8-Hydroxyquinoline–chloroformsingle drop microextraction and electrothermal vaporization ICP-MS for the fractionation of aluminium in natural waters and drinks

Abstract

A new method of cycle-flow single drop microextraction (SDME) combined with electrothermal vaporization (ETV)-ICP-MS was proposed for the fractionation of aluminium with 8-hydroxyquinoline (8-HQ) as extractant. Several factors affecting the separation of aluminium species, such as sample flow rate, microdrop volume, pH and extraction time were investigated, and the optimized microextraction conditions were established. The experimental results indicated that in a pH range of 5.0–7.5 labile monomeric Al species (free Al (Al³⁺, AlOH²⁺, and Al(OH)₂⁺)) could be extracted by the 8-HQ–chloroform microdrop while non-labile monomeric Al species (Al–citrate, Al–SO₄, Al–F, Al–EDTA, Al–humic) directly passed through the microdrop. Labile aluminium in the post-extraction organic phase was directly determined by ETV-ICP-MS. The total Al was determined using pneumatic nebulization (PN)-ICP-MS. The non-labile aluminium was obtained by subtraction of labile aluminium from the total aluminium. Under the optimized conditions, the detection limit of the method was 3.3 pg mL⁻¹ and the relative standard deviation for 1 ng mL⁻¹ of Al was 10%. After 8 min of extraction, the enrichment factor was 210. The proposed method has been successfully applied to the determination of Al species in natural water, coffee and tea infusions. The results were comparable with that obtained by the 8-HQ loaded silanized silica gel microcolumn system and conventional liquid–liquid extraction system.