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Colorimetric PBG Assay (Ehrlich)


Modified Ehrlich Reagent

  1. Dissolve 1.0 gm p-dimethyl aminobenzaldehyde in 30mL glacial acetic acid.
  2. Add 8.0 mL 70% perchloric acid.
  3. Bring to 50 mL with glacial acetic acid.
  4. Store in the dark at 4˚C for about 2 weeks.

Porphobilinogen (PBG) Assay

  1. Mix 2.0mL sample with 2.0mL fresh modified Ehrlich reagent.
  2. Measure absorbance at 555nm.

Standard PBG

  1. Prepare 0.54mg/mL (2.2mM) PBG stock in 0.1M Tris pH 7.65.
  2. (Store at -20˚C until needed.)
  3. Dilute 1:1000 in H2O.
  4. Mix 2mL with 2mL fresh modified Erlich reagent.
  5. Measure absorbance at 555nm.
    • 1mM PBG = 61 abs units at A555.