Polymers

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	Polymers
	Application Type
	Sample Prep and Inject
	Application ID
	Biodiesel ASTM 6584
	Description
	Determination of Free and Total Glycerin in B-100 Biodiesel Methyl Esters by Gas Chromatography

Glycerin content can indicate the quality of biodiesel. Glycerin can be in the form of free glycerin or bound glycerin in the form of glycerides. Total glycerin is the sum of these. A high content of free and total glycerin can lead to buildup in fuel tanks, clogged fuel systems, injector fouling and valve deposits. Unrelated glycerides and free glycerin make the product behave more like soap rather than fuel.

ASTM Method D6571 specifications serve as the benchmark which identifies the standards that pure biodiesel (B100) must meet before being used as a fuel or blended with petrodiesel. There are 14 different required tests according to ASTM D6751-03. The US National Biodiesel Board has adopted the ASTM biodiesel specification and analytical methodology. ASTM recommends test method D6584 for the analysis of glycerin in biodiesel fuel by gas chromatography.

Gas chromatography can also serve as a tool for process troubleshooting during biodiesel production to ensure trouble-free operation of the fuel in diesel engines. Monitoring the level of free glycerin and any unrelated mono-, di-, and triglycerides will indicate the efficiency and progress of the chemical reaction during the process of making biodiesel.

ASTM Method D6584 provides for the quantitative determination of free and total glycerin in B-100 methyl esters by gas chromatography. The range of detection for free glycerin is 0.005 to 0.05 mass%, and total glycerin from 0.05 to 0.5 mass %. This method is not applicable to vegetable oil methyl esters obtained from lauric oils, such as coconut oil and palmkernel oil.

Significant Markets

Biodiesel Manufactures

Biodiesel Blenders

Biodiesel Distributors

Biofuels CROs

Fleet Managers

ASTM Method D684

9. Calibration and Standardization

9.2 Standard Solutions – Prepare the five standard solutions in Table 3 by transferring the specified volumes by means of Microliter syringes to 10mL septa vials. Add to each of the five standard solutions 100uL of MSTFA. Close the vial and shake. Allow the vial to stand for 15 to 20 minutes at room temperature. Add approximately 8 mL n-Heptane to vial and shake.

**TABLE 3 Standard Solutions**
Standard Solution Number	1	2	3	4	5
uL of glycerin stock solution	10	30	50	70	100
uL of monoolein stock solution	20	50	100	150	200
uL of diolein stock solution	10	20	40	70	100
uL of triolein stock solution	10	20	40	70	100
uL of butanetriol stock solution	100	100	100	100	100
uL of tricaprin stock solution	100	100	100	100	100

9.4 Standardization
9.5 Inject 1 uL of the reaction mixture into the cool-on-column injection port and start the analysis.

10. Procedure
10.1 Weigh to the nearest 0.1 mg approximately 100 mg of sample directly into a 10 mL septa vial. Using Microliter syringes, add exactly 100 uL of each internal standard and MSTFA. Shake the vials, and allow to set for 15 to 20 minutes at room temperature. Add approximately 8 mL of n-Heptane to vial and shake.

10.2 Inject 1 uL of the reaction mixture into the cool on-column injection port and start the analysis.

LEAP's Approach

System shown with Agilent 7890 and Twin PAL

The Lower PAL is the Prep PAL and runs on Cycle Composer Software. All of the sample prep is performed with this PAL. There is a 100ul syringe for the solvent transfers. There are (7) 2mL solvent locations. There is a DISPTool that is hooked up to a 5 mL dilutor syringe for the 8 mL Heptane addition. There is a fast wash station that Wash1 is filled with Toluene and Wash 2 is filled with Heptane. There is an agitator that is set at 35 deg C and 500RPM to do the mixing.

The Upper PAL is the Inject PAL and runs under ChemStation Software control. This requires Agilent CTC Control Software supplied by Agilent. It is using a 5 ul syringe with a tapered needle to do 1 ul on column injections into the rear injection port. There is a fast wash station that Wash1 is filled with Toluene and Wash 2 is filled with Heptane.

The expected Sample Prep Time is approximately 26 minutes
The expected GC Runtime is approximately 31.81 minutes
The expected GC Cool down time is approximately 7 minutes

Software Control

The Lower PAL is the Prep PAL and runs on Cycle Composer Software.

The Upper PAL is the Inject PAL and runs under ChemStation Software control.

Screenshots

Cycle Composer 5 Standards Prep	Cycle Composer Sample Prep	Cycle Composer Prep Standards	ChemStation Sequence Table
ChemStation Sequence Table	ChemStation PAL Method for Injection	ChemStation and Cycle for injection