Commission Regulation (EC) No 423/2008 (repealed)Show full title

ANNEX IX

Determination of the loss of organic matter from ion exchange resins (Article 13 of this Regulation)

1. SCOPE AND AREA OF APPLICATION

The method determines the loss of organic matter from ion exchange resins.

2. DEFINITION

The loss of organic matter from ion exchange resins. The loss of organic matter is determined by the method specified.

3. PRINCIPLE

Extracting solvents are passed through prepared resins and the weight of organic matter extracted is determined gravimetrically.

4. REAGENTS

All reagents shall be of analytical quality.

Extracting solvents.

4.1. Distilled water or deionised water of equivalent purity.

4.2. Ethanol, 15 % v/v. Prepare by mixing 15 parts of absolute ethanol with 85 parts of water (point 4.1).

4.3. Acetic acid, 5 % m/m. Prepare by mixing 5 parts of glacial acetic acid with 95 parts of water (point 4.1).

5. APPARATUS

5.1. Ion exchange chromatography columns.

5.2. Measuring cylinders, capacity 2 l.

5.3. Evaporating dishes capable of withstanding a muffle furnace at 850 °C.

5.4. Drying oven, thermostatically controlled at 105 ± 2 °C.

5.5. Muffle furnace, thermostatically controlled at 850 ± 25 °C.

5.6. Analytical balance, accurate to 0,1 mg.

5.7. Evaporator, hotplate or infrared evaporator.

6. PROCEDURE

6.1. Add to each of three separate ion exchange chromatography columns (point 5.1) 50 ml of the ion exchange resin to be tested, washed and treated in accordance with the manufacturer's directions for preparing resins for use with food.

6.2. For the anionic resins, pass the three extracting solvents (points 4.1, 4.2 and 4.3) separately through the prepared columns (point 6.1) at a flow rate of 350 to 450 ml/h. Discard the first litre of eluate in each case and collect the next two litres in measuring cylinders (point 5.2). For the cationic resins, pass only solvents referred to in points 4.1 and 4.2 through the columns prepared for this purpose.

6.3. Evaporate the three eluates over a hotplate or with an infrared evaporator (point 5.7) in separate evaporating dishes (point 5.3) which have been previously cleaned and weighed (m0). Place the dishes in an oven (point 5.4) and dry to constant weight (m1).

6.4. After recording the constant weight (point 6.3), place the evaporating dish in the muffle furnace (point 5.5) and ash to constant weight (m2).

6.5. Calculate the organic matter extracted (point 7.1). If the result is greater than 1 mg/l, carry out a blank test on the reagents and recalculate the weight of organic matter extracted.

The blank test shall be carried out by repeating the operations referred to in points 6.3 and 6.4 but using two litres of the extracting solvent, to give weights m3 and m4 in points 6.3 and 6.4 respectively.

7. EXPRESSION OF RESULTS

7.1. Formula and calculation of results

• The organic matter extracted from ion exchange resins, in mg/l, is given by:

  500 (m1 – m2)

  where m1 and m2 are expressed in grams.

• The corrected weight (mg/l) of the organic matter extracted from ion exchange resins is given by:

  500 (m1 – m2 – m3 + m4)

  where m1, m2, m3 and m4 are expressed in grams.

7.2. The difference in the results between two parallel determinations carried out on the same sample must not exceed 0,2 mg/l.