Dimethyl carbonate as a green mobile phase modifier for liquid chromatography

In fifteen words or less, explain the significance of this contribution (Novel Aspect).: Dimethyl carbonate can be used as a liquid chromatography mobile phase subsitute for acetonitrile.

Abstract Text:

Linear alkyl carbonate solvents such as dimethyl carbonate (DMC) are considered to be environmentally safe with a low toxicology risk.  The modest viscosity of 0.625 mPa·s and the UV cutoff wavelength of about 215 nm makes DMC a potential alternative aprotic liquid chromatography (LC) modifier solvent to acetonitrile. A polarity parameter (P’) for DMC of 3.4 + 0.1 was determined by ratioing Hildebrand solubility parameters for three alcohols and DMC to the corresponding alcohol P’ values. The main issue is the limited solubility of DMC in water, about 14%. This water solubility limitation of DMC can be overcome by using ethanol as a co-solvent, still maintaining the green nature of the mobile phase,

In the hydrophilic interaction LC mode, we have shown DMC to be about a factor of 1.5 weaker solvent than acetonitrile, permitting enhanced retention at lower organic solvent percentages. Using a 70% DMC-30% ethanol-buffer mobile phase, we have shown DMC to be a viable solvent for the separation of carbohydrates such as glucose, fructose, and sucrose in the 100 ppm range on an amide column with charged aerosol detection. 

 Using reversed phase LC (RPLC), a test mixture of polar aromatic compounds (benzene sulfonate, amino benzoic acid, nitrobenzoic acid, salicylic acid, and N,N-dimethylaminobenzoic acid) has a reasonable retention factor (k) range between 1 and 9 over a DMC modifier percentage of 10 to 2% with no ethanol as the co-solvent with a C-18 column. For a similar retention factor range using methanol, the composition required variation from 60 to 10%. Average solvent strength parameters calculated from quadratic fits of ln k versus organic mobile phase fraction for caffeine, sulfathiazole, and two nitroaniline isomers have shown DMC to be significantly higher (2.8) than ethanol (1.7) or acetonitrile (1.6). An organic mobile phase modifier solution at a 5:3 DMC:ethanol ratio has proven to be an effective RPLC modifier solvent, with either UV or fluorescence detection, for hydrophobic polyaromatic hydrocarbons (PAHs) such as the seven ring coronene, reducing its retention by a factor of 5 as compared to acetonitrile.