Complexation effect of antimony compounds with citric acid and its application to the speciation of antimony(III) and antimony(V) using HPLC-ICP-MS

In this work, a complexation effect of Sb compounds with citric acid was ob served using electrospray mass spectrometry (ES-MS). It was found that both Sb(III) and Sb(V) could form complexes readily with citric acid in an aque ous solution at room temperature. These complexes were found to be very sta ble in various matrices (moat water and aqueous extracts of airborne partic ulate matter), therefore, a novel HPLC-ICP-MS analytical method for the spe ciation of Sb(III) and Sb(V) in environmental samples was developed by usin g the observed complexation effect. Sb(III)- and Sb(V)-citrate complexes we re separated on a PRP-X100 anion-exchange column with 10 mmol l(-1) EDTA-1 mmol l(-1) phthalic acid (pH 4.5) as a mobile phase. All complexes were ret ained on the separation column. and none of them eluted in the solvent fron t. Low detection limits of 0.05 mug l(-1) and 0.07 mug l(-1) were achieved for Sb(III) and Sb(V), respectively. The calibration curves were linear ove r the range of 1.0-250 mug l(-1) for the investigated Sb species. The preci sions, evaluated by using the relative standard deviation (%RSD) with a 2 m ug l(-1) standard solution. were 1.8% and 3.3% for Sb(III) and Sb(V), respe ctively. Several advantages of the developed method. such as improving chro matographic separation, stabilizing Sb compounds in a water sample, and pre venting Sb(III) from oxidizing to Sb(V) during the ultrasonic-assisted and microwave-assisted extraction of an airborne particulate matter (APM) sampl e using 26 mmol l(-1) citric acid as an extraction solvent. and alleviating the adsorption of Sb compounds on the sample surface, were observed. The d eveloped method enabled us to detect the most toxic Sb specie, Sb(III), in an APM sample for the first time.