THE CASE OF SULFAMETHOXAZOLE

To do so, the previously mentioned solutions are prepared so their final concentration corresponds to a mid-range OD, in order to minimize errors.
For raw material, the mid-range OD value is 0.673, corresponding to a concentration of 1 mg/100 mL. However, it is impossible to weigh 1 mg without any significant error. A new dilution should be considered.

Weighed raw material, sulfamethoxazole = 21 mg

A solution of 21 mg/100 mL is prepared by placing powder in a 100 mL volumetric flask, which should correspond to a theoretical OD of 14.13 according to the equation involving specific absorbance (cf. Case of sulfamethoxazole).
This solution is the raw sulfamethoxazole stock solution. To obtain a mid-range OD value, we will therefore make a 1/20 dilution.