According to Dow, "commercial grade" TEA can contain up to 15% DEA. That's a lot of variation/contamination. Even Patrick's beloved 20 Mule Team Borax has a much lower range of variation, and there it's probably mostly water.
It would be interesting to have someone collect and compare different batches of TEA and see what pH variations there are.
The way I read Dow is that Commercial TEA is a mixture of Tri- and Diethanolamine, approximately in the ratio of 85/15. It is designed for certain uses, but not to my knowledge touted for our sort of photographic use. It is not necessarilly an inferior product. I'm pretty sure Dow would not recommend it as an analytical reagent. It may in fact be superior to analytical grade for its intended uses.
The way I read Dow is that Commercial TEA is a mixture of Tri- and Diethanolamine, approximately in the ratio of 85/15.
Pat - please look closely, there are equal signs in there with the greater than and less than signs. I'm pretty certain you know how to read those statements.
For commercial grade TEA, it actually says:
That means that there is a minimum concentration of 85% for TEA, and at a maximum, 15% of DEA. So the actual product purchased could range from any ratio of 85% TEA/15% DEA to 100% TEA/0% DEA, as it is stated.
It's more than "approximately in the ratio of 85/15", they are saying it never has more than 15% DEA, I take you statement of "approximately" to mean that the concentration of the DEA will vary around the concentration of 15%. It doesn't say that.
Whether it actually makes it to 100% TEA on some occasions, it may not. And whether it is always at 85% TEA with 15% DEA, is may be. Perhaps 90% TEA/10% DEA is a more commonly produced mixture, but there's no way to tell from that sheet.
They are leaving a HUGE range of possible compositions available to themselves for what they actually supply. And who knows what other manufacturers produce.
If you really want to have a better idea of what you are getting, the TEA 99% grade or the TEA 99% LFG grade are better choices.
For up from the ashes, up from the ashes, grow the roses of success!