Journal: bioRxiv

Article Title: Portable low-cost optical density meter

doi: 10.1101/2021.05.14.444207

Figure Lengend Snippet: Blue food dye dilution series for three samples (D1, D2, and D3), comparing OD values obtained from the OD meter to values from a SpectraMax M3 spectrophotometer at 590 nm. At each step in the dilution series, the dye concentration was reduced by 20%, down to OD values of 0.08, 0.07, and 0.05 for D1, D2, D3, respectively. The dark references for samples D1 and D2 were acquired with cuvettes filled with blue dye ( I dark = 70 and 73, respectively). The dark reference for sample D3 was acquired using the 3D printed light blocking insert ( I dark = 22). The blank reference for all samples was acquired with pure water in a cuvette ( I blank = 1000, 1019, 980, for D1, D2, D3, respectively). Dashed lines are linear fits to the data points of the same color up to the OD range of each plot. (A) OD values up to 2.2. In this range the I dark calibration for D3 leads to underestimating the OD values above OD 1.1 (green points and line). The optimal I dark for this sample is 60, which properly linearizes the curve (purple points and line). (B) OD values up to 1.1. In this range the underestimation of OD in sample D3 due to the incorrect I dark calibration is not significant.

Article Snippet: At each step in the dilution series, the dye concentration was reduced by 20%, down to OD values of 0.08, 0.07, and 0.05 for D1, D2, D3, respectively. shows three dilution curves of blue food dye, with the SpectraMax OD value in the X axis and the low-cost device OD value in the Y axis.

Techniques: Spectrophotometry, Concentration Assay, Blocking Assay