EXPLANATION
Free and bonded glycerin content reflects the quality of biodiesel. A high quantity of free glycerin may cause problems during storage, or in the fuel system, due to separation of the glycerin. A high total glycerin content can lead to injector fouling and may also contribute to the formation of deposits at injection nozzles, pistons, and valves.
This test method quantitatively determines free and total glycerin in b-100 methyl esters by gas chromatography. The range of detection for free glycerin is 0.005 - 0.5 mass %, and total glycerin from 0.05 - 0.5 mass %. This procedure is not applicable to vegetable oil methyl esters obtained from lauric oils, such as coconut oil and palmkernel oil.
TEST SUMMARY
The sample is silyated with N-methyl-N-trimethylsilytri-fluoracetamide and analyzed by gas chromatography. Calibration is achieved by the use of two internal standards and four reference materials. Mono-, di-, and triglycerides are determined comparing to monoolein, diolein, and triolein standards, respectively. Average conversion factors are applied to the mono-, di-, and triglycerides to calculate the bonded glycerin content of the sample.
TEST PRECISION
Reproducibility of the method has not yet been determined.
Since there is no accepted reference material suitable for determining bias for the procedure in this test method, bias cannot be determined.