Colorimetric PBG Assay (Ehrlich)

COLORIMETRIC PORPHOBILINOGEN ASSAY (EHRLICH) 
 Modified Ehrlich Reagent 
 
 Dissolve 1.0 gm p-dimethyl aminobenzaldehyde in 30mL glacial acetic acid. 
 Add 8.0 mL 70% perchloric acid. 
 Bring to 50 mL with glacial acetic acid. 
 Store in the dark at 4˚C for about 2 weeks. 
 
 Porphobilinogen (PBG) Assay 
 
 Mix 2.0mL sample with 2.0mL fresh modified Ehrlich reagent. 
 Measure absorbance at 555nm. 
 
 Standard PBG 
 
 Prepare 0.54mg/mL (2.2mM) PBG stock in 0.1M Tris pH 7.65. 
 (Store at -20˚C until needed.) 
 Dilute 1:1000 in H 2 O. 
 Mix 2mL with 2mL fresh modified Erlich reagent. 
 Measure absorbance at 555nm.
 
 1mM PBG = 61 abs units at A555.