Gas chromatographic determination of water in organic compounds and of organic compounds in water after steam distillation

Dix, Kevin
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A gas chromatograph (GC) with a flame ionization detector (FID) is shown to be effective in the determination of water in organic compounds. Since the FID gives little response for water, a reaction is needed to convert water into a detectable species. The ketal, 2,2-dimethoxypropane (DMP), reacts quantitatively with water to yield the products methanol and acetone when an acid catalyst is present. Acetone is easily determined with a GC equipped with a capillary column and FID. A solid acid catalyst, Nafion, has been effective and is easily separated before sample introduction into the GC;Several organic solvents were analyzed using this indirect method for determining water. The method is effective for determining water from 0.001-3.5% w/w. Larger concentrations of water can be determined by reducing the sample size. Solid samples were also analyzed and the water found in additional spikes agreed with the amount added;Simple steam distillation is used for the isolation and concentration of organic compounds from water matrices. Organic compounds are spiked into a flask containing water and the mixture is then boiled. Typical distillation times take less than 25 minutes. The condensate is collected in a small collection tube and a portion is injected into a GC containing a capillary column. The recovery of most compounds with boiling points from 77 to 238°C is better than 90% and a concentration effect of ten is realized. This method is very effective for phenols which traditionally have been difficult to distill;When compounds are present at concentrations in the part-per-billion range, a further concentration is necessary. Steam distillation combined with solid phase extraction is shown to be effective in isolating and concentrating compounds from water at these low concentrations. A simple interface between the boiling apparatus and resin collection column is presented. Once the organic analytes are boiled and collected on the resin, they are removed with a small amount of ethyl acetate. The ethyl acetate solution is then injected into a GC. Compounds with boiling points above 400°C can be determined by turning off the flow of cold water in the condenser. Recoveries are better than 80% for compounds with boiling points between 132 to 404°C. ftn*DOE Report IS-T 1396. This work was performed under Contract W-7405-Eng-82 with the Department of Energy.

Chemistry, Analytic, Chemistry