Improved Methylene Blue Two-Phase Titration Method for Determining Cationic Surfactant Concentration in High-Salinity Brine

Abstract

The methylene blue (MB) two-phase titration method is a rapid and efficient method for determining the concentrations of anionic surfactants. The point at which the aqueous and chloroform phases appear equally blue is called Epton's end point. However, many inorganic anions, e.g., Cl(-), NO3(-), Br(-), and I(-), can form ion pairs with MB(+) and interfere with Epton's end point, resulting in the failure of the MB two-phase titration in high-salinity brine. Here we present a method to extend the MB two-phase titration method for determining the concentration of various cationic surfactants in both deionized water and high-salinity brine (22% total dissolved solid). A colorless end point, at which the blue color is completely transferred from the aqueous phase to the chloroform phase, is proposed as titration end point. Light absorbance at the characteristic wavelength of MB is measured using a spectrophotometer. When the absorbance falls below a threshold value of 0.04, the aqueous phase is considered colorless, indicating that the end point has been reached. By using this improved method, the overall error for the titration of a permanent cationic surfactant, e.g., dodecyltrimethylammonium bromide, in deionized (DI) water and high-salinity brine is 1.274% and 1.322% with limits of detection (LOD) of 0.149 and 0.215 mM, respectively. Compared to the traditional acid-base titration method, the error of this improved method for a switchable cationic surfactant, e.g., tertiary amine surfactant (Ethomeen C12), is 2.22% in DI water and 0.106% with LOD of 0.369 and 0.439 mM, respectively.

Phase behavior and interfacial properties of a switchable ethoxylated amine surfactant at high temperature and effects on CO2-in-water foams

“…in the aqueous phase was determined using methylene blue two phase titration as explained above and in previous publications. 56 The samples were then mixed using an IKA Ultra-Turrax T-25 with an 8 mm head at 6500 rpm for 2 minutes. Emulsions were formed and the curvature (W/O versus O/W) was determined from the conductivity, measured with a Cole -Parmer EC conductivity meter with Pt/Pt black electrode.…”

Cetyltrimethylammonium bromide‐coated agrosorbents and their high benzene adsorption performance from aqueous solution

“…The CTAB concentration was determined by a colorimetric two‐phase titration with SDS solution as a titrant in which a standard calibration curve of SDS solution volume against CTAB concentrations was constructed . Typically, 5 mL of CTAB solution was pipetted into a conical flask (50 mL).…”

Effects of surfactants on rheological properties of a dispersed viscoelastic microsphere

“…Erlenmeyer flask was shaken in SHA‐C digital water bath oscillator (Changzhou Guohua Electric Appliance Co., China) at 50°C for 48 h. After reaching adsorption equilibrium, the supernatant fluid was taken out and separated by centrifugation at 2000 RPM for 10 min by means of 80‐1 Tabletop Low speed Centrifuge (Jintan Medical Instrument Factory, China). The TX‐10 concentration C e was determined by uvspectrophotometry, and the concentration C e of CTAB and GXPS was determined by two‐phase titration method . The equilibrium of adsorption of surfactant on viscoelastic microspheres was calculated by the expression: where Q e is equilibrium adsorption of surfactant on viscoelastic microspheres, mg/g; C 0 and C e are the initial and equilibrium concentrations of surfactant, mg/L; V is volume of aqueous phase, L; m 0 is the weight of dry viscoelastic microspheres, g.…”