Sensitive ‘one drop’ flame atomic absorptiometric determination of cadmium in botanical samples using direct nebulization of chloroform extract

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Abstract
After microwave digestion of solid samples with an acid mixture in a pressurized double poly(tetrafluoroethylene) bomb and the removal of iron in the sample solution by extraction with 2-hydroxy-4-isopropylcycloheptatrienone dissolved in benzene, the cadmium–ammonium pyrrolidin-l-yldithioformate (APDC) complex was extracted into chloroform. Direct nebulization of the chloroform extract of cadmium–APDC complex into the flame gave a very sensitive signal intensity. The background corrected signal intensity obtained by nebulizing 40 µl of the extract was about 4.5 times larger than that obtained by nebulizing 100 µl of aqueous solution and the detection limit obtained with an injection volume of 40 µl was 1.2 ng ml–1 or 50 pg [signal-to-noise ratio (S/N)=3]. Cadmium was determined by ‘one-drop’ flame AAS with deuterium background correction with an injection volume of 40 µl of chloroform extract. The present method was successfully applied to the determination of cadmium in botanical certified reference materials, National Institute for Environmental Studies, certified reference material (NIES CRM) No. 1 Pepperbush and No. 10 Rice Flours (low and medium), and National Institute of Standards and Technology, Standard Reference Materials (NIST SRMs) 1571 Orchard Leaves, 1572 Citrus Leaves and 1575 Pine Needles and the results (112 ± 6 and 29 ± 2 ng g–1) for Orchard Leaves and Citrus Leaves were in good agreement with the certified values (110 ± 10 and 30 ± 10 ng g–1).