1.1This test method covers the determination of the purity of AMS (α-methylstyrene) by gas chromatography. Calibration of the gas chromatography system is done by the external standard calibration technique.

1.2This test method has been found applicable to the measurement of impurities such as cumene, 3-methyl-2-cyclopentene-1-one, n-propylbenzene, tert-butylbenzene, sec-butylbenzene, cis-2-phenyl-2-butene, acetophenone, 1-phenyl-1-butene, 2-phenyl-2-propanol, trans-2-phenyl-2-butene, m-cymene, p-cymene, and phenol, which are common to the manufacturing process of AMS. The method has also been found applicable for the determination of para-tertiary-butylcatechol typically added as a stabilizer to AMS. The impurities in AMS can be analyzed over a range of 5 to 800 mg/kg by this method. (See Table 1.) The limit of quantitation for these these impurities averages 4 mg/kg, while the limit of detection averages 1.2 mg/kg. (See Table 1.)

Compound	Repeatability (r)	Reproducibility (R)	Range Studied

Acetone	1.61 + 0.035*Acetone	0.47 + 1.10*Acetone	0.5 - 26
Cumene	−0.46 + 0.031*Cumene	7.88 + 0.19*Cumene	45 - 290
nPropylbenzene (NPB)	2.11 + 0.03*NPB	−7.81 + 0.37*NPB	55 - 195
Phenol	1.84	3.65 + 0.58*Phenol	1 - 40
tertButylbenzene (TBB)	−1.22 + 0.035*TBB	3.63 + 0.087*TBB	150 - 650
secButylbenzene (SBB)	4.23 + 0.019*SBB	21.60 + 0.25*SBB	200 - 765
mCymene	0.31 + 0.035*mCymene	2.34 + 0.35*mCymene	2 - 50
oCymene	1.63	8.00	29 - 31
pCymene	5.12	15.79	10 - 18
cis-2-Phenyl-2-Butene (CPB)	0.17 + 0.030*CPB	5.39 + 0.11*CPB	50 - 225
trans-2-Phenyl-2-Butene (TPB)	1.57	0.54 + 0.20*TPB	19 - 70
1-Phenyl-1-Butene (PB)	4.00 + 0.018*PB	0.17 + 0.19*PB	0.2 - 735
Acetophenone (AP)	-1.09 + 0.15*AP	1.17 + 0.63*AP	15 - 115
para-tert-Butylcatechol (PTBC)	2.21	17.82	10 - 19
2-Methylbenzofuran (MBF)	0.33 + 0.76*MBF	0.75 + 0.60*MBF	1 - 2
2-Phenylpropion aldehyde (PPA)	0.59 + 0.11*PPA	0.29 + 0.23*PPA	1.5 - 15
α-Methylstyrene Oxide (AMSO)	4.61	6.51 + 0.23*AMSO	13 - 32
DimethylBenzyl Alcohol (DMBA)	0.38	0.55 + 2.03*DMBA	0.1 - 1