Today all necessary chemicals arrived, so I started to synthesize the ONE TOUCH ULTRA control solution. I used:

• Deionized water
• Polyvinylpyrrolidone
• Sodium benzoate (min. 99%, Ph. Eur., BP, FCC, LM)
• EDTA (disodium salt)
• D(+)-Glucose (chemically pure)
• Indigo carmine (I was not able to purchase Amaranth)
  

Firstly I prepared a solution of 91ml deionized water, 8g polyvinylpyrrolidone, 0.5g sodium benzoate and 0.5g EDTA (disodium salt). As the EDTA (disodium salt) did not dissolve completely under room temperature I heated the solution up to approx. 50°C and stirred it frequently.

After the EDTA was completely dissolved the solution was allowed to cool down to room temperature again. After that one pinch of indigo carmine was added. The solution had now a volume of exactly 100ml. Then I dissolved 0.12g glucose and expected that the glucose meter would show approx. 120mg/dl, which wasn't the case. The glucose meter displayed: WARNING. Below 20 mg/dL. LOW GLUCOSE.

I added 0.38g glucose more to the solution. Now I got a proper reading: 135mg/dl, same as the original control solution.

Conclusion: The glucose meter does not read the real glucose concentration of the control solution. In the end it doesn't matter. I can prepare different control solutions by adding small amounts of glucose, compare the result of the commercial glucose meter with the results of my home brew one and find a mathematical dependence between the results.

Summarized: A control solution similar to the ONE TOUCH ULTRA one can be prepared by dissolving 8g polyvinylpyrrolidone, 0.5g sodium benzoate, 0.5g EDTA (disodium salt), 0.5g D(+)-Glucose and additionally a pinch of indigo carmine in 91ml deionized water.