New ACCUTRACE™ Plus fuel marker BPE (butyl phenyl ether) fights crime

In January 2024, a new ACCUTRACE™ Plus fuel marker BPE (butyl phenyl ether) has replaced the previous “Solvent Yellow 124” standard in the European Union. Consisting of naphthenic hydrocarbons as solvent and BPE, the new marker is laundering-resistant, contains no harmful additives and is easy to handle. Moreover, it can be detected quickly via GC-MS at extremely low levels. Shimadzu prepared a sensitive, accurate and convenient GC-MS method according to the European regulation.

The new Euromarker and its predecessor

Since 2001, a common fuel marker has been used in the European Union (EU) as a fiscal marker to avoid not only confusion of differently taxed fuels and diesel but also to detect fuel fraud, dilution, adulteration and theft that lead to a loss of tax revenue for governments and oil companies in the EU of several billion EUR each year. In many European countries, fuels such as agricultural diesel, mineral diesel and heating oil are subsidized. To combat the misuse of the lower tax fuels, they were historically marked with different azo dyes called “Solvent Red”. The yellow marker “Solvent Yellow 124” was established for heating oil EU-wide from 2002 because it was easier to analyze. Under the name “Euromarker” it is added to fuels not intended for motor vehicles in amounts of 6 mg/L. Solvent Yellow 124 itself hardly colors the fuel oil, so still a red dye is also added for easy differentiation. It can be detected very quickly and sensitively with an indicator reagent even when strongly diluted, alternatively it can be quantified using high performance liquid chromatography (HPLC). However, the last review from the European commission showed that Solvent Yellow 124 is not that robust against common removal techniques. Smart cheaters even found a way for “fuel laundering”.

Laundering-resistant – no harmful additives – easy to handle

Furthermore, some European countries expressed concerns about the toxicity of azo dyes. Consequently, the European Commission decided to adopt ACCUTRACE™ Plus as a new, safer and more robust Euromarker. The new marker BPE (butyl phenyl ether) is laundering-resistant, contains no harmful additives and is easy to handle. Moreover, it can be detected quickly via GC-MS at extremely low levels. The decision for ACCUTRACE™ Plus fuel marker has come into effect in January 2024.

Sample preparation and calibration

A stock solution of BPE in xylene was used to prepare a 7-point calibration between 0.1 and 12 mg/L in diesel. The samples were analyzed directly without any sample preparation. Thanks to the heart-cut technique, most of the fuel matrix was transferred to the FID and only a very small part of the sample, containing the BPE, was directed to a second, polar column and finally to the mass spectrometer. After introducing the BPE into the MS, the higher boiling compounds were removed from the first column by backflushing the system, hereby reducing contaminations, prolonging the cleaning intervals of the ion source and reducing the total analysis time.

Results

A representative second dimension chromatogram of BPE in diesel, showing base line separation of BPE from diesel, can be seen in Figure 1. Excellent linearity was observed within the tested concentration range between 0.1 and 12 mg/L in two consecutive days, with a correlation coefficient of R2 > 0.9999, as can be seen in Figure 2. The LOD and LOQ were calculated based on the signal-to-noise ratio (S/N), using five replicates of the lowest BPE standard (100 μg/L). An LOD of 2.8 μg/L and an LOQ of 9.2 μg/L were achieved, allowing a detection of adulterated diesel far below the requested quantification limit. To study the repeatability of the method, five consecutive injections of different BPE concentrations in diesel were performed over two days. At the lowest BPE concentration of 0.1 mg/L, an intraday repeatability of 0.8 % on day 1 and 1.8 % on day 2 were observed, resulting in an interday repeatability of 1.4 %. The results for all concentration levels are shown in Table 1. Recoveries between 93 % and 117 % were calculated in spiked diesel and gasoline samples, as can be seen in Table 2. Finally, the second dimension SIM chromatograms of spiked diesel and gasoline samples were compared (see Figure 3). It can be observed that in both spiked samples BPE is well separated from the matrix. The recommended analytical hardware and software configuration is listed below in Table 3.