Resolve Benzene, Other Aromatics, and Oxygenates in Reformulated Gasoline
Mar 01 2018
on behalf of Merck KGaA. The life science business of Merck operates as MilliporeSigma in the U.S. and Canada
Using a One-Column Approach with an SLB®-ILD3606 Column
The amount of benzene in gasoline is a concern because it is a known human carcinogen, and exposure to it is linked to detrimental health effects. The challenge with the analysis lies in the complex composition of gasoline, which consists of hundreds of different compounds. Reformulated gasoline also contains additives to produce more complete combustion and subsequent lower emissions of harmful compounds. These additives accomplish this by boosting the oxygen content, and are commonly referred to as “oxygenates.” Ethanol is a commonly used oxygenate. Therefore, to measure benzene in reformulated gasoline, it must be resolved from the aliphatic hydrocarbons, other aromatics, ethanol, plus any other oxygenates. This typically requires the use of a two-column switching procedure.1
We developed SLB-ILD3606 specifically for the determination of benzene, other aromatics, and oxygenates in gasoline. Table 1 lists its specifications. It employs an ionic liquid stationary phase and provides great peak shapes for oxygenates, resulting in improved resolution for all analytes.
To show selectivity and inertness capabilities, a mixture containing two aromatics, five alcohols, and one ketone was prepared in isooctane following the guidelines for a control standard to be used with ASTM® D3606. This mix was analyzed using temperature programming and the resulting chromatogram is shown in Figure 1. The inertness of the column resulted in sharp peak shapes for all alcohols, which in turn resulted in great resolution between ethanol and benzene (RS=12.6), and also between isobutanol and toluene (RS = 5.6).
Reformulated Gasoline Sample
Figure 2 shows the chromatogram resulting from the analysis of a reformulated gasoline sample on SLB-ILD3606. As shown:
• The extremely polar selectivity of this column resulted in the elution of benzene after the aliphatic portion and also great resolution between benzene and ethanol
• Several other aromatic and oxygenate compounds are also fully resolved
• A few aromatics (e.g. p-/m-xylene) and oxygenates (e.g. MTBE, TAME) are partially resolved
• This column can be used up to 260 °C, so allows the timely elution of the heavy polycyclic aromatic hydrocarbon (PAH) constituents in gasoline
• The phase stability of SLB-ILD3606 produces minimal bleed, even when subjected to a temperature ramp
These observations indicate that the SLB-ILD3606 is an effective alternative to the two-column switching procedure (according to ASTM D3606) currently required for the determination of benzene and other aromatics in reformulated gasoline.
1. ASTM® D3606, Benzene and Toluene in Unleaded Gasoline and Aviation Fuel.
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