Speciation analysis of antimony by high-performance liquid chromatography inductively coupled plasma mass spectrometry using ultrasonic nebulization

The two inorganic Sb species Sb(III) and Sb(V) as well as trimethlyantimony dichloride (TMSbCl2) were separated by anion exchange chromatography. HPLC eluents were directly aspirated into the plasma of an ICP-MS using ultraso nic nebulization (USN) with membrane desolvation. Leaching of Sb from glass bottles, especially pronounced under alkaline conditions, distinctly incre ased background Sb-121 signals. The use of conventional HPLC syringes made of glass resulted in non reproducible blank signals for Sb(V). To overcome these problems, polyethylene bottles for the storage of mobile phases and p lastic syringes for the injection of Sb compounds onto the analytical colum ns were employed. The analysis of Sb(III) standard solutions in the sub mu gl(-1) range prepared by dilution of stock standard solutions with high-pur ity water revealed that Sb(III) is easily oxidized to Sb(V) within a few ho urs. Deoxygenating the water for dilution of standards by flashing working standard solution with helium or using 1.25 mM EDTA - which served as mobil e phase for the chromatographic separation - for the dilution of standards, no oxidation of Sb(III) was observed, at least for 8 h. USN parameters, su ch as the temperature of the heating area and of the desolvation area as we ll as the sweep gas flow rate were systematically optimized. Decreasing the USN heating temperature from the conventional settings of 140-80 degreesC enhanced signal intensities by similar to 25% and caused no condensation of the aspirated mobile phase. After optimization detection limits for all th ree Sb species in the low ng l(-1) range could be established, namely 14 ng l(-1) for Sb(III), 12 ngl(-1) for Sb(V) and 9 ngl(-1) for TMSbCl2. (C) 2001 Elsevier Science B.V. All rights reserved.