Measurement of urinary delta-aminolevulinic acid (ALA) by fluorometric HPLC and colorimetric methods.

We devised a fluorometric HPLC method for determining delta-aminolevulinic acid (ALA) in the urine of lead-exposed workers. With this fluorometric HPLC method and the conventional colorimetric method, the concentrations of urinary ALA in 84 lead workers were determined and compared. In the measurement of urinary ALA at lower levels (< or = 5 mg/1), the value of urinary ALA obtained by the fluorometric HPLC method was much lower than that obtained by the conventional colorimetric method, indicating that the colorimetric method also measures urinary ALA-like compounds such as aminoacetone. On the other hand, the measurement of urinary ALA at higher levels (> 5 mg/1) demonstrated that the ALA value obtained by the fluorometric HPLC method corresponded well with that of the conventional colorimetric method. A correlation coefficient between the fluorometric HPLC method and the colorimetric method was 0.856 for 60 urine samples with ALA < or = 5 mg/1, and 0.996 for 24 urine samples with ALA > 5 mg/1.