Improvement in HPLC separation of porphyrin isomers and application to biochemical diagnosis of porphyrias.

Background: Identification of porphyrias relies on the measurement of different porphyrins in urine, feces and plasma. Separation of porphyrin isomers is essential for the differential diagnosis of some porphyrias.
Method: Separation of naturally occurring porphyrins was achieved on a Chromolith RP-18 column with fluorimetric detection using a methanol/ammonium acetate gradient mobile phase. Fecal and plasma porphyrins were extracted with acetonitrile and water at different pH values.
Results: Eight porphyrins including protoporphyrin eluted within 20 min with good resolution of each of the I and III positional isomer pairs for standards, urine and plasma, and within 50 min for feces. Improvement of the extraction method for fecal and plasmatic porphyrins resulted in high recovery (up to 89%) and reliable quantification of protoporphyrin.
Conclusions: The present RP-HPLC method is specific and efficient for routine analysis of porphyrins in human urine, feces and plasma.