I am quite busy to develop other analytical reactions for spectrophotometry these days. It is not always easy to get all the required chemicals as we have many restrictions in Germany regarding chemicals.
First, I want to develop a pH test using a double indicator system comprising methyl red and bromothymol blue to cover the complete pH range. I need to do a couple of experiments to determinate the optimal mixture of both solutions. Methyl red is also used to detect E. coli bacterium.
Second, I want to develop a nitrite test. Some of the gram negative bacteria species that most commonly cause urinary tract infections have enzymes that reduce the nitrate present in urine to nitrite. I will probably use Griess Reagent for nitrite determination. 1-Naphthylamine will be replaced by N-(1-naphthyl)ethylenediamine dihydrochloride because 1-Naphthylamine is carcinogenic. The required phosphoric acid is on the other hand not a problem to get as it is used in Germany as a rust remover.
To get pure Potassium nitrite or Sodium nitrite as a private person is a problem in Germany because both are toxic. I think I need to extract it from curing salt.
Preparing Griess Reagent
To get 50 ml 5% phosphoric acid from commercially available 85% phosphoric acid, we compute:
Means we need 5 parts 85% phosphoric acid and 80 parts deionized water.
To obtain 50 ml of 5% phosphoric acid we therefor need:
More information will follow as soon as I make progress.