Evaluation of the effectiveness of a high-speed method of screening phthalate esters in polymers using pyrolyzer/thermal desorption–gas chromatography-mass spectrometry

Abstract

The international analytical standard IEC62321–8 specifies a pyrolyzer/thermal desorption-gas chromatography-mass spectrometry (Py/TD-GC/MS) method of screening seven phthalate esters in polymers that requires an analysis time of 30 min. This article describes a new, high-speed method that dramatically reduces this analysis time to about 12 min with a method detection limit (MDL) under 30 mg/kg for all phthalate esters. When this high-speed method was used to analyze phthalate ester-containing reference materials of various base polymers, the phthalate ester recovery rates ranged from 92 to 115%. The conventional method described in IEC62321–8 and this high-speed method were also used to analyze real samples and reference materials (24 samples in total) to evaluate equivalence between the two methods. Linear approximation of a scatter plot of quantitative results obtained by both methods produced a regression line that showed good correlation between the methods with a slope of 1.0326 and a coefficient of determination (R2) of 0.9699. A Bland-Altman plot was also used to analyze the concentration range under 2000 mg/kg, which is near the phthalate ester level restricted by the RoHS (Restriction of the use of certain Hazardous Substances in electrical and electronic equipment) Directive (1000 mg/kg) and important for screening outcomes. As a result, the bias in the difference between the two methods was +20 mg/kg, the 95% confidence interval limits of agreement were -134 mg/kg and +175 mg/kg, and no fixed bias or proportional bias was observed. These findings indicate that the high-speed method is equivalent to the conventional method and can be used to screen for phthalate esters.