Another possibility if you know for sure a certain assay has a 0 intercept, then you could plot A=0.4834c+0.0183 using 0.1, 0.2, 0.3 all the way up to 1 in Excel, then add in 0, 0 to the data set & graph and then change the trendline to "set intercept = 0". This would give a new equation of A=0.4654c with still a respectable R^2 of 0.997. Changing the graph axes to switch the x an y values would then give c=2.1508A. The benefit of doing this way is increased sensitivity for very low absorbance values, where subtracting the 0.0158 (although very small) would give no detectable concentration below a 0.0158 absorbance threshold.