Antimony speciation in spirits stored in PET bottles: identification of a novel antimony complex

Abstract

Total antimony and its +V and +III oxidation state species were determined in twelve spirit samples (Greek raki and tsipouro) stored in polyethylene terephthalate bottles. Reliable and reproducible results were obtained following direct analysis by using ICP-MS providing total Sb concentrations between 0.4–4 μg L⁻¹. Antimony speciation analysis by LC-ICP-MS was also assessed, showing the presence of both inorganic Sb species along with an unknown Sb complex, which was the predominant species in all samples analysed. The structure of this complex was investigated by using liquid chromatography with high-resolution tandem mass spectrometry. The analysis gave evidence for an acetaldehyde–bisulphite pyruvate Sb complex with the formula: C₇H₁₄O₁₂S₂Sb. The proposed ligands are organic substances expected to be present in the raki matrix. In addition, the influence of high temperature storage conditions and extended exposure times up to two weeks, on Sb migration from PET bottles into raki samples was investigated. Total Sb and Sb species content was determined by ICP-MS and LC-ICP-MS, respectively. The concentrations determined were in the range of 5.6 to 28 μg Sb per L spirit after a week of storage at 60 °C. In which case, inorganic Sb(V) and Sb(III) became the predominant species in comparison to the “novel” organic Sb complex.