Abstract:

High-salinity oilfield fracturing water has interference on the quantitative analysis of polyethylene glycol tert-octylphenyl ether （Triton X-405） by ultraviolet spectroscopy. In this work, an appropriate amount of β-cyclodextrin （β-CD） was added as a “shielding” agent to reduce the interference of fracturing water. The results showed that the fracturing water could significantly reduce the absorbance and critical micelle concentration （cmc） of Triton X-405. In fracturing water, the absorbance of 100.0 mg/L Triton X-405 was decreased by 6.67% at the maximum absorption wavelength of 224 nm, and the cmc of Triton X-405 was also reduced from 103.978 mg/L to 97.056 mg/L. The impact of fracturing water on the absorbance of Triton X-405 could be significantly reduced by adding equimolar β-CD, and the decrease in absorbance of 100.0 mg/L Triton X-405 at 224 nm was only 1.99%. Triton X-405 could not form micelles in the mass concentration range of 20.0-160.0 mg/L by adding β-CD in water or in fracturing water. As a result, the recovery of Triton X-405 in fracturing water was improved from 88.3%-97.4% to 97.5%-99.6%. The results of FT IR, ¹H NMR and the method of continuous variations indicated that Triton X-405 and β-CD could form 1∶1 inclusion complex, and the Triton X-405 molecule could enter into the CD cavity both from the narrow rim and the wide rim. The shielding effect due to the formation of inclusion complex suppressed the interference of fracturing water on the determination of Triton X-405. The work could provide a new guidance for accurately determining Triton X-405 in high-salinity fracturing water.

Key words: Triton X-405, β-CD, fracturing water, quantitative determination