Abstract
A rapid method for the determination of ethylene oxide contents in POE type nonionic surfactants by near-infrared (NIR) spectroscopy was established.
POE type nonionic surfactants have strong absorption at 1.42μ and 1.74μ in near-infrared region. The band at 1.42μ is the O-H stretching vibration, and the band at 1.74μ is the first overtone of the C-H stretching vibration. The linear relationship is obtained between the absorbance ratio a1.74/a1.42 and EO contents of POE type nonionics. The absorbance ratio is not affected by concentration (0.21.2g/50ml) and by temperature (8°38°C) of the sample solution.
Based on these facts, in this method, a 0.7 to 1.0g of nonionics sample was dissolved into 50ml of carbon tetrachloride solution. The solution was mesured by NIR from 1.2 to 2.0μ in 10cm silica cell. The absorbances were obtained from peak-height of the band at 1.42 and 1.74μ. The EO contents was calculated from the absorbance ratio and the calibration curve.
This method allows determination of the EO contents in POE type nonionics within relative accuracy of 3.5% until about 30 moles.
