The standard curve is a graph that relates the absorbance at 400 nm with the concentration of haemoglobin in mg/dl. To obtain the concentration from the absorbance value, we enter in the x-axis (absorbance at 400 nm) with the value 0.40 (the line between 0.2 and 0.6), we extrapolate the line to the curve and read the correspondent value on y-axis (concentration in mg/dl): 100 mg/dl.
So, we convert the concentration from mg/dl to g/dl by dividing into 1000:
100 mg/dl x 1 g/1000 mg = 0.1 g/dl
Therefore, the concentration of haemoglobin of the patient is 0.1 g/dl.
