When a serum blank is required (icteric or hemolyzed specimen), label
another tube SB (Step 1. "Procedure" section). Add 1.0 mL "normal"
saline, 0.01 mL serum, mix by inversion, transfer to cuvet and read
absorbance (Asb) vs distilled water at 500 nm. Use this value to correct
that of the unknown as follows