you dont generate it to the best of my knowledge, you buy it in a small tank and using a regulator and some very small tubing, you bubble it gently through your sample. First you need to reduce the sample with a tiny amount of dithionite, then split it between 2 cuvettes, bubble one with the CO and do a difference spectrum. The absorbance at 450nm is proportional to P450 content. If you have a big shoulder at 420 you were too rough in the preparation and denatured the P450.