Simple and Rapid Quantitative Determination of Di(2-ethylhexyl)phosphoric Acid Concentration Using Near Infrared Spectroscopy

Since DEHPA has two long alkyl chains and a small phosphate group, and consequently is very hydrophobic as shown in Figure 1, it is usually used in apolar media such as hexane, octane, etc. Sodium salt of DEHPA has been also widely used in the form of a reverse micelle in an apolar media, and therefore used for a variety of extraction applications such as liquid-liquid protein extraction and aminoglycoside antibiotic extraction. In solid-liquid separation, impregnation of DEHPA into a porous polymer support in an organic solvent is an important process, and therefore adsorbed DEHPA in organic solvents should be quantitatively determined. To our best knowledge, gravimetric measurement, phosphorus elemental analysis, potentiometric titration with NaOH were the conventional method reported for the determination of DEHPA, while the spectrophotometric analysis of DEHPA in an organic solvent has not been taken into account. Total organic carbon method as a general quantitative determination tool for most organic materials cannot be used in organic media such as hexane