BOM and instructions:  http://www.appropedia.org/Open-Source_Photometric_System_for_Enzymatic_Nitrate_Quantification For technical details see paper: Wittbrodt BT, Squires DA, Walbeck J, Campbell E, Campbell WH, Pearce JM. (2015) Open-Source Photometric System for Enzymatic Nitrate Quantification. PLoS ONE 10(8): e0134989. doi: 10.1371/journal.pone.0134989 open access: https://www.academia.edu/14702947/Open-Source_Photometric_System_for_Enzymatic_Nitrate_Quantificatio...https://vimeo.com/135386657