[Improved method for the determination of urinary delta-aminolevulinic acid in lead workers]

An improved method for the determination of urinary delta-aminolevulinic acid (ALA) as an indicator of lead absorption is described. It is a modification of the analytical procedure described by Tomokuni and Ogata in 1972. In the present method, the spot urine from lead-exposed workers which was diluted 3-fold with distilled water beforehand was used as the sample to eliminate as much as possible the urinary matrix interference. In addition, methyl acetoacetate was used as the condensation reagent for ALA-pyrrole, because the color intensity of ALA-pyrrole was higher with the use of methyl acetoacetate than that with ethyl acetoacetate which was used in the original method. The urinary ALA value determined by the present method was similar to that measured using an internal-standard addition method. This method is suitable as a rapid and inexpensive screening procedure for the routine quantitative analysis of urinary ALA.