BS ISO 9197:2016 pdf download – Paper, board and pulps — Determination of water-soluble chlorides
5.4 Nitric acid, c(HNO 3 ) = 1,3 mol/l. Add with caution 82 ml of concentrated nitric acid, c(HNO 3 ) = 15,8 mol/l (about 70 % HNO 3 ), to 500 ml of water (5.1) and dilute to 1 l.
5.5 Additional solutions, as specified in the instructions for the ion chromatograph.
6 Apparatus Glassware and other apparatus used for this analysis shall be scrupulously clean. Soak all glassware for 5 min to 10 min in the nitric acid (5.4) and then rinse thoroughly with water (5.1). Clean, in water, forceps, scissors and the disintegrator used for sample preparation.
6.1 Wet disintegrator, a high-speed mixer, capable of disintegrating the sample completely with minimum damage to the fibres.
6.2 Ion chromatograph, having a pump, an injector loop of known volume, a column system suitable for the determination of chlorides and a conductivity detector.
6.3 Syringe, Class A, of capacity 5 ml and having a prefilter of about 0,2 µm pore width.
6.4 Tea-strainer or similar device, of stainless steel, for removing fibres from a suspension.
7 Sampling and preparation of sample If the test is being made to evaluate a pulp lot, the sample shall be selected in accordance with ISO 7213. If the test is made on another type of sample, report the source of the sample and, if possible, the sampling procedure used. From the sample received, select specimens so that they are representative of the whole sample. The procedure to be followed when sampling depends on the particular circumstances in each case. For sampling from lots of pulp, paper or board, the instructions in ISO 7213 or ISO 186, as relevant, are recommended. Since the amount of chlorides in the sample can be very low, take care not to contaminate it during sampling. Wear clean protective gloves at all times when handling the sample and the test pieces prepared from it.
The laboratory where the analysis is made shall be free from dust and fumes from chlorine-containing substances, such as hydrochloric acid or chlorinated solvents. Particular care should be taken in mill- site laboratories if the mill uses chlorine or chlorine dioxide as a bleaching agent. Keep specimens protected, wrapped in aluminium foil or in plastic bags, until required for analysis. Analyse specimens as soon as possible after sampling. Determine the dry matter content on a separate specimen using the procedure specified in ISO 287 (for paper and board) or in ISO 638 (for pulps).
8 Procedure
Carry out the procedure in duplicate. A blank test shall also be carried out in parallel with the entire determination. Weigh, to the nearest 0,01 g, a test piece, generally of between 2 g and 5 g. Split thick board and pulp sheets into thinner pieces to facilitate soaking. Select the size of the test piece so that the mass fraction of chloride ion of the extract is within the optimum range of the ion chromatograph.
Transfer the weighed test piece to the disintegrator (6.1) and add 250 ml ± 2 ml of water (5.1) at 23 °C ± 2 °C. Disintegrate the test piece until it is completely disintegrated, but no longer. After disintegration, soak the test piece for about 1 h while stirring gently to ensure complete extraction of chloride. Immediately after stopping the gentle stirring, withdraw a portion of the suspension, using the syringe (6.3). If this operation is hampered by the presence of fibres or fibre bundles, use the tea strainer or similar device (6.4) to remove fibrous material.
It is essential that the test piece solution be free from suspended material. Since the operation of the ion chromatograph (6.2) depends on its design, no detailed instructions may be given here. Operate the apparatus as instructed by the manufacturer (see also Annex A). For calibration, prepare from the chloride matching solution (5.3) a series of five calibration solutions, covering about one decade of concentrations, for example, from 1 mg/l to 10 mg/l. Run the calibration solutions and the test piece solution on the chromatograph as instructed by the manufacturer of the apparatus. Plot the readings for the calibration solutions against their chloride ion concentrations.
The five points for the calibration solutions should fall on a straight line. If they fail to do so, repeat the calibration with another set of calibration solutions, covering a higher or lower concentration range, as relevant. Check the calibration several times daily and whenever a new set of calibration solutions is used.