well, don´t take my word for it, but the way I understand it, the dilution with water and dye reagent do not matter in the measurement, because you use the same amounts of them on both the standard and the sample. So both OD´s you get are relative to each other. The reason why you dilute the samples anyway is to get to a OD-region which is nicely measurable, if there is a too high protein concentration in the tube, the test will produce wrong numbers. In the end all you do is compare the OD you got from your sample with the one of your standard. And you only can compare them if they are equally diluted.
But as I told you, I´m not the expert on this stuff either:(., so this stuff might be horrible wrong too. Some experts help here please?
you can make a Chart with your datapoints (OD´s of the standard) and then let Excel add a trendline to the chart. For this, you need to right-click on the graph and choose "add trendline --> linear".
I hope I could help you a bit,
greets,
kixxer
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