BS-EN-12916 pdf free download

BS-EN-12916 pdf free download.Methods of test for petroleum and its products.
4 Principle A known mass of sample is diluted with mobile phase (heptane). A fixed volume of this solution is injected into a high performance liquid chromatograph fitted with a polar column. This column has little affinity for non-aromatic hydrocarbons, whilst exhibiting a pronounced 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. At a predetermined time, after the elution of the DAHs, the column is backflushed to elute the T+AHs as a single sharp band. 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 monitored continually by a data processor. The amplitudes of the signals from the aromatics in the sample are compared with those obtained from previously measured calibration standards, in order to calculate the percentage by mass of MAHs, DAHs and T+AHs in the sample. The sum of the percentages by mass of the DAHs and T÷AHs is reported as the percentage by mass of POLY-AH in the sample, and the sum of the percentages by mass of MAHs, DAHs and T+AHs is reported as the percentage by mass of aromatic compounds in the sample. 5 Reagents and materials WARNING Protective gloves should be worn when handling aromatic compounds. NOTE The highest purity reagents and materials available should be used; those required to be of “H PLC” grade (gold label) are available commercially from major suppliers. 5.1 Cyclohexane, of > 99 % purity. NOTE Cyclohexane may contain benzene as an impurity.
6 Apparatus
6.1 Liquid chromatograph, consisting of a high performance instrument capable of pumping the mobile
phase at flow rates of between 0,5 mI/mm and 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.
6.2 Sample injection system, capable of injecting 10 p1 (nominal) of sample solution with a repeatability of better than 1 %.
NOTE I 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), when used correctly, can meet these repeatability requirements.
When using the partial filling mode, it is recommended that the injection volume should be 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.
The repeatability of the injection system may be checked by comparing peak areas from at least four injections of the system calibration standard (see 8.3).
NOTE 2 Sample and calibration injection volumes different from 10 p1 (typically in the range 3 p1 to 20 pI) may be used provided they meet these requirements for injection repeatability, refractive index sensitivity and linearity (see 9.4), and column resolution (see 8.6).
6.3 Sample filter, if required (see 10.1), consisting of a microfilter of porosity 0,45 pm or less, chemically inert towards hydrocarbon solvents, for the removal of particulate matter from the sample solutions.
6.4 Column system, consisting of a stainless steel HPLC column(s) packed with a commercial 3 pm, 5 pm or 10 pm amino-bonded (or amino/cyano-bonded) silica stationary phase meeting the resolution requirements given in 8.6. See Annex A for guidance on the selection and use of suitable column systems.
6.5 Temperature control, consisting of either a block heating, or an air-circulating, HPLC column oven or an
alternative form of temperature control, such as a temperature-controlled laboratory, capable of maintaining
a constant temperature to within ±1 °C in the range 20 °C to 40 °C.
NOTE The refractive index detector is sensitive to both sudden and gradual changes in the temperature of the eluent. All necessary precautions should be taken to establish constant temperature conditions throughout the liquid chromatograph system. The temperature should be optimized depending on the stationary phase.
6.6 Backflush valve, consisting of a manual, or air or electrically actuated automatic, flow-switching valve designed for use in HPLC systems, capable of operating at pressures up to 2 x 1 kPa.BS-EN-12916 pdf download.