BS EN 14582-2016 pdf free download.Characterization of waste — Halogen and sulfur content — Oxygen combustion in closed systems and determination methods
9 Equipment
9.1 Calorimetric bomb, with a capacity of not less than 200 ml and equipped with a purging system
This bomb shall not leak during testing and shall permit a quantitative recovery of the liquid. Its inner surface may be made of stainless steel or any other material that will not be affected by combustion gases. Materials used for the bomb assembly, such as the head gasket and wire insulation, shall be heat and chemical action resistant and shall not undergo any reaction that will affect the results. Bombs with pitted surfaces should never be used because of their tendency to retain halides and sulphate. After repeated use of the bomb, a film may build up on the inner surface.
This dullness should be removed by periodically polishing the bomb according to the manufacturer’s instructions. The internal surface of some calorimetric bombs may have a ceramic coating or platinum buckets, which have better resistance to corrosion.
9.2 Sample cup, platinum or stainless steel or quartz.
9.3 Firing wire, platinum or stainless steel or nickel/chromium alloy or an equivalent.
9.4 Ignition circuit, capable of supplying a sufficient current to ignite the sample without melting the wire.
9.5 Absorption flask (e.g. a 200 ml test tube equipped with a glass frit dip-tube for bubbling the combustion gases).
9.6 Usual laboratory equipment, as homogenization devices (e.g. mixers, stirrers, grinders, mills), analytical balance (accurate at least to 0,1 mg), etc.
9.7 Safety precautions The bomb shall not contain any organic residue (vapours of organic solvents, grease, etc.). Respect shall be given to the manufacturer’s instructions, especially to the oxygen pressure inside the bomb and the maximum allowable calorific value of the test portion.
NOTE Combustion of 1 g of hydrocarbons such as lubricating oil produces about 40 kJ (the calorific values of benzoic acid and isooctane are about 26 MJ/kg and 48 MJ/kg).
10 Procedure
10.1 General Before each series of determinations, a blank and quality check shall be carried out on a control mixture (7.2), according to Clause 12. Alternately running samples high and low in halogen or sulfur content should be avoided whenever possible as it is difficult to rinse the last traces of ions from the internal surfaces of the apparatus and a tendency for residual elements to carry over from sample to sample has been observed.
When a sample high in halogen or sulfur content has preceded a sample low in concentration, the test on the second sample should be repeated and one or both of the low values thus obtained should be considered suspect if they do not fall within the limits of repeatability of this method. It is good practice to insert a blank between each sample, unless the series of samples being analysed has similar expected concentrations.
When the composition or homogeneity of the sample is unknown, it is better to carry out the analysis in duplicate or triplicate and report the mean result from all determinations with the associated standard deviation.
In case of significant carry over it is recommended to collect the exhaustion gases of the sample and the following blank sample in one absorption liquid.
10.2 Choice of the absorption solution The combustion gases can be collected inside and/or outside the bomb in an absorption solution. Water is generally used when low concentrations of halogens and sulfur are expected (usually, less than 10 g/kg). Alkaline solution should be used for high contents of halogens and sulfur, to ensure neutralization of the acid compounds produced. The composition of absorption solutions depend on the determination technique and on the expected content of halogens and sulfur. Applicable examples are:
— Solution 1: Water (7.1.2);
— Solution 2: 0,3 mol/l potassium or sodium hydroxide solution: dissolve 16,8 g of KOH or 12,0 g of NaOH pellets (7.1.3) in water (7.1.2) and dilute to 1 l;
— Solution 3: Carbonate/bicarbonate solution: dissolve 2,52 g sodium bicarbonate NaHCO 3 and 2,54 g sodium carbonate Na 2 CO 3 (7.1.4) in water (7.1.2) and dilute to 1 l;
— Solution 4: 0,25 mol/l sodium hydroxide solution (dissolve 10,0 g NaOH pellets (7.1.3) in water (7.1.2) and dilute to 1 l) + 50 µl of hydrogen peroxide solution at 3 % (dilute 5 ml H 2 O 2 (7.1.5) into 50 ml); — Solution 5: 0,25 mol/l sodium hydroxide solution (dissolve 10,0 g NaOH pellets (7.1.3) in water (7.1.2) and dilute to 1 l) + 0,5 ml of hydrazine hydrate (7.1.6);
— Solution 6: Ascorbic acid-solution at 1 % or at 5 % prepared with pure reagent (7.1.7) in water (7.1.2). NOTE 1 More details regarding these solutions and there performances in terms of halogens and sulfur recovery are available in Annex C. When ion chromatography is used for the determination of halides and sulphate, the absorption solution may have the composition of the mobile phase, e.g. carbonate/bicarbonate solution.
It is recommended to add 0,5 ml of hydrogen peroxide solution (7.1.5) to the absorption solution before combustion to improve the oxidation of sulfur. However, hydrogen peroxide may oxidize iodide leading to an underestimation. When sulfur and iodine are to be determined in the same sample, it is recommended to carry out two different combustion operations. For iodine and bromine use 10 ml of 1 % ascorbic acid (solution 6) as an absorption solution to improve the reduction to iodide or bromide before opening of the bomb. The most suitable combinations of absorption solutions with determination techniques for the expected halogens or sulfur are presented in Table 2.BS EN 14582 pdf download.