Column Suitability for EN 15199 (Simulated Distillation) - Part 1
7 Apr 2022EN 15199 is a collection of European standards used to determine the boiling point distribution of petroleum products by gas chromatography (simulated distillation by gas chromatography). It consists of four parts based on the samples’ boiling points. The EN standards agree with the ASTM methods, and both standards have similar requirements and testing procedures. (Figure 1)
EN Standard | Sample type | The boiling point of the sample | ASTM Method | |
Initial boiling point | Final boiling point | |||
EN 15199-1 | Middle distillate and lubricating base oils | above 100 °C | below 750 °C | D6352 |
EN 15199-2 | Heavy distillates and residual fuels | above 100 °C | above 750 °C | D7169 |
EN 15199-3 | Crude oil | below 100 °C | above 750 °C | D7169 |
EN 15199-4 | Light fractions of crude oil | To n-nonane | D6730 |
Figure 1: Categorization of EN15199 standards based on the initial and final boiling point of the sample and corresponding ASTM methods (See ASTM Petrochemical Method Chromatography Product Guide for more details on the specific ASTM method).
Gas chromatographic simulated distillation analyses, except for light fractions, are performed using a high-temperature short column with a thin layer of PDMS (polydimethylsiloxane) due to the high final boiling point of the samples. EN15199 1-3, all three standards suggest using a 5m x 0.53mm column coated with a methyl silicone stationary phase. The 5m x 0.53mm x 0.09µm (for up to n-C120) or a 5m x 0.53mm x 0.17µm (for up to n-C100) have been successfully used in the method validation, and many laboratories will not deviate from that recommendation. Restek does not offer a 5m x 0.53mm x 0.09µm film thickness since it cannot be distinguished from a 5m x 0.53mm x 0.10µm (cat#70112). To demonstrate my point, I have modulated the first few paraffins in the simulated distillation runs using both film thickness columns (Figure 2). The difference in retention times of individual n-hydrocarbons between one and the other column is approximately 11 seconds.
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Figure 2: EZGC modulation of the analysis of n-hydrocarbons from n-C10 – n-C24 using 5m x 0.53mm columns with a film thickness of 0.09 and 0.10µm.
Further, I have compared the analysis of retention time standards on Restek SimDist 5m x 0.53mm x 0.10µm (Cat# 70112) and commercially available SimDist column 5m x 0.53mm x 0.09µm using EN15199-3 analysis conditions. The retention time standard is used to check the system’s performance (resolution and symmetry of the analytes) and to determine the relationship between the boiling point of n-paraffins and their retention times (Figure 3).
Figure 3: Analysis of n-paraffin standard (n-C5 – n-C100) using EN15199-3 analysis condition, xyz SimDist column 5m x 0.53mm x 0.09µm (top chromatogram) and Restek SimDist 5m x 0.53mm x 0.10µm (Cat# 70112) using on column injection
Both columns met the essential EN15119-3 method system requirements (Figure 4), and all the analytes were eluted in the method run time. The difference in the retention for early eluting analytes (n-C20) is approximately 30 seconds; however, it balances out over time with the n-C100 lagging for only 6s on the 0.10µm column in comparison to the 0.09µm column (Figure 3).
EN15199-3 Requirement | 5m x 0.53mm x 0.10µm | 5m x 0.53mm x 0.09µm | |
Resolution C50/C52 | 2-4 | 2.9 | 2.7 |
Skew C20 | 1-3 | 1.3 | 1.6 |
Figure 4: Comparison of resolution and skew values for the analysis in Figure 3. System suitability values met the method EN15199-3 requirements on both columns.
As demonstrated, there is very little difference between the columns with the 0.09µm film thickness compared to 0.10µm, especially when it comes to the elution of the high molecular weight n-paraffins. In the next installment, I will look at the recoveries on the 5m x 0.53mm x 0.10µm column for the EN15199-1 method.
Literature:
- EN 15199-1 Petroleum products - Determination of boiling range distribution by gas chromatography method - Part 1: Middle distillates and lubricating base oils
- EN 15199-2 Petroleum products. Determination of boiling range distribution by gas chromatography method Heavy distillates and residual fuels
- EN 15199-3 Petroleum products. Determination of boiling range distribution by gas chromatography method Crude oil
- EN 15199-4 Petroleum products. Determination of boiling range distribution by gas chromatography method Light fractions of crude oil