Speciation analysis for biomolecular complexes of lead in wine by size-exclusion high-performance liquid chromatography-inductively coupled plasma mass spectrometry
Résumé
Size-exclusion chromatography with ICP-MS detection was developed for speciation of lead in wine. The method required minimal sample preparation and allowed routine analysis of wine samples, showing the distribution of lead among biomolecular compounds within 30 min. The quantification of lead bound to biomolecules was done by comparing the chromatographic peak area with that of a signal obtained by flow-injection ICP-MS analysis. A study carried out on a population of 20 wines of different origin showed that mineral lead on which the toxicity conclusions were based may not exist in wine. Lead was found to be associated with one major biomolecular (ca. 10 kDa) species present in all wine samples, and one to three minor compounds whose number depended on the wine sample. The dominant species which accounted for 40-95% of lead was identified as the complex formed with the dimer of a pectic polysaccharide, rhamnogalacturonan II. Other minor species with apparent molecular masses in the range 500-3000 Da were not identified.