Codex Œnologique International

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METHODES DE MINERALISATION AVANT DOSAGE PAR SAA

COEI-2-MINERA Mineralisation methods of samples before determination by atomic absorption spectrometry

  1. Mineralisation by dry process

 

Method applicable for determining the following elements: calcium, magnesium, sodium, iron, copper, zinc.

1.1.    Obtaining cinders

  • Weigh with precision 5 g of oenological product (or 1 g in the case of products rich in mineral matters), in a platinum or silice capsule cleaned and tared beforehand.
  • Gently burn the sample with the flame of a Bunsen burner under a hood.
  • Put the capsule in a muffle oven at 525°C 25°C for 12 hours.
  • Take up the residue with a few ml of demineralised water.
  • Evaporate water over a water bath at 100°C.
  • Replace the capsule containing the sample in the oven.
  • The mineralisation is over when the cinders are white.
    1.     Putting the cinders in a solution
  • The cinders are solubilised with 2 ml of concentrated hydrochloric acid (R), bring to volume at 100 ml with demineralised water
  • Complementary dilutions:
  • Re-dilute the cinders solution in hydrochloric acid in order to be compatible with the sensitivity of the apparatus; see separately the method of each cation.
  • For the determination of calcium and magnesium, add lanthanum chloride during this dilution.
  • Do a blank test.
  1. Mineralisation by wet process

Method applicable for determining the following elements: arsenic, cadmium, lead in oenological products containing water.

 

2.1.    Case of aqueous products

  • Weigh with precision in a 50 ml polypropylene tube 3 grammes of pulverised oenological product, add 5 ml of nitric acid at 65%; close with a screw cap; leave 12 hours at room temperature then after unscrewing the cap place the tube in a water bath at 90°C for 3 hours under a hood; allow to cool; adjust the volume to 20 ml with demineralised water; shake; filter on an ashless filter paper (if necessary).
  • Do a blank test in the same conditions.
    1.     Case of dry products

The mineralisation is similar as for aqueous products but by using a test sample of 0.5 gramme of oenological product.