Multi-walled carbon nanotube modified with 1-buthyl 3-methyl imidazolium hexaflouro phosphate supported on sawdust as a selective adsorbent for solid phase extraction of Bi(III).

Multi-walled carbon nanotube (MWCNT) was dispersed and loaded with 1-buthyl 3-methyl imidazolium hexaflouro phosphate ([BMIM]PF(6)), supported on sawdust and used as a new adsorbent for preconcentration of trace amount of bismuth. In this method, Bi(III) ions are retained by the adsorbent in a column after formation of negative complex with iodide. BiI(4)(-) complexes are retained on MWCNT-[BMIM]PF(6) through the electrostatic interactions with positive charge of imidazolium ion. The adsorbed complex is eluted from the column with a solution of nitric acid and determined by flame atomic absorption spectrometry (FAAS). The effect of various parameters, such as pH, sample volume, concentration and volume of nitric acid as eluent, iodide concentration in sample solution, and interfering ions was investigated in order to achieve highest sensitivity. The calibration graph was linear in the range of 4-300 ng mL(-1) for Bi(III) in the initial solution. The limit of detection based on 3S(b) was 2.3 ng mL(-1) for Bi(III). The relative standard deviation for ten replicate measurements of 20 and 80 ng mL(-1) was 2.3 and 0.98%, respectively. The method was applied to the determination of Bi(III) ions in river water, tap water and drug samples.