The determination of chlorine in plastic using isotope dilution inductively coupled plasma mass spectrometry

Abstract

The determination of chlorine (Cl) in plastic using isotope dilution inductively coupled plasma mass spectrometry (ID-ICPMS) combined with different sample pretreatment procedures was examined in the present study. In order to validate the analytical results for Cl, certified reference materials (CRMs) of BCR 680 and BCR 681, which have certified Cl concentrations in the polyethylene resin pellets, were used. Both the microwave acid digestion and combustion-absorbent procedures were examined as different sample pretreatment procedures, and ICP triple quad mass spectrometer (ICP-MS/MS) with a mass-shift method in MS/MS mode using collision reaction gas of hydrogen (H₂) was applied for the accurate and precise determination of Cl by ID-ICPMS. In the case of the microwave acid digestion procedure combined with ID-ICPMS, an accurate determination could not be demonstrated due to a large Cl signal from the reagent blank, which resulted in a poor signal to background (S/B) ratio as well as poor isotope ratio measurement of Cl in ID-ICPMS. On the other hand, an accurate determination could be demonstrated using the combustion-absorbent procedure since any large Cl signal from the absorbent (0.1% H₂O₂) used as the reagent blank were not observed, which could provide a sufficient S/B ratio of Cl to achieve an accurate and precise Cl isotope ratio measurement in ID-ICPMS. From these results, though the microwave acid digestion procedure was unfortunately considered to be ineffective, the combustion-absorbent procedure combined with ID-ICPMS using ICP-MS/MS could be used for the accurate and precise determination of Cl in plastics.