I can confirm ziplock stuff is legit (at least the one I received few days ago).
I also used a drop test but a different one. I'm explaining how I proceeded just in case there is a flaw in the procedure.
View attachment 38689
Here's what is in the box
View attachment 38690
The test upper limit is 1mg/l. I did not have a sufficiently precise scale so I used 3 glasses containing 100ml of demineralized water.
View attachment 38691
I put 1g in the first glass
View attachment 38692
I made sure it was completely dissolved in the water. Concentration in glass 1 is now 10g/l. Then I took with the syringe 1ml from glass 1 and put it in glass 2. Concentration in glass 2 is now 100mg/l. Finally I took 1ml from glass 2 and put it in glass 3. Concentration in glass 3 is now 1mg/l.
Following the test kit instruction, I used the syringe to put 5ml of glass 3 in both of the vials. In one of the vial, I put 5 drops of reagent 1 followed by 5 drops of reagent 2. The color changed almost immediately but waited 5 minutes as specified in the notice.
Here's the result.
View attachment 38693
View attachment 38694
View attachment 38695
It is difficult to tell between 0.8mg/l and 1mg/l.