A method of high performance liquid chromatography-inductively coupled plasma mass spectrometry(HPLC-ICP-MS) with online enrichment was established for the determination of ultra trace migration of hexavalent chromium in toy materials.The hexavalent chromium in the sample was firstly concentrated with an Agilent BIO WAX NP5 anion exchange column(4.6 mm×50 mm

5 μm) using 10 mmol/L ammonium nitrate as mobile phase

then transfered to a Dionex AG7 anion column(4.0 mm×50 mm

10 μm) through a valve switching

separated by elution with 75 mmol/L ammonium nitrate

and finally analyzed by ICP-MS.The on line enrichment time was set at 4 min

the injection volume was 900 μL

the flow rate in enrichment path was 0.4 mL/min

and the off flow rate was 0.6 mL/min.Results showed that there was a good linearity for hexavalent chromium in the range of 2-20 ng/L

with a detection limit of 1.93 ng/L and a relative standard deviation(RSD) of 3.9%.Compared with the conventional sample injection

this method had an about 8.1 times higher enrichment factor with enrichment efficiency of 90%.Samples from three categories of toy materials according to Directive 2009/48/EC of the European Parliament and of the Council of 18 June 2009 on the Safety of Toys were spiked at 5 ng/L and 10 ng/L

and recoveries for hexavalent chromium were in the range of 93.4%-111%.