Abstract
The level of urinary δ-aminolevulinic acid (ALA) has been widely used as a measure of the biological effect of lead. The determination of urinary ALA has been carried out using ion-exchange column chromatography which is necessary for removal of interfering substances present in the urine, namely, porphobilinogen, urobilinogen and urea.1-3) These methods are more accurate for determining ALA in urine, but are time-consuming in large-scale routine analysis. A simpler and more rapid method for the determination of urinary ALA using liquidliquid extraction instead of column chromatography was developed in 1972.4) Presently, this simple method is widely used for the routine screening of workers exposed to lead. In this procedure, ALA-pyrrole is separated from most of the interfering substances present in the urine by extraction with ethyl acetate. Recently, we found that the recovery of ALA from normal urine is inversely correlated with the urine density, when urinary ALA is determined by this simple
