[A simple photometric test for the routine determination of delta-aminolaevulinic acid in urine for the control of lead exposure].

A simple and accurate method for determining urinary concentration of delta-aminolaevulinic acid (delta-ALA) is described. It is based on an improved application of the principle, first introduced by Tomokuni and Ogata, that a colourless pyrrole derivative is produced by the action of acetic acid ethyl ester on delta-ALA, which develops a violet colour on addition of Ehrlich's reagent. The influence of interfering substances was found to account for 20 plus or minus 3% in all examined urines samples. It is, therefore, recommended that an aqueous delta-ALA standard be prepared which contains only 80% of the concentration used in the calculation. Exact values are obtained in this way and the need for setting up a calibration curve by adding delta-ALA is avoided.