1,2-propylene glycol refractive index

The refractive index detector was one of the first on-line HPLC detectors used. Detection is based on changes in the refractive index of the effluent when an analyte is present versus the solvent alone. This detector is commonly used when an analyte does not have a suitable UV chromophore. An example would be the detection of carbohydrates in drug preparations or acetylcholine in an ophthalmic solution [102,103]. Figure 5.4 is a chromatogram of propylene glycol, propylene carbonate, and resorcinol in anhydrous ointment detected by a refractive index detector [104]. 

Poloxamer 331 occurs as a practically colorless liquid. It is a block copolymer condensate of ethylene oxide and propylene oxide with an average formula weight of 3800, a specific gravity of about 1.02, and a refractive index of about 1.452. It is very slightly soluble in water at 25°, but is freely soluble at 0° it is freely soluble in alcohol, but is insoluble in propylene glycol and in ethylene glycol. 

The microemulsions containing pilocarpine were formulated using lecithin, propylene glycol, and PEG 200 as co-surfactant and isopropyl myristate as the oil phase. The formulations were of low viscosity with a refractive index lending to ophthalmologic applications. ... 

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