Abstract:

The free alcohols in isomeric alcohol polyoxyethylene ethers were analyzed by headspace gas chromatography （headspace GC）. Headspace GC was performed with an HP-5 column （30 m×0.32 mm, 0.25 µm） and an FID detector. DMF was used as solvent. Through optimization of equilibrium temperature, equilibrium time and sample volume, the best GC detection conditions were found. The retention time was used for qualitative analysis and the external standard method was used for quantitative analysis. The test results showed that isodecyl alcohol was a mixture of two different alcohols, and isotridecyl alcohol was a mixture of alcohols with different carbon chain length and different degree of branching. The results showed that the calibration curves of isodecyl alcohol and isotridecyl alcohol were linear in range of 0.50-14.02 mg/mL and 1.02-20.35 mg/mL with linear correlation coefficients of 0.999 3 and 0.999 1, LODs of 0.30 and 0.54 mg/mL, and LOQs of 0.99 and 1.78 mg/mL, respectively. In the precision test, the RSD for isodecyl alcohol was≤0.75% and the RSD for isotridecyl alcohol was≤0.99%. The recovery of isodecyl alcohol and isotridecyl alcohol was from 97.4% to 104.7%, with RSD≤2.33% （n=6）. It could be found that the fluctuation in detection data of isodecyl alcohol ethoxylate was slight, while that of isomeric tridecanol ethoxylate was bigger. To reduce data fluctuation, the sample weight could be increased to make the peaks more obvious when detecting isotridecanol polyoxyethylene ether. This method was simple, accurate, rapid, highly sensitive, and suitable for the determination of free alcohols in isomeric alcohol polyoxyethylene ethers.

Key words: headspace gas chromatography, isomeric alcohol polyoxyethylene ether, isodecyl alcohol, isotridecyl alcohol