BS EN 12916:2019 pdf download.Petroleum products – Determination of aromatic hydrocarbon types in middle distillates – High performance liquid chromatography method with refractive index detection.
4 Principle A known mass of sample is taken and a fixed volume of this sample is injected into a high performance liquid chromatograph fitted with a polar column. Diesel fuels with a concentration of FAME up to 30 % (V/V) and petroleum distillates need to be diluted with heptane (Procedure A). Paraffinic diesel fuels are injected neat (Procedure B). This column has little affinity for non-aromatic hydrocarbons, while exhibiting a strong selectivity for aromatic hydrocarbons. As a result of this selectivity, the aromatic hydrocarbons are separated from the non-aromatic hydrocarbons and into distinct bands according to their ring structure, i.e. MAH, DAH and T+AH compounds. The column is connected to a refractive index detector which detects the components as they elute from the column. The electronic signal from the detector is continually monitored by a data processor. The amplitudes of the signals from the aromatics in the sample are compared with those obtained from calibration standards in order to calculate the mass fraction of MAHs, DAHs and T+AHs in the sample. The sum of the DAHs and T+AHs mass fractions is reported as the mass fraction of POLY-AH, and the sum of the MAHs, DAHs and T+AHs mass fractions is reported as the mass fraction of total aromatic hydrocarbons. When following Procedure A, the column may be backflushed after the aromatics have eluted from the column to allow any remaining components such as FAME to elute in a backflush peak. This will allow for a better cleaning of the column but care should be taken as it can affect the lifetime of the column.
5 Reagents and materials WARNING — Aromatic compounds can be volatile and flammable, their vapours can form explosive mixtures with the air, and they can cause acute or chronicle harm when inhaled or in case of contact with the skin. In addition, they can be water polluting. 5.1 General The highest purity reagents and materials available should be used; those required to be of high performance liquid chromatography (HPLC) grade are commercially available from major suppliers. 5.2 Cyclohexane, of 99 % (m/m) minimum purity (CAS registry number 110-82-7). NOTE Cyclohexane can contain benzene as an impurity. 5.3 Heptane, HPLC analytical grade, as the mobile phase (CAS registry number 142-82-5). Batch to batch variation of the solvent water content, viscosity, refractive index, and purity can cause unpredictable column behaviour. Drying (for example, by standing over activated molecular sieve type 5A) and filtering the mobile phase can help reducing the effect of trace impurities present in the solvent. It is recommended practice to de-gas the mobile phase before use; this can be done conveniently online or off-line by helium sparging, vacuum degassing or ultrasonic agitation. A failure to de-gas the mobile phase can lead to negative peaks. 5.4 1-Phenyldodecane, of 98 % (m/m) minimum purity (CAS registry number 123-01-3).BS EN 12916 pdf download.