Introduction toBiodiesel
Today, as oil prices climb and pollution levels soar,
there is significant worldwide interest in alternative
fuels. Biodiesel is one of themost popular alterna-
tive fuels available today. Itmay be used in engines,
either pure or blended with diesel fuel, to reduce
exhaust pollutants. It can be produced easily from
sunflowers, soy, rapeseed, tallow, lard, yellowgrease,
and other sources. Chemically, it is the product
obtainedwhen a vegetableoil or animal fat is react-
edwithanalcohol in thepresenceof acatalyst, such
as sodiumorpotassiumhydroxide, toproduce fatty
acidmethyl esters.
Methods used to test the quality of biodiesel fuels
canbe categorized into three types basedon the tar-
getcompounds:ASTMD6584andEN14105 test for
total glycerin, EN 14103 tests for fatty acidmethyl
esters (FAMEs), and EN 14110 tests for residual
methanol. Thesemethodsmay be performed using
either fused silicaormetal columns, but the column
chosenmusthaveextremelyhigh temperature toler-
ance. Restek offers both fused silica and metal
columns designed specifically for high temperature
biodiesel analysis. These columns, the Rtx®-
Biodiesel TG,MXT®-Biodiesel TG, Stabilwax®, and
Rtx-1®column lines,offeroutstandingperformance
for biodiesel testing.
AnalyzingTotal Glycerin inBiodiesel
Rtx®-BiodieselTGFusedSilicaColumns
Glycerin inbiodiesel falls out of solution, causinggumming in fuel systems and
malfunctioning of engine parts, which eventually leads to inferior engine per-
formance. Total glycerin presents itself in two forms: free glycerin and bound
glycerin in the form of glycerides. Derivatization is required for analysis, and
both ASTM D6584 and EN 14105 use N-methyl-N-trimethylsilytrifluoroac-
etamidederivatization reagent.
A10mx0.32mm IDRtx®-Biodiesel TG columnwith a2mx0.53mm ID reten-
tiongap is ideal for glycerin analysis.The retentiongap is factory coupledusing
Restek’s uniqueAlumaseal™ connector (Figure 1).This innovative connector is
leak-tight and low dead volume,making it advantageous for high temperature
work.Thedata inFigure2 show the elutionof glycerin,monoglycerides,diglyc-
erides, and triglycerides inB100biodiesel followingASTMMethodD6584, uti-
lizing cool on-column injection.TheRtx®-Biodiesel TG columnprovides good
resolution and signal-to-noise ratios formono-, di-, and triglycerides.
Figure2
TheRtx®-Biodiesel TG columnmeets resolution criteria
and shows excellent response for determiningglycerin inbiodiesel.
0
10
20
Column:
Rtx
®
-BiodieselTG, 10m, 0.32mm ID, 0.10µm connected to 2m x 0.53mm
Hydroguard™ tubing using Alumaseal™ connector (cat.# 10291)
Sample:
biodiesel (B100) plusmonoolein, diolein, triolein, glycerin, butanetriol, tricaprin
Inj.:
1µL, cool on-column
Inj. temp.:
oven track
Carrier gas:
hydrogen, constant flow
Flow rate:
4mL/min.
Oven temp.:
50°C (hold 1min.) to 180°C@ 15°C/min. (hold 7min.) to
230°C@ 30°C/min. to 380°C@ 30°C/min. (hold 5min.)
Det.:
FID
Det. temp.:
380°C
glycerin
butanetriol (IS)
tricaprin (IS)
monoglycerides
diglycerides
triglycerides
GC_PC00890
Rtx®-BiodieselTGColumns (fusedsilica)
Rtx®-Biodiesel TGColumns:
• Low columnbleed at high temperatures.
• Alumaseal™ connector provides leak-free con-
nection, retention gap extends column life.
• Complete resolution for all compounds from
interference peaks.
Compound
CAS# cat.#
price
MSTFA (N-methyl-N-trimethylsilytrifluoroacetamide)
10-pk. (10x1g)
24589-78-4 35600
$65
25g FlexTube
24589-78-4 35601
$75
SilylationDerivatizationReagents
Compound
Solvent cat.#
price
(s)-(-)-1,2,4-butanetriol
1,000 33024
$33
(s)-(-)-1,2,4-butanetriol (5mL)
1,000 33032
$113
diolein(1,3-di[
cis
-octadecenoyl]glycerol)
5,000 33022
$31
glycerin
500 33020
$31
monolein
(1-mono[
cis
-9-octadecenoyl]-rac-glycerol)
5,000 33021
$31
monopalmitin
5,000 33026
$33
tricaprin (1,2,3-tricaprinoyl glycerol)
8,000 33025
$33
tricaprin (1,2,3-tricaprinoylglycerol) (5mL)
8,000 33033
$113
triolein (1,2,3-Tri[
cis
-octadecenoyl]glycerol)
5,000 33023
$31
BiodieselCalibrationStandards
Concentration is µg/mL in pyridine. Volume is 1mL/ampul unless
otherwise noted.
Figure1
: TheAlumaseal™connector
TheAlumaseal™ connector is the best column connector for coupling fused silica andmetal
columns, even columns of different internal diameters. Made of aluminum, it is designed for
high temperature performance.These connectors have been factory-coupled and tested using
temperature programmedmass spectrometry and have shown no signs of leaks, even at 430°C.
TheAlumaseal™ connector offers:
•A leak-tight connection.
•Low dead volume.
•Low thermal mass.
•High inertness.
Description
temp. limits cat.#
price
10m, 0.32mmID, 0.10
to 330/380°C 10292
$250
10m, 0.32mmID, 0.10w/2m x
0.53mm retention gap**
to 330/380°C 10291
$295
15m, 0.32mmID, 0.10
to 330/380°C 10294
$305
15m, 0.32mmID, 0.10w/2m x
0.53mm retention gap**
to 330/380°C 10293
$365
**Connectedwith low-dead-volume Alumaseal™ connector.
•
800-356-1688
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