BS EN 12916 pdf free download

BS EN 12916 pdf free 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/VJ 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 (H PLC) grade are commercially available from major suppliers.
5.2 Cyclohexane, of 99 % (rn/rn) 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 % (rn/rn) minimum purity (CAS registry number 123-01-3).
6 Apparatus
6.1 Liquid chromatograph, consisting of a high performance instrument capable of pumping the mobile phase at flow rates from 0,5 mI/mm to 1,5 mi/mm, with a precision better than 0,5 % and a pulsation of< 1 % full scale deflection under the test conditions described in Clause 8. Make sure that the equipment for handling or testing the sample is not sensitive to FAME. Recommended materials are Polytetrafluoroethylene, Viton®1 and Nylon.
6.2 Sample injection system, capable of nominally injecting 10 iii of sample solution with a repeatability better than 1 %.
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 ioop volume. For complete filling of the loop, best results are obtained by overfilling the loop at least six times.
The repeatability of the injection system can be checked by comparing peak areas from at least four injections of the system calibration standard (see 8.4).BS EN 12916 pdf download.