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ISO 6588-1-2012 pdf free download
ISO 6588-1-2012 pdf free download.Paper, board and puips — Determination of pH of aqueous
extracts — Part 1:Cold extraction
Papier, carton et pótes — Determination du pH des extra its aqueux — Partie 1: Extraction àfroid.
Weigh 2,0 g ± 0,1 g of air-dry sample (6.2) in a 250 ml flask (5.1).
NOTE Since the amount of sample is not critical, there is no need to determine the dry matter content to adjust for minor differences In moisture content.
Add 100 ml of water (4.1) to the flask (5.1) containing the sample pieces. Check that all pieces are soaked. Seal the flask with its ground-glass stopper and leave it to stand for 1 h at a temperature between 20 °C and 25 °C. Shake the flask at least once during this time.
Filter the extract through a coarse, fritted glass filter into a small beaker (5.1). Immediately add 2 ml of potassium chloride solution (4.3) and continue with the measurement.
7.3 Determination of pH
Operate the p11-meter in accordance with the manufacturer’s instruction. Wash the electrodes with water (4.1); allow the water to drain from the electrodes, but do not wipe them. Calibrate the pH-meter (5.2), at a temperature between 20 °C and 25 °C, with two different buffer solutions (4.2) having pH- values such that the pH of the extract is between the pH-values of the buffer solutions. The first buffer solution should be chosen so that the pH-value of the buffer solution is in the same region as the electric zero point of the pH-meter (usually = 7). The reading for the second buffer solution should agree with its correct value to within 0,1 pH-unit.
I fthe pH-meter fails to show thecorrect p1-1-value forthe second buffer solution, consult the manufacturer’s manual. A deviation exceeding 0,2 pH-units indicates a faulty electrode. Also a slow but continuous increase or decrease in the reading indicates faulty electrodes.
After calibration, rinse the electrode several times with water (4.1) and once in a small quantity of the extract. Check that the temperature of the extract is between 20 °C and 25 °C. Immerse the electrodes in the extract. Record the pH when there is no measurable drift, within 30 s.
Before measuring the next sample, rinse the electrodes carefully with water (4.1) to remove any traces of sample or buffer solution.
At the end of a series of measurements, check the electrodes with buffer solutions.
Calculate the mean of the duplicate determinations.ISO 6588-1-2012 pdf free download.
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