DETERMINATION OF LEAD IN ILLICIT DRUGS BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY USING PALLADIUM AS CHEMICAL MODIFIER

A method for the determination of lead in illicit heavy drugs by electrothermal atomic absorption spectrometry using palladium as a chemical modifier was developed. A sample of drug, 0.5 g, was dissolved in 2 mi of HNO3 35.0% (v/v), diluting to 10 mi with ultrapure water. First, a comparative study of palladium, magnesium and palladium-magnesium used as chemical modifiers was carried out, and it was found that palladium alone is adequate to stabilize lead at a charring temperature of 1000 degrees C. The optimum atomization temperature was 2400 degrees C. A study on the insertion of a cool-down step before the atomization step and a study on the omission of the charring step were made. Neither approach was advantageous. A limit of detection of 31.4 mu g kg(-1) and a characteristic mass of 24.4 pg were obtained, with analytical recoveries between 98.0 and 105.0% for a 2.5-40 mu g l(-1) concentration range. The within-batch precision (n = 11) was oscillated between 6.4 and 0.2% for a drug solution spiked with 0 and 40 mu g l(-1), respectively. Finally, a study of some interferences, and a study of the precision and analytical recovery on the amount of sample were also carried out.