[Direct determination of lead in urine with a new micro-method of flame atomic absorption spectroscopy (loop-AAS)...

This paper describes a method for the direct determination of lead in urine using the newly developed loop AAS. In this technique, the sample to be analyzed is dried outside the flame on an electrically heated iridium loop. The loop is introduced into the flame of an AA-spectrometer by a precise transport mechanism. The detection limits of slightly and medium volatile elements are one or two orders of magnitude lower than those of conventional flame-AAS. By using an additional ceramic stagnation tube arranged in the flame, the power of detection is increased once more by about a factor 10. The high chemical resistance of iridium permits the use of strong acids for decomposition of the urine directly on the loop. The relative standard deviation is about 0.04 for a lead concentration of 90 micrograms/l. The detection limits are 3 to 10 micrograms/l depending on the AA-spectrometer used. The accuracy of the method is controlled by the analysis of control urine and by analyzing the same samples by graphite furnace-AAS.