BS 15199-1:2006 pdf download – Petroleum products — Determination of boiling range distribution by gas chromatography method — Part 1: Middle distillates and lubricating base oils
6.3 Carrier gas control
The chromatograph shall be able to deliver a constant carrier gas flow over the whole temperature range of the analysis.
6.4 Micro-syringe, of appropriate volume, e.g. 10 µl, for introduction of 1 µl of the calibration mixture and test portions.
NOTE 1 The micro-syringe may be operated either manually or automatically.
NOTE 2 Plunger in needle syringes are not recommended due to excessive carry over of heavy ends to the following analysis.
6.5 Volumetric flask, 10 ml capacity.
NOTE It is recommended that the refrigerator be of an explosion-protected design.
6.7 Analytical balance, able to weigh with a precision of 0,1 mg.
Samples shall be taken as described in EN ISO 3170 or EN ISO 3171 and/or in accordance with the requirements of national standards or regulations for the sampling of petroleum products. Store samples in either glass or metal containers. Plastic containers for sample storage shall not be used as prolonged contact with the sample can cause contamination of the sample due to possible leaching of the plasticizer.
8 Preparation of the apparatus
8.1 Gas chromatograph preparation
8.1.1 Set up and operate the gas chromatograph in accordance with the manufacturer’s instructions.
Typical operating conditions are shown in Table 2.
8.1.2 Deposits may form on the jet from combustion of decomposition products from the liquid stationary phase. These will affect the characteristics of the detector and should be removed.
NOTE The following parameters are affected by deposits on the jet: increase in inlet pressure; FID difficult to light;
increase in the CS 2 response and an off specification reference material. To clean the jet, it is recommended that it is put in an ultrasonic cleaner with a suitable solvent, and a cleaning wire used.
8.2 System performance check
Check the system performance at the intervals given and by the procedures specified in Annex B.
9 Sample preparation
Make a 2g/100ml to 3g/100ml solution of the sample in carbon disulfide. Transfer to an autosampler vial and immediately cap.
CAUTION — It is recommended that all work with carbon disulfide is carried out in an explosion protected fume cupboard.
10.1 Carry out the steps given in 10.2 to 10.4 each day before sample analysis. The first run of the day shall not be a blank, a reference material or a sample, due to the possible elution of extraneous components, which have built up in the injector, but it may be the calibration mixture (5.8).
10.2 Run the calibration mixture (5.8) using the specified procedure described in Clause 11.
NOTE Take care to ensure the test portion volume chosen does not allow any peak to exceed the linear range of the detector, or overload the column. A skew of > 3 indicates the sample is too concentrated and a skew of < 1 indicates an old column or dirty liner. As a guide, 1 µl of the calibration mixture (5.8) has been found to be suitable for columns with film thickness less than 0,17 µm.
10.3 Record the retention time of each component and plot the retention time versus the atmospheric boiling point for each component to obtain the calibration curve.
NOTE The atmospheric boiling points of the alkanes are given in Annex C.
A typical chromatogram of the calibration mixture (5.8) is given in Figure 4 and a typical calibration curve is given in Figure 5.
10.4 Run the Reference Material 5010 (5.9.2) using the specified procedure in Clause 11. Calculate the boiling range distribution of the reference material by the procedures specified in Annex A and compare this with the consensus values for the reference material used. If the results are not within the specified range, it is advised to carefully follow the manufacturer’s instructions regarding chromatographic problem solving and related diagnostics.
11.1 Run a solvent (blank) baseline analysis before the first sample analysis, and then after every five samples. Subtract blank baselines from subsequent analyses (see Figure 6).