Nonspecificity of urinary lead measurements by atomic absorption spectroscopy. A spectrophotometric method for correction.

Lead measurementsby direct AAS at 217 nm on a pooled urine sample gave values of 57 pg/i by the method of standard additions. In contrast, dithizone procedures gave values of 15-20 pg/i. Studies demonstrated that various urine salts and organic compoundscontributed to the absorbance at 217 nm. These native urine materials also give a similar absorbancevalue at 220 nm, a line not related to lead emitted by the lead hollow cathode tube. Thus, correction of the nonlead absorbance was possibleby subtracting the A220from A217.Utilizing this correction, the standard addition procedure gave values of 12 pg/i. The correction technic was also applied to the lead isolation-concentration technic of Kopito and Shwachman (3) which employs bismuth coprecipitation. The simplicity of operations, increased sensitivity and reproducibility obtained by coupling the AAS correction technic with bismuth coprecipitation recommends it as a method for serious consideration.