r GHTMDD-201 Manuscript received: September 28th, 1992 Bulletin of the Chemists and Technologists of Macedonia, Vol. 11, No. 1 - 2, pp. 37 - 39 (1992) ~ ISSN 0350 - 0136 UDC 546.815 : 543.4; 543.4: 633.1 Short communication DETERMINATION OF LEAD IN CEREALS BY ELECTROTHERMAL ATOMIC ABSORPTION SPECTROMETRY Trajce Stafilov and Vesna Rizova* Institute of ChemistI)', Faculty of Science, The "Sv. Kiril i Metodij" University, POB 162, 91000 Skopje, Macedonia *Republic Institute of Health Protection, 91000 Skopje, Macedonia A new method for lead detennination in cereals by electrothCl7nal atomic absorption spectrometry was given. After mineralization and dissolution of the samples, lead was extracted with sodium diefhyldithiocarbamate in carbon tetrachloride. With this method it is possible to detCl7nyze lead in cereals up to 0.0075 P g' g" The relative standard deviation for the concentration region from 0.025 to 0.1 pg'g- is from 1.42 to 12.05%. Key words: lead determination, electrothermal atomic absorption spectrometry, cereals INTRODUCTION The presence of lead in plants and animals is particularydue to its H~lativelyhigh natural abundance in soil, and partially to contamination by indUstry (smelteries of lead and zinc, production of batteries and dyes) and by traffic (vehicle exhausts). In the human body lead is accumulated in the bones, from which it is mobilized when changes in the organism occur, in which case it blocks the work of the enzymes which are taking part in the synthe<is of hemoglobin (1].Also, higher levels of lead in the body can cause other disorders such as disorders in heart functions, higher blood pressure, influence on CNS, etc. [2]. Because of the fact that lead can be absorbed into the body by consumption of lead-containing food- stuffs, it is a necessary to determine levels of lead in various types offood precisely and exactly. In the work reviewed in written studies many methods for lead determination in food are presented. Usually, a me- thod of flame atomic absorption spectrometry (AAS) [3-5], eleCtrothermal AAS [6-10], AAS with hydride system [11], spectrometry with inductively coupled plasma (ICP) [12] or amperometry [13] have been used. In this work, a method for lead determination in cereals by electrothermal atomic absorption spectro- metry (ETAAS) with previous extraction of lead by sodium diethyldithiocarbamate in carbon tetrachlor- ide is given. Instrnmentation EXPERIMENTAL A Perkin-Elmer Models 703 and 5000 atomic absorption spectrophotometer equipped with a deu- terium background corrector, HGA-400 graphite fur- naceand Model 056 strip chart recorder were used. A lead hollow cathode lamp was used as a source. Optimal instrumental conditions for lead determina- tion (temperature and time) are: drying 120 cC and 30 s; charing 550 cC and 20 s; atomizing 2100 cC and 5 s; cleaning 2700 cC and 3 s. Procedure 10g milled cereals were transferred to a porcelain crucible and heated in a muffle furnace at a tempera- ture of 150 cC for 30 minutes, then at 250 cC for an 1 hour and at 550 Cc for 8 hours. The obtained mineral residue, after cooling at room temperature, was dissol- ved in 10 cm3of 1% (v/v) HN03 solution. Then, a 5 cm3 of 50% solution of ammonium citrate was added and by the addingofa 20% solutionofNaOH, the pH value was adjusted to about 11.5 (from 10.5 to 12.5). After that, 5 cm3of 5% KCN were added and the mixture was transferred to a separatory funnel. 5 cm3 of 0.2% sodium diethyldithiocarbamate were added and the mixture was shaken for a minute. After 10 minutes, 5 cm3CCl4were added. The mixture was shaken for 1-2 minutes and after 10 minutes, the organic layer was filtered off and from this solution a volume of 20 mm3 was introduced in the graphite furnace with an Eppen- dorff pipette, and lead was determined by ETAAS. It is also necessary always to prepare the blank sample parallel with the cereals samples for the correc- tion of the zero value.