it seems like going forward it's prudent to run a control on every new bottle, until I'm convinced that new bottles can be trusted.

Is anyone else running into this same issue?

 

[ajw22]

I don’t think the TFT tips are from the same supplier as Taylor.

I suggest you contact TFT and discuss it with Rebecca.

@OTPirate