BS EN 237-2004 pdf download.Methods of test for petroleum and its products — BS 2000-428: Liquid petroleum
products — Petrol — Determination of low lead concentrations by atomic absorption spectrometry (Identical with IP 428:2004).
4.5 Methyl Isobutyl ketone (MIBK)
4.6 50 %i50 % (VA’) mixture of toluene and Iso-octane
4.7 Aliquat 336 (tricapryl methyl ammonium chloride)
4.8 10 % (V/V) Aliquat 336!MIBK Solution
Dissolve 100 ml (88,0 g ± 0.1 g) of Aliquat 336 with MIBK and make up to ii.
4.9 1 % (VA) Aliquat 336/MIBK Solution
Dissolve 10 ml (8,80 g ± 0,05 g) of Aliquat 336 with MIBK and make up to 11.
4.10 Iodine solution.
Dissolve 3,0 g ± 0,1 g of iodine crystals with toluene and make up to 100 ml.
4.11 Lead chloride (PbCI2). of 99 % mass purity grade.
4.12 Concentrated lead standard stock solution, c(Pb) = 1 000 mg/I.
Dissolve 335,6mg of lead chloride (4.11) previously dried at about 105°C for at least 3 h in about 200 ml of 10% Aliquat 336/MIBK solution (4.8) in a 250 ml volumetric flask (5.4). Dilute to the mark with the 10 % Aiiquat solution, mix, and store in a brown bottle having a polyethylene-lined cap. This solution contains 1 000 mg/I of lead.
NOTE 1 The concentrated lead standard stock solution is stable for at least 6 months.
NOTE 2 Smaller volumes may be prepared. eg. 100 ml. however the precisn statement as given in clause 10 has been established using 250 ml volumetric flasks.
4.13 Diluted lead standard stock solution, c(Pb) = 100 mg/I.
Using a pipette (5.5), transfer accurately 25,0 ml of the concentrated lead standard stock solution (4.12) Into a 250 ml volumetric flask (5.4), and dilute to the mark with the I % Aliquat 336/MIBK solution (4.9). Store in a brown bottle having a polyethylene-lined cap. This solution contains 100 mg/I of lead.
NOTE Smaller volumes may be prepared, e.g. 100 ml, however the precision statement as given in clause 10 has been established using 250 ml volumetric flasks.
4.14 Lead standard solutions, 2,5 mg/I, 5,0 mg/I, 7.5 mg/I and 10,0 mg/I of lead
Using a pipette (5.5) or a micro-burette (5.3), transfer accurately 2,5 ml. 5,0 ml. 7,5 ml and 10,0 ml of the diluted lead standard stock solution (4.13) to 100 ml volumetric flasks; add 5 ml of 1 % Aliquat 336!MIBK solution (4.9) to each flask; dilute to the mark with MIBK (4.5). Mix thoroughly and store in bottles having polyethylene-lined caps.
5.1 Flame atomic absorption spectrometer, suitable for measurements at a wavelength of 217,0 nm, and fitted with a burner feed with acetylene and air, suitable for use with organic solutions.
NOTE The attention of the user is drawn that the alternative procedure as described in Annex A requires the use of a flame absorption spectrometer that is suitable for measurements at a wavelength of 283,3 nm.
5.2 Lead hollow-cathode lamp.
5.3 Micro-burette, capacity 10 ml, conforming to class A of ISO 385-1.
5.4 One-mark volumetric flasks, capacity 50 ml. 100 ml, 250 ml and 11 conforming to class A of EN ISO 1042,
5.5 One-mark pipettes, capacity 2 ml, 5 ml, 10 ml, 20 ml, 25 ml and 50 ml, conforming to class A of ISO 648,
with suction ball.
5.6 Micropipette, 100 il Eppendorf type or equivalent.
5.7 Analytical balance, capable of weighing to the nearest 0,1 mg.
6 Sampling
Unless otherwise specified In the commodity specification, samples shall be taken as described In EN ISO 3170 or EN ISO 3171, andlor in accordance with the requirements of national standards or regulations for the sampling of petrol.
7 Procedure
7.1 General preparation
Note and record the temperature. T1, at which all volumetric measurements are made. The volumetric glassware is usually calibrated at 20 °C.
Prepare the calibration solutions and the test solution on the same day and measure on that day.
7.2 Preparation of calibration solutions (0.25 mg/i, 0.50 mg/i, 0,75 mg/I, and 1,0 mgIt of lead)
7.2.1 To a 50 ml volumetric flask containing 30 ml of MIBK (4.5), add 5,0 ml of low lead standard solution (4.14) and 5,0 ml of the toluer’ie/iso-octane mixture (4.6). Repeat this operation for each of the low lead standard solutions (2,5 mg/I, 5,0 mg/i, 7,5 mg/i, and 10,0 mg/I of lead). In the case of blank, add only 5,0 ml of the toluene/iso-octane mixture.
7.3.2 Add immediately 0,1 ml of the iodine solution (4.10) by means of a micropipette (5.6). Mix thoroughly and
allow to react for at least I mm.
7.3.3 Add 5 ml of 1 % Aliquat 336 Solution (4.9) and mix thoroughly
7.3.4 Dilute to volume with MIBK (4.5) and mix thoroughly.
7.4 Preparation of instrument
7.4.1 Install the lead hollow-cathode lamp (5.2) in the spectrometer (5.1) and leave the apparatus switched on for the time necessary to achieve stabi’ity.
7.4.2 Adjust the lamp current, the attenuation and the slit, to suit the characteristics of the apparatus. Adjust the wavelength to the region of 217,0 nm in order to obtain the maximum intensity.
7.4.3 Install the burner-head for acetylene-air and ignite the flame.
7.4.4 Using pure MIBK, adjust the flow rates of acetylene (4.2) and air (4.1) and the sample aspiration to obtain an oxidising flame, which is fuel lean and light blue in colour.
7.4.5 Aspirate pure MIBK (4.5) to set the zero of the instrument.
7.4.6 Aspirate the 1,0 mg/i calibration solution and adjust the burner position to get a maximum response.
7.4.7 Aspirate pure MIBK (4.5) to set the zero of the instrument and check the blank and the four calibration
solutions (7.2) for linearity.
7.5 Determination
Aspirate the calibration solutions (7.2) and the test solution (7.3) and record the absorbance values.
NOTE The stability of the instrument should be checked by analysing the 0,50 mg/I calibration solution every five samples. If the lead concentration as determined is lower than 048 mgII or higher than 0,52 mg/I. a new calibration is necessary and the last five samples should be re-analysed.
8 Calculation
Plot the absorbance values versus the concentration of the calibration solutions and determine the concentration of the test solution, Pb), expressed in milligrams per litre, from the graph. Modern analysers have internal calibration and calculation procedures giving direct results, in such case it is unnecessary to draw calibration graphs.
Calculate the lead content of the sample, C(Pb), expressed in milligrams per litre, using the equation:BS EN 237-2004 pdf download.