Determination of Ultra-trace Migration of Hexavalent Chromium in Toy Materials by Online Enrichment/High Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry

KeyWord:online enrichment  high performance liquid chromatography  inductively coupled plasma mass spectrometry  migration of hexavalent chromium  ultra trace  toy materials

Abstract:

      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¡Á50 mm,5 ¦Ìm) using 10 mmol/L ammonium nitrate as mobile phase,then transfered to a Dionex AG7 anion column(4.0 mm¡Á50 mm,10 ¦Ìm) 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 ¦ÌL,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%.