The natural occurence of trace metals in human teeth

Abstract

Since atomic absorption spectrophotometry was introduced for the determination of magnesium in blood serum by Willis in 1960, many studies have been published on the use of the method for determination of trace metals in biological materials. However, reports on trace heavy metals in teeth are scarce. Much more analytical data are necessary.The present report describes a method for using atomic absorption spectrophotometry for the determination of trace heavy metals (lead, copper, cadmium and zinc) in extracted human permanent teeth.(1) A tooth was dissolved in 5 ml of nitric acid, and then dried and ashed by heating in a silica crucible for 10 hr in a muffle furnace at 400-450°C. The ash was dissolved by gentle warming in 5ml of hydrochloric acid and transferred to a 20 ml volumetric flask. Distilled water was added to make 20ml of sample solution.(2) Mixed working standard solutions were used for the determination of lead, copper and cadmium.(3) Lead, copper and cadmium were chelated by 3ml of 1% ammonium pyrrolidine dithiocarbamate (APDC) and extracted simultaneously with 5 ml of methyl isobutyl ketone (MIBK) from 10 ml of the sample solution at pH 3.5. Zinc was determined directly in diluted water solutions.(4) Interferences of calcium in measurements were investigated. Calcium interferences were compensated by the addition of citric acid both to the working standards and sample solutions, and also by addition of calcium to the working standard solutions.(5) Detection limits were approximately 0.7 μg Pb, 0.3 μg Cu and 0.03μg Cd in a final volume of 20ml, equivalent to one whole tooth.