Determination of PAHs in Tires by GC/MS and NMR How Well Does the ISO 21461(NMR)Method Help Uphold the EU’s Original PAH Standards for the Tires?

摘要

The current EU rule uses ISO 21461 method which uses NMR(nuclear magnetic resonance)spectrometer signals from the "Bay-H" of PAHs to specify whether or not tires meet the EU’s PAH standards.However,few studies have been done to correlate the EU’s original PAH standards and the ISO 21461(NMR)method’s 0.35% rule.This study shoots for developing a GC/MS method with which to determine PAH concentrations in the tires and then compares the results obtained from the GC/MS and the ISO 21461(NMR)methods.A practical procedure for extracting targeted PAHs from tire rubber was developed using experiments that tested the following: 1)The PAH extraction efficiencies of 7 organic solvents,2)The effect of rubber bit size on PAH extraction efficiencies,3)The precision and accuracy of the developed method using custom-made rubber slabs.Once the PAH method was established based on these studies,additional studies included: a)How comparable the data are between toluene and acetone extractions of the EU-regulated 8 PAHs on 3 custom-made rubber slabs using both the NMR and the developed GC/MS methods,b)How comparable GC/MS and NMR data are from 50 commercial tires made after 01/01/2010 extracted with toluene,and c)How comparable are GC/MS and NMR data from 12 EU-made tires extracted separately with toluene and acetone.The results indicate the following: A)Toluene was the most efficient solvent for extracting PAHs from rubber,B)Rubber bit size did not affect extraction efficiencies of 4-and 5-ring PAHs,C)The developed GC/MS method averaged 69 % accuracy and 8.3 %RSD(percent relative standard deviation)using Soxhlet extraction with toluene,D)GC/MS data reflected the projected PAH concentration for the 3 custom-made rubber slabs whereas the NMR data did not follow the expected trend.E)Most importantly,of the 50 tires tested,ISO 21461(NMR)passed 82 %(41/50)of which 85 %(35/41)were considered as "false pass" based on the GC/MS results.F)Of the 12 EU-made tires,11 passed based on NMR results but only 4 passed based on "sum of 8 PAHs" and only 2 based on BaP(benzo[a]pyrene)concentration using the GC/MS method.On average,acetone extracts resulted in 14.1% higher Bay-H% data,yet provided lower BaP and "sum of 8 PAHs" values(by 90.1%> and 60.5%,,respectively),the pass/fail results were identical to the toluene extracts.Conclusions: The ISO 21461(NMR)method "for the most part" does not produce data proportionally reflecting the concentrations of BaP or "sum of 8 PAHs" in the tires.The PAH method presented here using GC/MS determines individual PAH levels in the tire extracts rather well.A good GC/MS method should be adopted as the official method for upholding the EU’s original PAH standards for tires.