BS EN 12916:2019 pdf free.Petroleum products – Determination of aromatic hydrocarbon types in middle distillates – High performance liquid chromatography method with refractive index detection.
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.Equal and constant volumes of the calibration and sample solutions are injected into the chromatograph. Both manual and automatic sample injection systems, using either complete or partial filling of the sample loop, can meet these repeatability requirements when used correctly. When using the partial filling mode, it is recommended that the injection volume is less than half the total loop volume. For complete filling of the loop, best results are obtained by overfilling the loop at least six times.BS EN 12916 pdf download.