BS ISO 9198:2020 pdf download – Paper, board and pulp — Determination of water-soluble sulfates
This document specifies a method for the determination of water-soluble sulfates in all types of pulp,paper and board. The lower limit of the determination is 20 mg of sulfate ion per kilogram of dry sample.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 186, Paper and board — Sampling to determine average quality
ISO 287, Paper and board — Determination of moisture content of a lot — Oven-drying method
ISO 638, Paper, board and pulps — Determination of dry matter content — Oven-drying method
ISO 7213, Pulps — Sampling for testing
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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water-soluble sulfates
in pulp, paper and board, the amount of sulfate ion that is extracted with water at 23 °C and determined under the conditions specified
4 Principle
Pieces of the sample are extracted with water at 23 °C in a disintegrator. An aliquot of the resulting suspension is used for determination of the sulfate ion content by ion chromatography.
5 Reagents
Use only reagents of recognized analytical quality and only water as specified in 5.1.
5.1 Distilled water or deionized water, of conductivity less than 0,1 mS/m at 25 °C.
5.2 Sulfate stock solution, r(SO 4 –2 ) = 1 000 mg/l.
Dry a portion of potassium sulfate (K 2 SO 4 ) at 140 °C. Transfer 181,5 mg ± 2 mg thereof to a 100 ml volumetric flask, dissolve the salt and make up to the mark with water (5.1).
material from clogging the syringe. Place the device over the fibres and withdraw the aliquot from the solution above this device. It is essential that the withdrawn aliquot be free from suspended material. Since the operation of the ion chromatograph (6.2) depends on its design, no detailed instructions can be given in this document. Operate the apparatus as instructed by the manufacturer. For calibration, prepare from the sulfate intermediate 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 sample solution (the aliquot) on the chromatograph as instructed by the manufacturer of the apparatus. Plot the readings for the calibration solutions against their sulfate 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 lower concentration range. However, the range of calibration solutions shall always bracket the sulfate concentration obtained from the aliquot. Check the calibration daily and whenever a new set of calibration solutions is taken into use. Read the sulfate peak of the extract (the aliquot). From the calibration graph, read the sulfate ion concentration of the extract, r, and of the blank, r 0.
9 Calculation
Calculate the mass fraction of water-soluble sulfates in the sample from the expression
ω is the mass fraction of sulfate ions in the sample, in milligrams per kilogram;
ρ is the sulfate ion concentration of the filtered extract, in milligrams per litre;
ρ 0 is the sulfate ion concentration of the blank solution, in milligrams per litre;
V is the volume of water (5.1) used in the disintegration (the volume specified is 250 ml);
m is the mass of sample taken, in grams;
ω d is the dry matter content of the sample, expressed as a percentage.
Calculate the mean and report the result to the nearest 10 mg/kg. Report values below 20 mg/kg as “less than 20 mg/kg”.
10 Precision
Five pulp and paper samples were extracted several times in a laboratory. From every extract, two aliquots were analysed. The results are shown in Table 1.BS ISO 9198 pdf download.