A number of analytical measurement assays have already been developed and documented with the open source colorimeter, including assays for measuring iron, nitrate, potassium and more. However there are still many more analytical measurements that can be carried out using this very simple and cheap measurement device. A list of assay development can be found on the main Assay PageColorimeter users are welcome (and encouraged) to contribute an assay or lab that they have developed with the colorimeter.    

Note that the purpose of this Wiki is to document and share information on measurement assays and labs. For now, updates to the open source colorimeter hardware and software will continue to be documented on the colorimeter blog.

 Parameter APHA Method Reference
 LED Wavelength Range
Preferred Method Overview of method
 Ammonia  Red LED (RGB) 0 - 8 ppm API test kit
 5 mL of tank water, add drops from bottles 1 and 2.
(& Magnesium)
 3500-Ca B   Eriochrome Blue Black R +  EDTA Titration method
  Mg calculated from calcium and total hardness measurement
 Iron 3500-Fe B     
 Lead    Hach Lead Columns
 Nitrate  Green LED (RGB) 0 - 200 ppm API test kit
 5 ml of tank water, add drops from bottles 1 and 2. Requires good mixing. 
 Nitrite 4500-NO2- B Green LED (RGB) 0 - 2ppm API test kit
 5 mL of tank water, add drops of nitrite bottle 1. 
  pH  557 nm pH 5.8-8.0 Phenol Red color change  
 Phosphate 4500-P 880 nm LED 0 - 2 ppm Hach PhosVer3 10 mL of sample, add packet and mix for 3 minutes on a stir plate. Stir plate
 Potassium  Red LED (RGB) 0 - 50 ppm LaMotte 5 mL of sample, add NaOH solution and NaTPB powder. Mix. Turbidity assay
 4500-Cl- C   Mercuric Nitrate Titration Method  
 Sulfate 4500-SO42-
 Green LED (RGB) 0 - 300 ppm Hach SulfaVer4 10 mL of sample, add contents of packet and shake. Turbidity assay
 Water hardness
 2340-C 625 nm (RGB)   Calmagite + EDTA Titration method  Off the shelf reagents or  Hach Hardness, Total (ManVer 2)

Other Assay Ideas

 MeasurementAPHA Method 
Colorimetric Assay or TitrationWavelength Development Stage Notes
 Zinc 3500-Zn B. Zincon method 620 nm Reagents in stock Hach powder pillows + off the shelf reagents
 Copper 3500-Cu C. Bathocuproine method484 nm Research 
 Manganese 3500-Mn  Persulfate method 525 nm  
 Boron 4500-B Carmine method 585 nm   
 Silica 4500-SiO2 Molybdosilicate method410 nm  
 Chlorine                    4500-Cl- G. DPD colorimetric method 515 nm  
 Atrazine    450 nm Research  not active
 Dissolved oxygen
 Alkalinity  Bromcresol Green-Methyl Red indicator