In enhanced oil recovery applications, surfactants are injected into reservoirs along with polymers and salts. The effluents eluted from lab experiments and field tests are analyzed by HPLC methods using an evaporative light scattering detector (ELSD) detector. When the surfactant concentrations are less than 100 ppm, HPLC methods are inaccurate. A novel two‐phase titration method is developed where surfactant concentrations can be quantified using a calibration curve constructed with UV/vis absorption. This method can analyze surfactant concentrations 5–80 ppm where dilution eliminates any high‐salinity interferences with the absorption measurements. The method is based on formation of a dye‐surfactant complex and the light absorption of the complex has a linear correlation with the surfactant concentration. Anionic surfactant concentrations lower than 100 ppm can be accurately quantified using this method with methylene blue. The method was also developed for low concentrations (<50 ppm) of cationic surfactants using methyl orange and indigo carmine. The indigo carmine method can be used without the use of an organic phase. All methods are applicable at salinities up to 3 wt%. Both the methylene blue method and the methyl orange method can be used to detect zwitterionic surfactants. These methods can be used in the presence of polymers without any prior treatments.

中文翻译：

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改进的两相滴定方法可量化化学强化采油应用中的表面活性剂浓度

在提高采油率的应用中，将表面活性剂与聚合物和盐一起注入储层。使用蒸发光散射检测器（ELSD）通过HPLC方法分析从实验室实验和现场测试中洗脱的废水。当表面活性剂浓度小于100 ppm时，HPLC方法不准确。开发了一种新颖的两相滴定法，其中可以使用通过UV / vis吸收构建的校准曲线来定量表面活性剂的浓度。该方法可以分析5-80 ppm的表面活性剂浓度，稀释后可以消除吸收测量中的任何高盐度干扰。该方法基于染料-表面活性剂配合物的形成，配合物的光吸收与表面活性剂浓度呈线性关系。低于100 ppm的阴离子表面活性剂浓度可以使用此方法与亚甲基蓝准确定量。还开发了使用甲基橙和靛蓝胭脂红用于低浓度（<50 ppm）阳离子表面活性剂的方法。可以使用靛红胭脂红方法而无需使用有机相。所有方法均适用于盐度不超过3 wt％的情况。亚甲基蓝方法和甲基橙方法均可用于检测两性离子表面活性剂。这些方法可以在聚合物存在下使用而无需任何预先处理。所有方法都适用于盐度不超过3 wt％的情况。亚甲基蓝方法和甲基橙方法均可用于检测两性离子表面活性剂。这些方法可以在聚合物存在下使用而无需任何预先处理。所有方法都适用于盐度不超过3 wt％的情况。亚甲基蓝方法和甲基橙方法均可用于检测两性离子表面活性剂。这些方法可以在聚合物存在下使用而无需任何预先处理。