The usage of modified silicagel for lead determination, preconcentration and separation by flame atomic absorption spectrometry

Lead is recognized worldwide as a poisonous metal. Thus the determination of this element is often required in environmental, biological, food and geological samples. However, these analyses are difficult because such samples contain relatively low concentrations of which fall below the detection limit of conventional analytical techniques such as atomic absorption spectrometry (AAS). Therefore, lead should be preconcentrated to with some preconcentration methods. In this study, silicagel was modified according to homogeneous route with ligand including functional groups such as thiobarbituric acid (L1), 5-amino-1, 3, 4-thiadiazole-2-thiol (L2), chromotropic acid (L4), thiosalicylic acid (L5) and o, o?-diethyldithiophosphate (L6). Modified silicagel sorbents (P1, P2s, P4, P5 and P6) was characterized by FT-IR, 13C CPMAS NMR, 29Si -NMR and 31P-NMR for O, O?-diethyldithiophosphate modified silicagel, elemental analysis, surface analysis by XPS and heat transfer analysis with TGA-DTA. Moreover, surface area was determined by BET analysis for modified silicagel sorbents. All techniques were shown that ligands were bound to silicagel. Inorganic lead determinations were made by AAS and organic lead species (tetreethyllead and tetramethyllead) was made by Gas chromatography- Mass Spectrometer (GC-MS) with SIM method. Optimum conditions for Pb (II) sorption parameters such as pH, contact time, amount of the sorbent, Pb (II) concentration and solution volume and for Pb (II) desorption parameters like eluent solution, its amount and concentration was determined by FAAS. For all sorbents, sorption capacities were obtained and enrichment factors were calculated. Optimum pH, contact time and sorbent amount was found as 5, 8, 30 minute and 0, 1 g, respectively, Eluent solution was chosen as a solution of EDTA for P1, P2S and P4, HNO3 for P5 and HCl for P6. Lead preconcentration factors of sorbents were found between 15 and 150. Also, sorbent capacities were obtained as an average 46 and 72 ?mol Pb (II)/g sorbent. Synthesized sorbents were used sour cherry juice spiked Pb (II) determination and it was observed that only P5 sorbent completely sorbed to Pb (II). Also, lead in foreign ions was sorbed by sorbents and only P5 sorbent showed selectivity to Pb (II) ions. P4 sorbents showed affinity to tetraethyllead and tetramethylead species. Limit of detection and limit of quantification were found as 3,69 ?gL-1 and 12,29 ?gL-1, respectively, for P5 sorbent. Key Words: Modified silicagel, Lead, Thiobarbituric acid, 5-Amino-1,3,4-Thiadiazole-2-thiol, Chromotropic acid, Thiosalicylic acid and o,o?-Diethyldithiophosphate, FAAS, GC-MS 1