Detection Target
Determination of methanol in biodiesel
Overview
This solution complies with ASTM D6751 Standard Specification for Biodiesel Fuel Blend Stock (B100) for Middle Distillate Fuels and EN 14214 Automotive fuels – Fatty acid methyl esters (FAME) for diesel engines – Requirements and test methods. Compared to traditional petroleum diesel, biodiesel has a smaller environmental impact. Biodiesel can be used as a pure fuel or mixed with petroleum diesel in any proportion. The ASTM D6751 and EN 14214 standards specify the maximum allowable concentration of contaminants in finished pure biodiesel (B100) and other physicochemical characteristics required for safe and reliable engine operation.
Apparatus
HKL-6751 GC for methanol in biodiesel
Features
HKL-6751 GC for methanol in biodiesel adopts 10.2 inch touch LCD. It can display the temperature of each way and Real-Time Operation conditions, so as to achieve the on line monitoring.
POST, indenpendt temperature control of six ways and five stages program temperature rise.
Self-diagnosis function: If there is a failure, the apparatus will automatic display the fault phenomenon, code and cause to help the operator find and solve the fault in short time.
Over temperature protection: The protective temperature can be set freely,if there is a way exceeds the setting temperature, the appratus will automatic power off and alarm.
Carrier gas protection: When the carrier gas is underpressure, the apparatus will automatic power off and stop heating to protect chromatographic column and thermal conductivity detector effectively.
Intelligent fuzzy control back gate system: Automatic tracing temperature and dynamic regulate the angle of the bakc gate. The apparatus can do precision control under room condition.
Equiped with packed column chapiter sampling, glass-lined sampling and capillary split/splitless sampling device with membrane cleaning fucntion. The apparatus also can install the gas sampler.
High precision and stable dual way. Maximum can install 4 kinds of detector.
Advanced gas rutine, it is available to use hydrogen flame detector and thermal conductivity detector.
Both FID and capillary tube inlet are EPC controlled.
Electronic flow pressure display system and internal work station device can be selected.
19 digits automatic liquid sampler.
Technical Parameters
Temperature control index
Temperature control range：Room temperature 5℃~400℃, Increment: 0.1℃
Temperature control accuracy: Better than ±0.1℃
Temperature programming:
5 stages, constant temperature time between stage:0~999min
Increment:0.1min,Temperature increment: 0.1℃
Heating rate: Maximum 40℃/min below 200℃
Maximum 20℃/min above 200℃
LOD
Compound | Max % m/m (EN 14214) |
Glycerin | 0.02 |
Mono-glycerides | 0.8 |
Di-glycerides | 0.2 |
Tri-glycerides | 0.2 |
Total Glycerin | 0.25 |
Method and Reagents
The analysis of glycerin, mono, di and triglycerides by gas chromatography (GC) requires a non-discriminative injection system able to transfer both volatile and heavy compounds without discrimination or degradation. A TRACE GC Ultra equipped with a true cold On-column inlet and a flame ionization detector (FID), automated by a TriPlus Autosampler for liquids was used, controlled through the Thermo Scientific Chrom-Card data system. The true cold On-column injector offered on the TRACE GC Ultra is a permanently cold system, able to prevent discrimination of the heavier fraction and to eliminate any risk of degradation of labile components like triglycerides, thus granting excellent recovery and proven sample integrity.
The analytical column used is a non-polar Thermo Scientific TRACE™ TR-BIODIESEL(G), 10 m, 0.32 mm ID, 0.1 μm f.t. This column is designed to provide excellent performance for this high temperature GC method, featuring enhanced mechanical robustness at high oven temperature, and thus prolonged lifetime. A 1 m x 0.53 mm ID pre-column is used, connected to the column by a leak-free high T purged connection.
A low dead volume leak-free metal tee has been specifically conceived for a reliable connection between the guard column and the analytical column at high temperature operation, preventing from the use of normal glass press-fit unions. Such a connector has proven to stay leak-free even with extremely large and frequent oven temperature variations (Figure 2).
Calibration is achieved by the use of two internal standards – 1,2,4-butanetriol (IS1) for glycerine and tricaprin (IS2) for mono-, di- and tri-glycerides, and four reference compounds – glycerin, mono-olein, di-olein and tri-olein.
Because glycerin and mono- and di-glycerides are polar and high boiling components, they must be derivatized to increase their volatility and reduce activity before injection into the GC. The method requires derivatization with MSTFA (N-methyl-N-trimethylsilyltrifluoroacetamide) in pyridine, which transforms these compounds into more volatile silylated derivatives. Below is a list of required reagents:
MSTFA (N-methyl-N-trimethylsilyltrifluoroacetamide)
n-Heptane
Pyridine
1,2,4-Butanetriol – internal standard solution 1,1 mg/mL in pyridine (IS1)
1,2,3-Tricaproylglycerol (tricaprin) - internal standard solution 2, 8 mg/mL in pyridine (IS2)
Reference materials: glycerol (glycerin), 1-monooleoylglycerol (monoolein), 1,3-di-oleolglycerol (diolein), 1,2,3-tri-oleoylglycerol (triolein)
Mono-glycerides check mix (monopalmitin, monostearin and monoolein), in pyridine Figure 2: Leak free high T purged connector