A procedure based on solid phase extraction with a strongly acidic cation-exchanger Dowex 50W×8-200 was proposed to pre-concentrate and determine ultra-traces of Li in different floral honeys. When loading 10% (m/v) honey solutions onto columns packed with the cation-exchanger, Li+ ions were retained on the resin along with K+ and Na+, while simple sugars were passed through columns and were entirely found in effluents. In turn, columns were washed with water and eluted with a 1.0 mol L-1 HCl solution to strip Li+ that was subsequently determined in respective eluates by flame optical emission spectrometry (FOES). The proposed method was characterized by a limit of detection (LOD) of 0.05 ng g-1 of Li and later used for analysis of several raw and commercial mono- and multi-flower honeys. It enabled to determine from 0.4 to 5.3 ng g-1 of Li with precision being within 8-11%. Accuracy of this sample pre-treatment procedure and analysis method was assessed applying spike recovery tests. Recoveries of added Li were found to be within 98 to 106%, demonstrating trustworthiness of results achieved.
lithium; honey; pre-concentration; determination; flame optical emission spectrometry
